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Towards predicting responses to an extreme event: traits that influence ground‐dwelling beetles' susceptibility to volcanic ash
Abstract
Extreme events are important determinants of environmental changes at multiple geographical and temporal scales, influencing the ecology and evolution of species. Volcanism in particular can modify entire landscapes through ash deposition, affecting the survival and abundance of susceptible species and favouring tolerant ones. However, there is still a lack of information for predicting which species will be more or less affected by volcanic disturbances. We test the hypothesis that the effect of volcanic ash will differentially affect taxa according to their morphological traits. We used a ground‐dwelling beetle community that was sampled before and immediately after the last eruption of the Puyehue‐Cordón Caulle (PCC) volcano. We measure traits that might help predicting responses to the ash deposition in insect species susceptible to the PCC volcanic eruption – i.e., their abundance decreased considerably – and compared them to others that were tolerant. We examined cuticle thickness, its structures (i.e., hairs) and microsculptures, and body size. We found that traits associated with smoothness of the cuticle (fewer hairs and microsculptures) and a small body enables species to better tolerate the negative effects of volcanic ash. These results are the first to explicitly test for traits that could help to predict which species will be more tolerant to volcanic ashes, a widespread disturbance associated with volcanism.
... Possibly as a consequence of being affected by a higher ash accumulation immediately after the eruption, forest beetle composition changed after the eruption showing different post-eruption indicator species. The density of hairs and microsculptures in the cuticle and body size of species had been associated with the susceptibility of mountain epigaeic beetle species to the negative effects of ash accumulation after the PCCVC eruption (Elizalde et al., 2023). In particular, within the genus Chiliopelates from the family Leoididae, a susceptible species to ash accumulation that was absent from post-eruption assemblages (Chiliopelates ventricosus) has higher microsculpture density in its cuticle compared with a tolerant species within the same genus (Elizalde et al., 2023). ...
... The density of hairs and microsculptures in the cuticle and body size of species had been associated with the susceptibility of mountain epigaeic beetle species to the negative effects of ash accumulation after the PCCVC eruption (Elizalde et al., 2023). In particular, within the genus Chiliopelates from the family Leoididae, a susceptible species to ash accumulation that was absent from post-eruption assemblages (Chiliopelates ventricosus) has higher microsculpture density in its cuticle compared with a tolerant species within the same genus (Elizalde et al., 2023). On the other hand, Leiodidae are saproxylic organisms, that is, they depend on dead or dying wood of moribunds or dead trees during some part of their life cycle. ...
Monitoring changes in species composition near active volcanoes is important to identify environmental factors that maintain biological diversity after major disturbances. We investigated the taxonomic composition of epigaeic beetles' assemblages in five mountains in north‐western Patagonia (Argentina) in the aftermath of the 2011 Puyehue Cordón‐Caulle Volcanic Complex eruption.
The associations of beetle composition with the thermal environment, vegetation structure and soil characteristics were analysed using 10 m × 10 m plots with nine pitfall traps each, established 100 m apart in altitude on each mountain in 2005, 2006 (pre‐eruption) and 2012, 2015 and 2016 (post‐eruption).
We found significant differences in beetle composition between forests and high‐Andean steppes before and after the eruption. The beetle composition of forests and high‐Andean steppes differed due to higher plant cover and lower pH and herb richness in forests. Six months after the eruption, the herbs almost disappeared and forests showed high ash accumulation and lower temperature than the high‐Andean steppes. In the medium term, plant cover, temperature and soil conditions—but not ash accumulation—remained as important correlates of beetle composition. Before the eruption, forest assemblages showed higher beetle diversity and Leiodidae indicator species, but Curculionidae predominated post‐eruption. Tenebrionidae and Carabidae were high Andean steppes indicators. Post‐eruption, the beetle composition in high‐Andean steppes did not change significantly except for an increase in Tenebrionidae indicator species.
We concluded that the conservation of landscape diversity and environmental gradients maintaining the differentiation between ecoregions is essential to protect epigaeic beetle composition and for species survival after volcanic disturbances.
The trait-based approach to ecology promises greater generality in our understanding of how species assemblages are structured. The value of this approach depends on linking traits with ecological functions, but no studies have tested the proposed functional values of many commonly used and easily measured traits. We used a cross-species comparison to investigate the function of the cuticular traits “pilosity” and “sculpturing” in ants. These traits have been linked to a range of environmental variables through a correlative approach, but the mechanisms underlying these associations are poorly understood. Here, we tested the association among these traits and with a suite of physiological traits (heat tolerance, desiccation tolerance, hydrophobicity and protection from physical forces). Further, we tested whether physiological traits differed between species that were active at day or night or ants from semi-arid and mesic environments. Many cuticlerelated traits were inter-correlated and not independent of other morphological traits, suggesting that it is appropriate to consider ant responses as an “ecological strategy”. Although within-assemblage variation was high, night-active and mesic ants had lower heat tolerance than day-active and semi-arid ants, reflecting similar differences in environmental exposure. Pilosity was associated with both heat and desiccation tolerance. Sculpturing was strongly linked to cuticle thickness and hardness and desiccation tolerance. However, it was negatively associated with heat tolerance, possibly because many highly sculptured ants were nocturnal in this study. This work provides strong support for the continued use of easily measured cuticle traits. However, empirical investigations of trait function across a broader range of ecosystems are critical to ensure that the ecological importance of trait-environment relationships and their inter-relatedness as components of an “ecological strategy” are better understood.
Open access, licensed under CC BY 4.0. © 2021 The Author(s).
Los organismos que sobreviven a una erupción volcánica son parte fundamental del legado biológico determinante de la subsecuente sucesión y desarrollo del ecosistema. En enero 2012, en el verano inmediato a la erupción del complejo volcánico Puyehue-Cordón Caulle, evaluamos la respuesta a corto plazo de la abundancia de coleópteros epigeos al depósito de ceniza. Estudiamos tres montañas (La Mona, Bayo, Challhuaco) en el noroeste de la Patagonia (Argentina), afectadas diferencialmente por el depósito de ceniza. Re-establecimos 32 sitios de muestreo con nueve trampas de caída distribuidas en 100 m2, ubicados cada 100 m de altitud desde la base a la cima de cada montaña, y muestreados previamente (enero 2005, 2006). Comparamos la forma pre- y post- eruptiva de la relación abundancia-elevación (AER). Determinamos la importancia relativa de predictores ambientales de AER (energía ambiental, cobertura de la vegetación, riqueza de especies de plantas, y atributos de suelo) pre- y post- erupción. La Mona y Bayo fueron más afectados por el depósito de ceniza; Challhuaco fue menos afectado. Los niveles de abundancia fluctuaron significativamente en Bayo, se mantuvieron constantes en La Mona y aumentaron levemente en Challhuaco. Luego de la erupción, la forma de AER cambió significativamente en Bayo, se apartó débilmente de la tendencia promedio en La Mona, y no cambió en Challhuaco. El porcentaje de gravas y la cobertura del dosel arbóreo fueron los predictores más importantes de AER pre-eruptivo; solamente la cobertura del dosel arbóreo permaneció como importante luego de la erupción. Los efectos a corto plazo del depósito de ceniza sobre la abundancia de coleópteros epigeos fueron sutiles y sugieren que la presencia de un gradiente en el depósito de ceniza puede conducir a patrones asociados en los legados biológicos. Un monitoreo a largo plazo será indispensable para comprender la recuperación estructural y funcional de estos ecosistemas montanos.
Las erupciones volcánicas son disturbios naturales que imponen múltiples cambios en los ecosistemas. Los artrópodos se ubican entre los organismos más diversos del planeta y desempeñan un papel clave en el funcionamiento de los ecosistemas. Sin embargo, la información existente sobre los efectos de los disturbios volcánicos sobre ellos es dispersa. El objetivo de esta revisión es identificar generalidades en las respuestas de los artrópodos al vulcanismo. Principalmente, (1) ¿qué efecto tienen las erupciones volcánicas sobre los artrópodos?, (2) ¿qué características hacen que ciertas especies sean más resistentes al vulcanismo?, (3) ¿cómo se ensamblan sus comunidades después de una erupción? Los artrópodos terrestres y acuáticos muestran respuestas similares al vulcanismo, que afecta a sus poblaciones y comunidades, y los ecosistemas a través de las funciones que los artrópodos realizan. La mayoría de los estudios que evaluaron el efecto de la ceniza volcánica encontraron efectos negativos sobre la mortalidad y diferente susceptibilidad entre especies. La mortalidad en una misma especie varía según la cantidad de ceniza y la forma de exposición (contacto con el cuerpo, alimentos contaminados, modificación del hábitat), y la humedad relativa. En las pocas comunidades de artrópodos donde se estudiaron los efectos de las erupciones volcánicas, la riqueza, composición y abundancia de las especies son afectadas de alguna forma. Identifiqué rasgos morfológicos, fisiológicos, comportamentales y de historia de vida que parecen importantes para determinar respuestas de las especies al vulcanismo. Sin embargo, los conocimientos actuales son limitados y acotados a pocas erupciones volcánicas. Los estudios de eventos volcánicos pueden proporcionar una validación a escala del ecosistema de las predicciones sobre cómo el cambio climático y los cambios inducidos por el hombre, como una mayor concentración de partículas en suspensión o de emisión de gases al ambiente, pueden afectar a las comunidades de artrópodos.
Las perturbaciones naturales constituyen componentes fundamentales en la dinámica de los ecosistemas. Aquellas de gran escala, como las ocasionadas por huracanes y volcanes, han sido poco estudiadas debido a su baja frecuencia, la ausencia de información de base por su baja predictibilidad, la imposibilidad de replicación y la dificultad de realizar estudios a largo plazo que evalúen la recuperación de los ecosistemas. La reciente erupción del complejo volcánico Puyehue-Cordón Caulle (junio 2011) cuya lluvia de cenizas cubrió 24 millones de hectáreas de la Patagonia, brinda una oportunidad única para estudiar este tipo de perturbación con información de base. El verano previo a la erupción se caracterizaron las comunidades de hormigas en áreas de la estepa patagónica posteriormente cubiertas por 4 cm de cenizas finas. El objetivo de este estudio es establecer si la deposición de cenizas afectó la abundancia, riqueza y composición de hormigas. Durante los veranos 2012 y 2013 se repitió el muestreo y los datos fueron comparados entre años. La abundancia tendió a ser menor después de la erupción, pero la riqueza y composición de hormigas fueron similares antes y dos temporadas posteriores a la erupción. El escaso efecto se debe principalmente al momento de la erupción, a que las hormigas son insectos sociales y al espesor de la capa de cenizas. La erupción ocurrió a fines de otoño cuando la actividad de las hormigas es reducida por las bajas temperaturas. Aun habiendo existido mortalidad de obreras durante la deposición, éstas representarían un bajo porcentaje de la colonia, garantizando su supervivencia. Solo cuatro de 13 especies cambiaron su incidencia, tres de ellas recién en la segunda temporada. Este retardo en la respuesta podría estar mediado por cambios en los recursos y el ambiente. No se descartan posibles efectos a largo plazo en las otras especies.
We describe a new genus and new species of pselaphine rove beetle, Batriscydmaenus tishechkini Parker and Owens, from lowland Panamanian rainforest. The new taxon marks a radical departure from the basic pselaphine anatomical groundplan, with a globose body shape and a dramatic reduction of foveae, sulci and striae—features that are considered plesiomorphic in Pselaphinae. This overt simplification of the integument is typical of myrmecophile and termitophile taxa within Pselaphinae. A probable symbiotic lifestyle of members of Batriscydmaenus is further implied by their compact antennae and the presence of suberect, spatulate setae covering the dorsum. The convergent evolution of this trend towards character loss in inquilinous pselaphines implies a “reductive” ecomorph, specialized for living inside social insect societies in part by abandoning many cuticular features of free-living pselaphines. Batriscydmaenus represents possibly the most extreme manifestation of this ecomorph known to date. Reductive anatomy poses a challenge to taxonomic assignment, but we confirm molecularly that the genus belongs to the tribe Batrisini, using gene fragments amplified from a paratype.
The insect exoskeleton is a multifunctional coat with a continuum of mechanical and structural properties constituting the barrier between electromagnetic waves and the internal body parts. This paper examines the ability of beetle exoskeleton to regulate internal body temperature considering its thermal permeability or isolation to simulated solar irradiance and infrared radiation. Seven Neotropical species of dung beetles (Coleoptera, Scarabaeinae) differing in colour, surface sculptures, size, sexual dimorphism, period of activity, guild category and altitudinal distribution were studied. Specimens were repeatedly subjected to heating trials under simulated solar irradiance and infrared radiation using a halogen neodymium bulb light with a balanced daylight spectrum and a ceramic infrared heat emitter. The volume of exoskeleton and its weight per volume unit were significantly more important for the heating rate at the beginning of the heating process than for the asymptotic maximum temperature reached at the end of the trials: larger beetles with relatively thicker exoskeletons heated more slowly. The source of radiation greatly influences the asymptotic temperature reached, but has a negligible effect in determining the rate of heat gain by beetles: they reached higher temperatures under artificial sunlight than under infrared radiation. Interspecific differences were negligible in the heating rate but had a large magnitude effect on the asymptotic temperature, only detectable under simulated sun irradiance. The fact that sun irradiance is differentially absorbed dorsally and transformed into heat among species opens the possibility that differences in dorsal exoskeleton would facilitate the heat gain under restrictive environmental temperatures below the preferred ones. The findings provided by this study support the important role played by the exoskeleton in the heating process of beetles, a cuticle able to act passively in the thermal control of body temperature without implying energetic costs and metabolic changes.
Extreme events can be a major driver of evolutionary change over geological and contemporary timescales. Outstanding examples are evolutionary diversification following mass extinctions caused by extreme volcanism or asteroid impact. The evolution of organisms in contemporary time is typically viewed as a gradual and incremental process that results from genetic change, environmental perturbation or both. However, contemporary environments occasionally experience strong perturbations such as heat waves, floods, hurricanes, droughts and pest outbreaks. These extreme events set up strong selection pressures on organisms, and are small-scale analogues of the dramatic changes documented in the fossil record. Because extreme events are rare, almost by definition, they are difficult to study. So far most attention has been given to their ecological rather than to their evolutionary consequences. We review several case studies of contemporary evolution in response to two types of extreme environmental perturbations, episodic (pulse) or prolonged (press). Evolution is most likely to occur when extreme events alter community composition. We encourage investigators to be prepared for evolutionary change in response to rare events during long-term field studies.
This article is part of the themed issue ‘Behavioural, ecological and evolutionary responses to extreme climatic events’.
Long-chain cuticular hydrocarbons (CHCs) are common components of the epicuticle of terrestrial arthropods. CHC serve as a protective barrier against environmental influences but also act as semiochemicals in animal communication. Regarding the latter aspect, species- or intra-functional group specific CHCs composition and variation are relatively well studied. However, comparative knowledge about the relationship of CHC quantity and their relation to surface area—volume ratios in the context of water loss and protection is fragmentary. Hence, we aim to study the taxon-specific relationship of the CHC amount and surface-area to volume ratio related to their functional role (e.g. in water loss). We focused on flower visiting insects and analyzed the CHC amounts of three insect orders (Hymenoptera, Lepidoptera and Diptera) using gas chromatography—mass spectrometry (GC-MS). We included 113 species from two grassland plots, quantified their CHCs, and measured their body mass and surface area. We found differences in the surface area, CHCs per body mass and the CHC density (= amount of CHCs per surface area) across the three insect taxa. Especially the Hymenoptera had a higher CHC density compared to Diptera and Lepidoptera. CHC density could be explained by surface area-volume ratios in Hymenoptera but not in Diptera and Lepidoptera. Unexpectedly, CHC density decreased with increasing surface area—volume ratios.
Coleoptera (beetles) is a massively successful order of insects, distinguished by their evolutionarily modified forewings called elytra. These structures are often presumed to have been a major driving force for the successful radiation of this taxon, by providing beetles with protection against a variety of harsh environmental factors. However, few studies have directly demonstrated the functional significance of the elytra against diverse environmental challenges. Here, we sought to empirically test the function of the elytra using Tribolium castaneum (the red flour beetle) as a model. We tested four categories of stress on the beetles: physical damage to hindwings, predation, desiccation, and cold shock. We found that, in all categories, the presence of elytra conferred a significant advantage compared to those beetles with their elytra experimentally removed. This work provides compelling quantitative evidence supporting the importance of beetle forewings in tolerating a variety of environmental stresses, and gives insight into how the evolution of elytra have facilitated the remarkable success of beetle radiation.
The ground beetle genus Ceroglossus contains co-distributed species that show pronounced intraspecific diversity in the form of geographical colour morphs. While colour morphs among different species appear to match in some geographical regions, in others, there is little apparent colour matching. Mimicry is a potential explanation for covariation in colour patterns, but it is not clear whether the degree of sympatric colour matching is higher than expected by chance given the obvious mismatches among morphs in some regions. Here, we used reflectance spectrometry to quantify elytral coloration from the perspective of an avian predator to test whether colour similarity between species is, indeed, higher in sympatry. After finding no significant phylogenetic signal in the colour data, analyses showed strong statistical support for sympatric colour similarity between species despite the apparent lack of colour matching in some areas. We hypothesize Müllerian mimicry as the responsible mechanism for sympatric colour similarity in Ceroglossus and discuss potential explanations and future directions to elucidate why mimicry has not developed similar levels of interspecific colour resemblance across space.
Body mass, volume and surface area are important for many aspects of the physiology and performance of species. Whereas body mass scaling received a lot of attention in the literature, surface areas of animals have not been measured explicitly in this context. We quantified surface area - volume (SA/V) ratios for the first time using 3D surface models based on a structured light scanning method for 126 species of pollinating insects from four orders (Diptera, Hymenoptera, Lepidoptera and Coleoptera). Water loss of 67 species was measured gravimetrically at very dry conditions for two hours at 15° and 30°C to demonstrate the applicability of the new 3D surface measurements and relevance for predicting the performance of insects. Quantified SA/V ratios significantly explained the variation in water loss across species, both directly or after accounting for isometric scaling (residuals of the SA/V ∼ mass(2/3) relationship). Small insects with a proportionally larger surface area had the highest water loss rates. Surface scans of insects to quantify allometric SA/V ratios thus provide a promising method to predict physiological responses, improving the potential of body mass isometry alone that assume geometric similarity. This article is protected by copyright. All rights reserved.
Se examina el efecto insecticida de las cenizas volcánicas en general y sus efectos ambientales, con especial énfasis en las cenizas acumuladas como consecuencia de la erupción del complejo volcánico Puyehue-Cordón Caulle, que actualmente afecta un área de más de 7,5 millones de hectáreas en la Patagonia Argentina. Se determinó la composición química de las cenizas provenientes del complejo Puyehue- Cordón Caulle por EDS, y se comprobó que los componentes mayoritarios son el O, Si, Al, Fe, Na y K. A través de bioensayos de laboratorio, utilizando dos especies de insectos como modelo biológico, se determinó que las cenizas se adhieren profusamente a la superficie corporal y resultan tóxicas para ambas especies cuando se mezclan con el sustrato en baja concentración. La susceptibilidad a las cenizas difirió entre ambas especies en bioensayos de siete días de exposición continua [CL99(Oryzaephilus surinamensis L.) = 10.25 mg.g-1; CL99((Tribolium castaneum (Herbst)) = 4.96 mg.g-1]. De estos resultados, se desprende que el impacto de la ceniza del complejo Puyehue- Cordón Caulle sobre la comunidad de artrópodos puede ser radical en la fase aguda de la deposición, y que sus efectos podrían ser substancialmente cualitativos en la fase crónica de la exposición. Así también, la recuperación de las poblaciones afectadas por la ceniza en las zonas con clima desértico, donde persiste la ceniza seca, será más lenta, hecho que tendrá consecuencias tangibles a largo plazo para las plantas hospederas de insectos, para la polinización y sobre el desarrollo de las poblaciones de vertebrados insectívoros. En contraste, en las regiones húmedas, la presencia de cenizas representa un cambio manifiesto en el ecosistema debido al aporte de nutrientes, que en combinación con la retención de agua por las cenizas, llevará a la recuperación cuali y cuantitativa de las poblaciones bajo condiciones favorables.
This paper presents a new and simple method to find indicator species and species assemblages characterizing groups of sites. The novelty of our approach lies in the way we combine a species relative abundance with its relative frequency of occurrence in the various groups of sites. This index is maximum when all individuals of a species are found in a single group of sites and when the species occurs in all sites of that group; it is a symmetric indicator. The statistical significance of the species indicator values is evaluated using a randomization procedure. Contrary to TWINSPAN, our indicator index for a given species is independent of the other species relative abundances, and there is no need to use pseudospecies. The new method identifies indicator species for typologies of species releves obtained by any hierarchical or nonhierarchical classification procedure; its use is independent of the classification method. Because indicator species give ecological meaning to groups of sites, this method provides criteria to compare typologies, to identify where to stop dividing clusters into subsets, and to point out the main levels in a hierarchical classification of sites. Species can be grouped on the basis of their indicator values for each clustering level, the heterogeneous nature of species assemblages observed in any one site being well preserved. Such assemblages are usually a mixture of eurytopic (higher level) and stenotopic species (characteristic of lower level clusters). The species assemblage approach demonstrates the importance of the 'sampled patch size,' i.e., the diversity of sampled ecological combinations, when we compare the frequencies of core and Satellite species. A new way to present species-site tables, accounting for the hierarchical relationships among species, is proposed. A large data set of carabid beetle distributions in open habitats of Belgium is used as a case study to illustrate the new method.
The aim of this work was to evaluate the toxicity of volcanic ash from the volcanic complex Puyehue-Caulle Range on the grasshopper, Dichroplus vittigerum, and compare the results with the effect of diatomaceous earth, an organic pesticide. To test this, we carried out 2 experiments: (i) an acute toxicity test, which consisted of exposing adults of D. vittigerum differentially to volcanic ash and diatomaceous earth, and (ii) a study to determine the survival time of the adult stage by separately exposing the insects to diatomaceous earth and volcanic ash, and by simulating with fans the wind gusts that occur naturally in the area of influence of the volcano. The laboratory data showed that constant exposure to volcanic ash and diatomaceous earth induces mortality in adult grasshoppers. Interestingly, the toxicities of the 2 products were very similar. These results suggest that the onset of the volcanic eruption with the consequent suspension of the pyroclastic material in the air may have had a negative impact on D. vittigerum populations through the mortality of individual adults. In summary, volcanic ash has an insecticidal effect similar to that of diatomaceous earth.
1. New logical and analytical frameworks for studying functional traits have led to major advances in plant and freshwater ecology at local and global scales. The ecological and taxonomic diversity of terrestrial adult beetles ( C oleoptera) means that functional trait approaches should have considerable power to illuminate the function not only of these animals but also of the ecosystems in which they occur.
2. Even though the functional trait concept is not new in ecology, it is still plagued with inconsistencies in methodology and terminology. Plant‐based studies have shown that an integrated and relatively consistent functional trait approach facilitates comparisons between studies, and allows the full utility and predictive capacity of trait‐based approaches to be realised.
3. This review outlines a logical framework for adult beetle functional trait studies using uniform terminology and methodology similar to those used by plant ecologists. Beetle life‐history and ecomorphological trait studies are synthesised and it is shown that a combination of both is analogous to the functional trait approach. A general functional trait list for beetles and potential functional links is outlined, as are potential analysis approaches. A consistent functional trait approach, coupled with advances in molecular techniques, has the capability to provide deeper insights into beetle community assembly and how beetles impact ecosystems and will enable worldwide comparisons and predictions to be made.
Volcanic eruptions are natural disturbances that impose multiple changes in ecosystems. Arthropods
are among the most diverse organisms on the planet and play key functional roles in all ecosystems. Existing information on the effects of volcanic disturbances on arthropods is scattered. The aim of this review is to find generalities in the responses of arthropods from terrestrial and aquatic environments to volcanism. Mainly (1) what effects do volcanic disturbances have on arthropods?, (2) what characteristics make certain species more or less susceptible to volcanic disturbances?, and (3) how do arthropod communities reassemble after a volcanic disturbance? Terrestrial and aquatic arthropods show similar responses to volcanic disturbances. Volcanism can affect arthropod populations, communities, and ecosystems through the functions that arthropods perform. Most studies evaluated the effect of volcanic ash as the primary volcanic disturbance type and found that most species have higher mortality than controls, but species show different susceptibility to volcanism. However, mortality of a certain species varies by the amount of ash, how the species was exposed to ash (i.e. body contact, contaminated food, modification of the habitat), and relative humidity. In the few arthropod communities studied, richness, composition and abundance of species are affected to some degree by volcanic eruptions. I gathered information on a number of morphological, physiological, behavioral and life-history traits that seem important to determine species responses to volcanic disturbance. However, current knowledge of arthropod responses to volcanism is limited, and limited to few volcanic eruptions. More broadly, studies of volcanic events may provide ecosystem-scale insights on how climate change and human-induced changes, such as higher concentration of particles in suspension or gas emission to the environment, might affect arthropod communities.
Volcanic eruptions have important effects on terrestrial ecosystems. The biotic effects of volcanic ash on insect populations vary from widespread and catastrophic to subtle and localized. Volcanic eruptions may increase insect mortality through the effects of the ash plume, and these vary by taxon or specific biological features. The Puyehue–Cordon Caulle Volcanic Complex is the most recent eruption in Patagonia. Here we explore and describe the effects of the eruption of this volcanic complex on invasive Vespula spp. populations. These wasps are very abundant social hymenoptera that have recently invaded Patagonia. We placed baited traps following the gradient of deposited ash, and revisited them once a week during February to April. No wasps were caught where ash deposition levels exceeded 3.0 cm. The number of wasps caught in sites with minimal ash deposits was similar to that of previous years. In locations where ash layers are intermediate, a few wasps were observed, but only during the peak of wasp abundance. We show that Vespula spp. populations were severely affected by the ash deposition and plume, caused by this eruption. These results show catastrophic effects of ash deposition over a large area, even at great distances from the eruption epicenter. We conclude that wasp mortality explained by the volcanic eruption may reach distant areas, and cause local extinction. In areas where active volcanoes are common, invasive insects may encounter an additional obstacle in their invasion success.
We studied the vegetation of Kasatochi Island, central Aleutian Islands, to provide a general field assessment regarding the survival of plants, lichens, and fungi following a destructive volcanic eruption that occurred in 2008. Plant community data were analyzed using multivariate methods to explore the relationship between pre- and post-eruption plant cover; 5 major vegetation types were identified: Honckenya peploides beach, Festuca rubra cliff shelf, Lupinus nootkatensis Festuca rubra meadow, Leymus mollis bluff ridge (and beach), and Aleuria aurantia lower slope barrens. Our study provided a very unusual glimpse into the early stages of plant primary succession on a remote island where most or the vegetation was destroyed. Plants that apparently survived the eruption dominated early plant communities. Not surprisingly, the most diverse post-eruption community most closely resembled a widespread pre-eruption type. Microhabitats where early plant communities were found were distinct and apparently crucial in determining plant survival. Comparison with volcanic events in related boreal regions indicated some post-eruption pattern similarities.
The indicator value (IndVal) of a species has long been the most popular measure to express species importance in community classifications. Nevertheless, a few problems concerning the original definition of IndVal still require clarification and some modifications are also in order so as to exploit the capabilities of the method more fully. In particular, we propose novel component terms (specificity, concentration and fidelity) that may be incorporated in the calculation of IndVal and also suggest some minor, although important terminological amendments. We argue that the choice among these terms should largely depend on whether the target classification is based on abundance or presence–absence data. The expanded capabilities of the approach and the sensitivity of IndVal variants to the sharpness of classifications are illustrated by actual examples coming from a benthic macroinvertebrate survey along the Danube River and a study of dolomite grassland communities in the Buda Hills, Hungary. We found that analyses by the original IndVal plus the new variants may give a more complete picture on any classification than a particular selection among component terms of IndVal. The use of several indices simultaneously is particularly recommended when selection of indicator species is the primary objective of the study.
This paper reviews the history of ecological studies after major volcanic eruptions, from Krakatau to Mount St. Helens. The impacts of lava, pyroclastic flows, lahars and tephra are highlighted, and both mechanisms and rates of recovery are analyzed. Volcanoes occur in all climates and geographic settings, so they provide unusually diverse settings useful to compare how volcanism affects successional processes. In addition to climate, especially the length of the growing season, succession is affected primarily by impact scale, its frequency, severity of an event and the characteristics of the resulting substrates, e.g. the degree of fertility. Typically, lavas develop most slowly, while tephra surfaces allow rapid recovery. Volcanic effects on vegetation may persist. Frequent eruptions may depress timberlines, reduce diversity and support unusual floras. Recovery requires physical and biological site amelioration, dispersal and, often, regeneration of survivors, followed by a complex array of biotic interactions that include facilitation, competition and herbivory. Understanding the recovery of volcanic landscapes has provided deeper understanding of ecological processes and provided valuable insight into restoration of analogous habitats such as mine tailings.
Theory suggests that species with particular traits are at greater risk of extinction than others. We assumed that a decline in abundance in forest fragments, com- pared to continuous forest, equated to an increase in extinction risk. We then tested the relationships between five traits of species and decline in abundance for 69 beetle species in an experimentally fragmented forest landscape at Mt. Wog Wog in southeastern Australia. The experiment was controlled and replicated. Monitoring ran for two years before forest fragmentation; in this paper, we examine data for five years postfragmentation. We tested five hypotheses: (1) Species that occur naturally at low abundance are more likely to decline as a result of fragmentation than are abundant species. (2) Isolated species are more likely to decline than species that are not isolated. (3) Large species are more likely to decline than small species. (4) Species in trophic groups at the top end of food chains are more likely to decline than species in trophic groups lower in the food chain. (5) Because traits are often shared by related species, populations of more closely related species will respond in the same way. We found that: (1) rare species were more likely to decline than abundant species; (2) isolated species were more likely to decline than species that were not isolated; (3) body size was not correlated with response to fragmentation; (4) among species that declined, predators declined most; and (5) taxonomically related species did not respond in the same way to fragmentation. Thus, our results confirm theories predicting that isolated, rare, or predaceous species will be lost first from fragmented landscapes.
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We reviewed empirical data and hypotheses derived from demographic, optimal foraging, life-history, community, and biogeographic theory for predicting the sensitivity of species to habitat fragmentation. We found 12 traits or trait groups that have been suggested as predictors of species sensitivity: population size; population fluctuation and storage effect; dispersal power; reproductive potential; annual survival; sociality; body size; trophic position; ecological specialisation, microhabitat and matrix use; disturbance and competition sensitive traits; rarity; and biogeographic position. For each trait we discuss the theoretical justification for its sensitivity to fragmentation and empirical evidence for and against the suitability of the trait as a predictor of fragmentation sensitivity. Where relevant, we also discuss experimental design problems for testing the underlying hypotheses. There is good empirical support for 6 of the 12 traits as sensitivity predictors: population size; population fluctuation and storage effects; traits associated with competitive ability and disturbance sensitivity in plants; microhabitat specialisation and matrix use; rarity in the form of low abundance within a habitat; and relative biogeographic position. Few clear patterns emerge for the remaining traits from empirical studies if examined in isolation. Consequently, interactions of species traits and environmental conditions must be considered if we want to be able to predict species sensitivity to fragmentation. We develop a classification of fragmentation sensitivity based on specific trait combinations and discuss the implications of the results for ecological theory.
This paper presents a new and simple method to find indicator species and species assemblages characterizing groups of sites. The novelty of our approach lies in the way we combine a species relative abundance with its relative frequency of occurrence in the various groups of sites. This index is maximum when all individuals of a species are found in a single group of sites and when the species occurs in all sites of that group; it is a symmetric indicator. The statistical significance of the species indicator values is evaluated using a randomization procedure. Contrary to TWINSPAN, our indicator index for a given species is independent of the other species relative abundances, and there is no need to use pseudospecies. The new method identifies indicator species for typologies of species releves obtained by any hierarchical or nonhierarchical classification procedure; its use is independent of the classification method. Because indicator species give ecological meaning to groups of sites, this method provides criteria to compare typologies, to identify where to stop dividing clusters into subsets, and to point out the main levels in a hierarchical classification of sites. Species can be grouped on the basis of their indicator values for each clustering level, the heterogeneous nature of species assemblages observed in any one site being well preserved. Such assemblages are usually a mixture of eurytopic (higher level) and stenotopic species (characteristic of lower level clusters). The species assemblage approach demonstrates the importance of the "sampled patch size," i.e., the diversity of sampled ecological combinations, when we compare the frequencies of core and satellite species. A new way to present species-site tables, accounting for the hierarchical relationships among species, is proposed. A large data set of carabid beetle distributions in open habitats of Belgium is used as a case study to illustrate the new method.
Monitoring changes in species composition near active volcanoes is important to identify environmental factors that maintain biological diversity after major disturbances. We investigated the taxonomic composition of epigaeic beetles' assemblages in five mountains in north‐western Patagonia (Argentina) in the aftermath of the 2011 Puyehue Cordón‐Caulle Volcanic Complex eruption.
The associations of beetle composition with the thermal environment, vegetation structure and soil characteristics were analysed using 10 m × 10 m plots with nine pitfall traps each, established 100 m apart in altitude on each mountain in 2005, 2006 (pre‐eruption) and 2012, 2015 and 2016 (post‐eruption).
We found significant differences in beetle composition between forests and high‐Andean steppes before and after the eruption. The beetle composition of forests and high‐Andean steppes differed due to higher plant cover and lower pH and herb richness in forests. Six months after the eruption, the herbs almost disappeared and forests showed high ash accumulation and lower temperature than the high‐Andean steppes. In the medium term, plant cover, temperature and soil conditions—but not ash accumulation—remained as important correlates of beetle composition. Before the eruption, forest assemblages showed higher beetle diversity and Leiodidae indicator species, but Curculionidae predominated post‐eruption. Tenebrionidae and Carabidae were high Andean steppes indicators. Post‐eruption, the beetle composition in high‐Andean steppes did not change significantly except for an increase in Tenebrionidae indicator species.
We concluded that the conservation of landscape diversity and environmental gradients maintaining the differentiation between ecoregions is essential to protect epigaeic beetle composition and for species survival after volcanic disturbances.
Extreme climate events are predicted to increase in the future, which will have significant effects on insect biodiversity. Research into this area has been rapidly expanding, but knowledge gaps still exist. We conducted a review of the literature to provide a synthesis of extreme climate events on insects and identify future areas of research. In our review, we asked the following questions: 1) What are the direct and indirect mechanisms that extreme climate events affect individual insects? 2) What are the effects of extreme climate events on insect populations and demography? 3) What are the implications of the extreme climate events effects on insect communities? Drought was among the most frequently described type of extreme climate event affecting insects, as well as the effects of temperature extremes and extreme temperature variation. Our review explores the factors that determine the sensitivity or resilience to climate extremes for individuals, populations, and communities. We also identify areas of future research to better understand the role of extreme climate events on insects including effects on non-trophic interactions, alteration of population dynamics, and mediation of the functional the trait set of communities. Many insect species are under threat from global change and extreme climate events are a contributing factor. Biologists and policy makers should consider the role of extreme events in their work to mitigate the loss of biodiversity and delivery of ecosystem services by insects.
Volcanic eruptions often modify the structure and function of ecosystems at large geographical scales. However, the extent to which species diversity patterns respond to these major natural disturbances is still poorly known. We tested the shape of the species richness – elevation relationship (SRER) and its environmental correlates (thermal environment at ground level, vegetation structure and soil attributes) before and 6 months after (in the first summer) the most recent eruption of the Puyehue Cordon Caulle volcanic complex (PCCVC), which caused an extensive ash accumulation in northwestern Patagonia, Argentina.
We re‐established 32, 100‐m ² sampling plots of nine pitfall traps, placed every 100 m of altitude from the base to the summit of three mountains differentially affected by ash deposition, and from which we had pre‐eruption data on richness and environmental variables.
Coverage‐based rarefaction/extrapolation curves showed a local post‐eruptive decrease in richness on only one mountain. Generalised additive models (GAMs) showed no significant differences between pre‐ and post‐eruptive SRER shapes. Partial least squares structural equation modelling (PLS‐SEM) showed that woody vegetation and the thermal environment accounted for most of the variation in richness before and after the eruption. Soil attributes were only indirectly associated with beetle richness and the association was mediated by woody vegetation. Ash accumulation ameliorated the thermal environment, promoting a local increase in beetle richness.
The rapid recovery of the SRER shape and its environmental correlates suggest that the structuring of local diversity patterns at temperate latitudes of the southern hemisphere is resilient to major volcanic eruptions.
Ecosystem restoration can play a vital role in conserving biodiversity, but its effectiveness can be difficult to assess for hyperdiverse biota such as insects. Species traits of insects can be used to understand their functional responses to restoration, but their use often requires considerable effort, and few studies have examined what additional insight can be gained from this approach. We used a spatially and temporally controlled restoration experiment to examine beetle species, grouped by flight ability, family membership and feeding guild, as indicators of ecosystem functional change. We tested for the effects of reduced vertebrate grazing on beetle assemblages sampled from two different microhabitats (next to log and in open ground) one year prior and two years after a vertebrate grazing treatment was applied. We compared the responses of the different beetle functional groupings, and then related these to the effort involved in employing these indicators. We found that beetle species traits gave several functional insights into their responses to reduced grazing, including responses to changes in vegetation structure and biomass. Species richness indicators and abundance indicators of beetle functional groups showed similar responses in many cases, whereas biomass indicators gave additional insights related to the extra biomass of vegetation and detritus resulting from the reduction in grazing. We found that most results were revealed by using family groups as indicators for functional change. This is because the traits that often define beetle families, such as size, flight ability and feeding guilds each have distinctive functional roles, allowing a link from family to function, and supporting the idea that phylogeny is often a useful shortcut to species ecology. We conclude that in our study system, the least-cost approach to identifying functional responses of beetles to reduced vertebrate grazing, and possibly other restoration actions, is to use abundance indicators of the most common family groups.
Intense use of insecticides has resulted in the selection of extreme levels of resistance in insect populations. Therefore understanding the molecular basis of insecticide resistance mechanisms becomes critical. Penetration resistance refers to modifications in the cuticle that will eventually slow down the penetration of insecticide molecules within insects’ body. So far, two mechanisms of penetration resistance have been described, the cuticle thickening and the altering of cuticle composition. Cuticular modifications are attributed to the over-expression of diversified genes or proteins, which belong to structural components (cuticular proteins mainly), enzymes that catalyze enzymatic reactions (CYP4G16 and laccase 2) or ABC transporters that promote cuticular translocation. In the present review we summarize recent studies and discuss future perspectives.
I Development in the Egg.- References.- II The Integument.- Properties of the cuticle.- Formation and shedding of the cuticle.- References.- III Growth.- Moulting.- Metamorphosis.- Determination of characters during post-embryonic development.- Regeneration.- Diapause.- References.- IV Muscular System and Locomotion.- Anatomy and histology.- Physiological properties of insect muscles.- Locomotion.- References.- V Nervous and Endocrine Systems.- Nervous system.- Visceral nervous system.- Endocrine system.- References.- VI Sense Organs: Vision.- Compound eye.- Simple eyes.- References.- VII Sense Organs: Mechanical and Chemical Senses.- Mechanical senses.- Hearing.- Chemical senses.- Temperature and humidity.- References.- VIII Behaviour.- Kinesis and related phenomena.- Orientation.- Co-ordinated behaviour.- References.- IX Respiration.- Tracheal system.- Development of the tracheal system.- Transport of oxygen to the tracheal endings.- Elimination of carbon dioxide.- Respiration of aquatic insects.- Respiration of endoparasitic insects.- Respiratory function of the blood.- Regulation of respiratory movements.- References.- X The Circulatory System and Associated Tissues.- Circulatory system.- Haemolymph.- Haemocytes.- Pericardial cells and so-called 'nephrocytes'.- Fat body.- Oenocytes.- Light-producing organs.- References.- XI Digestion and Nutrition.- Fore-gut.- Peritrophic membrane.- Mid-gut.- Hind-gut.- Secretions of the alimentary canal.- Digestion of some skeletal and other substances of plants and animals.- The role of lower organisms in digestion.- Nutrition.- References.- XII Excretion.- Urine.- Intermediary nitrogen metabolism.- Malpighian tubes.- Histophysiology of the Malpighian tubes.- Accessory functions of Malpighian tubes.- Malpighian tubes during moulting and metamorphosis.- Cephalic excretory organs and intestinal excretion.- Storage excretion.- References.- XIII Metabolism.- Chemical transformations.- Some chemical products of insects.- Pigment metabolism.- Respiratory metabolism.- References.- XIV Water and Temperature.- Water relations.- Temperature relations.- References.- XV Reproductive System.- Female reproductive system.- Male reproductive system.- Mating, impregnation and fertilization.- Some factors controlling fertility and fecundity.- Special modes of reproduction.- Sex determination.- Transmission of symbiotic micro-organisms.- References.- Index of Authors.- General Index.
Tools for performing model selection and model averaging. Automated model selection through subsetting the maximum model, with optional constraints for model inclusion. Model parameter and prediction averaging based on model weights derived from information criteria (AICc and alike) or custom model weighting schemes.
[Please do not request the full text - it is an R package. The up-to-date manual is available from CRAN].
Large‐scale disturbances can be important components of the temporal landscape of natural ecosystems, but generalities regarding ecosystem impacts are difficult due to their infrequent and unpredictable nature. Volcanic eruptions figure as one of the most prominent of these natural disturbances, but the effects on microbes and ground‐dwelling arthropods, which modulate carbon and nutrient turnover, are relatively unknown.
We evaluated the effects of the 2011 Puyehue‐Cordón Caulle eruption in Patagonia, Argentina, on the litter and soil microbial and faunal communities in natural and afforested semi‐arid ecosystems located 70 km west of the epicentre of the eruption. We hypothesized that volcanic ash deposition would strongly reduce soil faunal and microbial communities due to insecticidal effects of ash on arthropods, with a concomitant reduction in ecosystem processes.
Our objective was to quantify the impact of the volcanic eruption by comparing pre‐ and post‐eruption time points in the same study site, with nearly identical field methodology. We measured environmental variables of soil and litter moisture, pH, microbial biomass, and soil and litter microbial enzymatic activity. We evaluated ground‐dwelling arthropods and nematodes using pitfall traps and soil extraction, respectively. Additionally, a parallel, controlled‐condition experiment of simulated ash deposition was conducted to evaluate ash effects on litter decomposition and enzymatic activity.
In the field, post‐eruption soils had lower soil water content, pH and soil organic matter. Additionally, nematode abundance and soil microbial enzyme activity were significantly reduced. In contrast, ground‐dwelling arthropods and litter enzymatic activity increased significantly. Finally, with simulated ash deposition, litter decomposition increased fourfold for native litter decomposition.
Large‐scale disturbances may play a key role in biogeochemical cycling in affected natural ecosystems, but not necessarily due to their catastrophic effects. In contrast to our original predictions, we observed a marked stimulation of biotic activity and carbon turnover in the aftermath of the Puyehue volcanic eruption, which demonstrates that the biotic component of these ecosystems has a substantial capacity to respond to these disturbances in short time frames. These results can contribute to placing the role of these large‐scale infrequent disturbances in a more robust ecological context.
A Lay Summary is available for this article.
Indicator species are species that are used as ecological indicators of community or habitat types, environmental conditions, or environmental changes. In order to determine indicator species, the characteristic to be predicted is represented in the form of a classifi cation of the sites, which is compared to the patterns of distribution of the species found at the sites. Indicator species analysis should take into account the fact that species have diff erent niche breadths: if a species is related to the conditions prevailing in two or more groups of sites, an indicator species analysis undertaken on individual groups of sites may fail to reveal this association. In this paper, we suggest improving indicator species analysis by considering all possible combinations of groups of sites and selecting the combination for which the species can be best used as indicator. When using a correlation index, such as the point-biserial correlation, the method yields the combination where the diff erence between the observed and expected abundance/frequency of the species is the largest. When an indicator value index (IndVal) is used, the method provides the set of site-groups that best matches the observed distribution pattern of the species. We illustrate the advantages of the method in three diff erent examples. Consideration of combinations of groups of sites provides an extra fl exibility to qualitatively model the habitat preferences of the species of interest. Th e method also allows users to cross multiple classifi cations of the same sites, increasing the amount of information resulting from the analysis. When applied to community types, it allows one to distinguish those species that characterize individual types from those that characterize the relationships between them. Th is distinction is useful to determine the number of types that maximizes the number of indicator species.
Abstract Cuticular microsculpture “cells” were measured on 78 species of UK ground beetles. The data were analyzed to establish whether the type of microsculpture could be linked to ground beetle size (length) or ecological preferences. Larger species tended towards isodiametric patterns, while more of the smaller species showed a transverse or effaced pattern. There was no indication that preferences for dry or moist habitat were linked to microsculpture type, which had been suggested in the literature.
Extreme events can have larger impacts on ecosystems than gradual changes of average conditions. This chapter provides a unified framework that identifies the different dimensions of extreme driver events and extreme ecological response. Extreme ecological responses occur in response to extreme events, trends and regime shifts whenever drivers surpass the system's capacity to absorb changes. Extreme ecological responses often involve structural, compositional and functional changes that often result in slow, hysteretic or irreversible recovery. Incorporating extreme ecological response into ecological theory will require a better integration of approaches and understanding of its causes and consequences.
AimOur aims were: (1) to study the shape of the species richness-elevation and abundance-elevation relationships (SRER and AER, respectively) in epigaeic mountain beetles; and (2) to analyse how richness and abundance of the beetles vary across the full gradient and within the forests and steppes in association with environmental variables representing productivity, thermal limitation, water-energy dynamics, environmental heterogeneity and soil characteristics. LocationFive mountains at temperate latitudes in north-western Patagonia, Argentina. Methods
We collected beetles using 486 pitfall traps arranged in fifty-four 100m(2) grid plots of nine traps, established at intervals of about 100m of elevation from the base to the summit of each mountain. We used multi-model selection and the Akaike information criterion to find the best ecological explanation for species richness and abundance variation. ResultsThe AER was hump-shaped in four mountains and negative in one; the SRER was negative in one case, humped in two cases, and either low-plateau or humped in the remaining two. Across the full gradient, the increase in vegetation cover, mainly associated with the presence of forests, predominately accounted for SRERs and AERs. In the forests, energy variables combined with precipitation, soil attributes and environmental heterogeneity accounted for richness and abundance. In the steppes, potential evapotranspiration and plant productivity were important. Main conclusionsWe confirmed different forms in the shape of SRERs, and the predominance of hump-shaped patterns in AERs. Vegetation type (forests versus steppes) accounted for most of the variation in species richness and abundance on all mountains. Associations with local environmental factors were rather more variable and changed with the spatial extent of analysis, thus confirming the spatial dependence of the species richness/abundance-environment relationships.
1. Altitudinal gradients offer a unique scenario to elucidate how the increase in harsh climatic conditions towards the top of the mountain interacts with other environmental factors at regional and local scale to influence the spatial variation in local species composition and biodiversity maintenance. We analysed the altitudinal variation in the taxonomic composition of epigaeic beetle assemblages across five mountains in north-western Patagonia (Argentina) to address whether substantial change in species composition was associated (i) at regional spatial scale, with changes in vegetation types, and the presence of dry and moist mountains, and (ii) at local spatial scale, with variation in temperature, plant cover and richness and several soil characteristics.
2. We collected beetles using 486 pitfall traps arranged in fifty-four 100-m2 grid plots of nine traps settled at about 100 m of altitude apart from each other, from the base to the summit of each mountain. We used multivariate analyses to identify beetle assemblages and to evaluate their association with environment.
3. We identified different beetle assemblages, associated more with vegetation types rather than with mountains; indicator species showed higher degree of fidelity and specificity to vegetation types rather than to mountains. Local variation in temperature, plant cover and richness, and soil characteristics influence the variation in species composition.
4. Our study suggests the existence of a regional beetle fauna that is shared across these mountains. Major regional changes in vegetation types and local variation in environment drive the variation in the species composition of beetle assemblages at these latitudes.
The Earth’s history is punctuated by large explosive eruptions that eject large quantities of magma and silicate rock fragments into the atmosphere. These tephra particles can sometimes be dispersed across millions of square kilometres or even entire continents. The interaction of tephra with or in receiving environments may induce an array of physical, chemical and biological effects. The consequences for affected systems and any dependent communities may be chronic and localised in the event of frequent, small eruptions, while larger and rarer events may have acute, regional-scale impacts. It is, therefore, necessary to document the range of possible impacts that tephra may induce in receiving environments and any resulting effects in interconnected systems. We collate results from many studies to offer a detailed multidisciplinary and interdisciplinary review of the immediate post-eruptive effects of tephra emission into the atmosphere, onto vegetation, soil or ice/snow surfaces and in aquatic systems. We further consider the repercussions that may be induced in the weeks to years afterwards. In the atmosphere, tephra can influence cloud properties and air chemistry by acting as ice nuclei (IN) or by offering sites for heterogeneous reactions, respectively. Tephra on vegetation causes physical damage, and sustained coverage may elicit longer-term physiological responses. Tephra deposits on soils may alter their capacity to exchange gas, water and heat with the atmosphere or may have a specific chemical effect, such as nutrient input or acidification, on sensitive soils. Tephra deposition onto snow or ice may affect ablation rates. Rivers and lakes may experience turbidity increases and changes in their morphology as a result of fallout and prolonged (months or years) erosion from the tephra-covered catchment. In the first weeks after deposition, tephra leaching may affect river chemistry. The abundance and speciation of phytoplankton populations in lakes may be altered by tephra-induced changes in water chemistry or sediment–water nutrient cycling. In the oceans, tephra deposition may fertilise Fe-limited waters, with potential impacts on the global carbon cycle. Embracing the full complexity of environmental effects caused by tephra fall demands a renewed investigative effort drawing on interdisciplinary field and laboratory studies, combined with consideration of the interconnectivity of induced impacts within and between different receiving environments.
The eruption of Mount St. Helens in southwestern Washington on 18 May 1980, ejected tons of volcanic ash that settled over large portions of eastern Washington, northern Idaho, and western Montana. Although most of these areas received only a light dusting, the heaviest deposits in the central path of the ash plume formed a layer of ash 5 to 8 cm thick (Cook
et al.
1981). The ash consisted of microscopic, jagged particles that were highly abrasive and easily damaged the epicuticular wax layer of insects, causing desiccation and eventual death (Brown and Hussain 1981). The impact of ash on a variety of agricultural-related insects in the fallout area has been described (Akre
et al.
1981; Fye 1983; Howell 1981; Johansen
et al.
1981; Klostermeyer
et al.
1981). This note reports the effects of ash on small larvae of a major forest defoliator, the Douglas-fir tussock moth,
Orgyia pseudotsugata
(McDunnough), as determined in laboratory and field experiments.
Conversion of natural habitats to agriculture reduces species richness, particularly in highly diverse tropical regions, but its effects on species composition are less well-studied. The conversion of rain forest to oil palm is of particular conservation concern globally, and we examined how it affects the abundance of birds, beetles, and ants according to their local population size, body size, geographical range size, and feeding guild or trophic position. We re-analysed data from six published studies representing 487 species/genera to assess the relative importance of these traits in explaining changes in abundance following forest conversion. We found consistent patterns across all three taxa, with large-bodied, abundant forest species from higher trophic levels, declining most in abundance following conversion of forest to oil palm. Best-fitting models explained 39–66 % of the variation in abundance changes for the three taxa, and included all ecological traits that we considered. Across the three taxa, those few species found in oil palm tended to be small-bodied species, from lower trophic levels, that had low local abundances in forest. These species were often hyper-abundant in oil palm plantations. These results provide empirical evidence of consistent responses to land-use change among taxonomic groups in relation to ecological traits.
There is a great amount of variation in microsculpture on the surface of Carabid Beetles. On the elytra, subject of this study, microsculpture may be entirely lacking, but as a rule consists of engraved microlines, either forming a network of meshes from isodiametric to more or less stretched, or of very dense transverse lines, a system of diffraction gratings causing iridescence. Since this phenomenon appears in many non-related genera and groups, for instance within the large genus Bembidion, it is concluded that diffraction grating is clearly polyphyletic in the Carabid family. An investigation of Baltic Amber Carabidae showed that the different types of microsculpture were developed already in early Oligocene and gave no support to the hypothesis-plausible in itself and confirmed in genus Bembidion-that diffraction grating is a derivative condition. The biological importance of iridescence is doubtful. In certain situations it may have a repulsive effect on predators, for instance birds. But, since it occurs also in certain cavernicolous species never exposed to light, this cannot be the only valid explanation. Other possible effects of iridescence, such as protection against over-heating or ultraviolet light, were doubted. It seems that no generally valid selective value of diffraction grating can be applied and that, in many cases, it may be preserved only as "not harmful".
Indicator species are species that are used as ecological indicators of community or habitat types, environmental conditions, or environmental changes. In order to determine indicator species, the characteristic to be predicted is represented in the form of a classification of the sites, which is compared to the patterns of distribution of the species found at the sites. Indicator species analysis should take into account the fact that species have different niche breadths: if a species is related to the conditions prevailing in two or more groups of sites, an indicator species analysis undertaken on individual groups of sites may fail to reveal this association. In this paper, we suggest improving indicator species analysis by considering all possible combinations of groups of sites and selecting the combination for which the species can be best used as indicator. When using a correlation index, such as the point-biserial correlation, the method yields the combination where the difference between the observed and expected abundance/frequency of the species is the largest. When an indicator value index (IndVal) is used, the method provides the set of site-groups that best matches the observed distribution pattern of the species. We illustrate the advantages of the method in three different examples. Consideration of combinations of groups of sites provides an extra flexibility to qualitatively model the habitat preferences of the species of interest. The method also allows users to cross multiple classifications of the same sites, increasing the amount of information resulting from the analysis. When applied to community types, it allows one to distinguish those species that characterize individual types from those that characterize the relationships between them. This distinction is useful to determine the number of types that maximizes the number of indicator species.
Question: How do forest herb species differ from each other in their spatial and temporal dynamics during recovery from volcanic disturbance, and how are dynamics related to species traits?
Location: Northeast of Mount St. Helens, Washington, USA.
Methods: Following deposition of volcanic tephra in 1980, we measured herb density and cover in permanent 1-m2 plots during 1980-2005 in three old-growth forests with differing tephra depths. For 26 species, we calculated the frequency of plots with residuals (individuals that survived the eruption) versus re-establishment on the tephra, timing of establishment, turnover, influence of nearby conspecific plants, importance of three components of cover increase, and relationship of flowering frequency to succession.
Results: Tephra depth affected species behavior. Deep tephra produced fewer residuals, a greater increase in shoot size, and more shoot turnover; favored species that established late; and allowed establishment of early seral herbs. Nearby presence of conspecifics increased permanence of first establishment and rate of plot occupancy. Most species spread significantly in deep tephra but not in shallow tephra. Among species, frequency of flowering increased with fewer residuals, later establishment, and higher turnover. Species behavior seldom differed among growth forms based on leaf longevity and vegetative spread.
Conclusion: Population dynamics at the small-plot scale differed from those of the entire population. The timing and permanency of establishment and mechanism of expansion differed among species and with tephra depth. There was some consistency among species with similar habitat breadth and degree of flowering, but little consistency associated with the usual growth form classification.
1. Pitfall data, collected periodically between 1980 and 1996, were used to analyse the spatial and temporal body size pattern of ground beetle assemblages (Carabidae) in a former polluted grassland.
2. Two hypotheses were tested: (i) Siemann et al .'s efficiency–specialisation hypothesis that predicts that during succession (or regeneration) processes the mean body sizes of consumer assemblages decrease and (ii) Blake et al .'s hypothesis that predicts that smaller body sizes are found with increasing level of disturbance.
3. Biovolume was considered as a determinant of ground beetle body size. This was analysed by using a digital–optical volume measurement. The mean error associated with the idealisation of the ground beetle body shape as an ellipsoid was determined as 10.24 ± 2.5%.
4. A significant decrease in average ground beetle body size was recorded in moving from the pollution (1980) to the post‐pollution (1996) period. The mechanisms linked with ecological succession after factory closure (1990) were discussed as the main causal factor sustaining Siemann et al .'s hypothesis.
5. The analyses of the mean body size during the transition period from the pollution to the post‐pollution period demonstrate that Blake et al .'s hypothesis was also partly supported, and may overlay the effects driven by succession.
6. It is therefore concluded that both hypotheses may be used to explain not only the change in body size from a highly polluted to a less polluted area, but also the relationship between habitat structure and predatory ground beetles.
Abstract The wing surfaces of 97 insect species from virtually all relevant major groups were examined by high resolution scanning-electron-microscopy, in order to identify the relationships between the wing microstructures, their wettability with water and their behaviour under the influence of contamination.
Isolated wings with contact angles between 31.6° and 155.5° were artificially contaminated with silicate dusts and subsequently fogged until drops of water (“dew”) formed and rolled off. The remaining particles were counted via a digital image analysis system. Remaining particle values between 0.41% and 103% were determined in comparison with unfogged controls. Some insects with very unwettable wings show a highly significant “self-cleaning” effect under the influence of rain or dew.
Detailed analysis revealed that there is a correlation between the wettability and the “SM Index” (quotient of wing surface/(body mass)0.67) with values ranging from 2.42 to 57.0. Furthermore, there is a correlation between the “self-cleaning” effect and the SM Index, meaning that taxa with a high SM Index, e.g. “large-winged” Ephemeroptera, Odonata, Planipennia, and many Lepidoptera, have very unwettable wings and show high particle removal due to dripping water drops. The “small-winged” insects, such as Diptera and Hymenoptera, and insects with elytra, such as Blattariae, Saltatoria, Heteroptera and Coleoptera, show completely opposite effects. This is clearly a result of the fact that species with a high SM Index are, in principle, more restricted in flight by contamination than species with a low SM Index which can also actively clean their own wings. The wings primarily serve a protection function in insects with elytra, so that the effects of contamination are probably of minor importance in these insects. Copyright © 1996 The Royal Swedish Academy of Sciences. Published by Elsevier Science Ltd.