Distribution Of Arthropods Research Articles

The effects of edge-interior and understorey-canopy gradients on the distribution of saproxylic beetles in a temperate lowland forest

Spatial distribution of arthropods in woodlands has crucial implications for biodiversity conservation and forest management. However, its determinants are insufficiently known. In particular, studies on arthropod vertical distribution in temperate woodlands report contrasting patterns that are difficult to explain in the current theoretical framework. Using flight intercept traps, we investigated vertical and horizontal distribution and diversity of saproxylic beetles in the understorey and the upper canopy at the edge and in the interior of a temperate, closed-canopy, deciduous forest in South-Eastern Czech Republic. At the forest edge, number of species was >60% higher than in the interior. Preference for forest edge were better pronounced in the understorey than in the canopy. Although number of species did not differed between the forest strata, vertical distribution of individual species as well as the whole assemblages differed between edge and interior. In the forest interior, most (∼80%) species exhibited higher preference for the canopy than at its edge. Multivariate analysis indicated that beetle distribution was affected by variables related to habitat openness and light availability. The results suggest that: (i) Vertical stratification of arthropod assemblages and individual species is context-dependent and variable even within a single forest patch. (ii) Vertical and horizontal distribution of arthropods is driven mainly by sunlight availability and habitat openness. (iii) In the closed canopy forest, the horizontal edge-interior gradient affects distribution of saproxylic beetles more than the vertical understorey-canopy gradient.

The role of geography and environment in species turnover: phytophagous arthropods on a Neotropical legume

AbstractAimBroad‐scale patterns in the distribution of phytophagous arthropods have been explained by species turnover due to host plant, environment, geographical distance and historical biogeography. In this study, variability due to plant species turnover was eliminated by focusing on the arthropods utilizing a single widely distributed plant species, Parkinsonia aculeata L. (Leguminosae: Caesalpinioideae). This enabled us to examine the effects of geography and climate on arthropod species turnover.LocationNeotropics (USA to Argentina).MethodsA statistical approach was used to determine whether arthropod assemblages across the range of P. aculeata differed significantly between biogeographical areas. We determined whether host‐specific arthropods have more restricted ranges, contributing to higher species turnover. Finally, generalized dissimilarity modelling (GDM) was used to correlate significant differences in assemblages between biogeographical provinces with environmental differences and geographical separation.ResultsPhytophagous arthropod assemblages differed significantly between biogeographical areas. Most herbivores had a small geographical distribution. We did not detect higher species turnover for host‐specific species. The GDM model explained 21.8% of the variance in species assemblages. Of the variables examined, climate and geographical distance were both better predictors of variation in phytophagous arthropod assemblages on P. aculeata than biogeographical areas, with climate the better predictor of the two.Main conclusionsObserved patterns in turnover of the phytophagous insect fauna of P. aculeata are consistent with expected broad‐scale responses to historical processes and climatic variation. Climate and geography explain similar proportions of compositional dissimilarity, and most species, regardless of host‐specificity, have restricted geographical ranges. The statistically significant differences observed between arthropod assemblages in different biogeographical provinces are likely to be caused by a combination of niche‐based processes and to some extent dispersal limitation. Although variability due to host plant has been eliminated in the current study, there remains no simple explanation for broad‐scale patterns in the distribution of phytophagous arthropods.

Trees as templates for trophic structure of tropical litter arthropod fauna

Litter arthropod abundance in tropical forests is patchily distributed in space and time. This patchiness can be described by three general hypotheses relating plant-based effects to litter arthropod distribution. The tree hypothesis (H1) posits that environments maintained underneath tree canopies are different from those between canopies in ways that shape arthropod abundance. The species hypothesis (H2) refines this scenario, positing that different plant species might maintain distinct litter environments to which arthropod abundances respond. Without regard to specific plant effects, seasonal changes in litter profiles (H3) can account for temporal patchiness in arthropod abundance. The ecosystem size hypothesis provides a mechanism for tree, species and seasonal effects. It links increasing food chain length with habitat availability and its heterogeneity.In a Panamanian rainforest we sampled litter arthropods in quadrats located near (1 m) and far away (30 m) from the parent trunk of 93 tree individuals (to test the tree hypothesis) from 10 tree species (to test the species hypothesis) in the early wet season, when litter is deepest. To test for effects of seasonal changes of litter profiles, we then resampled 25 trees (i.e., five individuals from each of five species) in the late wet season, when climatic conditions are similar, but litter is shallowest.We found weak support for all tree, species and seasonality hypotheses. With few exceptions, trees and species did not sustain different arthropod abundances, neither early nor late in the wet season. Collembola abundance increased late in the wet season, when litter is shallowest. Supporting the ecosystem size hypothesis, accumulated litter either due to trees, species and seasonality sustained higher predator abundance and higher predator to prey ratios.Our results suggest that plants may account for detrital, brown, food web structure; but these effects are mostly through plant-based provision of structural support. This study adds to growing evidence relating the ecosystem size hypothesis to litter environments and suggest a framework to understand plant-based bottom-up forces in structuring litter communities.

Assessing the effects of variables and background selection on the capture of the tick climate niche.

BackgroundModelling the environmental niche and spatial distribution of pathogen-transmitting arthropods involves various quality and methodological concerns related to using climate data to capture the environmental niche. This study tested the potential of MODIS remotely sensed and interpolated gridded covariates to estimate the climate niche of the medically important ticks Ixodes ricinus and Hyalomma marginatum. We also assessed model inflation resulting from spatial autocorrelation (SA) and collinearity (CO) of covariates used as time series of data (monthly values of variables), principal components analysis (PCA), and a discrete Fourier transformation. Performance of the models was measured using area under the curve (AUC), autocorrelation by Moran’s I, and collinearity by the variance inflation factor (VIF).ResultsThe covariate spatial resolution slightly affected the final AUC. Consistently, models for H. marginatum performed better than models for I. ricinus, likely because of a species-derived rather than covariate effect because the former occupies a more limited niche. Monthly series of interpolated climate always better captured the climate niche of the ticks, but the SA was around 2 times higher and the maximum VIF between covariates around 30 times higher in interpolated than in MODIS-derived covariates. Interpolated or remotely sensed monthly series of covariates always had higher SA and CO than their transformations by PCA or Fourier. Regarding the effects of background point selection on AUC, we found that selection based on a set of rules for the distance to the core distribution and the heterogeneity of the landscape influenced model outcomes. The best selection relied on a random selection of points as close as possible to the target organism area of distribution, but effects are variable according to the species modelled.ConclusionTesting for effects of SA and CO is necessary before incorporating these covariates into algorithms building a climate envelope. Results support a higher SA and CO in an interpolated climate dataset than in remotely sensed covariates. Satellite-derived information has fewer drawbacks compared to interpolated climate for modelling tick relationships with environmental niche. Removal of SA and CO by a harmonic regression seems most promising because it retains both biological and statistical meaning.

Influence of Agricultural Activities on Grassland Arthropods in Inner Mongolia

Arthropod pest outbreaks are becoming more common in the grasslands of Inner Mongolia, China, most likely due to the expansion of agriculture. The area of cropland has increased from 43,300 km2 in 1949 to 76,300 km2 in 2005. To understand the effects of agricultural activities on arthropod distribution, sweep net sampling was conducted in a natural grassland. We collected 1287 individuals belonging to 23 families and 9 orders of arthropods from 41 sites. We divided these samples into two guild types (predator and herbivore) and analyzed six groups (grasshoppers, herbivorous Coleoptera, herbivorous Hemiptera, Cicaddidae, Araneae, predatory Coleoptera) of them. Using a negative binomial regression analysis we analyzed the relationships between each group’s sampled population size and measured environmental factors including pesticide application and mean temperature of the previous year, agricultural site, and vegetation condition. The best model for each group was determined using Akaike’s information criterion. Grasshoppers showed a significant positive response to pesticide application and degraded vegetation, whereas spider (natural enemies of some insect pests) showed a negative response to these factors. The population of grasshoppers increased at sites where pesticides were applied, vegetation was degraded, and spider numbers were reduced. Other groups were not significantly correlated with pesticide application and degraded vegetation. Some of the environmental factors we studied promoted pests the following year. Our results also suggest that the current use of pesticides may not be effective for pest control and that alternative options should be considered in the grasslands of Inner Mongolia.

Negative interaction between twospotted spider mites and aphids mediated by feeding damage and honeydew

Among the herbivorous arthropods that feed on strawberry, the most important are the two-spotted spider mite (TSSM), Tetranychus urticae Koch, and several species of aphids. Mites and aphids belong to different guilds that coexist in the field and feed on the undersides of strawberry leaflets. However, the occurrence of large numbers of individuals of both species on the same leaflet is rarely recorded. We hypothesize that negative interactions between TSSM and aphids explain the intraplant distribution of these herbivores. We first examined the spatial coincidence of both herbivores in the field. Under experimental conditions, we then analyzed: (i) the rate of increase of TSSM and the aphid Chaetosiphon fragaefolii (Cockerell), growing individually and together; (ii) the effect of honeydew on TSSM preference; and (iii) the effect of previous strawberry leaflet damage by TSSM on C. fragaefolii preference. The proportion of TSSM that coincided with at least one aphid decreased as the percentage of leaflets with TSSM increased. The spatial coincidence index between aphids and TSSM increased together with the percentage of TSSM-infested leaflets. TSSM showed both a lower rate of increase when they shared the same leaflet with C. fragaefolii and lower fecundity on strawberry discs with honeydew. The rate of increase of C. fragaefolii did not change on co-occupied leaves, but the aphid species moved to the other side of leaflets shared with TSSM. Negative interactions resulting in a tendency for species to avoid each other, such as demonstrated herein, can affect distribution and performance of herbivorous arthropods.

Dengue in the context of “safe blood” and global epidemiology: to screen or not to screen?

The aim of a safe blood supply is constantly challenged by emerging and reemerging infectious agents. Emergence is favored by modern economy and lifestyles including international travel, circulation of goods and livestock, animal and human migration, expanding arthropod distributions, and other environmental and ecological factors. A “worst-case” scenario is an emerging blood-borne pathogen that is responsible for mostly asymptomatic infections in healthy individuals (i.e., blood donors) and is only detected when clinically-important morbidities and/or mortality are observed in immunosuppressed transfusion recipients revealing the significance of the new transfusion-transmitted pathogen.

Shrubs and species identity effects on the distribution and diversity of ground-dwelling arthropods in a Gobi desert

Disentangling the relationship between shrub vegetation and ground-dwelling arthropods at multiple levels of taxonomic resolution is essential to developing a suitable management strategy for the conservation of shrub-associated arthropod biodiversity in shrubland ecosystems. Using Gobi desert (dominated by shrub species Nitraria sphaerocarpa and Reaumuria soongorica) occurring widely in inland arid areas of northwest China as a model system, we sampled ground-dwelling arthropods by pitfall trapping method under canopies of both shrubs and in intershrub bare areas during spring, summer and autumn. Our aim was to determine whether the presence and species identity of shrubs influence the distribution of ground-dwelling arthropods and whether the influence of shrub presence and species identity differs among trophic and taxonomic groups. At the community level, total arthropod abundance and species richness were significantly greater under shrubs than in intershrub bare habitats, whereas more arthropods were captured under N. sphaerocarpa than under R. soongorica. At the trophic group level, the abundance of predator and decomposer arthropods was significantly greater under shrubs than in intershrub bare habitats, whereas herbivore and decomposer arthropods were more abundant under N. sphaerocarpa than under R. soongorica. At the family level, the abundance of Carabidae, Gnaphosidae, Karschiidae, Tenebrionidae and Thomisidae was consistently much greater under shrubs than in intershrub bare habitats, whereas that of Formicidae, Philodromidae and Tettigoniidae did not differ between the shrub microhabitats and the intershrub bare habitats. However, the abundance of Curculionidae under R. soongorica and the abundance of Geotrupidae under N. sphaerocarpa were significantly lower than that in intershrub bare habitats. N. sphaerocarpa was commonly preferred by arthropods in the families of Curculionidae and Tenebrionidae, whereas R. soongorica was commonly preferred by arthropods in the family Geotrupidae, but shrub species identity did not affect the abundance of the remaining families. Our results suggest that shrubs and species identity play important roles in structuring ground-dwelling arthropod communities, but the response of arthropods differed among trophic or taxonomic groups. This study may have important implications for the conservation of invertebrate biodiversity in Gobi desert ecosystems.

Experimental sward islets: the effect of dung and fertilisation on Hemiptera and Araneae

Abstract. 1. Cattle avoid grazing around their dung. This pattern persists after the decomposition of the initial dung patch leading to the formation of taller grass patches, termed islets. It is known that islets hold a disproportionate amount of the arthropods in grazed grasslands.2. An experimental manipulation was set up to investigate the relative effects of vegetation structure and nutrient input on arthropod distributions. Herbivorous bugs (Hemiptera) and predatory spiders (Araneae) were sampled in artificially generated islets treated with dung, fertiliser, a cutting regime to mimic grazing and a fallow control.3. The densities of both Hemiptera and Araneae were affected by the presence of increased nutrient input through dung and fertiliser. The densities of different herbivore taxonomic families were influenced by food plant quality and the predators by the subsequent increase in prey density.4. Delphacidae (Hemiptera) showed a preference for taller more nutrient rich swards treated with fertiliser, whereas Cicadellidae (Hemiptera) were more abundant in those swards treated with dung. Lycosidae (Araneae) were more common in dung‐treated swards, whereas Linypiidae (Araneae) were more common in the taller fertiliser‐treated swards.5. Higher Hemiptera species richness was found in the fertiliser‐ and dung‐treated swards. It is believed that this effect was because of nutrient availability.6. It is likely that the presence of cattle dung islets in grazed grassland plays an important role in the maintenance of biodiversity, through increasing structural heterogeneity.

Ground-Dwelling Arthropod Distribution and Movement Across a Fragmented Riparian Forest

Abstract The ability to predict patterns of species dispersal across habitat edges takes on increasing conservation relevance as land-scapes become more fragmented. We assessed edge responses for four ground-dwelling arthropod taxa by measuring their distribution and movement patterns across a forest edge associated with a forested riparian buffer and an adjacent upslope clearcut at a single site. We used Spatial Analysis by Distance Indices to describe the spatial distribution of arthropods, habitat variables, and the associations between them across a 49 × 63 m pitfall trapping grid with 80 trapping stations. We used mark-release-recapture techniques to measure the distance, rate, and direction of arthropod movement within and between habitat types. Scaphinotus angusticollis (Coleoptera; Carabidae) was restricted to the cool, moist portion of the riparian buffer and was not observed to cross the forest edge. The carabids Pterostichus lattini and Scaphinotus marginatus had more eurytopic distributions ac...

Impacts of emerald ash borer-induced tree mortality on leaf litter arthropods and exotic earthworms

a b s t r a c t Because leaf litter occurs at the interface between the soil and atmosphere, the invertebrates inhab- iting it represent important linkages between above- and below-ground food webs. The responses of these organisms to forest disturbance brought about by invasive species should therefore have far- reaching ecological effects. The purpose of this study was to explore how canopy gap formation (gap fraction 1-10%) and fallen ash trees (logs) resulting from extensive (>99%) ash tree mortality caused by the invasive emerald ash borer (EAB) affect the distributions of litter-dwelling arthropods and earth- worms. These organisms did not vary in abundance across the gap fraction range studied but, as predicted from the literature, many taxa (e.g., Aranea, Coleoptera, Collembola, Diplopoda, Isopoda, Opiliones and exotic earthworms) were more abundant next to logs than away from them. Contrary to expectations, arthropods did not become more concentrated next to logs as canopy openness increased, with isopods exhibiting the opposite response. These results suggest litter-dwelling arthropods in EAB-infested forests are favored by inputs of ash wood to the forest floor but are largely unaffected by increases in canopy openness, at least across the gap fraction range studied. Published by Elsevier GmbH.

Hedgerow effects on the distribution of beneficial arthropods in a pear orchard in Southern France

Farming intensification in recent decades has led to an alarming level of degradation and loss of wildlife and its habitat such as hedgerows. The relationship between biodiversity and ecosystem functioning has emerged as a central issue in ecological sciences, but the impact of regarding hedgerow function as a potential source of biological control agents against agricultural pests remains poorly understood. In this paper, we assessed effects of the arthropod community in a neighbouring hedge on the distribution of the pest psylla, Cacopsylla pyri, in a pear orchard over three consecutive years (1999-2001). We measured the diversity of the arthropod community in the hedge and in the orchard at increasing distances from the hedge using Shannon index diversity. Other indices and statistics such the Hellinger and L1 distances were used to measure dissimilarities between spatial and temporal population distributions patterns. Our results showed in particular a decreasing diversity gradient as distance from the hedge increased and a convergence between predator populations in the orchard and the hedgerow during psylla proliferation. The beneficial arthropod exchanges occurring between the mixed hedgerow and the pear orchard during the pest proliferation period suggested that field border management could be used in an integrated pest management strategy aimed at reducing insecticide use.

Landscape and a political border determine desert arthropods distribution

We studied the distribution of arthropods in the Arava desert on both sides of the Israeli-Jordanian border, to assess the impact of different anthropogenic pressures on the local fauna. We examined how different landscape units, proximity to agricultural fields, and human societies, might affect the diversity of ground dwelling beetles, and spiders, using ordination and diversity estimation methods. Our results suggest that although both countries contain similar habitats, each has its own unique characteristics, probably due to different cultural practices. The immediate repercussion is that loss of a habitat on one side of the border cannot be compensated with preservation of the same habitat across the border, due to fauna dissimilarity. For example, beetle species can be assembled according to landscape units, but within each landscape unit they show dissimilarities that are based on the geopolitical location. Spiders fail to assemble according to landscape units but cluster as a unique group within Israel. Both landscape unit type and the border, were found to be important for the overall species diversity of this ecosystem and therefore “redundancy” should be carefully applied, especially across geopolitical borders.

Identifying appropriate sampling and modelling approaches for analysing distributional patterns of Antarctic terrestrial arthropods along the Victoria Land latitudinal gradient

AbstractBiotic communities in Antarctic terrestrial ecosystems are relatively simple and often lack higher trophic levels (e.g. predators); thus, it is often assumed that species’ distributions are mainly affected by abiotic factors such as climatic conditions, which change with increasing latitude, altitude and/or distance from the coast. However, it is becoming increasingly apparent that factors other than geographical gradients affect the distribution of organisms with low dispersal capability such as the terrestrial arthropods. In Victoria Land (East Antarctica) the distribution of springtail (Collembola) and mite (Acari) species vary at scales that range from a few square centimetres to regional and continental. Different species show different scales of variation that relate to factors such as local geological and glaciological history, and biotic interactions, but only weakly with latitudinal/altitudinal gradients. Here, we review the relevant literature and outline more appropriate sampling designs as well as suitable modelling techniques (e.g. linear mixed models and eigenvector mapping), that will more adequately address and identify the range of factors responsible for the distribution of terrestrial arthropods in Antarctica.

Bromeliad architectural complexity and vertical distribution predict spider abundance and richness

AbstractHabitat complexity is a main predictor of the distribution of arthropods on vegetation. However, it remains poorly known whether plant architecture and fine‐scale spatial distribution affect the species richness and composition of associated arthropod guilds. In this study, we extensively sampled bromeliad species with a variety of rosette architectures in a megadiversity region. The aims were to investigate whether (i) possible differences in spider species composition among bromeliad species are related to the distinct architectures of the plants, and (ii) bromeliad architectural complexity (an intrinsic feature) and vertical distribution (an extrinsic feature) are good predictors of spider abundance and richness. Contrary to our expectations, spider species composition did not vary significantly among bromeliad species with different architectures. We found a positive effect of the mean number of leaves on spider abundance and species richness, but it occurred indirectly through spider abundance; factoring out the indirect effect revealed a negative effect of leaf number on species richness. Bromeliad species with wider vertical distributions harboured more spider species. Our results suggest that the dominance of a few spider species and reduced space for orb‐web spiders to attach their webs are the main explanations for lower spider richness on bromeliad species with higher architectural complexity. Our findings highlight the importance of both intrinsic and extrinsic plant features as co‐determinants of predator arthropod diversity.

Arthropod colonisation of a debris-covered glacier

The largest debris-covered glacier in the Alps (Miage Glacier, western Italian Alps) has been studied to explore the effects of debris-cover extent and depth on the spatial distribution of ground-dwelling arthropods. A multitaxa approach has been used to compare taxa richness and distribution to the functional role (dietary habits) of each taxon along the glacier tongue. Spiders and ground beetles have been studied in detail. Taxa richness declines with distance from the wooded sites (in front of the glacier tongue) to those above the glacier tongue. At each of the supraglacial sites, spiders, ground beetles, aphids, springtails and flies were found. A change in the dominance of the different functional roles was observed along the tongue. Wooded sites are characterised by predatory (e.g. spiders, beetles), detrivore (e.g. springtails and certain flies), phytophagous (e.g. aphids, certain beetles) and parasitoid (e.g. certain wasps) assemblages, whereas at the debris-covered sites, aphids, flies and springtails are likely to be prey for spiders and beetles. The species richness of the predominant predators (spiders and beetles) shows a positive relationship with vegetation cover and debris thickness. Two mutually exclusive spider and ground beetle assemblages were found; one within the debris cover and one within the wooded sites. In our opinion, debris-covered glaciers are acting as a refuge area for the cryophil stenotherm species living at higher altitudes which descend the glacial tongue to lower elevations. A similar hypothesis supports the biogeographical interpretation of the distribution of many boreo-alpine relict species in the Alps. We discuss our results in the light of possible future scenarios which suggest an increase in debris cover with global warming.

The occurrence of arthropods in processed rice products in Malaysia

Objective To determine distribution of arthropods in processed rice products such as rice flour and rice cereal-based infant food. Methods Random samples of rice flour and rice cereal-based infant food purchased from commercial outlets were examined for the presence of arthropods using a modified Berlese Tullgren Funnel Method. Mites were mounted prior to identification and weevils were directly identified. Results For non-expired products, infestation was found in 6.7% of rice flour and none was found in rice cereal-based infant food samples. The arthropods found in the flour samples were Cheyletus spp., Suidasia pontifica (S. pontifica), Tarsonemus spp., Tyrophagus putrescentiae (T. putrescentiae), Sitophilus granarius (S. granarius) and Sitophilus oryzae (S. oryzae). Others which cannot be identified were Oribatid and Prostigmatid mites. The most common mites in rice flour were Tarsonemus spp. (69.1%), followed by S. pontifica (18.2%). For expired products, only one sample of rice cereal-based infant food was infested and the infestation was by mites of the family Tydeidae. Conclusions This study demonstrates the presence of 4 allergenic species of S. pontifica, T. putrescentiae, S. granarius and S. oryzae in rice flour. These arthropods can contribute to the incidence of anaphylaxis upon consumption by atopic individuals. There was no infestation of arthropods in rice cereal-based infant food surveyed except for an expired product in a moderate rusty tin container.

The role of grassland sward islets in the distribution of arthropods in cattle pastures

Abstract.1. It is well documented that cattle reduce their grazing activity in the vicinity of cattle dung, which gives rise to distinct patches, or islets as they have been termed, of longer sward. The influence of such islets on pasture utilisation and agronomic performance has been widely studied, but very little information is available concerning their influence on grassland biodiversity.2. In this study the abundance and distribution of arthropods in relation to islets was assessed, using suction sampling, at 26 commercial farms and in a replicated pasture management experiment in the south and east of Ireland.3. Islets were found to cover approximately 24% of pastures and to contain between 40% and 50% of arthropod individuals.4. Islets consistently contained a higher density of arthropods, even when the difference in mean sward height between islets and more strongly grazed sward was accounted for. The relative concentration of arthropods in islets declined with increasing mean sward height, which may be related to the recovery of well‐grazed non‐islet sward. Islets appear to act as refugia from sward removal.5. The potential importance of islets in maintaining arthropod biodiversity within intensively grazed pastures and the wider grass‐based farming landscape is discussed, particularly with reference to standard agronomic practices such as sward topping and chain harrowing, which aim to remove the sward heterogeneity created by grazing livestock.

The importance of beta diversity in local gall-inducing arthropod distribution

Many studies over the past twenty years have documented the richness of arthropod galling species around the world, and some have proposed hypotheses to explain local and global patterns of galling species richness. However, few studies have been directed toward understanding how the gall-inducing species are locally distributed. The aim of this study was to determine the distribution of gall-inducing arthropods species at Coiba National Park, a tropical habitat on the Pacific coast of Panama. Our results suggest that more gall-inducing species had an aggregated distribution, and gall-inducing arthropod diversity shows a strong beta diversity component. Geographic distance was not correlated with similarity in gall-inducing species composition between the studied sites. This fact has important implications when trying to estimate gall-inducing arthropod richness and general patterns, and could cause contradictory results for hypotheses that attempt to explain the local and global patterns of galling species richness.

The Ground-Dwelling Arthropod Community of Península Valdés in Patagonia, Argentina

This is the first study based on a planned and intensive sampling effort that describes the community composition and structure of the ground-dwelling arthropod assemblage of Península Valdés (Patagonia). It was carried out using pitfall traps, opened for two weeks during the summers of 2005, 2006 and 2007. A total of 28, 111 individuals were caught. Ants (Hymenoptera: Formicidae) dominated this community, followed by beetles (Coleoptera) and spiders (Araneae). The most abundant species were Pheidole bergi Mayr (Hymenoptera: Formicidae) and Blapstinus punctulatus Solier (Coleoptera: Tenebrionidae). Two new species were very recently described as new based on specimens collected during this study: Valdesiana curiosa Carpintero, Dellapé & Cheli (Hemiptera, Miridae) and Anomaloptera patagonica Dellapé & Cheli (Hemiptera, Oxycarenidae). The order Coleoptera was the most diverse taxa. The distribution of abundance data was best described by the logarithmic series model both at the family and species levels, suggesting that ecological relationships in this community could be controlled by a few factors. The community was dominated by predators from a trophic perspective. This suggests that predation acts as an important factor driving the distribution and abundances of surface-dwelling arthropods in this habitat and as such serves as a key element in understanding desert, above-ground community structure. These findings may also be useful for management and conservation purposes in arid Patagonia.