No full-text available
To read the full-text of this research,
you can request a copy directly from the author.
Herbivory in Relation to Plant Nitrogen Content
... Additionally, many plants produce chemical defences against herbivorous insects, with high carbon to nitrogen ratios (C/N) being associated with accumulation of carbon-based phenolics which can reduce herbivory (Bryant et al., 1983;Fürstenberg-Hägg et al., 2013;Lindroth et al., 2001;Wittstock & Gershenzon, 2002). Nitrogen content is especially important in plant-insect interactions as protein and nitrogen concentrations are positively correlated in leaves (Throop & Lerdau, 2004), and studies have shown that nitrogen concentrations directly affect growth and diet choice in many herbivorous insects, leading to insect preferences for higher nitrogen in leaves (Mattson, 1980;Osier & Lindroth, 2001;Rausher, 1981). ...
... We also investigated whether predictions stemming from the general-purpose genotype (GPG) or frozen-niche variation ( (Strong et al., 1984) including in old field plant communities, arable weeds, and alpine plant communities (Karley et al., 2008;Leingärtner et al., 2014;Schädler et al., 2003). Nitrogen has been shown to be important for growth and development of insect herbivores and therefore has often been used as a proxy for nutritional value of plants (Mattson, 1980;Wang et al., 2020;White, 1984). Our data suggest a different pattern in M. batesii: we found that M. batesii in their natural habitats preferred host plants with higher C/N ratios and lower nitrogen levels ( Figure 4). ...
Closely related sexual and parthenogenetic species often show distinct distribution patterns, known as geographical parthenogenesis. Similar patterns, characterized by the existence of separate sexual and parthenogenetic populations across their natural range, can also be found in facultative parthenogens – species in which every female is capable of both sexual and parthenogenetic reproduction. The underlying mechanisms driving this phenomenon in nature remain unclear. Features of the habitat, such as differences in host‐plant phenotypes or niche breadth, could favour sexual or asexual reproductive modes and thus help to explain geographical parthenogenesis in natural insect populations. Megacrania batesii is a facultatively parthenogenetic stick insect that displays geographical parthenogenesis in the wild. We aimed to explore whether sexual and parthenogenetic populations of M. batesii displayed niche differentiation or variations in niche breadth that could explain the separation of the two population types. To do this, we sampled host plants from across the range of M. batesii and quantified phenotypic traits that might affect palatability or accessibility for M. batesii, including leaf thickness, toughness, spike size and density, plant height, and chemical composition. We also quantified host‐plant density, which could affect M. batesii dispersal. We found little evidence of phenotypic differences between host plants supporting sexual versus asexual M. batesii populations, and no difference in host‐plant density or niche breadth between the two population types. Our results suggest that habitat parameters do not play a substantial role in shaping patterns of geographical parthenogenesis in wild populations of M. batesii. Instead, population sex ratio variation could result from interactions between the sexes or dispersal dynamics.
... Additionally, we measured plant performance based on plant height and biomass, as well as chemical traits in leaves, including carbon/nitrogen (C/N) ratios, total phenolics, total proanthocyanidins (PACs), and flavonol levels. These chemical traits were measured because nitrogen is a limiting element for herbivores (Mattson Jr 1980), and phenolic compounds such as flavonoids, that include PACs and flavonols, are abundant in cranberries and can play an important role in plant-herbivore interactions (Neto et al. 2010;Barbehenn and Constabel 2011;Rodriguez-Saona et al. 2011;Pradit et al. 2019;Rodriguez-Saona et al. 2021). ...
... In addition to morphological characteristics, nutrient composition could also undergo alterations in modern genotypes through the domestication process (Fernandez et al. 2021;Salazar-Mendoza et al. 2023). Importantly, high C/N ratios are indicative of poor-quality hosts for herbivores since nitrogen is a crucial component for their growth and reproduction (Mattson Jr 1980;Zavala et al. 2017). Contrary to Mondolot et al. (2008), who reported effects of domestication on C/N ratios of cassava leaves, our data revealed that variation in C/N ratios among cranberry genotypes is not associated with the domestication gradient. ...
Plant genotypes often exhibit varying resistance levels to herbivores. However, the impact of this genotypic variation on resistance against multiple herbivores remains poorly understood, especially in crops undergoing recent process of domestication. To address this gap, we studied the magnitude and mechanism of resistance in 12 cranberry (Vaccinium macrocarpon) genotypes to three leaf-chewing herbivores – Sparganothis fruitworm (Sparganothis sulfureana), spotted fireworm (Choristoneura parallela), and spongy moth (Lymantria dispar) – along a domestication gradient (native ‘wild’ genotypes, ‘early hybrid’ genotypes, and ‘modern hybrid’ genotypes). Like cranberries, S. sulfureana and C. parallela are native to the United Sates, while L. dispar is an invasive pest. We measured the survival and growth of larvae on each genotype, as well as variation in plant performance (height and biomass) and leaf defensive chemical traits (C/N ratio, total phenolics, total proanthocyanidins, and flavonols levels) in these genotypes to elucidate potential resistance mechanisms. We found differences in C. parallela and L. dispar larval performance across genotypes, with larvae performing better on the modern hybrid genotypes, while S. sulfureana showed no differences. Morphological and chemical traits varied among genotypes, with total phenolics being the only trait correlated with C. parallela and L. dispar larval performance. Notably, the wild genotypes ‘McFarlin’ and ‘Potter’ had higher total phenolics and were more resistant to both herbivores than the modern hybrids ‘Demoranville’ and ‘Mullica Queen.’ This research contributes to a comprehensive understanding of the impact of crop domestication on multiple insect herbivores, offering insights for future breeding efforts to enhance host-plant resistance against agricultural pests.
... Alpine ecosystems, where nitrogen availability is strongly limited, highlights the importance of crude protein in forage selection by alpine herbivores (DeLuca et al., 2002). Pikas act as allogenic ecosystem engineers by forming hay piles that enhance soil development and fertility in low-productivity alpine and subalpine talus fields, which are often shallow, alkaline, and nitrogen-poor (Mattson, 1980). Unlike many alpine species, pikas do not hibernate, relying instead on the hay piles to sustain them through winter. ...
Lagomorphs show dietary flexibility as a result of spatial and temporal distinction in the food availability which in turn influences the ecology of a species. Royle’e pika (Ochotona roylei), a specialist herbivore, is endemic to Himalayan belt. During the present study, feeding ecology of Royle’s pikas and their dietary responses to seasonal variations were examined from eighty-six study plots at Jagran Forest Range, in the northern region of Azad Jammu & Kashmir. Data of monthly diet composition, and monthly temporal changes in the selection of various food items from Royle’s pika population was collected, using focal scan sampling method, from the study plots. The overall diet of Royle’s pikas at Jagran comprised of 40.685% flowers, 15.411% mature leaves, 14.579% roots, 14.474% young leaves, 8.056% stems, 3.742% fruits, and 3.052% whole plants. The diet of pikas exhibited a wide erraticism across the study months (H = 14.989; df = 7; p = 0.0361). Royle’s pikas spent significantly more time feeding on flowers during the summer and monsoon seasons (71.23% and 78.93% respectively), than in autumn, where no flower consumption recorded. The diet of Royle’s pikas did not show a greater diversity during the study period (Shannon – Wiener index (H′) = 2.11 – 3.98); whereas, a high mean monthly dietary evenness index, was recorded (J = 0.87 – 0.99) across various study months. The results show that Royle’s pikas adapt seasonal shifts in their diet consumption as chief food items changed temporally in study area, and it is more prominent in autumn season, when ground vegetation vanishes out completely. Moreover, among various plants, Parnassia nubicola had the highest selection ratio (31.812) in the pika diet at Jagran Forest Range. The findings of the current study contribute to a better understanding of the dietary flexibility of Royle’s pikas in Western Himalayan region of Azad Kashmir, in response to local environmental conditions that may figure out lagomorph ecology and evolution.
... Plant defence traits, that is functional traits that promote plant fitness in the presence of antagonists relative to the absence of antagonists (Didiano et al., 2014), are often divided into physical and chemical defences (Table 1; Moore & Johnson, 2017). Physical defences are those that deter herbivores from feeding on plant tissues through morphological or anatomical traits (Hanley et al., 2007), while chemical defences encompass traits related to the tissue's nutritional quality (Mattson, 1980;Poorter et al., 2004) and defensive phytochemicals (Raguso et al., 2015). Another strategy to counteract antagonists is collaboration with mutualists. ...
The increased positive impact of plant diversity on ecosystem functioning is often attributed to the accumulation of mutualists and dilution of antagonists in diverse plant communities. While increased plant diversity alters traits related to resource acquisition, it remains unclear whether it reduces defence allocation, whether this reduction differs between roots and leaves, or varies among species.
To answer these questions, we assessed the effect of plant species richness, plant species identity and their interaction on the expression of 23 physical and chemical leaf and fine root defence traits of 16 plant species in a 19‐yr‐old biodiversity experiment.
Only leaf mass per area, leaf and root dry matter content and root nitrogen, traits associated with both, resource acquisition and defence, responded consistently to species richness. However, species richness promoted a decoupling of these defences in leaves and fine roots, possibly in response to resource limitations in diverse communities. Species‐specific responses were rare and related to chemical defence and mutualist collaboration, likely responding to species‐specific antagonists' dilution and mutualists' accumulation.
Overall, our study suggests that resource limitation in diverse communities might mediate the relationship between plant defence traits and antagonist dilution.
... In agroecosystems, C. bonplandianus populations infected with begomovirus are higher than in other ecosystems, probably due to the rich organic compounds that support more of these plants, consequently increasing viral infections. This agrees with reports that plants in nitrogen-rich soils are highly infected by viral species vectored by herbivorous insects [23][24][25][26][27] . Begomovirus infection strongly inhibits the growth and reproductive development of C. bonplandianus. ...
Invasive species are considered the second worst threat to biodiversity after habitat destruction, which was altered the function and service of the ecosystem. However , some exotic species fail to become invasive due to newly acquired enemies in the introduced range, as described by the 'increased susceptibility' hypothesis. In the present study, we have tested the increased susceptibility hypothesis: does begomovirus infection play an important role in the invasiveness of Croton bonplandi-anus in its introduced range. To understand the role of viral infection on the invasiveness of C. bonplandianus, the healthy and viral infected population density of C. bonplandianus was measured at different ecosystems by the quadrat method. Several first-and second-order branches, number of inflorescence per plant, number of buds/inflorescence, number of male and female flower/ inflorescence, number of seed/inflorescence, pollen and seed viability, chlorophyll content were measured in infected and healthy populations of C. bonplandianus. Results showed that the infected population of C. bon-plandianus was higher in agroecosystems than in other ecosystems. The number and length of the inflores-cences were maximum in healthy plants (24.74 ± 1.78 and 5.78 ± 0.13 respectively) than infected population (7.28 ± 0.88 and 2.04 ± 0.08 respectively). The number of male and female buds per inflorescences were also recorded maximum in healthy plants (21.19 ± 0.86 and 4.44 ± 0.13 respectively) and significantly different from the infected plants (9.99 ± 0.63 and 2.16 ± 0.12 respectively). Further, to identify the nature of the virus, viral DNA was isolated from the infected plant and confirmed through Rolling Circle Amplification followed by digestion to release the 2.7 kb and anticipated 1.3 kb. The above fragments were cloned, sequenced and analysed to identify the nature of the virus molecules. Surprisingly, 2.7 kb matched the papaya leaf curl virus, whereas 1.3 kb showed significant similarity with the alpha satellite, which is associated with the chilli leaf curl virus. Based on the results, we concluded that begomovirus infection has strongly affected reproductive traits of C. bonplandianus thus resulting in their failure to become an invasive species at the introduced range. However, the infected population of C. bonplandianus acts as a pathogen reservoir for various crop diseases, namely papaya and chilli leaf curl diseases.
... Consequently, porina performed better when feeding on plant material grown in a high Olsen P environment. It is widely acknowledged that P fertilisers enhance photosynthesis in plants and physiological processes which leads to increased growth, higher protein content, and greater biomass 61 . It is also known that managing soil fertility can mediate the chemical composition of plants and their susceptibility to insect pests 62 . ...
The increasing expenses and environmental repercussions associated with phosphorus (P) fertiliser underscore the necessity for precision-managed application methods. These changes affect pastoral systems, where cool-season grasses like perennial ryegrass and meadow fescue form beneficial relationships with Epichloë endophytes. Understanding how fertilisers influence these endophytes, host grasses, and insect pests is crucial, as Epichloë endophytes enhance resistance to some herbivorous insects. This study examined the indirect impact of various P fertiliser regimes on cool-season grasses, which serve as food sources for porina larvae (Wiseana copularis), a significant pasture pest in New Zealand. Endophyte-infected (Epichloë sp. LpTG-3 strain AR37) perennial ryegrass and meadow fescue infected with E. uncinata (strain MaxR (AR1017)), alongside their endophyte-free counterparts were grown in P-enriched soil with varying Olsen P levels (9, 18, 28, and 78 mg/L). Freeze-dried foliage was added to semi-synthetic diets and fed to porina larvae in a no-choice assay. Measurements included diet consumption, porina survival, weight gain. Measurements in foliage included fungal alkaloid concentration, fungal biomass, and plant nutrient levels. Endophyte infection of AR37 and MaxR significantly reduced porina diet consumption, larval weight gain and survival irrespective of soil Olsen P levels to the plant. Loline alkaloid concentration in MaxR-infected herbage increased with increasing soil Olsen P levels while fungal mass remained unchanged. In endophyte-free grasses, porina larvae significantly increased their diet consumption, weight gain and survival as the Olsen P level available to the host plant increased. While endophyte strains AR37 and MaxR continue to protect their hosts under different Olsen P regimes, these results suggest that the improved performance of porina on endophyte-free plants is largely driven by P-induced changes in food quality. Here, we discuss the implications of porina damage in New Zealand pastures in the context of decreasing P availability.
... This phenomenon has already been studied in some Canarian endemic species, such as Cneorum pulverulentum (Pérez-Méndez et al. 2016). Nitrogen-fixing plants, known for their high palatability as already mentioned, also showed a major tendency to disappear due to presumably their susceptibility to invasive herbivores (Johnson et al. 1987;Mattson 1980;Simonsen and Stinchcombe 2014). Our study highlighted the potential vulnerability of Fabaceae, emphasizing their susceptibility to herbivory (Cubas et al. 2019), which poses significant risks to ecosystem stability and biodiversity (Barker et al. 2022). ...
Whether species extinctions have accelerated during the Anthropocene and the extent to which certain species are more susceptible to extinction due to their ecological preferences and intrinsic biological traits are among the most pressing questions in conservation biology. Assessing extinction rates is, however, challenging, as best exemplified by the phenomenon of ‘dark extinctions’: the loss of species that disappear before they are even formally described. These issues are particularly problematic in oceanic islands, where species exhibit high rates of endemism and unique biological traits but are also among the most vulnerable to
extinction. Here, we document plant species extinctions since Linnaeus' Species Plantarum in Macaronesia, a biogeographic region comprised of five hyperdiverse oceanic archipelagos, and identify the key drivers behind these extinctions. We compiled 168 records covering 126 taxa, identifying 13 global and 155 local extinction events. Significantly higher extinction rates were observed compared to the expected global background rate. We uncovered differentiated extinction patterns along altitudinal gradients, highlighting a recent coastal hotspot linked to socioeconomic changes in Macaronesian archipelagos from the 1960s onwards. Key factors influencing extinction patterns include island age, elevation, introduced herbivorous mammals, and human population size. Trait-based analyses across the floras of the Azores and Canary Islands revealed that endemicity, pollination by vertebrates, nitrogen-fixing capacity, woodiness, and zoochory consistently tended to increase extinction risk. Our findings emphasize the critical role of geography and biological traits, alongside anthropogenic impacts, in shaping extinction dynamics on oceanic islands. Enhancing our knowledge of life-history traits within island floras is crucial for accurately predicting and mitigating future extinction risks, underscoring the urgent need for comprehensive biodiversity assessments in island ecosystems.
... Elephants are heavy consumers of plant matter, eating up to 250 kg of forage daily depending on body weight (Kohi 2013). Although elephants also need nitrogen-rich plant tissues such as grasses and tree leaves (Mattson Jr 1980), much of their food comprise carbohydrates, mostly fiber and specific-nutrient sources including leaves, twigs, tree barks, and roots (Ben-Shahar and Macdonald 2002;Prajapati 2008). Elephant range should, therefore, be able to provide these diverse sources of nutrients to elephants in all seasons as well as at different times of the day. ...
African elephants (Loxodonta africana) are megaherbivores of the African savannas requiring extensive ranges that can provide critical resources for their survival and reproduction at different spatiotemporal scales. We studied seasonal differences in home range sizes and daily distance to the nearest surface water sources by five male and 10 female African elephants in the eastern Okavango Panhandle in northern Botswana between 2014 and 2017. We hypothesized that (i) elephant home ranges would be larger in the wet than in the dry season (because critical resources tend to be less localized in the wet than in the dry season), (ii) the daily distance of the elephants to the nearest ephemeral surface water sources would be larger in the dry than in the wet season because many of the ephemeral water sources would be dry in the dry season and elephants would start moving towards permanent water sources such as rivers, and lastly (iii) that the differences in elephant home ranges and daily distance to water would differ between sexes. Our results showed that elephant home ranges were larger in the wet than in the dry season, and that they differed between sexes with female elephants having smaller home ranges in the late wet season. The mean daily distance to the nearest ephemeral surface water sources was larger in the dry than in the wet season. There was an inverse relationship between elephants' daily distance to permanent surface water and to ephemeral water sources. The findings indicate the need for large conservation areas and functional connectivity between landscapes to enable the highly mobile savanna elephants to access critical seasonal resources such as water and forage in semi‐arid savannas. Such landscapes are critical, especially in the face of climate change, when high air temperatures and droughts may exacerbate forage and water shortage and intensify human–elephant interactions in surrounding agroecosystems.
... As it is known, nitrogen is a limiting element for living things. It has been determined that changes in nitrogen availability affect the nutritional and defense properties of the plant (Mattson, 1980), the quality of host plant components (such as C, N, and defense metabolites), herbivore productivity and reproductive strategies (Awmack & Leather, 2002). Since host selection also causes various mating preferences, it has been argued that the mechanisms underlying these preferences will contribute directly to the understanding of speciation, and the functions of chemosensory genes that have an effect on smell and taste in speciation and host selection are sought to be investigated (Eyres et al., 2017). ...
Insects, the most common and most successful animals on earth, establish long-term and stableecological relationships with bacteria. Aphids (Hemiptera: Aphididae) are an insect group of agri-cultural importance that can feed on many herbaceous, shrubs, and woody plants as hosts andare also in close relationship with endosymbiont bacteria. It is seen that aphid is going to furtherincrease their current pest potential in the near future due to their high adaptability and rapidreproduction ability. In order to be effective and successful in the biological control of aphids, manyfeatures of aphids are required to be known and clarified. Therefore, determining the interactionsamong aphid, host plant, and endosymbiont in this relationship might make biological controlof aphids more effective. In this review, what is known about the relationship among aphids, theprimary endosymbiotic bacterium Buchnera aphidicola, and the host plant is examined, and thepossibilities of using symbiont bacteria in the biological control of aphids are discussed.
... One possible explanation of the difference between A. valida and L. rhomboides consumption of nutrient-enriched resources may lie in differences in nutritional requirements between the consumer species. Herbivores are generally nutrient limited, and thus the nutrient content of primary producers can dictate herbivore food selection (Mattson 1980;Hay 1991;Sterner and Hessen 1994;Elser et al. 2001;Fink and Von Elert 2006;Kraufvelin et al. 2006). However, organisms require different amounts of energy and nutrients based on their specific physiological constraints (Sterner and Elser 2002;Sterner and Hessen 1994). ...
Introduced seaweeds can alter the structure and productivity of marine food webs, especially when they lack top-down control by native herbivores. However, relatively little is known about the role of consumption of introduced seaweeds by native herbivores, and the potential role of seaweed nutrient content to mediate local herbivore consumption. In southeastern USA estuaries, the introduced red seaweed, Gracilaria vermiculophylla, has transformed unvegetated intertidal mudflats into a patchwork of non-native seaweed beds. We used a series of laboratory feeding assays to assess how invertebrate and fish species on the Georgia coast utilize G. vermiculophylla as a novel food resource. Because G. vermiculophylla readily absorbs nutrients, we also tested the role of nutrient enrichment on its consumption. We found that G. vermiculophylla was not significantly consumed by the mud snail Ilyanassa obsoleta nor the mud crab Eurypanopeus despressus, but it was rapidly eaten and even preferred over the native seaweed Ulva lactuca by adult pinfish Lagodon rhomboides. Nutrient enrichment of G. vermiculophylla did not affect consumption rates by the amphipod Ampithoe valida, but did double consumption rates by pinfish over unenriched seaweed. The differential responses of native consumers highlight the importance of evaluating multiple species when investigating introduced species' impacts on recipient communities. Given that consumer identity and nutrient content of the seaweed mediated the consumption of the non-native seaweed, site-specific patterns of consumer populations and environmental conditions could lead to patchy abundance and impacts of the non-native seaweed.
... Possibly, higher allocation of C than N is more important as a strategy to regrow and reduce herbivory attacks following a single herbivory event, as suggested previously (Schultz et al., 2013). Lowered N could also reflect a lower plant nutritional quality for herbivores, thus this may be seen as another tactic to potentially reduce herbivore attacks (Mattson, 1980). ...
Silicon (Si) supplementation can enhance symbiotic functions in some legumes (Fabaceae) with their nitrogen‐fixing rhizobia, such as root nodulation and nitrogen fixation. However, it is still poorly understood how Si influences legume–insect interactions. Here, we investigated how a symbiotic legume responds not only to Si supplementation but also to herbivory treatment with varying infestation levels in two events.
We conducted a controlled climate chamber experiment by growing Medicago truncatula plants inoculated with rhizobia. For half of the plants, the soil was kept without Si (−Si), whereas the other half was regularly supplemented with Si (+Si). We then infested the plants with caterpillars of Spodoptera littoralis with 0, 1 or 3 larvae and 0, 1 or 1 larva in single herbivory attack and in double herbivory attack, respectively. To understand plant responses to such treatment combinations, we examined 16 functional traits.
Nodule number, nodule fresh mass and nodule leghaemoglobin concentrations were not affected in single attack plants. However, increasing levels of herbivory led to decreases in such measured traits in double attack plants. Foliar C to N ratio increased in single attack plants but decreased in double attack plants with increasing levels of herbivory, indicating contrasting resource allocation. Herbivory did not affect the content of foliar Si, which was higher in +Si than −Si plants. Si and herbivory led to reduced foliar phenolics in double attack plants, suggesting a potential trade‐off between silicification and phenolic production. Si and herbivory led to increased trichome densities in single attack plants, but patterns were less clear in double attack plants. Herbivory but not Si reduced plant biomass with increasing levels of herbivory in double attack plants. Relative growth rates of the caterpillars, as proxy for plant resistance, decreased mainly due to herbivory treatment, when fed on single attack plants.
Using a trait‐based approach, we provide novel insights to better understand the response of a legume to Si supplementation and different herbivory levels and events. We conclude that herbivory predominantly exerts much stronger effects than Si on various plant traits, pointing to a necessity to respond to herbivory by induced defence strategies.
Read the free Plain Language Summary for this article on the Journal blog.
... The diet of large herbivores such as elephants is composed of many plant species, because it is more economical to include suboptimal species than to take the time to discriminate (Crawley 1983). Leaves, green fruits and seeds are generally heavily defended chemically, compared with grasses (Mattson 1980;Wink 1993). For example, condensed tannins have detrimental effects in many mammals by reducing protein digestibility (Mole and Waterman 1987). ...
This July-August 2002 study assessed the physical and chemical properties of 14 natural mineral licks and their use by African elephants in Aberdare NP in Central Kenya and recorded the elephant use of 2 artificial salt licks, in the same Park, for 15 days. The mineral licks were postioned by GPS and classified according to extend of present use: light, moderate, heavy and abandoned. A total of 56 samples were taken from the mineral licks and 52 control samples were taken from locations about 200m away each of the licks. The mineral licks or 'eaten earths differed from the uneaten earths primarily in their significantly higher sodium and iodine concentrations'. The mineral lick samples contained a higher clay content than did the control samples. 'This work therefore isolated sodium iodine and clay content as the possible stimuli for geophagy among the elephants' in this area. The authors note: 'Sodium preference could be attributed to palatability, clay has a possible medicinal function and also retards leaching of sodium and iodine. It appears elephant seek inorganic sources to supplement iodine well as sodium and it would be important to assess licks for both elements in areas where range is becoming more restricted as the animals may not be able to access mineralized soils areas they used to. The age and sex of the animals using two artifical salt licks in the vicinity of tourist hotels were recorded over a 15 day period.
... In the case of nutrients, we quantified phosphorus and nitrogen concentration, which have been shown to be predictive of herbivory across many plant taxa (Huberty & Denno, 2006;Mattson, 1980), including oaks (Eatough Jones et al., 2008;Forkner & Hunter, 2000). ...
Ecological theory predicts that herbivory should be weaker on islands than on mainland based on the assumption that islands have lower herbivore abundance and diversity. However, empirical tests of this prediction are rare, especially for insect herbivores, and those few tests often fail to address the mechanisms behind island–mainland divergence in herbivory. In particular, past studies have not addressed the relative contribution of top‐down (i.e. predator‐driven) and bottom‐up (i.e. plant‐driven) factors to these dynamics.
To address this, we experimentally excluded insectivorous vertebrate predators (e.g. birds, bats) and measured leaf traits associated with herbivory in 52 populations of 12 oak (Quercus) species in three island–mainland sites: The Channel Islands of California vs. mainland California, Balearic Islands vs. mainland Spain, and the island Bornholm vs. mainland Sweden (N = 204 trees). In each site, at the end of the growing season, we measured leaf damage by insect herbivores on control vs. predator‐excluded branches and measured leaf traits, namely: phenolic compounds, specific leaf area, and nitrogen and phosphorous content. In addition, we obtained climatic and soil data for island and mainland populations using global databases. Specifically, we tested for island–mainland differences in herbivory, and whether differences in vertebrate predator effects or leaf traits between islands and mainland contributed to explaining the observed herbivory patterns.
Supporting predictions, herbivory was lower on islands than on mainland, but only in the case of Mediterranean sites (California and Spain). We found no evidence for vertebrate predator effects on herbivory on either islands or mainland in any study site. In addition, while insularity affected leaf traits in some of the study sites (Sweden‐Bornholm and California), these effects were seemingly unrelated to differences in herbivory.
Synthesis. Our results suggest that vertebrate predation and the studied leaf traits did not contribute to island–mainland variation patterns in herbivory, calling for more nuanced and comprehensive investigations of predator and plant trait effects, including measurements of other plant traits and assessments of predation by different groups of natural enemies.
... The present study indicated that the infestation of the adult beetle Coffee White Stemborer of X. quadripes peaked in June (monsoon), when compared to January and March (pre-monsoon). In this case, it is possible that seasonal variation of temperature and rainfall were increasing the feeding rate and extending the activity of feeding and breeding in organic plantations (Mattson, 1980;Thapa and Lantinga, 2016). Moreover, the different climate conditions affected the adult beetle of X. quadripes in terms of distribution, where premonsoon to monsoon periods were more appropriate for the flight period of the adult beetle of X. quadripes (Sekhar, 1958& Kung, 1977. ...
Xylotrechus quadripes (Chevrolat), the Coffee White Stem Borer, is a major pest of arabica coffee plantations (Coffea arabica L.) in southern Laos and some Asian countries. This study was conducted on an arabica coffee plantation in Bolaven Plateau, southern Laos, during January, March and June 2021. The study was undertaken to assess the number of adult beetles, larvae and their exit holes of the Coffee White Stem Borer, or X. quadripes, as well as their relationship. The result indicated that there was a significant difference in the number of adults depending on the collection date; moreover, the number of adults gradually increased from January to June. However, there was no significant difference between the number of larvae and exit holes for the collection date. On the whole, there was a relatively strong positive relationship between the number of adults and larvae versus the number of exit holes. This finding was the fundamental data to support the farmer in terms of properly controlling and managing their coffee plantations in the region.
... This suggests that leaves are replaced by fruits in the diet of dormice in our study areas, and the replacement becomes more prevalent during summer with the decreasing nutritional value of aging leaves. Younger leaves are easy to digest and are richer in nitrogen and water, making them a better source for both hydration and nutrients than older leaves (Mattson 1980;Hörtensteiner & Feller 2002). The discrepancy in the proportions of leaves in our study compared to the results from the Netherlands (Kuipers et al. 2012) and Slovakia (Holišova 1968) might be attributed to the reduced availability of suitable young leaves in our study sites, given the limited size of the woody area (6.76 ha) and sparse tree cover in the dune area. ...
The garden dormouse (Eliomys quercinus) faces significant population declines across Europe, prompting urgent conservation measures. A critical aspect of these efforts is understanding the species’ dietary composition and preferences within specific areas and how this changes throughout the year. We compared garden dormouse diets between two habitats in West Flanders, Belgium with faecal analysis from May to October, covering almost their entire active phase. Our findings revealed a diverse diet of both plant and animal matter, with notable variations between habitats and seasons. Blackberries and other fruits, leaves, and to a lesser extent flowers, were the predominant plant-based food sources in both study areas, with seasonal fluctuations indicating a dietary shift throughout the dormice’s active period. Spring diets consisted primarily of young leaves and flowers, changing to increased fruit consumption in summer. Beetles emerged as a main animal food source throughout the entire active period. Snails were prominently eaten in the woody area, while millipedes prevailed in the diet in the dune environment, both more in spring than later in the active season. These insights highlight the importance of maintaining diverse fruit sources and preserving beetle, snail, and millipede populations for garden dormouse conservation. This study provides valuable insights into dormouse dietary preferences and thus contributes to targeted conservation strategies being essential for the survival of the dormouse.
... Because nitrogen is widely known as limiting for plant growth in terrestrial ecosystems, it's availability in soil has played a major role in the conceptual development of the plant sciences (Mattson 1980;Lambers et al. 1998;Vidal and Gutiérrez 2008). And, to "grow or defend" has been the basis of prominent theories of plant allocation, with N-limitation typically being involved (Herms and Mattson 1992). ...
Theories have been widely proposed and tested for impacts of soil nitrogen (N) on phytochemical defenses. Among the hundreds of distinct cardenolide toxins produced by milkweeds (Asclepias spp.), few contain N, yet these appear to be the most toxic against specialist herbivores. Because N- and non-N-cardenolides coexist in milkweed leaves and likely have distinct biosynthesis, they present an opportunity to address hypotheses about drivers of toxin expression. We tested effects of soil N and herbivore-damage on cardenolide profiles of two milkweed species differing in life-history strategies (Asclepias syriaca and A. curassavica), and the toxicity of their leaves. In particular leaf extracts were tested against the target enzymes (Na⁺/K⁺-ATPase extracted from neural tissue) from both monarch butterflies (Danaus plexippus) as well as less cardenolide-resistant queen butterflies, D. gilippus. Increasing soil N enhanced biomass of Asclepias syriaca but had weak effects on cardenolides, including causing a significant reduction in the N-cardenolide labriformin; feeding by monarch caterpillars strongly induced N-cardenolides (labriformin), its precursors, and total cardenolides. Conversely, soil N had little impact on A. curassavica biomass, but was the primary driver of increasing N-cardenolides (voruscharin, uscharin and their precursors); caterpillar induction was weak. Butterfly enzyme assays revealed damage-induced cardenolides substantially increased toxicity of both milkweeds to both butterflies, swamping out effects of soil N on cardenolide concentration and composition. Although these two milkweed species differentially responded to soil N with allocation to growth and specific cardenolides, leaf toxicity to butterfly Na⁺/K⁺-ATPases was primarily driven by herbivore-induced defense. Thus, both biotic and abiotic factors shape the composition of phytochemical defense expression, and their relative importance may be dictated by plant life-history differences.
... The high C:N in plant tissue relative to the biomass of insect herbivores means that most herbivores are N limited (Elser et al., 2000) and will preferentially feed on plant tissue with high N concentrations when available (Mattson, 1980). Because EcM can increase plant N uptake by up to 86% (Hobbie & Hobbie, 2008;Plassard et al., 2000;Read, 1991;Read & Perez-Moreno, 2003) and facilitate higher N concentrations in plant tissue (Tibbett & Sanders, 2002), EcM colonisation should have a positive impact on herbivory and herbivore performance (Expectation 1a). ...
Increasing atmospheric CO2 concentrations are changing how plants interact with their biotic mutualists and antagonists, but few syntheses consider how the three‐way interactions between mycorrhizae, plants and herbivores will shift under rising CO2.
We summarise the mechanisms by which ectomycorrhizal (EcM)‐associated plants, their mycorrhizae and insect herbivores interact with each other under current conditions and evaluate a set of expectations for how these interactions might shift under higher CO2. We then outline priorities for future work on EcM–plant–herbivore interactions as atmospheric CO2 continues to rise.
EcM colonisation has variable but often positive effects on herbivory, while herbivory has consistently negative impacts on EcM colonisation. Mechanistic evidence suggests that the positive EcM effect on herbivory will strengthen and the negative impact of herbivory on EcM will be ameliorated under higher CO2.
Synthesis: While more empirical evidence on fungal–plant–herbivore interactions is needed in EcM systems, our synthesis suggests that EcM associations may play an under‐recognised role in dictating future terrestrial carbon capture by mediating herbivory and the ability of plants to compensate for herbivory as atmospheric CO2 continues to rise.
... Finally, diet quality (i.e. the nutritional content of a particular diet) is dynamic and sensitive to environmental perturbation. For example, leaf quality tends to decline with age, decreasing in nitrogen and water content while increasing in fibre and toughness (Mattson, 1980). Drought, atmospheric CO 2 and temperature can each alter protein and carbohydrate content in plants (Rosenblatt and Schmitz, 2016). ...
Natural and anthropogenic stressors are dramatically altering environments, impacting key animal physiological traits, including cardiac performance. Animals require energy and nutrients from their diet to support cardiac performance and plasticity; however, the nutritional landscape is changing in response to environmental perturbations. Diet quantity, quality and options vary in space and time across heterogeneous environments, over the lifetime of an organism and in response to environmental stressors. Variation in dietary energy and nutrients (e.g. lipids, amino acids, vitamins, minerals) impact the heart's structure and performance, and thus whole-animal resilience to environmental change. Notably, many animals can alter their diet in response to environmental cues, depending on the context. Yet, most studies feed animals ad libitum using a fixed diet, thus underestimating the role of food in impacting cardiac performance and resilience. By applying an ecological lens to the study of cardiac plasticity, this Commentary aims to further our understanding of cardiac function in the context of environmental change.
... Phosphorus and nitrogen in leaves have been shown to be positively associated with leaf herbivory across a number of plant taxa (Huberty & Denno, 2006;Mattson, 1980), including oaks (Eatough Jones et al., 2008;Forkner & Hunter, 2000). To quantify these traits, we colorimetrically quantified nitrogen (indophenol blue method) and phosphorus (molybdenum blue method) concentration using a Biorad 650 microplate reader (Bio-Rad Laboratories, Philadelphia, PA, USA) at 650 and 700 nm, respectively (Walinga et al., 1995). ...
The evolutionary processes that underlie variation in plant genome size have been much debated. Abiotic factors are thought to have played an important role, with negative and positive correlations between genome size and seasonal or stressful climatic conditions being reported in several systems. In turn, variation in genome size may influence plant traits which affect interactions with other organisms, such as herbivores. The mechanisms underlying evolutionary linkages between plant genome size and biotic and abiotic factors nonetheless remain poorly understod. To address this gap, we conducted phylogenetically controlled analyses testing for associations between genome size, climatic variables, plant traits (defenses and nutrients), and herbivory across 29 oak (Quercus) species. Genome size is significantly associated with both temperature and precipitation seasonality, whereby oak species growing in climates with lower and less variable temperatures but more variable rainfall had larger genomes. In addition, we found a negative association between genome size and leaf nutrient concentration (found to be the main predictor of herbivory), which in turn led to an indirect effect on herbivory. A follow‐up test suggested that the association between genome size and leaf nutrients influencing herbivory was mediated by variation in plant growth, whereby species with larger genomes have slower growth rates, which in turn are correlated with lower nutrients. Collectively, these findings reveal novel associations between plant genome size and biotic and abiotic factors that may influence life history evolution and ecological dynamics in this widespread tree genus.
... Positive effects of AM fungi on aphid performance can be mediated by their effects on plant N uptake and the increase of tissue quality (Wilkinson et al., 2019). Nitrogen is often a limiting factor in insect herbivore diets, thus, nitrogen acquisition by insects is strongly correlated with higher food utilization (Mattson, 1980). AM fungimediated increases in plant growth may result in increased plant tolerance to herbivorous pests (Bennett et al., 2006) or AM fungi may negatively impact herbivores via increased production of host plant defences (e.g. ...
Symbiosis plays a critical role in plant biology. Temperate grasses often associate with several symbiotic fungi simultaneously, including Epichloë endophytes and arbuscular mycorrhizal (AM) fungi, in shoots and roots, respectively. These symbionts often modulate plant–herbivore interactions by influencing nutritional traits (i.e. AM fungi‐mediated nutrient uptake) and/or the secondary chemistry (i.e. endophytic alkaloids) of their host plant. Moreover, such grasses also accumulate large amounts of silicon (Si) from the soil, which can be deposited in tissues to act as a physical anti‐herbivore defence.
Recent evidence suggests that both endophytes and AM fungi independently facilitate Si uptake. However, the consequences of their interactions with piercing‐sucking insects (i.e. aphids), or whether Si supply, endophytes, and AM fungi interact in this regard, are currently unknown. While Si deposition may be less effective against aphids than other herbivores (i.e. chewing caterpillars), Si supply can also alter plant secondary metabolite defences, which could affect sucking insects.
In a factorial greenhouse experiment, we evaluated whether these components, acting alone or in combination, altered (1) foliar primary chemistry, (2) Si and symbiont‐chemical (endophytic alkaloids) defences, as well as (3) performance of the bird cherry‐oat aphid (Rhopalosiphum padi) feeding on tall fescue (Festuca arundinacea).
Endophytes decreased all aphid performance parameters, including population growth and reproduction by 40%, but their impact was reversed by the presence of AM fungi, leading to a 52% increase in aphid performance compared with plants solely hosting endophytes. This improvement in performance was associated with reduced loline alkaloid levels and higher shoot nitrogen in AM‐endophytic plants. Endophytes and AM fungi exhibited antagonism, with endophytes reducing AM colonization by 34% and AM presence decreasing endophyte loline alkaloids by 44%. While both fungi jointly increased Si accumulation by 39% under Si‐supplied conditions, Si had no noticeable effects on aphids. Moreover, although Si supply had no identifiable effects on AM colonization, it reduced endophyte peramine alkaloids by 24%.
Synthesis. Our findings indicate that symbiotic fungal partnerships and silicon provision may benefit plants but could weaken anti‐herbivore defences when combined. Revealing the complex interactions among diverse fungal symbionts and showcasing their effects on different anti‐herbivore defences (chemical and physical) and herbivore performance for the first time.
... Furthermore, aspartate, glutamate, and glutamine serve as crucial nitrogen storage and transport compounds in plants, with their accumulation closely associated with nitrogen availability [35][36][37]. Meanwhile, nitrogen represents a primary limiting resource for phytophagous pests, whereby reduced plant nitrogen nutrition affects the population abundance of these pests as well as the extent of damage inflicted upon the host plants [38,39]. Notably, this study observed a decreased level of glutamate and glutamine in cotton plants under salt stress conditions, which may indicate a reduced ability to assimilate nitrogen. ...
The degree of global soil salinization is gradually deepening, which will inevitably affect agricultural ecology. It has been found that salt stress induces the resistance of host plants to phytophagous pests. However, little is known about the effects of salt-stressed cotton plants on the fitness of cotton aphids (Aphis gossypii Glover). In this study, we investigated the differences between cotton metabolomes under mild (75 mM NaCl) and moderate (150 mM NaCl) salinity conditions and their effects on the fitness of cotton aphids. The results showed that 49 metabolites exhibited significant upregulation, while 86 metabolites were downregulated, with the increasing NaCl concentration. The duration of nymphal aphids under 150 mM NaCl significantly extended to 6.31 days when compared with the control (0 mM NaCl, 4.10 days). Meanwhile, the longevity of adult aphids decreased significantly under 75 and 150 mM NaCl, with an average of 10.38 days (0 mM NaCl) reduced to 8.55 and 4.89 days, respectively. Additionally, the total reproduction number of single females decreased from 31.31 (0 mM NaCl) to 21.13 (75 mM NaCl) and 10.75 (150 mM NaCl), whereas the survival rate of aphids decreased from 81.25% (0 mM NaCl) to 56.25% (75 mM NaCl) and 34.38% (150 mM NaCl) on the 12th day. These results support the hypothesis that plants growing under salt stress are better defended against herbivores. Furthermore, 49 differential metabolites were found to be negatively correlated with the longevity and fecundity of adult aphids, while 86 different metabolites showed the opposite trend. These results provide insights into the occurrence and control of cotton aphids amidst the escalating issue of secondary salinization.
... All animals preferentially ate plants with positive nutritional value (Fig. 7), but only cows and horses clearly avoided toxic plants (Fig. 8). However, it is difficult to separate positive and negative signals since there may be trait correlations that differ among plant groups: leguminous plants could be both toxic and nutritious with nitrogen-based herbivore defence substances such as cyanogenic glycoside in Trifolium (Table 2) whereas less nutritious plants could also be toxic but with a nonnitrogen-based defence (Mattson 1980 (Linnaeus 1749) and in Tengmalm's data (Tengmalm 1779(Tengmalm -1780. (Loh et al. 2020, Wunderlich et al. 2023. ...
In 1749, Linnaeus published Pan Svecicus, a thesis that was defended by his student Nils Hesselgren. The thesis describes food preference trials in cows, goats, sheep, horses, and pigs, and includes 2325 tests with 643 plant species. The data had surprisingly little bearing on the text in the thesis, and even though the experiments quickly became internationally known, the data were merely repeated, rather than discussed. We have digitized the data and linked the species names to modern nomenclature and present the first analysis and discussion of the results. Pigs were most selective (eating 32% of the 204 plant species that were tested on all animals), followed by horses (59%), cows (66%), sheep (82%), and goats (85%). The ruminants (especially goats and sheep) had high overlap in food choice, and the pigs deviated most (despite the fact that pigs are more closely related to the ruminants than are horses). Among plant orders, Fabales and Poales were generally preferred, while Lamiales and Ranunculales were avoided, especially by cows and horses. Cows and horses were also more keen to avoid toxic plant species. All animals showed a preference for species that are today considered nutritious. We now make the data available, for further analyses in ecology, history of science, and other disciplines.
... Given that nitrogen content in plants is a limiting factor for insect herbivores (Mattson, 1980), C/N ratios can serve as valuable indicators of food quality (Royer et al., 2013). In July 2020, two random plants from each of 10 randomly selected pots for each of the four treatments were chosen for nitrogen and carbon analyses (n = 10 replicates per treatment). ...
While phytoplasma infections in plants are known to affect their interactions with aboveground herbivores, the impact of different genotypes on these infections and their effects on belowground herbivores remains largely unexplored. In cranberry (Vaccinium macrocarpon), infection by the phytoplasma Candidatus Phytoplasma sp. subgroup 16SrIII-Y leads to false blossom disease. This study investigates whether cranberry infection by this phytoplasma affects the performance and feeding behavior of a foliar feeder (spongy moth, Lymantria dispar) and a root feeder (oriental beetle, Anomala orientalis). Using phytoplasma-infected and uninfected cranberries of two genotypes ("Ben Lear" and "Crimson Queen"), the survival, growth and consumption of L. dispar and A. orientalis larvae were measured. To assess the effects on plant morphological and chemical traits, we also examined the impact of phytoplasma infection on shoot and root growth, carbon and nitrogen content, and the levels of defensive compounds such as proanthocyanidins (PACs). Results indicate that larvae of L. dispar and A. orientalis generally showed larger size and more efficient tissue consumption on infected plants, with these effects varying by cranberry genotype, possibly due to differences in phytoplasma titer. Phytoplasma infection was associated with stunted growth, elevated nitrogen content, and lower PAC levels in both shoots and roots of infected cranberry plants compared to un-infected ones. These findings indicate that phytoplasma infection potentially manipulates plant chemical composition by increasing nutrient levels and decreasing defensive compounds, enhancing herbivore performance both above and belowground. This study sheds light on the intricate interplay among plants, phytoplasma infection, and insect herbivore communities.
... Furthermore, Wenting et al. (2023), notes that carrion contains valuable nutrients, including vital elements difficult to obtain in nature, such as cobalt (Co), as well as selenium (Se), which are accumulated in larger quantities in dead organisms. Mattson (1980) also talks about the importance of nitrogen to animals, and indeed, determines that arthropod herbivores tend to select food items based on their respective nitrogen dietary needs. Survival of juveniles and adults of A. vulgare is likely related to the nitrogen availability in their diets (Faberi et al., 2011), and as bodily remains tend to contain a higher nitrogen concentration (6-12 %) than plant detritus (1-2 %; Parmenter & MacMahon, 2009), it is plausible that the individuals of A. vulgare could be complementing their nutritional needs, especially during the dry season, where appropriate food items might be scarce, by consuming carrion. ...
Resumen.-La necrofagia involucra alimentarse de carroña. Como algunos de los principales promotores involucrados en el proceso de descomposición, los cadáveres son mayormente consumidos por artrópodos de los órdenes Diptera y Coleoptera, así como la subclase Acari, aunque algunas veces otras especies pueden cumplir tal función. Observamos una de aquellas instancias tras levantar una roca, encontrando una gran concentración de cochinillas (Armadillidium vulgare) consumiendo los restos de una serpiente Toluqueña Rayada (Conopsis lineata). Este es el primer reporte, hasta donde sabemos, de este tipo de comportamiento inusual en México. Las cochinillas son usualmente detritívoras; entonces, sugerimos que el cambio en la conducta proviene de un posible intento de complementar su dieta, y por lo tanto incrementar la supervivencia de los organismos al adquirir nutrientes difíciles de obtener encontrados en la carne descompuesta, especialmente durante la temporada de sequía, época donde tuvo lugar este evento.
Abstract.-Necrophagy involves feeding upon carrion. As some of the main drivers involved in the process of decomposition, carcasses are mainly consumed by arthropod members of orders Diptera and Coleoptera, as well as the subclass Acari, though sometimes other species may carry out such a function. We observed one such instance after lifting a rock, finding a large concentration of pillbugs (Armadillidium vulgare) consuming the remains of a Lined Tolucan Earthsnake (Conopsis lineata). This is the first report, to our knowledge, of this type of unusual behavior in Mexico. Pillbugs are usually detritivores; thus, we suggest that the change in conduct stems from a possible attempt to complement their diet and increase the survival of the organism by acquiring hard-to-obtain nutrients found in decaying flesh, especially during the dry season, when this event took place.
... Root herbivory effects on N transfer in mixed plant cultures, therefore, depend not only on plant functional identity, but also plant species identity including successional stage of origin. Such responses of plants to root herbivory might be mediated by host preference and root susceptibility to grazing (Mattson 1980;Ritchie 1998;Bardgett and Wardle, 2003). Overall, our results showed RLN-mediated N transfer to benefit Banksia only in the late successional scenario. ...
Aims
Plant community dynamics are influenced by interspecific interactions. Previous studies have shown that soil organisms play a key role in such interactions, but few studies have quantified soil fauna contributions.
Methods
We investigated the effects of root lesion (RLN) and bacterial feeding (BFN) nematodes on the interaction between seedlings of nitrogen-(N)-fixing tree species of Acacia and non-fixing Banksia from early and late successional stages of a temperate forest in a pot experiment.
Results
Nematodes had consistent, albeit minor, negative effects on both N-fixers and non-fixers in the early successional stage scenario. By contrast, BFNs increased biomass production of both species in late-stage monocultures and in Banksia in mixed cultures. Moreover, RLNs negatively affected late-stage Banksia in monocultures but promoted its biomass production when grown with Acacia. Reduced ¹⁵N concentration in Banksia indicates that the switch was driven by transfer of N from Acacia facilitated by RLN.
Conclusions
Soil nematodes thus moderate interspecific interactions differently in early and late successional stages.
... They also suggest that implementing organic methods for cultivating healthy soils can significantly contribute to the achievement of sustainable and resilient crop yields, even when faced with hemipteran pest pressures. Additionally, the lower nitrogen levels in plants grown on organic farms may make them less attractive to herbivores, contributing to the reduced pest pressure observed in organic systems (Mattson, 1980). Different studies suggest that organic farming practices, including the maintenance of organically managed soils and microorganisms, may unintentionally lead to a decrease in plant pest attraction by enhancing plant resistance. ...
The global population is increasing at a rapid pace, posing significant challenges to sustainable development and food security. This review paper examines the advantages and challenges of organic farming as a potential solution to address the pressing issues in modern agriculture and food production. Organic farming offers a range of benefits, including improved soil fertility, higher profitability, reduced external input usage, land reclamation, improved market access, and enhanced farmer capacity and self-reliance. Organic farming practices prioritize environmental sustainability by reducing chemical usage and reliance on biological methods of pest control, as well as enhancing biodiversity, which strengthens ecological balance and resilience against pests and diseases. However, organic farming also faces challenges that need to be addressed for its widespread adoption. These challenges include uncertainty surrounding legislative environments, psychological and sociological costs of conversion, financial risks during the transition period, securing marketing channels for organic produce, and diminishing profit margins. Efforts should be made to provide farmers with the necessary support, including technical assistance, subsidies, and access to markets, to overcome these challenges. Despite the challenges, the potential of organic farming in promoting sustainable agriculture and ensuring a secure food system cannot be overlooked. It offers a natural and environmentally friendly approach to food production, prioritizing the health of both humans and the ecosystem.
... 58 The nutrient composition of plant material, particularly N/P ratios, modulates insect performance and fitness. 59,60 The relationship between P and N is central to understanding how P affects the nutritional quality of plants and hence insects feeding on those plants. Nitrogen and P are both essential components of plant proteins and nucleic acids, and alterations can impact the growth and development of herbivores. ...
BACKGROUND
Fertiliser applications are well‐established tools in pasture‐based agricultural landscapes. This study focuses on the impact of phosphorus (P) fertiliser on grass grub (Costelytra giveni), a major pasture pest. This research investigates the interplay between P, plant growth, and grass grub fitness in Epichloë endophyte‐infected perennial ryegrass (Epichloë sp. LpTG‐3 strain AR37) and meadow fescue infected with E. uncinata (strain MaxR; AR1017), alongside their endophyte‐free counterparts. In a glasshouse trial, plants were grown in P‐enriched soil with varying Olsen P levels (9, 18, 28 or 78 mg L⁻¹), and grass grubs were introduced. Their survival and weight gain, and plant performance were measured. In a bioassay, grass grubs were placed in specimen vials with P‐enriched soils (Olsen P levels 9, 18, 28 and 78 mg L⁻¹) and provided with identical plant material to assess their diet consumption and weight gain.
RESULTS
In the glasshouse trial, results highlighted a notable decrease in the survival of grass grub on plants infected with MaxR endophyte, but not with AR37, as well as increasing soil Olsen P levels in both plant species. While grass grub decreased plant performance at the low Olsen P level (9 mg L⁻¹), this effect diminished with increasing P. Likewise, results from the bioassay showed a decrease in diet consumption with increasing soil Olsen P levels. In both trials increasing Olsen P levels correlated with diminished grass grub performance, revealing a nuanced relationship between soil fertility and pest dynamics.
CONCLUSION
The study underscores the pivotal role of selected Epichloë endophyte–grass associations in mitigating grass grub damage across varying phosphorus levels. This study highlights the potential to integrate P applications for sustainable pest control against grass grub. Further field trials are required to validate these findings. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
... In each plot, we measured four traits for each observed tree species: specific leaf area (SLA, i.e. the area of a fresh leaf divided by its dry weight), individual leaf area (LA), leaf nitrogen content (N) and spine density. These traits were selected for their functional relevance regarding a photosynthetic efficiency-leaf longevity tradeoff (SLA and N; Reich et al., 1997;Wright et al., 2004), tolerance to drought and nutrient stress (LA and SLA;Westoby et al., 2002), leaf attractiveness to herbivores (N; Cooper & Owen-Smith, 1985;Mattson, 1980) and defence against large herbivores (spine density; Gowda, 1996;Cooper & Owen-Smith, 1986). ...
African savannahs are characterised by a high plant diversity, partly resulting from a high turnover in community compositions across space. However, it is poorly understood what is driving this spatial turnover in plant communities. Here, we investigate to which extent the presence of rocky outcrops (also called kopjes) explains the community composition of trees in an African savannah, and how we can understand the responses of tree species to rocky outcrops by their functional traits. Along a precipitation gradient, we visited 24 sites in Serengeti National Park (Tanzania). At each site, we characterised tree communities, as well as their functional traits, in both a kopje and an adjacent open savannah plot (matrix plot). We found that kopjes harboured elevated tree abundances and species richness. Their dominant trees were more often evergreen, had a higher specific leaf area, a lower leaf nitrogen content and a lower spine density, than dominant trees in the savannah matrix. Differences in tree communities between kopjes and savannah matrix plots were generally the largest at sites with low precipitation. Our results indicate that kopjes are strong drivers of tree biodiversity, possibly due to locally increased soil moisture and low fire frequencies. The uniqueness of kopje tree communities may have important implications for higher trophic levels and ecosystem functioning.
... Several nutritional influences on foraging choices of moose and other cervids have been suggested, including minerals (Robbins, 1994), plant secondary metabolites (Freeland & Janzen, 1974), energy (Belovsky, 1978;Schoener, 1971), or protein (Mattson, 1980). While each of these food constituents is important, there has been little evidence for the maximization or limitation of any single constituent being the main driver of foraging choices in northern cervids . ...
Understanding how the nutritional properties of food resources drive foraging choices is important for the management and conservation of wildlife populations. For moose (Alces alces), recent experimental and observational studies during the winter have shown macronutrient balancing between available protein (AP) and highly metabolizable macronutrients (total non‐structural carbohydrates [TNC] and lipids). Here, we combined the use of continuous‐recording camera collars with plant nutrient analyses and forage availability measurements to obtain a detailed insight into the food and nutritional choices of three wild moose in Norway over a 5‐day period in summer. We found that moose derived their macronutrient energy primarily from carbohydrates (74.2%), followed by protein (13.1%), and lipids (12.7%). Diets were dominated by deciduous tree browse (71%). Willows (Salix spp.) were selected for and constituted 51% of the average diet. Moose consumed 25 different food items during the study period of which 9 comprised 95% of the diet. Moose tightly regulated their intake of protein to highly metabolizable macronutrients (AP:TNC + lipids) to a ratio of 1:2.7 (0.37 ± 0.002SD). They did this by feeding on foods that most closely matched the target macronutrient ratio such as Salix spp., or by combining nutritionally imbalanced foods (complementary feeding) in a non‐random manner that minimized deviations from the intake target. The observed patterns of macronutrient balancing aligned well with the findings of winter studies. Differential feeding on nutritionally balanced downy birch (Betula pubescens) leaves versus imbalanced twigs+leaves across moose individuals indicated that macronutrient balancing may occur on as fine a scale as foraging bites on a single plant species. Utilized forages generally met the suggested requirement thresholds for the minerals calcium, phosphorus, copper, molybdenum, and magnesium but tended to be low in sodium. Our findings offer new insights into the foraging behavior of a model species in ungulate nutritional ecology and contribute to informed decision‐making in wildlife and forest management.
... Positively correlated with herbivore resistance Mattson (1980), Hunter (2016) N.E. Harms et al. ...
Natural or anthropogenic movement of plant species outside their historical ranges may result in exposure to new environmental conditions and a lack of natural enemies, thus promoting their establishment and spread into new areas. A biogeographical comparison of native and invasive populations can provide insight into the mechanisms of successful invasions and guide effective management strategies, such as biological control, by targeting plant traits that promote invasiveness. We studied the Eurasian aquatic plant, Nymphoides peltata, in situ in the native (China, Korea) and invaded (USA) ranges to determine whether there were differences in natural enemy attack rates (percent leaf damage, frequency of leaf herbivory or disease), productivity (plant cover, reproduction), and leaf traits (leaf elemental content, leaf toughness, dry matter content, specific leaf area) between areas. We also investigated whether there was evidence of a tradeoff between natural enemy attack and growth or reproduction, as would be predicted by invasion theory. Plant cover (23-29 % higher) and reproductive output (eight times more seeds / m 2) were consistently higher in the invaded range. Leaf traits consistently differed between ranges, which we would expect if plants in the invaded range had fewer herbivores or other pests. The amount of leaf damage present was similar between ranges, but the frequency of herbivory was 50 % greater, on average, in the native than invaded range. Although we did not quantify suppression of N. peltata by natural enemies, we found evidence of more frequent herbivory in Asia and reduced reproduction and plant cover compared to the USA, which supports further investigation into viability of biological controls.
... Este resultado de mayor producción de pupas en plantas de maíz V6 indica que la cantidad de pupas producidas aumenta a medida que la planta envejece hasta alcanzar un punto máximo, después del cual disminuye (Fig. 4). Estos resultados podrían explicarse por dos factores: las hojas de maíz, exceptuando las hojas nuevas recién formadas, se vuelven más rígidas a medida que la planta crece, lo que podría llevar a que las larvas consuman menos follaje debido al aumento en el contenido de fibra (Mattson 1980, Bergvinson et al. 1995, y por consecuencia, se reduzca su supervivencia. El área foliar de la planta tiende a aumentar con el tiempo, lo que teóricamente se traduce en una menor canibalización debido a que a mayor área, se reduce la probabilidad de encuentros entre larvas. ...
The parasitoid Telenomus remus Nixon can be used as a biological control agent for the fall armyworm Spodoptera frugiperda (J.E. Smith) in Mexico. Its commercial importation was authorized in 2015, but it is currently not used as a biological control agent presumably due to the lack of simple and economical methods for its reproduction. A methodology for the reproduction of T. remus was developed using simple procedures, materials, and facilities to promote its future technical transfer to low-tech farmers. Specifically, S. frugiperda was reproduced under semi-field conditions (i.e., an area protected with anti-aphid mesh, without controlling environmental conditions) using simple methods (mainly covering maize plants), economical materials (local maize plants and organza fabric), and in a climate-controlled area, T. remus was reared on eggs from an S. frugiperda colony in semi-field conditions. This system can be sequential and scalable. In its individual component, each organza bag that contained V6 maize plants can be used to produce 24 pupae of S. frugiperda, which can theoretically produce 5,010 T. remus.
... texana, though they similarly found no effects of herbivory on female flowering (Theis et al., 2009). Removal of plant tissue can reduce the availability of nutrients to support floral development as plants reallocate resources towards defence and regrowth and simultaneously experience reduced photosynthetic capacity with the direct loss of foliar tissue (Mattson, 1980). That we observed similar but dampened effects of mechanical damage on flower phenology in C. pepo ssp. ...
Background
Damage from insect herbivores can elicit a wide range of plant responses, including reduced or compensatory growth, altered volatile profiles, or increased production of defence compounds. Specifically, herbivory can alter floral development as plants reallocate resources towards defence and regrowth functions. For pollinator-dependent species, floral quantity and quality are critical for attracting floral visitors; thus, herbivore-induced developmental effects that alter either floral abundance or attractiveness may have critical implications for plant reproductive success. Based on past work on resource trade-offs, we hypothesize that herbivore damage-induced effects are stronger in structural floral traits that require significant resource investment (e.g., flower quantity), as plants reallocate resources towards defence and regrowth, and weaker in secondary floral traits that require less structural investment (e.g., nectar rewards).
Scope
In this study, we simulated early-season herbivore mechanical damage in the domesticated jack-o-lantern pumpkin Cucurbita pepo ssp. pepo and measured a diverse suite of floral traits over a 60-day greenhouse experiment.
Key Results
We found that mechanical damage delayed the onset of male anthesis and reduced the total quantity of flowers produced. Additionally, permutational multivariate analysis of variance (PERMANOVA) indicated that mechanical damage significantly impacts overall floral volatile profile, though not output of sesquiterpenoids, a class of compounds known to recruit specialized cucumber beetle herbivores and squash bee pollinators.
Conclusions
In summary, we show that C. pepo spp. pepo reduces investment in male flower production following mechanical damage, and that floral volatiles do exhibit shifts in production, indicative of damage-induced trait plasticity. Such reductions in male flower production could reduce the relative attractiveness of damaged plants to foraging pollinators in this globally relevant cultivated species.
Nutrient composition varies greatly across landscapes, influencing the spatiotemporal dynamics of populations. However, few studies have explored this pattern across multiple scales. We tested how nutrient limitation affects herbivore populations, from individual behavior to landscape‐level dynamics, using the Australian plague locust Chortoicetes terminifera . Our study combined field populations and long‐term survey data across their range. At the individual level, juvenile locusts selected a carbohydrate‐biased intake target of 1 protein (p) to 2 carbohydrate (c) and exhibited the highest growth rates and shortest development times when fed artificial diets matching this 1p:2c ratio during their final juvenile instar. In the field, locusts exposed to protein‐biased plants corrected their nutritional imbalance by initially selecting carbohydrate‐heavy diets (up to a 1p:20c ratio). Over a week after removal from the protein‐rich environment, they returned to the 1p:2c intake target once the deficiency was balanced. At the landscape level, locust outbreaks were negatively correlated with soil nitrogen and exhibited a non‐linear relationship with soil phosphorus, peaking at approximately 4% phosphorus content. By disentangling the interaction between mean annual precipitation and soil nitrogen, using comprehensive locust surveys and remotely sensed soil and weather data spanning decades, we show how environmental factors drive population dynamics. This study integrates lab, field and remote sensing approaches, highlighting the importance of nutrient balancing across scales for herbivores. Specifically, we demonstrate that low‐nitrogen environments promote locust outbreaks, likely by reducing plant protein‐to‐carbohydrate ratios. Incorporating soil quality data into locust plague forecasting models could significantly improve prediction accuracy.
Puddling, a behavior in which butterflies and other insects aggregate on mineral-rich substrates such as mud, animal excrement, carrion, and even human perspiration, is a well-documented phenomenon in both temperate and tropical regions. This behavior is thought to compensate for the limited access to micronutrients in the adult diet that are important for fitness, primarily sodium and nitrogen, essential for nervous system function, growth, and reproductive processes. In this review, we consolidate existing knowledge on butterfly puddling and highlight key gaps in our understanding. The review is organized into 4 main themes: the benefits of puddling, social dynamics in puddling, sensory cues for site selection, and behavioral variation across species and regions. We explore how nutrient preferences are influenced by diet, environmental factors, and evolutionary history, with a particular focus on the role of sodium and nitrogen. We also discuss the potential reproductive benefits of puddling, including its impact on mating success and fecundity. In addition, we consider the sensory and social mechanisms butterflies use to locate suitable puddling sites. Lastly, we give a short overview on puddling in moths. This review identifies several areas for future research, particularly in understanding the adaptive significance of puddling across different taxa and environments.
Plant-soil feedbacks (PSFs) occur when a plant species modifies soil physicochemical and biological properties in ways that affect growth of a plant subsequently grown in the same soil. PSFs are influenced by both herbivory, and climatic conditions, but it is unclear how foliar herbivory and climate change interact to modify PSFs. A PSF experiment was conducted to assess the effect of foliar herbivory on Medicago sativa and Trifolium repens, when grown in monoculture and mixture. PSFs were assessed in soils from a field experiment simulating ambient rainfall and prolonged drought (50% reduction) for six years. All soils were sterilized and then re-inoculated to create the respective biological rainfall legacy treatments including a sterile control. The cotton bollworm, Helicoverpa armigera, was used to induce herbivore treatments. Neither legume showed significant PSFs in the absence of herbivory. However, foliar herbivory induced positive PSFs for legumes in soil with drought legacies, and negative to neutral PSFs in soil with ambient rainfall legacies, when grown in monocultures. By contrast, herbivory induced strong positive PSFs in soils with ambient rainfall legacies, and negative PSFs in soils with drought legacies, in mixtures, possibly due to competition for space and resources. Herbivory-induced PSFs in soils with prolonged drought legacies appeared to be related to differences in leaf N concentration and rhizobia colonization likely due to effects on herbivore-induced systemic resistance. Our results indicate that foliar herbivores alter plant species co-existence and community dynamics under future climate change scenarios through changes in PSFs.
Symbiotic nitrogen fixation (SNF) represents the largest natural input of bioavailable nitrogen into the biosphere, impacting key processes spanning from local community dynamics to global patterns of nutrient limitation and primary productivity. While research on SNF historically focused largely on herbaceous and agricultural species, the past two decades have seen major advances in our understanding of SNF by tree species in forest and savanna communities. This has included important developments in the mathematical theory of SNF in forest ecosystems, experimental work on the regulators of tree SNF, broad observational analyses of tree N-fixer abundance patterns, and increasingly process-based incorporation of tree SNF into ecosystem models. This review synthesizes recent work on the local and global patterns, environmental drivers, and community and ecosystem effects of nitrogen-fixing trees in natural ecosystems. By better understanding the drivers and consequences of SNF in forests, this review aims to shed light on the future of this critical process and its role in forest functioning under changing climate, nutrient cycling, and land use.
The dual pressures of global warming and increased anthropogenic activities pose significant threats to terrestrial vegetation ecosystems. To better understand the impacts of climate change and human activities on terrestrial vegetation ecosystems, we reconstructed the changes in vegetation and plant biomass over the past 4500 years using n-alkane records from sediments of two alpine lakes in northwestern China: Xiannv Lake and Tianchi Lake. Our results indicate that changes in the spatial variability of plant biomass are not related to temperature and precipitation. Furthermore, CO2 fertilization and nutrient inputs from dust contributed to the observed changes in plant biomass. We also compared the history of human activities in the Tianshan Mountains, the eastern Silk Road, and the Hunsandak Sandy Land, and find that the demand for plant resources—whether for human settlement, military construction, or warfare—may have caused a sudden decline in terrestrial vegetation, thereby disrupting the positive effects of dust on plant biomass growth.
Defensive metabolites and nutrient restriction of host plants are 2 major obstacles to the colonization of insect herbivores. The green peach aphid (GPA) Myzus persicae (Sulzer) broadly colonizes plants with diverse nutritional and defensive traits. However, how GPA adapts to nutritional and defensive traits within different plants remains largely unknown. To elucidate this, we first investigated the performances and transcriptomes of GPA feeding on cabbage Brassica oleracea and pepper Capsicum annuum. The green peach aphid had lower weight and fecundity when feeding on cabbage than on pepper. The transcriptomic analysis found 824 differentially expressed genes (DEGs), and 13 of the top 20 Kyoto Encyclopedia of Genes and Genomes pathways are related to nutrient metabolism, energy metabolism, and detoxification. Specifically, we found 160 DEGs associated with the metabolism of protein and amino acids, sugar and lipids, and xenobiotic substances, 86 upregulated in cabbage-fed GPA. Fourteen cathepsin B genes were strongly upregulated in cabbage-fed GPA, and were enriched in lysosome pathway and 2 dominated gene ontology terms peptidase activity and proteolysis. In addition, cabbage-fed GPA upregulated sugar and lipid digestion, while downregulated lipid biosynthesis processes. Furthermore, 55 metabolic detoxification enzyme genes were differentially expressed between GPA on 2 hosts, and detoxification enzyme activities of GPA indeed changed accordingly to the host. Then, we found that cabbage has lower amino acids nutrition quality for GPA compared to pepper. Our results suggested that adjustment of nitrogen nutrient metabolism, sugar and lipid metabolism, and metabolic detoxification in a host-specific manner play crucial roles in the adaptations of GPA to different host plants.
Black soldier fly larvae (BSFL) have attracted attention due to their ability to upcycle various biological side streams into valuable biomass, such as proteins, lipids, and chitin. In this study, we investigated the impact of high-fiber diets on larval growth performance and the shift of microbes in the gut. We tested empty fruit bunches (EFB), potato pulp (PP), and cottonseed press cake (CPC), with chicken feed (CF) used as a control diet. We found that larvae reared on the EFB, PP, and CPC were smaller than control larvae at the end of development due to the low nutritional value of the diets. However, survival rates of more than 90% were observed regardless of the diet. We used a cultivation-dependent approach to analyze the microbial community in the gut of BSFL, isolated, and identified a total of 329 bacterial strains. Bacillaceae were most frequently isolated from larvae reared on the high-fiber EFB diet. These isolates were predicted to degrade cellulose in silico and this was subsequently confirmed in vitro using the Congo Red assay. Whereas the members of Enterobacteriaceae and Morganellaceae were mostly found in guts of larvae reared on the high-protein diets CPC and CF. We conclude that the gut microbiome plays a crucial role in the digestion of fiber-rich plant organic material, thereby enabling the BSFL to successfully complete their life cycle also on substrates with low nutritional value. As a result, BSFL convert industrial side streams into valuable biomass, reducing waste and promoting sustainability.
IMPORTANCE
Organic side streams from various industries pose a challenge to the environment. They are often present in huge amounts and are mostly discarded, incinerated, used for biogas production, or as feed for ruminant animals. Many plant-based side streams contain difficult-to-digest fiber as well as anti-nutritional or even insecticidal compounds that could harm the animals. These challenges can be addressed using black soldier fly larvae, which are known to degrade various organic substrates and convert them into valuable biomass. This will help mitigate agro-industrial side streams via efficient waste management and will contribute to the more economical and sustainable farming of insects.
Atmospheric gases, such as carbon dioxide (CO2) and ozone (O3), influence plant–insect interactions, with variable effects. The few studies that have investigated the direct effects of elevated CO2 (eCO2; 750–900 ppm) or elevated O3 (eO3; 60–200 ppb) on insects have shown mixed results. Instead, most research has focused on the indirect effects through changes in the host plant. In general, the lower nitrogen levels in C3 brassicaceous plants grown at eCO2 negatively affect insects and may result in compensatory feeding. Phytohormones involved in plant resistance may be altered by eCO2 or eO3. For example, stress-related jasmonate levels, which lead to induced resistance against chewing herbivores, are weakened at eCO2. In general, eCO2 does not affect herbivore-induced plant volatiles, which remain attractive to natural enemies. However, floral volatiles and herbivore-induced plant volatiles may be degraded by O3, affecting pollination and foraging natural enemy behavior. Thus, eCO2 and eO3 alter plant–insect interactions; however, many aspects remain poorly understood.
When combined with other woodland stresses, introduced and native insects have the potential to kill large numbers of trees, impacting forest carbon budgets and climate change mitigation goals. If disturbance from insects, pests, and other bio-stresses is avoided by developing a sound forest management strategy, it is likely that the maximal C sequestration capacity of forests will be realised. Pesticides are used as main means of defence against insect pest problems because they offer an immediate fix. Chemical insect pest treatment is extremely expensive. Furthermore, the overuse and reckless application of pesticides to treat insect pest problems has significant repercussions for a variety of natural enemies, insect pollinators, natural enemies, health of people and the surrounding environment, culminating in the emergence of chemical resistance in insects. Therefore, in order to maintain the balance of the ecosystem, it is necessary to seek alternative insect-pest management strategies that take into account the minimal use of chemical insecticides as well as the protection and preservation of natural enemies. One such dependable strategy that can be used in pest management as an environmentally friendly management method is host plant resistance. Insect-resistant plant and tree development has been shown to have a sustained, cumulative effect on the population of insect pests and is also thought to be environmentally safe. However, the traditional methods for developing host plant resistance in trees can be time-consuming and demanding. Alternative biotechnological technologies, such as morphological, biochemical, or DNA marker-assisted selection, genome editing, and gene transformation, can be utilised to exploit insecticidal traits and adjust the intensity and pattern of genetic material expression. These methods can be utilised to develop unique plant resistance traits that safeguard forest trees against damaging insect-pests. Forest restoration and the reduction of carbon losses caused by these bio-stresses can both benefit from the use of biotechnological technologies for resistance against pests.
Drought may impact plant–soil biotic interactions in ways that modify aboveground herbivore performance, but the outcomes of such biotic interactions under future climate are not yet clear. We performed a growth chamber experiment to assess how long‐term, drought‐driven changes in belowground communities influence plant growth and herbivore performance using a plant–soil feedback experimental framework. We focussed on two common pasture legumes—lucerne, Medicago sativa L., and white clover, Trifolium repens L. (both Fabaceae)—and foliar herbivores—cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), and two‐spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). Soil was collected from a field facility where rainfall had been manipulated for 6 years, focussing on treatments representing ambient rainfall and prolonged drought (50% reduction relative to ambient), to consider the effects of biological legacies mediated by the prolonged drought. All soils were sterilized and re‐inoculated to establish the respective home (i.e. where a given plant is cultivated in its own soil) and away (i.e. where a given plant is cultivated in another species' soil) treatments in addition to a sterile control. We found that the relative growth rate (RGR) and relative consumption of larvae were significantly lower on lucerne grown in soil with ambient rainfall legacies conditioned by white clover. Conversely, the RGR of insect larvae was lower on white clover grown in soil with prolonged drought legacies conditioned by lucerne. Two‐spotted spider mite populations and area damage (mm ² ) were significantly reduced on white clover grown in lucerne‐conditioned soil in drought legacies. The higher number of nodules found on white clover in lucerne‐conditioned soil suggests that root–rhizobia associations may have reduced foliar herbivore performance. Our study provides evidence that foliar herbivores are affected by plant–soil biotic interactions and that prolonged drought may influence aboveground–belowground linkages with potential broader ecosystem impacts.
Climate change significantly impacts insect pest dynamics, leading to the emergence of new threats in agriculture, public health and ecosystems. This chapter explores the implications of climate change on insect pest populations and discusses management strategies. Climate-induced shifts in temperature and precipitation patterns create conducive environments for pest proliferation, amplifying economic losses and ecological disruptions. Diverse insect pests are observed globally, each with distinct behaviors and impacts on different host species. Current management strategies, including cultural, biological and chemical control methods, face challenges in efficacy and sustainability under changing environmental conditions. Integrated pest management (IPM) approaches, leveraging interdisciplinary collaboration, offer promise in addressing emerging pest threats. Effective management requires proactive measures to adapt to evolving pest dynamics and mitigate risks to agricultural productivity and environmental stability. This chapter underscores the urgency of interdisciplinary research and adaptive management to confront the escalating challenges posed by emerging insect pests in the context of climate change.
A laboratory study of energy flow in different-aged pea aphids was accomplished by the balance sheet method. Growth, reproduction, molted exoskeletons, oxygen consumption, and honeydew production were monitored daily. Absolute amounts of energy expended on reproduction, growth, maintenance, and rejecta all varied with age of the aphid. Efficiencies of production and respiration also varied with the life history stage. Assimilation efficiency did not vary with age. Gross productions efficiency (@? = 49%) and assimilation efficiency (@?=83%) are higher in this insect than in most other insects reported. The reason for such high efficiency may be the unusually high amino acid content of pea phloem sap. Rates of exudation of amino acids and sugars from pea phloem through severed aphid stylets and greater than twice the total daily energy requirement of continuously feeding aphids. This would be true even for passively feedings aphids. Under the study conditions the daily ingestions of one average adult aphid is approximately 8% of the daily net primary production of a 0.15 a (dry wt) pea seedling.
It is proposed that tropical nutrient-poor white sand soils produce blackwater rivers, rivers that are rich in humic acids and poor in nutrients, because the vegetation growing on these soils is exceptionally rich in secondary compounds. The humic acids (= tannins and other phenolics) may even be only the more conspicuous of the secondary compounds that leach out of the living vegetation and the litter. While the water and the soil (including litter) may be expected to have a low productivity and animal biomass solely on the basis of its low nutrient content, it is quite possible that large amounts of secondary compounds are also debilitating to the animal community. An exceptionally high concentration of secondary compounds is expected in the vegetation growing on white sand soils for two reasons. First, this is an expected outcome in habitats where the loss of a leaf to an herbivore or through deciduous behavior is relatively a much greater loss than on nutrient-rich soils. Second, the plants growing there belong for the most part to families exceptionally rich in secondary compounds, a characteristic which is in turn selected for by the chemical defense requirements of plants growing in low diversity stands. The small amount of data that is available from Sarawak white sand habitats shows that the carrying capacity for animals is very greatly reduced. The postulated cause is reduced primary productivity and/or much of the productivity being used by the plant for secondary compounds (unharvestable productivity), or stored for seed crops at very long intervals (unavailable productivity). It is proposed that mast fruiting at the community level, as displayed by trees in the Dipterocarpaceae, is a mechanism of escape from seed predators that is unique to this part of the tropics (S.E. Asia) because this area has reduced animal communities (both on white sand soil sites and in general), and because the climate is sufficiently uniform for such an intra- and inter-population cueing system to evolve. Without experimentation, it is impossible to know, however, if the animal community is reduced solely due to overall lowered primary and harvestable productivity, or as well to the inevitable reduction in animal numbers when many of the trees in a habitat wait more than a few years for their highly synchronized seed crops. The occurrence of numerous tropical habitats with a very low diversity of trees inviolates the currently popular dogma that diversity is mandatory for stability in tropical habitats. I propose that the trees in such monotonous habitats are exceptionally well-protected chemically with respect to foliage, and have either very toxic seeds or well-developed mast cycles.
Seeds of legumes were highest and fleshy fruits and acorns were lowest in protein and phosphorus among seed and fruit samples from 103 species common to southern forests. Legume seeds and kernels of walnuts (Juglans sp.) and hickories (Carya spp.) were most digestible, and kernels were highest in crude fat and lowest in fiber content. Nylon bag dry-matter digestibility of all 103 seed and fruit samples was related significantly to acid detergent fiber content. Despite their moderately high protein and phosphorus contents, dried fruits such as achenes, samaras, and nuts had high fiber contents and were therefore of less use to animals than the other groups of seeds and fruits analyzed.
Preview Article: http://www.jstor.org/stable/3800427
Serial sections were used to show that the nymphs of both Pectinariophyes stalii (Spangberg) and Chaetophyes compacta (Wlk.) feed on xylem sap of their food-plants, which are species of Eucalyptus in Australia. The sap is used to derive general nutrients and calcium ions which are used in the construction of their calcareous dwelling tube. The two species live in similar habitats, but their life-histories differ markedly. Females of both species laid eggs on new shoots in early summer in Queensland; P. stalii took 6 weeks to develop and overwintered as an adult, whereas C. compacta took 40 weeks and overwintered as a juvenile. The different rates of growth and nutrient and calcium uptake are discussed in relation to observed differences in damage to the host-tree.
The maintenance nitrogen (N) requirement of the tammar wallaby, Macropus eugenii, a specles adapted to semiarid habitats, was estimated to be 0.24 g per kg W*0.75 per day of dietary N, or 0.23 g per kg W*0.75 per day of truly digestible N. In contrast, the red-necked pademelon, Thylogale thetis, a wallaby restricted to subtropical rain forest, required 0.60 g per kg W*0.75 per day dietary N, or 0.53 g per kg W*0.75 per day of truly digestible N for mamtenance. Apparent digestibility of dry matter (DM) was lower (P < 0.001) by the pademelons (59%) than by the tammars (72%), and DM intake was higher (39 versus 25 g per kg W*0.75 per day) (P < 0.001). Intake of free water was also greater (P < 0.001) by the pademelons than by the tammars (169 versus 107 ml per 100 g DM intake). It is concluded that the red-necked pademelon is not as 'rummant-like' in its digestive physiology and metabolism as macropod species from more and environments.
High rates of nitrogen applied at one time or over a 4-year period markedly changed the botanical composition of shortgrass range. Blue grama and buffalograss cover declined and western wheatgrass increased. Total yields were significantly increased, largely because of the increase of annual forbs. Thus the only desirable change in the composition resulting from the high N application was the increase of western wheatgrass. Over the 5-year period, the NO3- N accumulated in the 12- to 24-inch soil depth, whereas the grass roots were concentrated in the top foot of soil. The high rates of N increased crude protein significantly, thereby enhancing the palatability of the forage. Forbs on the high N plots were searched out and readily grazed by the sheep. Crude protein content was higher in the forbs than in the grasses in the fall. This study shows that high N rates applied either at one time or in yearly applications are neither economical nor practical because of the shift in the composition to undersirable annual forbs and slow recovery by the perennial grasses. The 150-lb N/acre rate applied once might be considered more practical than the other rates used in this study. Over the 5-year period this N rate produced 1,705 lb more total herbage than the check or 11.4 lb of herbage/lb of N. Neither the yield nor the crude protein increase was large enough to justify nitrogen fertilization of this range as an economic practice.
This chapter relates feeding behavior and nutrition to the other aspects of insect functioning that are sufficiently well surveyed and understood to provide the possibility of integration. The food preferences of some acridids are strictly limited and a degree of discrimination is usually to be discerned even in those of polyphagous propensities. Many of these latter require little pressure to feed outside their range of native preference and this may lead to their becoming pests. The indications are that for species of such catholic tastes nutritional factors enter into their choice of food. Nutrition in the strict chemical sense of certain locusts, their needs, while qualitatively similar to those of the generality of insects, is noteworthy for a few unusual features. These relate to the requirement for ascorbic acid, inositol, and unsaturated fatty acids and to the critical importance of large amounts of choline in larval growth. A need for the lipogenic factors, choline and inositol, and unsaturated fatty acids seems to characterize all those orthopteroid insects that have been studied in detail. The need for dietary carotene to ensure normal pigment metabolism in locusts may be a peculiarity of those particular species in which pigmentation is bound up with the special physiological phenomena of phase.
This chapter reviews the quantitative measurement of nitrogen deficiency in plants. It proposes five plant parameters for estimating nitrogen stress: leaf nitrogen, dry weight, leaf elongation, leaf area, and carbon dioxide exchange rate (CER). The criteria for choosing the parameters that should be used are as follows: (1) the parameter that has the greatest meaning for the objectives of the project, (2) the equipment and expertise that are available, and (3) the measurement that uses the least resources. The conventional approaches to deficiency through response curves and tissue analyses are inadequate bases to quantify deficiency rigorously except in special circumstances. By analogy with water stress, an attempt has been made to establish the basic requirements for a concept of nutrient stress and a proposal has been offered on the way they might be put into practice. The chapter discusses the factors affecting nitrogen stress and a number of applications of nitrogen stress.
A ubiquitous pest of all manner of timber in the sea, teredo— the shipworm, causes damage worth millions of pounds every year all over the world. Hidden protectively within the “heart” of both fixed and floating timber, and hardly visible from the outside, these borers work silently and reduce to soft sawdust even if it is the most resistant timber. Rasping with their shells mechanically, these living drills draw a major part of their nourishment from the hard cellulose. Unseen even by experts, this exotic menace converted solid pillars and piers into weak and fragile “honeycombs.” Along the entire seafront, bridges collapsed, piers crashed and boat hulls and wharf-piling crumbled. Like an unseen typhoon, it swept up the coast leaving a trail of destruction along its path. Though present in all seas, shipworms are particularly destructive in the tropical waters where they eat in discriminately every material of plant origin.
Publisher Summary A great deal is known concerning the qualitative nutritional requirements of insects. The quantitative aspects of insect nutrition have, however, received less attention, and there have been few studies on the rates of intake and the efficiency of food utilization. In particular, relatively little is known concerning the intake, digestibility and efficiency of conversion of defined diets. Quantitative work with artificial diets has usually involved only measurements of the amount of a particular nutrient required per unit of diet. Insects as a group feed upon a remarkably diverse list of organic substances. At the same time most species show a high degree of specificity in their choice of food. It seems apparent that adaptive nutritional differences must be sought on a quantitative level and that a meaningful comparative nutrition of insects will not emerge until quantitative studies are emphasized. The determination of absolute requirements for dietary constituents depends upon the measurement of intake. Differences in food efficiency can be demonstrated only by measuring intake and growth. Digestibility should also be measured since it can be expected to vary widely with different foods. The efficiency with which digested food is used for growth will vary not only with the maintenance requirement for energy but also with the balance of nutrients.
Fifth-instar larvae (165 ± 15 mg) of the monarch butterfly Danaus chrysippus, when supplied with fresh leaves of milkweed Calotropis gigantea, attained maximum weights of 738, 721, 642 and 558 mg at 19°, 27°, 32° and 37°C, respectively. Feeding rates, which did not differ significantly between males and females, were 210, 361, 592, and 548 mg dry food g-1 live larva d-1 at these temperatures. Assimilation efficiency decreased from 58% at 19°C, to 47% at 37°C. Conversion efficiency ( K2) was 45% at 32°C, 40% at 27°C, 36% at 37°C, and 26% at 19°C. Fifth-instar larvae consumed about 480 mg dry food, assimilated about 230 mg of this at 27°, 32°, and 37°, and converted about 100 mg at 19°, 27°, and 32°C. Larvae consumed a maximum of 665 mg at 19°C and converted least (83 mg) at 37°C. /// Гусеницы 5-го возраста бабочек Danaus chrysippus при кормлении свежими листьями Calotropis gigantea достигают максимального веса 738,721, 642 и 558 мг при 19°, 27°, 32° и 37°C соответственно. Скорость потребления пищи существенно не различается у самцов и самок и составляет 210, 361, 592 и 548 мг сух. веса /г-1 живого веса /сутки-1 при Этих температурах. Коэффициент ассимиляции снижается с 58% при 19°C до 47% при 37°C. Эффективность использования пищи ( K2) составляла 45% при 32° при 27°C, 36% при 37°C и 26% при 19°C. Гусеницы пятого возраста потредляли около 480 мг сухой пищи и усваивали до 230 мг при 27, 32 и 37° и использовли при этом на прирпст около 100 мг при 19, 27 и 29°C. Максимальное потребление - 665 мг - наблюдалось при 19°C и минимальное использование пихи (83 мг) - при 37°C.
The concepts of natural selection and competition are distinguished, and the competition coefficients are rigorously defined; r-selection is not relevant to competition, but K-selection is a consequence of exploitative competition wherein consumers and resources are directly interconvertible. When only a single resource limits a population, competition coefficients are proportional to the ratio of saturation densities and are reciprocal. When several limiting resources exist, competition coefficients must be ≤1 and competitive exclusion will not occur. Under exploitative competition K and competitive ability are inversely related. Alpha-selection is defined as the evolutionary process by which competitive ability increases and refers to the acquisition of interference phenomena whereby individuals impair the reproductive rate dN/Ndt of competitors. Possession of interference mechanisms may require adjustments of energy budgets, so that α-selection is a mechanism of evolutionary reduction of r and K. Interference competition results in competitive exclusion because the competition coefficients are nonreciprocal and >1. Alpha-selection can occur at either low or high density, and hence may be a ubiquitous force in evolution. It is concluded that species dominance in competition can not in principle be predicted from knowledge of r or K alone.
Eight hand-reared white-tailed deer (Odocoileus virginianus) fawns were randomly paired and pairs were randomly assigned to 1 of 4 isocaloric diets containing 11, 15, 20, and 25 percent crude protein (dry matter basis) to study their protein requirement. Thirty-two complete digestibility, nitrogen balance, and energy balance trials were carried out. Partition of dietary energy was not significantly affected by protein level in the diet, except that proportion of energy lost in urine, presumably ketones, increased significantly (P
Data from dimension analysis of forest biomass and production are combined with analyses of plant tissues, soil, and precipitation to describe nutrient cycling in a cool-temperate deciduous forest on a podzol. Mean concentrations of nutrient elements measured (N, P, S, Ca, K, Mg, Mn, Na, Fe, Zn, Cu) in tissues are relatively low, and nutrient stocks in vegetation are low compared with other forests because of the low concentrations and the relative youth of the forest (cut in 1909-17). The largest fractions of nutrients in aboveground net primary production (NPP) go into leaves--58-78% of all nutrients except Na (45%)--although leaves are only 40% of aboveground NPP. Net community (woody) growth included @?30% of aboveground NPP, but smaller fractions of nutrients (7% of N and K to 21% of Ca and 28% of Na). Nitrogen, P, and some other elements are retracted from dying leaves; but concentrations of Ca, Mn, and Na increase from living to dead leaves, branches, and stem wood. Return to the soil from aboveground is primarily by leaching for K and Na but by litterfall for other elements. @'Throughflow@' is defined as nutrient uptake needed beyond that in NPP to provide for both leaching and increase in dead tissues before they fall. For Na, throughflow exceeds uptake into NPP; but negative throughflows for N and P reflect conservation of these elements. Belowground plant nutrient stocks are 0.25 to 0.5x and belowground uptake rates into NPP are 0.1 to 0.2x aboveground values for most elements, but belowground values are higher for N, P, Na, and Fe. Significant amounts of some elements, especially S, Ca, K, and Na, are exuded from roots as part of the total, above- and belowground throughflow. Behaviors of nutrient elements can be characterized by ratios expressing concentration into leaves vs. woody tissues and relative leachability and throughflow vs. conservation. Relative turnover rates compare litterfall plus leaching with aboveground stocks or with nutrient contents of NPP. Turnover rates increase in the sequence: N and P; Ca; Mg, K, Fe, and Mn; S; and Na. Means and coefficients of variation of foliage nutrient concentrations express some differences between ecosystems. Comparing different ecosystems, coefficients of variation are low for N and P, intermediate for Ca, K, Mg, and Al, and high for Si, Mn, Fe, Cl, and Na. Differences in these and other expressions of element behavior can be interpreted on the basis of function in plants.
Meadow spittlebug nymphs, Philaenus spumarius (L.), feeding on tomato plants ingested the xylem sap and assimilated the contained amino acids. The diet on other plant species is probably similar. Xylem sap provides a dilute solution of nutrients in a form easy to ingest and assimilate. The large excess of water associated with this mode of feeding is important in preventing desiccation of the insects. Ingestion of xylem sap results in a loss of essential nutrients to the plant and a depression of primary production. Consequently, this unusual type of producer-consumer interaction is important in the study of community energetics.
The concentrations of N, P, Mn, and Al in plants of two ombrotrophic bogs and four adjacent environments were examined. The current year's foliage of the evergreen bog species, as contrasted with the older leaves, invariably possessed higher concentrations of N and P and lower concentrations of Al and Mn. Within the bog species, the composition of the current year's foilage of the evergreens was not significantly different for any of the elements from that of the deciduous species. Foliage of the bog species was lower in content of N and P than the foliage of plants of other habitats and reflects the paucity of available N and P in the bog substrate. Broad-leaved evergreen leaves of bog plants appear to manufacture more photosynthate per acquired unit of N or P than do deciduous leaves, primarily because of their longevity. The high occurrence of evergreenness in infertile environments may therefore reflect a decreased need to acquire N and P from a substrate deficient in these elements. Mn and Al contents were comparable in the bog plants to plants of other habitats, despite potentially toxic levels of these elements in acid bogs. Apparently many bogs plants selectively exclude Mn and Al.
Dry matter, energy, nitrogen and ash budgets of the form ingestion (I) = growth (G) + respiration (R) + feces (F) were evaluated for the larvae of Euchaetias egle (Drury) fed Asclepias syriaca L. at 27°C, 87 + % RH, 14 h light. Gross efficiencies of growth (100G/I) were 14.6% (dry matter), 20% (energy equivalents), 34.5% (nitrogen) and 3.8% (ash). Net efficiencies of growth 100 G/(I - F) were 42.6% (dry matter) and 49,6% (energy equivalents). Comparison of economies of growth of E. egle with Danaus plexippus L., reared under similar conditions, suggests a difference in digestive or assimilative processes between the two species. Comparison of efficiency of energy utilization and rate of growth with D. plexippus did not support the hypothesis that efficiency is inversely related to rate of energy utilization. Comparisons of efficiencies of both matter and energy utilization with other lepidopteran larvae did not support the hypothesis of greater efficiencies of resource utilization by oligophagous than by polyphagous Lepidoptera. /// У гусениц Euchaetias egle (Drury), которых кормили Asclepias syriaca L. при 27°C, 87 + % RH и 14-часовом световом дне, определяли содержание сухого вешества, энергетический баланс, содержание азота и золы по формуле: потебление (I) = рост (G) + дыхание (R) + непереваренные остатки (F). Величина роста составляла при 100 G/I 14,6% (по сух.в-ву), 20% (энерг.экв.), 34,5% (N) и 3,8% (зола). Чистые коэффициенты роста при 100 G/(I-F) составляли 42,6% (сух.в-во) и 49,2% (энерг.экв.). Сравнение экономики роста у E. egle и Danaus plexippus L. содержавшихся в сходных условиях, свидетельствуют о различии процессов пишеварения или ассимиляции у двух видов. Сравнение коэффициентов утилизации энергии и скорости роста с таковыми у D. plexippus не подтверждают предполжения, что эти коэффициенты обратно пропорциональны скрости утилизации энергии. Сравнения коэффициентов усвояения вешества и энергии у других гусениц бабочек не подтверждают гипотезу о наличии более вычоких коэффициентов учвояемости пишевых ресурсов у олигофагв по сравнию с полифагами.
Larvae of Aphodius rufipes L. live in cow pats. They are "bulk feeders" eating dung rather unselectively. Their ingestion, respiration, and production during instars II and III (there are three instars) were determined in the laboratory at 17°C. The efficiency of assimilation (7.0-10.4%) was low, but ingestion rate was high in comparison with other terrestrial detritus feeders. Daily food intake was 380-530% of dry body weight in instar II and 175-300% during the two first weeks of instar III. Also, the growth rate was high and the total growth was accomplished in about six weeks. It appears that energy for rapid growth, necessitated by the instability of the larval habitat, was obtained through a very high ingestion rate which compensates for the poor assimilation of dung. /// Личинки Aphodius rufipes L. обитают в экскрементах коров. Они являются "валовыми потребителями", так как питаютчя навозом, не проявляя особой избирательности. Определяли потребление пиши, дыхание и продукцию личинок ІІ и ІІІ возрастов (всего у личинок З возраста) в лабораторных условиях при температуре 17°C. эффективность усвоения пиши (7,0-10,4%) была низкой, но скорость потребления пиши высока в сравнении с другими наземными потребителями детрита. Суточное потребление пиши сосатавляет 380-530% от сухого веса тела во ІІ возрасте и 175-300% - в течение двух первых недель ІІІ возраста. Таким образом, скорость роста личмнок высока, и обший рост заканчивается примерно в течение 6 недель. По-видимому, энергия для быстрого роста, необоходимого в результате нестабильности местообитания личинок, поступает за счет высокой скорости потребления плши, что компенсирует низкую усвояемость экскрементов.
Duncecap larkspur plants clipped in vegetative growth stage (late June) for 2 consecutive years produced only leaves and no flower stalks the third year. These plants were significantly smaller and contained a significantly lower concentration of total alkaloids than those plants clipped later in the summer or than unclipped control plants. This susceptibility to injury by clipping may help interpret results of other control methods. Total alkaloid content of previously unclipped larkspur plants was highest in the early growth stages and declined throughout the summer. Total alkaloid content in late June ranged from 1.7% to 2.8% and was not correlated with amount or pattern of precipitation.
Leaf litter of twenty-six species of trees, shrubs and woodland herbs, enclosed in coarse mesh nylon net bags, disappeared more rapidly on a soil with a mull humus form than on a soil with moder humus because large invertebrates such as earthworms and millipedes were able to feed on it. In the first 5 months of decomposition they removed at least 40% of the ash (Fraxinus excelsior) litter on the mull site and 10% on the moder site. The percentage carbon and energy contents of the litters changed only slightly in the first year after leaf-fall. The percentage nitrogen content increased more on the mull than on the moder site. The absolute amount of nitrogen in most litters decreased but in several litters on the moder site it increased. In litter of Quercus petraea the main difference between the nitrogen increases on the two sites occurred in the spring and early summer months.
Eight constant temperature baths, maintained at increments of 2@?C, were used in the laboratory to evaluate rates of growth, food consumption, and egestion of the carnivorous stonefly nymph, Acroneuria californica. Oxygen consumption rates were determined using a Gilson differential respirometer. Experimental temperatures were adjusted seasonally to approximate environmental levels. Growth remained constant over the lower temperature range for each experimental period, then decreased rapidly in the upper portion of the temperature range. Food consumption, respiration, and assimilation efficiency increased with increasing water temperature. Energy budgets illustrate the pattern of energy utilization over the experimental temperature ranges evaluated. At temperatures approximating environmental levels, assimilation efficiency was approximately 86%, whereas gross and net growth efficiencies were 33% and 41% respectively. Metabolic losses accounted for approximately 50% of the food consumed. These yearly mean values, however, vary considerably with temperature and stage of nymph development. Optimal temperature ranges for A. californica nymphs were estimated to be 16@?-22@?C in summer, 10@?-18@C in fall, 6@?-12@C in winter, and 10@?-16@?C in spring. Growth rates determined in the laboratory are compared with those in the field.
The importance of various fungal samples, isolated from plant detritus, and of the plant detritus itself in the trophic niche of Asellus aquaticus (L.) and A. coxalis Dollf., was studied in the laboratory. We observed that: (1) The fungi and not the plant detritus, from which they are isolated, constitute the energy source for both species. In fact, the animals to whom the sterilized detritus was offered died within a few days. The animals to whom the fungal colonies were given had significantly higher survival and body growth compared to the controls; (2) The various fungal samples, offered as sole source of food, were used with different efficiency, both by animals of the same species and by animals of different species; and (3) The heterogeneous fungal populations, present in nature in the detritus, constitute a food resource mosaic which permits an even distribution of the trophic resources between two ecologically similar, cohabitating detritivorous species. /// Исскедивали значение разных григов, изолированных из растительного детпита, и самого растительного детрита в трофических нишах Asellus aquaticus (L.) и A. coxalis Dollf. в лабораторных условиях. Наблюдалось: 1. грибы, а не растительный детрит, в котором они развиваются, представ лрет основной энергетический ресурс для обоних видов. Животные, которых кормили стерилизованным детрнтом, погигали в течение нескольких дней. Жнвотные, питавшиеся гпибным мицелием, имели более бысок\r=?\ю выживаемость и размеры в сравнении с контролем; 2. разкичные группы грибов, пррдложенные в качестве основной пищи, утилизировались с различной эффективностью, как животными одного вида, так и представителрми разных видов; 3. гетерогенные грибные популяции, имеющиеся в детрите в естестенных условиях, образуют мозанку пищевых ресурсов, опрелеляюшую выровненное распределение плщевых запасов между двумя экологически хсодными и соседствукюцими в одном местообнтании детрнтофагами.
Mass and energy budgets (ingestion = growth + respiration + egestion) of the larvae fed leaves of Populus deltoides L. were determined. Gross efficiency of growth (100 × growth/ingestion) = 19 per cent (energy) and 13.7 per cent (mass) and net efficiency of growth (100 × growth/ingestion-egestion) = 57 per cent (energy), 46 per cent (mass). Calculation of maintenance cost by indirect calorimetry (6 kcal) was 30 per cent less than calculated by difference from the energy budget (9.4 kcal). /// Определяли бюджет вещества и энергии (потребление = рост + дыхание + выделение) у личинок, которых кормили лнстьями Populus deltoides L. Суммарный коэффициент роста (100 × рост/потребление = 19% (энергия) и 13,7% (биомасса), а коэффициент чистого роста (100 × рост/потребление-выделение) = 57% (энергия) и 46% (биомасса). Расчет траты на обман непрямой калориметрией (6 ккал) на 30% меньше, чем рассчитанный по разице энергетического бюджета (9,4 ккал).
Investigations of large and fine particle feeding detritivores (shredders and collectors) fed on conditioned hickory leaves (Carya glabra) revealed density-dependent intra- and interspecific interactions. Shredder (Tipula and Pycnopsyche) growth rates ranged from 0.47 to 1.53% increase in body wt/day depending upon density, species combinations, and culture temperature. Collector (Stenonema) growth rate ranged from 0.13 to 1.80% body wt/day, being greatest at high densities, particularly in combination with shredders. Food consumption ranged from 15.7 to 33.2% body wt/day for shredders and 4.0 to 23.2% body wt/day for collectors. After non-shredder feeding losses are accounted for, estimated shredder standing crop required to account for processing of report leaf litter inputs compare generally to measured shredder standing crop.
Results of a laboratory experiment where we measured the influence of grasshoppers (Melanoplus sanguinipes) feeding upon leaves of hydroponically grown blue grama grass (Bouteloua gracillis) are presented. Performance of both the plant and animal conditions are given: growth rate of the plants held at three temperatures, amount of food ingested by the grasshoppers, digestive efficiencies, weight change of grasshoppers, the amount of litter cut, and the pH change of the root medium. The experiment indicates that thee are plant processes triggered by grasshopper feeding which result in increased energy transport levels within the plant. Most of this energy expenditure occurs in the belowground complex of the plant. Moreover, regrowth potentials of the plant on which grasshoppers had been feeding is much higher than for plants that had simply been clipped. Hence, we suggest that perhaps the largest single effect displayed by aboveground insect grazers on grassland ecosystem plants (viz., grass) is the increase in belowground respiration and root exudation.
The main sources of the nitrogen which was added to sessile oak litter decomposing in oak woodlands were atmospheric precipitation, insect frass and plant material which fell from the tree canopy. Neither the soil fauna nor the soil microflora were important sources of nitrogen. A maximum of 25% of the inorganic nitrogenous compounds in the rain was taken up by the litter. This was equivalent to 1.3 kg of nitrogen per ha in 91/2 months' decomposition. In years when caterpillars were abundant in the tree canopy the nitrogen increase in the litter amounted to 6.6 kg/ha, the bulk of this being derived from caterpillar frass and other plant material which fell from the tree canopy as a result of insect attack. The addition of this nitrogen-rich material to the oak litter did not accelerate its decomposition in the first year after lead-fall.
Delineation of the effects of plant moisture stress on carbohydrate and nitrogen content of important range species is needed for proper intensity of range use of summer ranges when high plant water stress conditions exist. Water potential of big sagebrush shows great seasonal variation, ranging from a low of -70.3 bars in September to a high of -8.3 bars in April. Starch content did not significantly change in water stressed plants, but sugar content significantly increased in leaves, stem, and roots. Leaf nitrogen content significantly decreased in water stressed plants, while stem nitrogen content significantly increased. Sugar increases in the leaves, stem, and roots and nitrogen accumulation in the stem of water stressed plants may be of adaptive significance.
Twenty-four white-tailed deer fawns (Odocoileus virginianus), 4 mo old, were used in a 2 × 2 factorial design to examine the effects of 10 weeks feeding of 2 levels each of protein and of energy upon 56 blood and plasma assays. Twenty-three substances were not affected by the diets. Hemoglobin, mean corpuscular hemoglobin concentration (MCHC), serum urea, and ornithine were affected solely by protein content. Fifteen assays including calcium, phosphorus, alkaline phosphatase, alanine aminotransferase (SGPT), creatine phosphokinase (CPK), nonesterified fatty acids (NEFA), cortisol, triiodothyronine, insulin, isoleucine, leucine, phenylalanine, histidine, threonine, and glycine were affected solely by the energy content. Six assays including erythrocytes, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), sodium, chloride and valine were affected by both protein and energy content. Interaction effects were observed for glucose, cholesterol, citrulline, taurine, glutamic acid, aspartic acid and glutamine/asparagine. The large number of differences in blood constituents noted with respect to dietary energy and protein intake suggest that a small set of assays will allow evaluation of the nutritional status with respect to dietary protein and energy of wild deer populations.
Climax perennial grasses from Rhodesia showed greater preference than earlier seral species, or crop cultivars, for the ammonium source of nitrogen. It is suggested that succession in high-altitude African grassveld is towards the calcifuge habit.
Forest succession on north slopes in interior Alaska results in the development of sphagnum bogs on sites formerly occupied by productive forest. This process is one of gradual deterioration of site associated with the accumulation of moss layers on the forest floor. Advancing succession is accompanied by an increasing nitrogen deficiency in black spruce trees. Black spruce growing on the sphagnum bogs are extremely nitrogen deficient. As the moss layers thicken, the soils become increasingly cold with permafrost rising to within as little as 15 inches of the surface of the sphagnum soils. Examination of the depth distribution of nitrogen revealed very small quantities of nitrogen in the upper and warmer portions of these profiles, with the bulk of the nitrogen located in the very cold and latest to thaw, lower layers. In contrast, in the soils under birch of the nitrogen was located in the warmest upper layers. Under these conditions, much higher rates of mineralization of soil nitrogen must be obtained. The results show why burning, although changing many factors including volatilization of an undetermined amount of nitrogen, may lead to a large increase in available nitrogen because of the change in depth distribution of the nitrogen in the soil.
The aim of this study was to gather quantitative field and laboratory data on the utilization of deciduous leaves as food by Lepidostoma quercina Ross (Trichoptera: Lepidostamatidae) and estimate the effect of this food processing on the stream ecosystem. Samples were taken monthly in a riffle-pool section of Berry Creek, Benton County, Oregon. Maximum larval density was 382 per m^2, instantaneous growth rate was 2.7% per day, instantaneous mortality rate was 1.4% per day, and production was 0.19 g^@?m^-^2^@?yr^-^1. The life cycle of L. quercina and its period of maximum larval growth correspond closely with the period of maximum availability of its prefered food (alder leaves) in the stream. Consumption and fecal production rates were measured gravimetrically. Rates (mg^@?mg^-^1^@?day^-^1) increased with temperature, food quantity, and conditioning time of the leaves, and decreased with increased size of the larvae. Mean respiration rates of larvae were higher at 10@?C than at 5@?, but there was no significant difference in mean rates at 10, 15, or 20@?C. Respiration rate decreased with increased size of the larvae. Size-specific respiration rates showed regulation of respiration with respect to temperature for small individuals (present in the field in September and October when temperatures are variable) and little or no regulation by large individuals (present in December and January). Stimulation modeling of larval growth based on laboratory data demonstrated that growth and production of L. quercina in the field may be limited by a lack of high-quality food (alder leaves) in late summer and early fall. Consumption of leaves by the simulated population was estimated as 3.1 g^@?m^-^2^@?yr^-^1. Lepidostama quercina comprised only a small part of the secondary production in Berry Creek (0.19g^@?m^-^2^@?yr^-^1, vs. 2.2 g^@?m^-^2 for simuliids) and processed only a small portion of the allochthonous input to the stream. However, significant quantities of fecal material were produced and it was estimated that these fine particle would be sufficient to support @1 to @2 of the production of simuliids, the dominant riffle species in Berry Creek.
Sericostoma personatum Spence was given autumn-shed leaves with differing nitrogen content: Fagus silvatica L. - 1.33% N of ash free weight, Picea abies (L.) Karst. - 1.48% N, Quercus borealis Michx. - 2.15% N, and Alnus glutinosa (L.) Gaertn. - 4.82% N. Leaves were preferred in the sequence Alnus - Quercus - Fagus/Picea. Ingestion by Sericostoma was significantly lower when fed Alnus than Fagus, Picea, and Quercus. Growth was significantly greater on Alnus and Quercus than on Picea and Fagus. Gross growth efficiency (G/I), calculatedon the basis of ash free weight, was 1.53-9.38% and was positively correlated with leaf nitrogen. Calculated on a nitrogen basis, G/I was 13-22%. The nitrogen content of the detritus may explain the low utilization efficiencies commonly reported for detritivores. /// Sericostoma personatum был предложен осенний олад с различным содержанием азота: Fagus Silvatica L. - 1,33% N, от веса золы, Picea abies (L.) Karst - 1,48% N, Quercus borealis Michx. - 2,15% N и Alnus glutinosa (L.) Gaertn - 4,82% N. Ряд предпочитамости листьев следующий: Alnus, Quercus, Fagus/Picea. Потребление пищи Sericostoma было значительно ниже при кормлении Alnus, по сравнению с Fagus Picea и Quercus. Прирост значительно выше при кормлении Alnus и Quercus, чем Picea и Fagus. Эффективности роста (G/I), рассчитанная по весу золы, составляла 1,53-9,38% и имела прямую зависнмость от содержания азота. Расчеты G/I по азоту составляли 13-22%. Содержание И в детрите может объяснить низкую степень усвоения, обычьо наблюдаюцуюся у детритофагов.
The nitrogen increase which often accompanies the initial stages of vascular plant decomposition cannot be attributed solely to an increase in microbial protein. Evidence from litter bag experiments carried out in terrestrial, freshwater and estuarine environments indicates that as much as 30% of the nitrogen content of aged detritus may exist in the form of non-protein nitrogen compounds. Possible sources of these compounds include: (1) amino sugars such as glucosamine and chitin, (2) complexes such as phenol-protein, protein-lignin or protein-chitin, (3) complexes of inorganic clays and amino groups, and (4) nitrogen containing humic acids. Chitin, presumably originating from fungal cell walls was shown to constitute from 25 to 50% of the non-protein nitrogen contained in detritus which had decomposed under aerobic conditions. It is suggested that these non-protein nitrogen containing compounds, because of their resistance to chemical degradation, may not be easily digested and assimilated by many detritivores. This, in turn, may raise questions concerning the usefulness of detrital C/N ratios as food value indicators. /// Увеличение содержания азота часто наблюдающееся в начальных стадиях разложения сосудистых растений, не может быть лишь результатом увеличения белка микрофлоры. Результаты опытов с разложением подстилки в четках, проведенные в почве, пресноводных водоемах и эстуарирх, показали, что 30% детрита может чодериать небелковые формы азота. Возможные группы этих соединений: 1. аминосахара (глюкосамин, хитин); 2. комплексные соединения (феноротеин, лигнопротеин или соединение хитина и протенна); 3. комплексные соединения из глинистых частиц и аминогрупп; 4. аминокнслоты. Хитин, источником которого являются в основном стенки грибиых клеток, включает 250-50% небелкового азота, содержащегося в детрите, разлагающемся в аэробных условиях. Установлено, что эти небелковые азотсодержащие соединения, в результате их устойчивости к химическому разложению, не могут легко перевариваться и устаиваться многими детритофагами. Это, в свою очередь, может служнть поводом к обсуждению вопросов, касающихся использования величины C/N в детрите как показателя пищевой ценности субстрата.
Weights and survival of early and slightly later lots of lithophanine larvae were compared on the same host plants. Corresponding lots were usually composed of siblings. Fifteen species (eight genera) of larvae and fourteen species (nine genera) of plants were utilized. A total of 26 tests were conducted. Early lots had significantly greater weights than late lots in 12 of 15 analyses and significantly higher survival in 20 of 24 analyses. These results support the idea that spring foliage must be viewed as an ephemeral resource. /// Сравнивали вес и выживаемость ранних и более поздних партий личинок Lithophanine на одних и тех же растениях-хозяевах. Соотвествующие партии обычно состояли из сибсов (особей одного помета). Исследовано 15 видов (из 8 родов) личинок и 14 видов (9 родов) растений. Проведено 26 опытов. Ранние партии имели несколько больший вес, чем более поздние в 12 определениях из 15 и более высокую выживаемость в 20 определениях из 24. Эти результаты подтвержают мнение, что весенная листва должна рассматриваться как эфемерный ресурс.
Channels of relatively rapid water movement, termed @'water tracks,@' in black spruce bogs in former glacial Lake Agassiz are often associated with a rich flora and shallow peat. Adjacent areas of lesser water movement are characterized by a depauperate, less productive flora and deeper peats. Black spruce foliage, collected from transects running from the good site in the water track with vigorous stands to the very poor muskegs bearing stunted trees one-fourth mile distant, was analyzed for 13 mineral elements. Nitrogen and phosphorus levels were significantly correlated with site quality; potassium displayed an inverse correlation. Levels of N and P were low, generally below the point at which deficiency symptoms have been reported for this or other spruces. The inverse relationship of potassium is a growth dilution effect, since the levels appear sufficient on all sites. The higher levels of nitrogen on good sites may be attributed to nitrogen fixation by speckled alder, which is abundant on the good sites but absent on poorer sites. More rapid decomposition of litter, indicated by lesser depth of peat accumulation, movement of enriched water, and nearness of mineral subsoil, may influence the level of N and P in the water track. Other elements were not related to site quality for black spruce.
A study of the wood-associated invertebrates was undertaken in seven streams of the Coast and Cascade Mountains of Oregon. The amount of wood debris was determined in terms of both weight and surface area. Standing crop of wood per unit area decreases with increasing stream order. Invertebrates associated with wood were functionally categorized and their biomass on wood determined. Major xylophagous species were the caddisfly (Heteroplectron californicum), the elmid beetle (Lara avara) and the snail (Oxytrema silicula). Standing crop of these species is greater on wood in the Coast Range than in the Cascades, which is attributed to species composition of available wood debris. The density of L. avara was strongly correlated with the amount of wood available irrespective of stream size within a drainage. The standing crop of invertebrates was about two orders of magnitude greater on leaf debris than on wood. A potential strategy for wood consumption, based on microbial conditioning, is presented. The data are used to develop a general scheme of wood processing by invertebrates in small stream ecosystems. Their impact is similar to that of invertebrates which process leaf litter in terrestrial and aquatic environments when the full decomposition cycle of wood debris is considered.
The effect of nutrient enrichment of red mangroves (Rhizophora mangle) was studied by comparing two mangrove—covered islands in the Indian River at Ft. Pierce, Florida, USA, one (high nutrient) with and one (low nutrient) without a breeding colony of pelicans and egrets. Repeated measurements taken on > 100 tagged branches in each area revealed higher growth rates at the high nutrient site. Trees at the high nutrient site showed greater additions of (1) leaves; (2) reproductive parts; (3) new lateral branches; and (4) larger increments to existing stems. Growth in the fertilized stand also began earlier in the year and had a second maximum not shared by the low nutrient area. Both leaves and fruits at the high nutrient site were richer in nitrogen. More striking than the effects on plant growth, however, was the proportionately much greater stimulation of herbivory by insects in response to nutrient enrichment. Larvae of the five lepidopteran species that we observed feeding on buds or leaves were either more abundant or only present in the high nutrient area, as was the scolytid beetle that infested seedlings before they dropped from the parent tree. This difference in herbivory between sites disappeared when the birds seasonally migrated away from their nesting areas at the high nutrient site. This observation and the demonstration that the mangrove skipper Phocides pigmalion attains a higher growth efficiency on high nutrient leaves are both consistent with the hypothesis that increased nutritive value of vegetation (correlated with the increased concentration of nitrogen) is responsible for the 4x greater losses to herbivores in the high nutrient. Implications for environmental management and in more complex communities are discussed.
(1) The larvae of Callosobruchus analis (F.) develop within the cotyledons of a number of pulses. Dwarf green peas were selected as the host in a study of the morphometrics and energetics of the larvae, pupae and callow adults of this species. (2) Peas containing a single larva were held at 30 degrees C and 70% r.h. They were divided into six groups of about thirty. One group was dissected every 8-10 days. The head widths, body lengths and live and dry weights of the larvae were recorded. Production was measured from those data. The last group of peas to be dissected had been X-rayed at weekly intervals during the larval development period. Consumption and production were estimated from the radiographs. The respiration rates of the insects were measured with a Gilson respirometer before the peas were dissected. The energy content of each stage was determined with a Phillipson microbomb calorimeter. (3) Larvae pass through five instars whilst in the pea. The relationships between dry weight and length and dry weight and live weight were of the expected form. The duration of each instar was determined by combining the data from direct observations and the radiographs. (4) The energy components of the budgets for larvae at the mid-point of the final larval instar were: consumption (C)=43.7 cal (183.0 J), production (P) = 20.4 cal (85.4 J), respiration (R) = 17.9 cal (74.9 J), egesta (FU) (determined by difference) = 5.4 cal (22.7 J), and assimilation (A) = 38.3 cal (160.3 J). The overall energy budget for larvae including the non-productive tunnelling phase of the fifth instar, was: [Note: see the image of page 117 for these equations.] C=P+R+FU 57.0=28.4+20.4+8.6 cal 238.4=118.8+85.3+36.0 J A=48.8 cal (204.3 J) (5) A comparison of the P to R ratio (=141.8%), assimilation efficiency (85.0%), net biological efficiency (58.7%) and gross biological efficiency (49.9%) with those of other arthropods indicates that legume seeds are a favourable niche. This species is an efficient converter of energy.
In each of 2 experiments, 6 different yearling white-tailed deer (Odocoileus virginianus) were fed 6 equicaloric concentrate diets with varying crude protein content. Maintenance requirement for protein was computed to be met by a diet containing 5.8 ± 2.0% crude protein (moisture-free basis). Each additional unit of dietary nitrogen resulted in 0.23 ± 0.01 units increase in retained body nitrogen and 0.66 ± 0.03 units increase in urinary nitrogen loss. Metabolic fecal nitrogen component was estimated to be 0.53 g/100 g dry matter consumed.
(1) This study derives a series of energy budgets for the burrow inhabiting wolf spider Geolycosa godeffroyi (Koch) in the Australian Capital Territory. (2) It examines the relationship between energy budgets derived by the extrapolation of various laboratory measurements of respiration rate with those derived independently by measuring consumption in the field in addition to production. (3) The lowest possible respiration rate (resting metabolic rate) is determined over the entire size and temperature range found in the field and takes account of the sophisticated behavioural thermoregulation shown by the spiders. (4) The increase in respiration rate due to a number of variables is determined. These include nutritional state, reproductive condition, size, temperature cycles, season, acclimation and sex. The increase in respiration due to many of these factors is cumulative. (5) On extrapolation to field conditions using actual spiders' temperatures the estimated metabolic heat loss varied by at least 2.5 times according to the type of respiration data used. (6) From a knowledge of the effect of some variables on respiration rate it is argued that the respiration rate in the field should be about three times the resting metabolic rate. (7) Budgets derived using field measurements of both production and consumption give respiration estimates between 3 and 4 times the resting metabolic rate. (8) Budgets derived using the higher respiration rates are in accord with those for other spiders derived by different techniques. (9) The effect of different types of respiration estimates on published energy budgets is considered in detail. (10) It is suggested that the methodologies used to derive energy budgets have a gross influence on the estimates of metabolic heat loss and introduce considerable bias. (11) When the methodologies are considered it is doubtful that some of the generalizations about production efficiency that have been proposed can be substantiated.
The effect of the nature and concentration of the nitrogen source on respiratory activity and removal of carbohydrate from the medium in suspension cultured sycamore (Acer pseudoplatanus L.) cells was determined. Comparison was also made of the rates of uptake of the two alternative nitrogen sources, nitrate and glutamate, at differing initial nitrogen concentrations within the range 7-14 mM. The initial pH of the culture medium before inoculation was 5.2; after inoculation the pH of both nitrate and glutamate cultures rose to reach an eventual level in the range 7.0-7.1. Glutamate was removed from the medium more slowly than nitrate. Under the particular conditions of culture used the growth of the cells was nitrogen limited. Sugar uptake from the medium continued for some time after the nitrogen in the medium was depleted. The data show that although cell division and protein content are nitrogen-limited, dry weight and fresh weight yields may also be determined in a complex interaction through carbohydrate availability. There were no obvious differences in respiratory activity between cultures grown on nitrate or glutamate.
Suspension cultured sycamore (Acer pseudoplatanus L.) cells will grow with either nitrate or glutamate as sole nitrogen source. Under the particular culture conditions used, cell growth is nitrogen limited. Within the range of initial nitrogen concentrations used (7-14 mM), cell growth on nitrate or glutamate at the same initial nitrogen concentrations is generally comparable. The rate of cell growth on these two nitrogen sources is also comparable with that observed when urea or urea plus nitrate is the prime nitrogen source. Increased nitrogen concentrations result in proportional increases in the final yield of numbers of cells, soluble protein and fresh weight. Dry weight yield by contrast shows both an absolute and relative decline with increasing nitrogen concentrations. At higher initial nitrogen concentrations differences are apparent in the pattern of cell growth between nitrate and glutamate grown cells.
Some parameters of nitrogen utilization between the ambrosia beetle Xyleborus dispar in mutualistic association with its symbiotic fungus Ambrosiella hartigii, were examined. Qualitative and quantitative analyses of the major nitrogenous excretory products were made on the various life stages of X. dispar. The main nitrogenous product found in excreta and hindguts of beetles, larvae, and pupae, was uric acid (range 7·6–14·8 μg uric acid/beetle). No ninhydrin-positive compounds were located in excreta of the beetles. The concentration of ammonia-nitrogen in the various life stages averaged between 0·70 and 1·13 μg NH3-N/beetle.Total nitrogen determinations were made on sapwood samples of Malus sylvestris (0·34 ± 0·005% N by dry weight), attacked wood, ‘pre-brood’ (0·31 ± 0·005% N by dry weight), and attacked wood ‘post-brood’ (0·17 ± 0·02% N). Similar determinations of the artificial medium (l-asparagine medium) indicated that a nitrogen requirement of about 0·08–0·1% N by dry weight was necessary before oviposition could occur.Fixation of atmospheric nitrogen by individual X. dispar beetles in vitro was not indicated using the acetylene ethylene reductase method. Proteolytic enzyme activity was not found on examination of diapause beetles, their excreta, larval and pupal excreta, and the ambrosial and mycelial forms of A. hartigii.Comparative concentrations of soluble proteins and free amino acids suggested that fungus in the mycangia was built up from free amino acids of the insects. At the period of emergence, flight, and attack of new hosts, the females were found to have a concentration of soluble proteins more than double that found in the beetles during the remainder of the year. The free amino acids were the lowest values recorded during this period (March–October).
Food intake and respiratory heat loss are the major pathways of energy flow through animal communities. In certain cases flow rates can be estimated for the total population from selected measurements of individual species. Metabolic parameters (Y) of arthropods from the floor of a Liriodendron tulipifera forest were correlated with size (X) of species: Y = aX/sub b/. This power function relationship is similar to the active surface area hypothesis of animal metabolism. The species examined ranged in size from 2.1 mg to 1.6 g live weight, and spanned a diversity of food habits and taxonomic categories. Food consumption was proportional to the 0.68 power of body weight. Metabolism (..mu..l O/sub 2/ hr/sup -1/) varied with the 0.84 power of body weight, while metabolic rate (..mu..l O/sub 2/ g/sup -1/ hr/sup -1/) was inversely proportional (b= -0.16) to body size. Within closely related species, /sup 137/Cs turnover rates were closely correlated with metabolic rates. These rates varied with temperature and followed a Q/sub 10/ of approximately two. By applying appropriate temperature corrections, body size relations can be used to estimate food intake and metabolism of species in their natural habitats. Radiotracers also may permit measurement of temporal fluctuations in metabolism resulting from activity in the field. 23 references, 4 figures, 2 tables.
Distribution of nutrient elements (N, P, K, Ca, Mg, S, Fe, and Na) varied substantially among the tissues and species of a late successional oak-pine forest at Brookhaven, New York. Mean nutrient concentration in the biomass was 2.3 times higher in Vaccinium angustifolium than in Pinus rigida; but in net production mean nutrient concentrations were high in Quercus alba and Q. ilicifolia, intermediate in Q. coccinea, Gaylussacia baccata, Vaccinium angustifolium, and V. vacillans, and low in P. rigida and Kalmia angustifolia. With the exception of Kalmia the species of the lower strata and earlier woody successional stages of the forest contained higher mean nutrient concentrations in the biomass than did the upper strata and climax tree species. Among tissues flowers, leaves, and fruits contained the highest concentrations; heartwood, the lowest. Weighted mean nutrient concentrations were higher for net primary production than for biomass by ''enrichment ratios'' mostly between 1.5 and 3.0 in the Brookhaven forest and comparable forests for which data are available. Nutrient element profiles showed the contrasts in concentrations of different elements in species as deviations from the means for the forest as a whole. The contrasting nutrient profiles may express niche difference in nutrient use among the plant species of the community. (auth)
The limnephilid caddisfly, Clistoronia magnifica, was reared through three generations on a detritus-based diet enriched with wheat grains and green grass. Developmental time was reduced and weight of mature larvae and pupae was increased by addition of enchytraeid worms to the above diet. Supplemental feeding on animals is also likely in the field but its importance would be underestimated because, in comparison with detritus, animal tissue would be a small component of the gut contents.
The same nine plots were used in this study as in our previous study on inhibition of nitrification (Rice and Pancholy, 1972). These consisted of three stands representing two stages of old field succession and the climax in each of three vegetation types in Oklahoma: tall grass prairie, post oak-blackjack oak forest, and oak-pine forest. Soil samples were analyzed three times during the growing season of 1972 for exchangeable ammonium nitrogen, nitrate, and numbers of Nitrosomonas and Nitrobacter. Results were similar to those obtained during the entire year of 1971. The amount of ammonium nitrogen was lowest in the first successional stage, intermediate in the intermediate successional stage, and highest in the climax. The amount of nitrate was highest in the first successional stage, intermediate in the intermediate successional stage, and lowest in the climax. The numbers of nitrifiers were highest in the first successional stage usually and decreased to a very low number in the climax. These data furnish additional evidence that the nitrifiers are inhibited in the climax so that ammonium nitrogen is not oxidized to nitrate as readily in the climax as in the successional stages. This would aid in the conservation of nitrogen and energy in the climax ecosystem. Some inhibition of nitrification occurred in the intermediate stage of succession also. Previous studies of tannins indicated that these are inhibitory to nitrification, so all important plant species in the intermediate successional stage and the climax were analyzed for total tannin content. A method for extracting and quantifying condensed tannins from soils was developed and the amounts of tannins were determined in each 15-cm level down to 60 cm in the same two plots in each vegetation type. Gallic and ellagic acids, which result from the digestion of hydrolyzable tannins in oak species, were also extracted and quantified in the climax oak-pine forest. All the important herbaceous species, including the grasses, were found to have considerable amounts of condensed tannins. The highest amounts of tannins occurred in the oaks and pine, however. Condensed tannins, hydrolyzable tannins, ellagic acid, gallic acid, digallic acid, and commercial tannic acid (hydrolyzable tannin), in very small concentrations, were all found to completely inhibit nitrification by Nitrosomonas in soil suspensions for 3 weeks, the duration of the tests. Slightly larger concentrations were required to inhibit nitrification by Nitrobacter under similar conditions. The concentrations of tannins, gallic acid, and ellagic acid found in the soil of the research plots were several times higher than the minimum concentrations necessary to completely inhibit nitrification. The inhibition of nitrification was always greater in the climax stand than in the intermediate successional stage in each vegetation type, and the concentration of tannins in the top 15 cm of soil was always higher in the climax stand than in the intermediate successional stage. Moreover, the amounts of tannins calculated to be added to each plot each year are much less than the amounts found in the soil, indicating that the tannins accumulate over a period of time. Thus, it appears that the tannins and tannin derivatives may play a continuous and rather prominent role in the inhibition of nitrification by vegetation.
Some theories on the foraging strategies of generalist herbivores suggest that the food choices of such animals are greatly influenced by the quality and antiquality components of potential foods. Many herbivores selectively feed on young rather than mature foliage. It has been hypothesized that young leaves are preferred because they have higher contents of protein and/or lower contents of toxic secondary compounds. These and several other hypotheses were tested with data from a long-term study of the feeding ecology of howler monkeys (Alouatta palliata), using a cost/benefit approach. Samples of young and mature leaves from the same species were analyzed for total protein, cell wall constituents, total phenolics, presence of condensed tannins, and total nonstructural carbohydrates. The results support the hypothesis that more than one factor determine howler leaf choices. The most important factors (relating to food content) appeared to be protein and fiber content, with perhaps some influence from seco...