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Resource regulation by a twig‐girdling beetle has implications for desertification

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Abstract

Abstract 1. Resource regulation by insects is the phenomenon by which herbivory enhances resources for the progeny of the herbivore. This report provides an example of resource regulation with implications for desertification in the Chihuahuan Desert of North America.2. Female Oncideres rhodosticta beetles chew girdles around mesquite (Prosopis glandulosa) stems before ovipositing in those stems. The mesquite plants respond by producing compensatory stems below the girdle. Mesquite volume was significantly correlated with the total number of beetle girdles across a suite of low shrub density grassland and high shrub density dune sites, and plants in dune sites had more old and new girdles than mesquite in grasslands.3. Smaller, younger shrubs in grassland responded more vigorously to girdling than did larger, older shrubs in dune landscapes. Stems on shrubs within grassland produced significantly more and longer compensatory stems per girdle than stems on shrubs in dunes. Soil capture by individual plants positively correlated with stem density, and stem density is increasing in the younger plants as a response to beetle damage.4. This study suggests that the interaction between O. rhodosticta and mesquite is an example of resource regulation that increases the stem density and soil capture ability of mesquite. Because the conversion of productive grasslands to mesquite dune landscapes is one of the most important drivers of desertification in the Chihuahuan Desert, feedbacks between organisms that promote an increase in the size and soil capture ability of mesquite may exacerbate desertification.

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... Stem-boring insects play important functional roles in forest ecosystems, as they contribute to nutrient cycling [21][22][23], alteration of tree architecture [23,24], resource regulation [25], and alteration of the composition and hydrology of forests [25,26]. Therefore, the study of factors structuring their communities has important implications for forest conservation. ...
... Stem-boring insects play important functional roles in forest ecosystems, as they contribute to nutrient cycling [21][22][23], alteration of tree architecture [23,24], resource regulation [25], and alteration of the composition and hydrology of forests [25,26]. Therefore, the study of factors structuring their communities has important implications for forest conservation. ...
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... Gall-inducers generally induce overcompensation through multiple shoot regrowth on their host plants (Nakamura et al., 2003;Kurzfeld-Zelxer et al., 2010;Tewari et al., 2013). Stemborers can induce different compensatory regrowth responses, for example the studied lepidopteran borers induce the regrowth of 5-8 shoots (Utsumi and Ohgushi, 2007), whereas the studied beetle borers induce the regrowth from 2 to 4 branches (Martínez et al., 2009;Duval and Whitford, 2008). In our study, the number of new growing branches of S. purpurea after branch removal ranged from 0 to 4, which resulted in a moderate overcompensation. ...
... Ecosystem engineering (through branch removal and regeneration) can have profound impacts on the ecosystem (e.g., Feller and Mckee, 1999;Duval and Whitford, 2008;Martínez et al., 2009). In particular, it might enhance arthropod diversity by creating new habitats with high availability of resources such as oviposition sites and nutrients (Calderón-Cortés et al., 2011). ...
Article
Ecosystem engineering by insect herbivores occurs as the result of structural modification of plants manipulated by insects. However, only few studies have evaluated the effect of these modifications on the plant responses induced by stem-borers that act as ecosystem engineers. In this study, we evaluated the responses induced by the herbivory of the twig-girdler beetle Oncideres albomarginata chamela (Cerambycidae: Lamiinae) on its host plant Spondias purpurea (Anacardiaceae), and its relationship with the ecosystem engineering process carried out by this stem-borer. Our results demonstrated that O. albomarginata chamela branch removal induced the development of lateral branches increasing the resources needed for the development of future insect generations, of its own offspring and of many other insect species. Detached branches represent habitats with high content of nitrogen and phosphorous, which eventually can be incorporated into the ecosystem, increasing nutrient cycling efficiency. Consequently, branch removal and the subsequent plant tissue regeneration induced by O. albomarginata chamela represent key mechanisms underlying the ecosystem engineering process carried out by this stem-borer, which enhances arthropod diversity in the ecosystem.
... These beetles are essentially homogeneous in their behaviours, with adults often feeding, mating and ovipositing on the same host-plant individual (Hanks 1999). Depending on the intensity of the attack, they can cause plant mortality, reduction of reproductive capacity, changes in stem structure, penetration of pathogens, as well as alterations in the recruitment and age structure of the host-plant populations (Caraglio et al. 2001;Romero et al. 2005;Uribe-Mú and Quesada 2006;Duval and Whitford 2008;Martínez et al. 2009). ...
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In this study, the host-plant range of Onciderini beetles was investigated during 4 years in an Atlantic rainforest of southeastern Brazil. Twelve species of Onciderini beetles girdled thirty-six plant species in the study site. In total, 1046 plants were girdled by Onciderini beetles as follows: 44.6% were Vochysiaceae, 15% were Mymosaceae, 12% were Melastomataceae, 9% were Lauraceae, 4% were Anacardiaceae and 15% were distributed among Meliaceae, Euphorbiaceae, Bombacaceae, Fabaceae, Thymelaeaceae, Cecropiaceae, Myrtaceae, Lecythidaceae, and Myrsinaceae. Onciderini beetles did not select hosts randomly. Most of the associations (70%) with host plants were caused by polyphagous beetles and different plant families showed different ratios of polyphagous, oligophagous and monophagous Onciderini in the study site.
... A literature search of published papers using as keywords ÔshrublandÕ and ÔdesertificationÕ together in the abstract revealed a substantial number (46%) of entries (143 papers) from the Chihuahuan Desert of southwestern United States (e.g. Huenneke et al. 2002;Jackson et al. 2002;Bestelmeyer 2005;Duval & Whitford 2008;Eldridge et al. 2009) andSouth Africa (e.g. Adeel 2008;Sankaran & Anderson 2009). ...
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Ecology Letters (2011) 14: 709–722 Encroachment of woody plants into grasslands has generated considerable interest among ecologists. Syntheses of encroachment effects on ecosystem processes have been limited in extent and confined largely to pastoral land uses or particular geographical regions. We used univariate analyses, meta-analysis and structural equation modelling to test the propositions that (1) shrub encroachment does not necessarily lead to declines in ecosystem functions and (2) shrub traits influence the functional outcome of encroachment. Analyses of 43 ecosystem attributes from 244 case studies worldwide showed that some attributes consistently increased with encroachment (e.g. soil C, N), and others declined (e.g. grass cover, pH), but most exhibited variable responses. Traits of shrubs were associated with significant, though weak, structural and functional outcomes of encroachment. Our review revealed that encroachment had mixed effects on ecosystem structure and functioning at global scales, and that shrub traits influence the functional outcome of encroachment. Thus, a simple designation of encroachment as a process leading to functionally, structurally or contextually degraded ecosystems is not supported by a critical analysis of existing literature. Our results highlight that the commonly established link between shrub encroachment and degradation is not universal.
... The new stems below the girdles were longer in the grassland than in the dunes. The volume of plant-captured soil was correlated with shrub stem density (Duval and Whitford, 2008). Positive correlations of mesquite volume with both old and new girdles suggest a feedback loop where girdling increases stem density, stem dense shrubs provide greater resources to emerging female O. rhodosticta the following year, and the plant responds by growing more new stems. ...
Chapter
Animal–plant interactions in concert with climate variability and ­anthropogenic stress contribute to desertification (ecosystem degradation) and/or ­resilience and resistance of desertified ecosystems. Stem girdling by a cerambycid beetle and stem cutting by jackrabbits (Lepus californicus) stimulate compensatory stem production, resulting in increased stem density. Capture of aeolian sand increases with higher stem densities, which results in dune formation over time. Some shrub species exhibit compensatory growth in response to herbivory while other species ­exhibit reduced vigor or death. Animals that destroy adult shrubs or seedlings affect the species composition of plant communities and may be essential for maintenance of desirable ecosystems. Australian bettongs, rodents, and insects in Mongolia, and a South American fossorial rodent (Ctenomys spp.) are reported to be essential for the maintenance of productive savannas and grasslands. The cutting of grass flowering ­tillers by heteromyid rodents is of little consequence in lightly grazed desert grassland, but results in loss of most of the tillers of grasses in intensely grazed grassland for years after domestic livestock have been excluded. Animals also have indirect effects on desertification processes and on the stability of desertified ecosystems. Indirect effects include seed dispersal, seed capture, production of “safe” germination and establishment sites, and stimulation of nutrient cycling processes.
... The current report extends the geographical area of association between O. rhodosticta and Prosopis glandulosa to the southern Chihuahuan Desert, notably increasing the area reported by Duval and Whitford (2008), as based on Linsley et al. (1961) and their own field surveys. The outbreak of O. rhodosticta was associated with a historically low rainfall amount in 1998. ...
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This study evaluated the effect of an outbreak of the cerambycid beetle, Oncideres rhodosticta, on branch growth and inflorescence production of the mesquite Prosopis glandulosa var. torreyana, and on larvae mortality in girdled branches at two sites (dry and wet) in the southern Chihuahuan Desert of Mexico. We compared stem growth responses to girdling in branches of similar sized trees from both sites over 42months. The number of larvae per girdled branch was similar between sites, indicating similar ovipositing effort regardless of water stress. However, the proportion of dead larvae was significantly lower in trees at the dry site. On average, girdling reduced 96% of the stem length at both sites. At the end of the first year, 25% of the original stubs survived at the dry site, compared to 90% at the wet site. Girdling also broke apical dominance and allowed for the development of lateral buds from the surviving stubs, which produced many fewer branches and inflorescences at the dry site compared to the wet site, where a compact crown was developed. Water stress and girdling have a combined effect on mesquite architecture and reproduction, since more stubs died at the dry site while new branches from surviving stubs developed at the wet site, recovering the original lost biomass but changing the appearance of the tree.
... They suggested that this was a positive feedback loop as the result of an evolved strategy by the moth. Duval and Whitford (2008) found that a cerambycid beetle, Oncideres rhodosticta, girdles branches of mesquite , Prosopis glandulosa, which induces high levels of branching through the induction of dormant buds. These densely branched trees are preferred for further oviposition, setting up a resource regulation cycle that results in increasing beetle densities in very densely branched trees that catch soil and promote dune formation. ...
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Resource regulation occurs when herbivory maintains or increases plant susceptibility to further herbivory by the same species. A review of the literature indicates it is a widespread plant–animal interaction involving a diverse array of herbivores. At least three mechanisms can produce this positive feedback cycle. First, phytophagous insect and mammalian herbivore damage can stimulate dormant buds to produce vigorous juvenile growth, which is preferred for further attack. Juvenilization cycles may have repeatedly evolved because herbivores are able to take advantage of a generalized plant compensatory response to any type of damage. Second, herbivores can manipulate plant source–sink relationships to attain more resources, and this alteration of plant growth may benefit subsequent herbivore generations. Third, herbivory can alter plant nutrition or defensive chemistry in a way that makes a plant susceptible to more herbivory. Resource regulation probably occurs because damage to resources preferred by the herbivores induces a generalized plant response that produces more preferred resources. Alternatively, manipulation of plant resources to induce resource regulation may have evolved in herbivores with a high degree of philopatry due to selection to alter plant resources to benefit their offspring. Resource regulation can stabilize insect population dynamics by maintaining a supply of high-quality plant resources. It can also increase the heterogeneity of host-plant resources for herbivores by altering the physiological age structure and the distribution of resources within plants. Resource regulation may have strong plant-mediated effects on other organisms that use that host plant, but these effects have not yet been explored. KeywordsCompensatory growth-Dormant bud-Herbivory-Indirect interactions-Philopatry-Population dynamics
... californicus) and mesquite stems pruned by stem girdler beetles, Oncideres spp. (Duval and Whitford, 2008). The higher humidity and moderate temperatures in the center of pack-rat middens provide an environment that enhances the growth of wood-decomposing fungi (Zak and Whitford, 1988). ...
Article
The potential role of two species of pack rats (Neotoma albigula and Neotoma micropus) as keystone ecological engineers was examined by estimating the species diversity of invertebrates living in the nest middens, and nitrogen mineralization rates in soils associated with the middens. Although pack-rat middens in tarbush (Flourensia cernua) shrublands were smaller than those in creostebush (Larrea tridentata) shrublands, they housed a higher abundance and diversity of arthropods. The Neotoma spp. middens were an important microhabitat for crickets (Gryllus sp.), wolf spiders (Lycosa spp.), and lycid beetle larvae (Lycidae) in all of the shrub habitats. There were five arthropod taxa that occupied all middens in the creosote-bush shrubland, and 12 arthropod taxa that occupied all middens in the tarbush shrubland. Soils associated with pack-rat middens had significantly higher soil organic-matter content than reference soils. Nitrogen mineralization was significantly higher in soils associated with pack-rat middens than in reference soils. Neotoma spp. create habitats with moderate microclimates that are essential for several invertebrates, thus contributing to maintenance of biodiversity. The effects of middens on soil organic matter and nitrogen mineralization create nutrient-rich patches. Neotoma spp. affect biodiversity and critical ecosystem processes, thus supporting the designation of keystone ecological engineers.
... root sequestration of nutrients, nitrogen fixation, and harboring diverse microbe communities; Li et al. 2017;Ochoa-Hueso et al. 2018), or by increasing the differences between vegetated and unvegetated patches via animal activities (e.g. herbivory by insects and overgrazing by livestock; Allington and Valone 2014;Cai et al. 2020;Duval and Whitford 2008). ...
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Abstract Aims: Perennial plants play important roles in maintaining ecosystem functions by forming fertile islands beneath their canopies. Little is known about how the fertile island effect varies among different patch types and across climatic gradients, or what drives the strength of its effect. Methods: We assessed biotic (plants, biocrusts, litter) and abiotic (soil infiltrability, labile carbon, enzymes) fertile island effects beneath three plant patch types (tree, shrub and grass patches), and collected data on biotic (canopy size, grazing intensity) and abiotic (soil texture, electrical conductivity and pH) drivers at 150 sites along an extensive aridity gradient in eastern Australia. Results: The fertile island effect was generally apparent beneath trees, shrubs and grasses, with biotic (plants) and abiotic (soils) attributes regulated differently by plant canopy size. The fertile island effect intensified with increasing aridity, with the greatest litter and soil resources accumulated beneath trees. Conclusions: Our study provides evidence of the fertile island effect across the whole spectrum of the aridity gradient, with the effect depending on the target attribute and plant patch type. Forecasted increases in aridity will likely strengthen the fertile island effect beneath trees, reinforcing the importance of trees in drier environments to support critical ecosystem functions and services. Keywords: Climate gradient, Fertile patch, Plant canopy, Plant-soil feedbacks, Relative interaction index, Soil properties
... Females oviposit in this portion, providing freshly dead tissue for the larvae to develop on (Paulino Neto et al. 2006;Calderón-Cortés et al. 2011). Among these beetles, the genus Oncideres has the greatest number of species (Monné 2002), being exclusive to the American continents and occurring from the southern USA to Argentina (Di Iorio 1994Iorio , 1996Duval & Whitford 2008;Paro et al. 2012;Rodríguez-del-Bosque 2013). ...
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The objective of this study was to analyze whether the morphology of girdled twigs has an effect on the number of incisions and the reproductive success of Oncideres ocularis (Coleoptera: Cerambycidae). Eight parameters of girdled branches were evaluated. Surface area showed the highest coefficient of determination for the number of eggs laid per branch and for the number of hatched larvae. Surface area, volume and length of girdled branches correlated significantly with the number of laid eggs and hatched larvae, as has been reported for similar insects.
... Studies had evaluated the effect of girdling on the structure of plant communities (Caraglio et al. 2001;Romero et al. 2005;Duval & Whitford 2008) and the preference of host plants choice (Ansley et al. 1990;Paulino Neto et al. 2005;Uribe-Mu & Quesada 2006;Paro et al. 2011). But few studies had focused on the influence of plants and environment on the biology and reproduction of twig girdler beetles (Rodríguez-del-Bosque & Cedillo 2008;Rodríguez-del-Bosque 2013). ...
Article
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Oncideres ocularis (Cerambycidae) is a twig girdler beetle with potential to become a pest of Fabaceae forest plantations. The diversity of agroecosystems can affect populations of insect pests and their natural enemies, and intercropping may provide resources such as food, alternative prey and hosts, and shelter for the natural enemies. The objective of this work was to verify if the number of larvae and the action of natural enemies of this twig girdler vary along the girdled branch and with the different plantation methods. Fresh branches of Acacia mangium girdled by O. ocularis were collected at two types of plantations, a monoculture and an intercropping with eucalyptus and Brachiaria spp. The dead and living larvae were removed from the galleries along the branch (basal, middle, and apical sections). The number of larvae was different between sections of the girdled branch for all variables analyzed. The total number of larvae of O. ocularis did not differ between the types of plantation, but larvae survival was significantly higher in the intercropping than in monoculture. The type of plantation also affected the action of predators on larvae in the early instars, besides varying along the branch. In intercropping systems with eucalyptus, acacia, and grasses, the predators may not be able to reduce the population of this twig girdler.
... Oncideres, the most species-rich genus of girdler species (Monné 2005), is exclusively found in the Americas from Argentina to USA (Di Iorio 1996;Paulino Neto et al. 2005;Duval and Whitford 2008). The genus is widely distributed in all parts of Brazil (Monné 2005;Lemes et al. 2012;Paro et al. 2012;Lemes et al. 2014a). ...
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Species of Oncideres Serville, often referred to as twig girdlers, girdle tree branches prior to oviposition to promote larval development. The behavior creates a unique niche that is utilized by other beetle species. The objective of this study was to compare emergence of insects from branches girdled by Oncideres saga Dalman in an intercropping system and a monoculture of Acacia mangium Willd. in the Atlantic Rainforest of Minas Gerais, Brazil. Twenty-four Coleoptera species emerged from the branches: 17 Cerambycidae; three Cleridae; and one individual each from Cantharidae, Cucujidae, Elateridae, and Trogossitidae. Although branches from the intercropping system yielded more individuals, branches from the monoculture had higher species richness, including almost all of the cerambycid species and all of the potential predators. The use of girdled twigs may confer a reproductive advantage to subsequent cerambycid colonists, which are probably attracted to the volatiles released by the girdled branch. Beetles belonging to other families may prey on the Cerambycidae dwelling inside the branches. Potential predators may be ecologically important, contributing to the natural biological control of O. saga. Collecting and burning the infested branches is the technique most extensively used to control the twig girdlers. However, this also destroys beneficial organisms as well as the subsequent colonists that depend upon these branches.
... In cultivated cotton this insect can cause significant reduction in boll production and even mortality (McGregor 1916;Morrill 1927), but experimental research has provided no evidence of impacts on the fitness of desert cotton (Karban 1993). In contrast, although the beetle known as the mesquite twig girdler (Oncideres rhodosticta) feeds on mesquite, the interaction may be mutualistic, in that girdling stimulates young mesquite trees (Prosopis glandulosa) to increase stem density, which increases the resource-capture ability of the plant, but the potential impacts on plant fitness have not been examined (Duval and Whitford 2008). Finally, Miller et al. (2009) examined the impacts of insect herbivory on population density of the tree cholla cactus (Opuntia imbricata) across an elevation gradient in the Chihuahuan Desert, finding evidence that the nature of the interaction varies with environmental context. ...
Article
Premise of research. Biotic interactions have long been considered to be of less importance in structuring desert systems than other ecosystem types, but biotic interactions often play a critical role in meeting the challenges posed by the extreme conditions of desert environments. The Sonoran Desert, in particular, is home to several textbook examples of mutualisms, such as the interactions between the iconic saguaro cactus and its bat pollinators. But what do we know about the diversity, ecology, and evolution of plant-animal, plant-plant, and plant-microbe interactions and their impacts on individual plants and plant species in the Sonoran Desert? Methodology. To address this question, we review the published research on seven common kinds of plant biotic interactions by revisiting the respective literature, identifying gaps in our knowledge, and outlining future research directions. Pivotal results. Numerous gaps in our knowledge of plant biotic interactions in the Sonoran Desert were identified. Studies of insect herbivory, bee pollination, and plant-microbe interactions are poorly represented in the Sonoran Desert literature. Across all categories of interaction, few have examined the impacts of interactions on plant fitness or context-dependent variation in the outcomes and strengths of interactions. For the most part, interactions have been studied at single locations and over short periods of time, resulting in an incomplete understanding of their diversity, ecology, and evolution. Conclusions. Plant biotic interactions shape the habitats in which they occur and play an important role in the maintenance of species diversity. Therefore, we call for increased efforts to fill the gaps in our understanding of plant biotic interactions in the Sonoran Desert, with an emphasis on studies linking interactions to plant fitness and the context-dependent nature of interactions. Without this knowledge we have limited capacity to predict the outcomes of global change on species interactions and to develop measures to conserve the biodiversity of the Sonoran Desert region.
... Species such as C. lorentinus therefore play important functional roles in forest ecosystems because they can act as ecosystem engineers. They manipulate their host plants to build a variety of structures which are subsequently occupied by other organisms (Calderón-Cortes et al. 2011), and in turn, contribute to nutrient cycling (Amman 1977;Schowalter 1981), alteration of tree architecture (Feller 2002;Martínez et al. 2009), resource regulation (Duval and Whitford 2008) and alteration of the composition and hydrology of forests (Feller and McKee 1999). ...
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Branches of Quercus species killed by Coraebus florentinus (Coleoptera, Buprestidae) are a chief resource for many saproxylic insects, mainly of the orders Coleoptera and Diptera, in the oak forests of the southern Iberian Peninsula. To investigate the biology of these species, a total of 127 dry oak branches that had been previously colonised by C. florentinus were collected and kept in the laboratory, in conditions comparable to the outdoor climate. For 4 years, the emergence of saproxylic insects from the branches was monitored. We obtained 651 individuals, belonging to 19 species of 6 families. Three buprestids (Anthaxia hungarica, A. millefolii and Agrilus angustulus) and one cerambycid (Chlorophorus ruficornis) made up 68% of the total abundance. Results on host tree preferences indicated that A. hungarica and C. ruficornis show more affinity to holm oaks (Q. ilex). Conversely, A. angustulus and A. hastulifer prefer cork oaks (Q. suber). Preimaginal stages have long durations, but vary in relation to the body size of species: smaller species such as A. angustulus and A. millefolii exhibit shorter larval time, reaching the maximum of emergences after 12 months monitoring, whereas larger species such as A. hungarica and C. ruficornis display a longer pre-adult period (3 and 4 years, respectively). The insects were found to be active in spring and summer and to have a balanced sex ratio in all of the species studied. Finally, our results also indicate the importance of long-term maintenance of these branches in the natural environment for the conservation of saproxylic biodiversity in the Iberian “dehesa”.
... The compensation effect has been seen in other type of systems in stressful environments. For example, Duval and Whitford (2008) showed that stem girdling by the girdler beetle on Prosopis glandulosa Torr. individuals increase the production of stems in this species, and therefore enhance its ability to capture sand, leading to further enhancement of stem growth (Appendix Fig. 4). ...
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Aims Plant species response to erosion or burial has been extensively studied, but few studies have examined the combined effects of erosion and subsequent burial on plants. In active sand dunes of northern China, Artemisia wudanica falls to the ground following wind erosion, accumulating sand among fallen stems in a process that may facilitate its further growth and development. Therefore, we hypothesize that subsequent sand burial might compensate for the negative effects of erosion in the growth of A. wudanica. Methods A common garden experiment was conducted using A. wudanica seedlings to evaluate their growth in response to different degrees of burial and erosion as observed at the field. Seedlings were selected and randomly assigned to six erosion treatments, two burial treatments, twelve erosion and subsequent burial treatments, and control. Each treatment was replicated six times. Results Compared with the control treatment, total biomass and the relative growth rate of shoots were stimulated in the erosion and subsequent burial treatments (significantly under the 10 cm burial), hampered in erosion only treatments, and were not affected in the burial only treatments. Adventitious roots and ramets were only observed under burial only and erosion and subsequent burial treatments. Conclusions Our results indicate that subsequent sand burial following erosion compensate for the negative effects of erosion on the growth of A. wudanica seedlings, and greatly contributed to their tolerance to wind erosion.
Article
The longhorn beetles play important roles in the forest ecosystem processes and their diversity is affected by many environmental disturbances worldwide. This study aimed at understanding how the structural heterogeneity of the habitat can affect the longhorn beetle assemblage in three areas of an Atlantic Forest, which suffered differential impacts in the past and are now in different successional stages. The area in the most advanced successional stage had mainly lower density of trees, but with greater availability of dead wood, especially larger diameter classes. They are important forest components that contribute to the structural diversity of the habitat providing resources for a variety of dependent species. This area has also shown the greatest richness and abundance of longhorn beetles. Our results suggest that these beetles are closely associated with the structural heterogeneity of forests and can be valuable indicators for assessing biodiversity and quality of forest habitat. It also shows that old-growth forest remnants can be the key to the maintenance of the diversity of the longhorn beetles and, consequently, of the ecosystem services they provide
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Biotic interactions are vital to ecosystem functioning. Interactions among individuals lie at the core of population and community dynamics, and therefore play a central role in the existence and persistence of species. Plants form the food base of most terrestrial ecosystems and are therefore not surprisingly involved in a substantial portion of biotic interactions. Plants, animals, and microbes face great challenges to survival in the desert environment, and these interactions play a critical role in the survival of many species. The Sonoran Desert flora is well documented and certain of its iconic interactions are well understood. For example, saguaros and the bats that pollinate them and disperse their fruits have become textbook examples of mutualisms (e.g., Shreve and Wiggins 1964; Turner et al. 2005). However, what do we know about plant-animal, plant-plant, and plant-microbe interactions in the Sonoran Desert more generally? What role do such interactions play in the ecology and evolution of the Sonoran Desert ecosystem? How are these interactions affected by global changes, and how can we conserve interactions? These questions inspired a discussion session convened at the Next Generation Sonoran Desert Researchers (NGSDR) 2012 Summit. Ultimately, participants identified the following five critical needs regarding research and conservation. We need to (1) improve our knowledge of the natural history (diversity, ecology, evolution) of interactions, both as individual entities and as players in the broader ecological community; (2) monitor interactions on broad spatio-temporal scales to be able to identify the consequences of climate change, especially for seasonal interactions involving migratory species; (3) identify the human activities with the greatest impacts on interactions; (4) develop criteria to compile a “priority interaction list” to improve and strengthen our ecosystem conservation efforts; and, finally, (5) use interactions to restore disrupted habitats and ecosystems. Here we provide a comprehensive yet concise overview of biotic interactions involving the flora, fauna, and microbiota of the Sonoran Desert, summarizing and expanding results of the NGSDR 2012 Summit discussion. We briefly present the broad categories of interspecific interactions involving Sonoran Desert plants, identify and describe threats known to negatively affect them as well as positive links with human activities, and present ongoing conservation needs and restoration efforts. We conclude by suggesting future research directions and recommendations required for urgent conservation and restoration efforts. All living organisms on Earth are involved in interactions with other organisms. Interactions are “mutualistic” when both organisms benefit and “antagonistic” when only one benefits at the expense of the other. They are “facultative” when participants do not strictly depend on one another and interact with several other species; they are “obligate” when at least one species relies on the other and rarely interacts with other species, making the interaction a matter of life and death in some cases. Although obligate interactions represent only a minor fraction of the immense web of biotic interactions, their more constant association and higher specificity make them easier to study (Davidson and McKey 1993; Futuyma and Agrawal 2009). In contrast, facultative interactions are both more common and complicated, since species interact with many partners and the associations can fluctuate between mutualistic and antagonistic (e.g., Bentley 1977; Ness 2006). Here, we focus on interspecific interactions in which Sonoran Desert plants regularly engage. We group them based on the harm or benefits animals and microbes confer. This includes two forms of antagonism, herbivory and parasitism, and five forms of mutualism, pollination, seed dispersal, biotic protection, facilitation, and microbe-mediated nutrition. These are detailed below. An extensive bibliography is provided in appendix 1. Plants are the most common terrestrial food resource for animals. Most plant-consuming animals are insects; among vertebrates, most are mammals (Herrera and Pellmyr 2002). Plants in desert habitats are particularly important for animal consumers, because they represent a critical source not only of nutrients but also water. Effects of herbivores on plant fitness differ depending on the plant parts consumed. For example, the loss of reproductive parts, such as flower buds, is worse for the plant than having some leaves eaten. In the Sonoran Desert, herbivory studies have focused on mammal consumption of woody legumes and cacti, insect...
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This study examined the potential of animals as vectors for mesquite seedling establishment via fecal deposition. Cattle, deer, and coyote fecal material containing emerging mesquite was located in May 1994 on a clay loam site in north Texas and assigned to two grass competition treatments (clipped to 3-cm height, or unclipped) and three moisture treatments (rainfall, rainfall + four 1.25-cm irrigations, or rainfall + one 10-cm irrigation). Except for a 2-week period in August 1993 when feces were deposited, cattle grazing was excluded from the site during the study and for several years prior to study initiation. Seedling emergence and survival were quantified throughout 1994, a dry year, and 1995, which had precipitation well above normal. By spring 1995, survival of 1994 seedlings (all treatments pooled) was 16.6, 9.3, and 1.3% at deer, cattle, and coyote fecal sites, respectively. Survival of 1994 seedlings was not affected by moisture or clipping treatments. New cohorts of emerging seedlings occurred from the same fecal sites during 1995. High rainfall during summer 1995 increased percent survival of 1995 seedlings when compared to survival of 1994 seedlings, even though grass growth was much greater in 1995 than in 1994. A strong trend emerged in which survival of 1995 seedlings appeared to be greater when surrounding perennial grasses were clipped (37.0% in clipped plots vs. 9.4% in unclipped plots), but this was not statistically significant (P less than or equal to 0.14). By spring 1996, average number of seedlings emerged per site (1994 and 1995 cohorts combined) was 7.8, 5.2, and 4.5; number of established seedlings per site was 0.8, 0.6, and 0.3; and percent survival was 12.1, 13.5, and 6.5% at cattle, deer, and coyote sites, respectively. Mesquite seedlings were capable of establishing from feces of all three animal vectors within dense, ungrazed stands of perennial grass.
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Emergence and survival of honey mesquite (Prosopis glandulosa var.glandulosa Torr.) seedlings was quantified on sites with contrasting grazing histories: long-term continuous grazing (LTG) and long-term protection (LTP) from grazing by cattle. On each site, different levels of heroaceous defoliation were imposed at monthly intervals (no defoliation=ND, moderate=MD and heavy=HD). The two weeks following seed dissemination appeared to be the most critical toProsopis establishment on LTP-ND plots. Openings in the herbaceous layer created by moderate defoliation of grasses on the LTP site increased germination and/or survival 7-to 8-fold during this period. However, increasing the degree of defoliation from moderate to heavy did not stimulate additional emergence on either the LTP or LTG site. Emergence from scarified seed placed in cattle dung (17 to 30%) was lower than that of bare seed placements in various microhabitats (43-60%). However, deposition of scarifiedProsopis seed in dung in conjunction with graminoid defoliation may be the most likely combination of events when livestock are present. Emergence from seeds transported into grasslands by other fauna likely would be low, unless seeds were deposited in areas where grasses had been defoliated.Prosopis survival was comparably high in dung and bare seed placements after one growing season. survival of seedlings present two weeks after seed dissemination ranged from 74 to 97% at the end of the second growing season. Seedling survival and shoot development (biomass, leaf area and height) were similar on LTP and LTG sites, regardless of the level of herbaceous defoliation or seed placement. In addition, the magnitude and patterns of net photosynthesis, stomatal conductance and xylem water potential were comparable among one-year-old seedtings on ND, MD and HD plots, even though differences in herbaceous species composition and above- and below-ground biomass between these treatments were substantial. Such data suggest competition for soil resources between grasses andProsopis may be minimal early in the life cycle ofProsopis. High rates ofProsopis emergence and establishment on LTP-MD plots are counter to the widespread assumption that long-term and/or heavy grazing is requisite forProsopis encroachment into grasslands. Results are discussed with regard to factors contributing to the recent, widespread invasion of this woody legume into grasslands of southwestern North America.
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Examines the tenthredinid sawfly Euura lasiolepis on Salix lasiolepis. Normally, as willows age they become less susceptible to galling, but heavy Euura galling maintains willows at a young, relatively susceptible juvenile stage. The Euura form more galls on long shoots. Long shoots are found on clones with young branches. Heavy galling stunts or kills growth distal to the gall, stimulating sprouting by indefinitely dormant buds located near branch bases. The resulting young branches keep the clone susceptible to further galling. Increasing branch age of lightly galled clones confers resistance to galling. -from Authors
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Discrete clusters of woody plants form in herbaceous clearings following the invasion of mesquite Prosopis glandulosa var. glandulosa, an arborescent legume. The growth rate of these clusters varies with precipitation and size. A simulation model was developed in which the establishment of other woody species beneath invading Prosopis occurred within 10-15 yr. As a cluster developed around the Prosopis nucleus, species richness increased rapidly for 35-45 yr and became asymptotic at 10 species per cluster. Estimated age of the oldest Prosopis plant found in clusters was 172-217 yr, but model-derived size-age relationships predicted that 90% of clusters and mesquite plants at the site are <100 yr old. A lack of field evidence of mortality among large clusters and Prosopis plants suggests that populations are young and expanding geometrically. There was no evidence of density-dependent restrictions on recruitment or expansion. Thus, as new clusters are initiated and existing clusters expand, coalescence to continuous canopy woodlands may eventually occur. Predicted long-term mean radial trunk growth of Prosopis (0.8-1.9 mm.yr) was reasonable in comparison with short-term field measurements on Prosopis in other, more-mesic systems (2-4 mm/yr). Model output was consistent with historical observations suggesting that the conversion of savannas to woodlands in the Rio Grande Plains has been recent and coincident with both heavy grazing by livestock and seasonal shifts in precipitation that began in the late 1800s. -from Author
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Examines growth of honey mesquite as it was affected by clipping of sideoats grama grown with it, and investigated whether addition of various nutrients would affect the competitive ability of the 2 species in the presence of simulated grazing. It was hypothesized that woody legumes such as mequite may be better able to compete in infertile soils because of their low soil N requirements. -from Authors
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Intra- and interspecific competition experiments were conducted in the greenhouse with seedlings of Prosopis glandulosa var glandulosa Torr (honey mesquite) and Buchloe dactyloides (Nutt) Engelm (buffalo grass). Growth of P glandulosa seedlings by themselves, as measured by number of leaves, stem length, basal diameter, above-, belowground, and total biomass per plant, decreased as plant density increased All of these parameters increased on a per pot basis Root: shoot ratios increased as plant density increased Above-, belowground, and total biomass per plant of B dactyloides decreased with increasing B dactyloides density in monoculture. Root: shoot ratios increased with increasing grass density. A single B dactyloides plant did not significantly reduce above-, belowground or total biomass of P glandulosa seedlings as compared to P glandulosa grown by itself However, B dactyloides densities of two or more caused a significant decrease in all P glandulosa biomass measurements. Root: shoot ratios for both P glandulosa and B dactyloides increased by a factor of two from the lowest to highest grass density when grown together Slopes of log-log regressions of plant density and biomass for both intra- and interspecific interactions were less than zero, showing that both intra- and interspecific competition occurred. Slopes of intra- and interspecific regressions for aboveground biomass of P glandulosa were not significantly different However, slopes of belowground and total biomass were steeper for interspecific competition than for P glandulosa intraspecific competition This suggests that B dactyloides is a better competitor for soil resources than seedlings of P glandulosa, especially at a high grass density In addition, the presence of one seedling of P glandulosa did not have any effect on the slope of regressions of above-, belowground or total biomass of B dactyloides Thus, P glandulosa is probably not an invader of high density, highly productive B dactyloides grasslands; rather, it is a colonizer of open, low-density areas
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It is suggested that the mutually beneficial relationships between flowers and their pollinators and between fruits and fruit-eaters can be extended to cover a much wider range of plant-consumer interactions. The ability to photosynthesize is by itself of limited value to a plant if growth and reproduction are restricted by the availability of nutrients. Hence natural selection should favour adaptations that increase the rate of supply of a scarce resource. By enlisting the "help" of a consumer a plant may facilitate cycling and increase the supply of a nutrient in short supply; in particular the deposition of sugary honeydew by aphids may increase the rate of nitrogen fixation beneath the plant by providing an energy source for free-living nitrogen-fixing bacteria. Consumers may also affect the growth form of a plant in a beneficial way; grasses, for example, survive best when cropped and are probably totally co-evolved with grazers: one would not be possible without the other. A speculative paper such as this almost certainly contains errors of interpretation, but even if only some of the suggestions are correct the common viewpoint that plants defend themselves against consumers will have to be radically changed. /// Установлено, что мутуалистические отношения между цветами и их опылителями, плодами и их потребителями могут быть распространены на гораздо более широкий круг взаимодействий в системе растение - консумент. Способность к фотосинтезу, сама по себе ограниченная величина для растений, а рост и размножение ограничены доступностью элементов питания. Поэтому естественный отбор может стимулировать развитие адаптаций, повышающих скорость потребления ресурсов, находящихся в недостаточном количестве. При "помощи" потребителей растение может стимулировать круговорот и повысить приток элемента при недостаточном запасе; в частности, выделение медвяной росы тлями может повысить скорость фиксации азота под растением путем создания источника энергии для свободноживущих азотфиксирующих бактерий. Консументы могут также влиять на рост растений стимулирующим образом. Например, злаки лучше развиваются в условиях выпаса и очевидно в целом коэфолюционировали вместе в фитофагами: существование одних невозможно без других. Такая спекулятивная статья, как эта, почти наверняка содержит ошибки в интерпретации. Но, даже если некоторые из ее доводов верны, обынная точка зрения, что растения защищаются против потребителей, должна быть радикально пересмотрена.
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Compensatory growth in plants subjected to herbivory may alleviate the potential deleterious effects of tissue damage, whether to vegetative or reproductive organs. Tissue destruction is rarely, if ever, translated monotonically into a proportional reduction of final yield. Internal mechanisms of compensation involve modifications of plant metabolism; external mechanisms of compensation involve modifications of the plant environment that are favorable to plant growth and yield. /// Компенсаторный рост растений в резупьтате выедания фитофагами может смягчать потенциальный отрицательный эффект повреждения тканей вегетативных либо репродуктивных органов. Деструкция тканей редко, если это наблюдается вообще, отражается в пропорциональном снижении окончательного урожая. Внутренние компенсаторные механизмы включают модификалии метаболизма растений; внешние компенсаторные механизмы вкпючают модификации среды, способствующие росту и урожайности растения.
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Both shade and herbaceous competition reduced the germination and growth of Prosopis glandulosa Torr. (honey mesquite). Natural and artificial shade was used and herbaceous competition was manipulated by clipping and herbicide. Greatest growth of P. glandulosa seedlings was in full sunlight when there were no competitors. Plants in shade without competitors or in full sunlight with competitors had intermediate growth, while those in shade with competitors were the smallest. Natural shading by P. glandulosa trees caused similar trends, although significant differences were not always found. Prosopis glandulosa germination in the laboratory was 93 ± 5% versus 2%-19% in the field. No P. glandulosa seedlings survived after one growing season in two grassland plots with high biomass, compared with 8% in the herbicided plot. Lack of P. glandulosa seedling germination and growth under mature P. glandulosa trees appears to be the result of reduced light levels and herbaceous plant competition. These factors also result in low numbers of seedlings in grasslands and, coupled with herbivory or fire, could account for their absence.
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Oncideres rhodosticta Bates (Coleoptera: Cerambycidae) causes severe pruning of small branches of mesquite, Prosopis glandulosa Torr., in many areas of Texas. Adults emerge from galleries in girdled branches from late August through November. They feed on tender bark of mesquite around the buds, thorns, and small limbs. Eacli female girdles about one branch and deposits about 8 elliptically ovate eggs beneath the bark of the branch. Within 10-14 days, 98% of the eggs hatch and the larvae feed upon the sapwood, opening the oviposition scar to expel frass after about 3 months. Pupation occurs in late August and early September and is preceded by a prepupal stage. Each larva consumes about 1.44 cc of mesquite wood during its development. Parasites and predators kill 15-22% of the larvae while 34-55% die from undetermined causes. Larvae are attacked by parasites in the families Chalcedectidae, Pteromalidae, Eupelmidae, and Eurytomidae, as well as by predators in the family Cleridae. Twig girdler larvae may compete for space and food with other cerambycids and several species of bostrichids. About 31% of all girdled branches are broken off by wind storms and livestock before adults emerge, resulting in high mortality of the larvae from high temperatures in the branches near the soil surface.
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Most studies of plant–herbivore interactions in dioecious species have evaluated foliar herbivory. In this studie we evaluated preferences of branch removal by the insect borer Oncideres albomarginata chamela in the tropical dioecious tree Spondias purpurea L. The objectives were to determine the preferences and patterns of the removal of branches, to evaluate the effect of branch removal in the vegetative regeneration of branches, and to evaluate the effect of branch removal on the regeneration of fertile branches of male and female trees of S. purpurea. During three consecutive years of study, damage caused to branches by the girdled borer was associated with plant gender. The proportion of branches removed by the insect was greater for female than for male trees. The effects of branch removal were evaluated in attacked regenerated and unattacked branches. Removed branches regenerated a year after the insect borer attacked them. Branch removal affected the probability of producing fertile branches. The preference by O. a. chamela is apparently associated with the nutritional quality of the host.
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Four sources of evidence are used to support the Plant Vigor Hypothesis that many herbivore species feed preferentially on vigorous plants or plant modules, as opposed to the Plant Stress Hypothesis arguing that stressed plants are beneficial to herbivores. Evidence includes patterns of within-plant species utilization by galling insects where females select large plant modules and larvae survive better than on smaller modules. Independent evidence concerns patterns of herbivory between plant species habitually growing in rich resource environments which are heavily utilized. In forestry literature, many cases are known of most attacks by insect herbivores occurring on young and open-grown trees. Similarities in exploitation of plants by moose Alces alces and galling insects are compared and accounted for by the common responses to vigorously growing plant parts. Consequences of vigorous module utilization include resurce regulation, or the utilization of resources such that resource quality is maintained, concentration of feeding in early successional vegetation, among insect herbivores an increased probability of competition among females for oviposition sites as opposed to larval competition, a lack of induced defenses in plants in some cases, and general problems with defending rapidly growing modules. Complications with the Plant Vigor Hypothesis include in certain instances the possible role of early induction of plant defenses and subsequent increased resistance with age and the pattern in some cases of herbivores preferring vigorous plant modules on plants in drier sites over those in adjacent wetter sites. -from Author
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Sumario: Impact of desertification on climate (Human impact on surface and atmospheric conditions in drylands. Impact of human activities in drylands on climate) -- Impact of climate on desertification (Impact of climate on soils and vegetation. Impact of climate on the hydrological cycle. Human land use in drylands and the influence of climate) -- Global climate change and the future of dryland climate (Linkages between interannual climatic variations in drylands and the global climate system. Future climate changes in drylands) -- Mitigation and rehabilitation strategies to combat desertification (Mitigation and rehabilitation strategies) -- Summary, conclusions and recommendations Bibliografía: P. 220-258
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In a laboratory wind tunnel study the relationship between soil loss; wind velocity; and the number, height, and diameter of plant stalks was determined. Soil loss from the "vegetated' tests was compared to soil loss from a bare soil. The results illustrate that even sparse standing vegetation can significantly reduce soil loss. -from Authors
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Many mandibulate insects that feed on milkweeds, or other latex-producing plants, cut leaf veins before feeding distal to the cuts. Vein cutting blocks latex flow to intended feeding sites and can be viewed as an insect counteradaptation to the plant's defensive secretion. Experimental vein severance renders milkweed leaves edible to generalist herbivores that do not show vein-cutting behaviors and ordinarily ignore milkweeds in nature.
A list of Cerambycidae in the Chiricahua Mountain area, Cochise County
  • E G Linsley
  • J N Knull
  • M Statham
Linsley, E.G., Knull, J.N. & Statham, M. ( 1961 ) A list of Cerambycidae in the Chiricahua Mountain area, Cochise County, Arizona. American Museum Novitates, 2050, 1 – 34.
Biopedurbation influences on ecosystem properties and processes in the northern Chihuahuan Desert
  • Killgore
Killgore, A. ( 2004 ) Biopedurbation infl uences on ecosystem properties and processes in the northern Chihuahuan Desert. MS thesis, New Mexico State University, Las Cruces.