Arthropod Diversity Patterns Research Articles

Vineyards compared to natural vegetation maintain high arthropod species turnover but alter trait diversity and composition of assemblages

Agriculture is a major contributor to habitat transformation, homogenising biological communities, and reducing biodiversity at local and regional scales. Over time, biotic homogenisation causes regional biotas to become genetically, taxonomically, and functionally similar, impacting the functioning and resilience of natural and agricultural systems. Here, we assessed alpha and beta diversity, trait diversity, and trait composition of spider and beetle assemblages in biodiversity-friendly vineyards and natural fynbos vegetation (a low-growing sclerophyllous vegetation type) in the Cape Floristic Region biodiversity hotspot to evaluate the influence of viticulture on large-scale patterns of arthropod diversity. Transects spanning from vineyards into fynbos were used to analyse differences in arthropod assemblages between the two biotopes. Spider species richness was significantly higher in fynbos compared to vineyards, but both systems supported relatively high spider and beetle alpha diversity. Spider beta diversity did not differ between the systems, but beetle beta diversity was significantly lower in vineyards. This difference was due to a lower level of assemblage nestedness, whereas beetle species replacement was similar in vineyards and fynbos. Only spider trait richness and beetle trait divergence were significantly lower in vineyards compared to fynbos. Assemblage composition of both taxonomic groups differed between biotopes, due to different species trait associations with each biotope. Plant-dwelling spiders and small-bodied beetles were strongly positively associated with fynbos, and predatory beetles with vineyards. Common spiders and predatory beetles were strongly negatively associated with fynbos. Our results indicate that vineyards support high arthropod diversity when compared to the natural vegetation. This supports the concept that sensitively managed agroecosystems can maintain species-rich assemblages at different spatial scales.

Interspecific green leaf-litter selection by ground detritivore arthropods indicates generalist over specialist detritivore communities

Reasons for the higher-than-expected soil and litter faunal diversity are still poorly understood – the so-called ‘enigma of soil animal diversity’ - especially regarding the extent of specialization of arthropod detritivores towards leaf-litter species. Here, we assess soil detritivorous arthropod diversity patterns in relation to eight, green leaf-litter species, in an old-growth, diverse southern Afrotemperate forest. Here, green leaves are often found scattered across the forest floors after turbulent weather, providing vital nutrients for ground-dwelling arthropods in a nutrient-poor system, possibly selecting for specialization. Litter bags containing species-specific green leaf litter of common southern Afrotemperate trees were placed in five forests. We found no evidence that leaf-litter species support unique detritivore assemblages, except for one species, nor did we find differences in richness between leaf-litter species. Significant differences in arthropod abundance were noted between some leaf-litter species, which did not relate to patterns for leaf-litter decomposition. Therefore, we support the hypothesis that ground-dwelling, detritivore arthropods are largely generalist towards leaf-litter species. Additionally, we demonstrate that decomposition rates were largely independent of the diversity of detritivorous arthropods. Competition for nutrients in the litter layer is predictably high, due to the nutrient poor quality of southern Afrotemperate forests. This competition could attract certain decomposers to leaf-litter species of higher nutrient status, as shown for one leaf-litter species here. The ‘enigma of soil diversity’ might best be explained not through specialized interactions between detritivorous arthropods and leaf-litter species, but rather through other mechanisms, such as microbial and fungal activity and their interactions with arthropods.

A Small-Scale Analysis of Elevational Species Richness and Beta Diversity Patterns of Arthropods on an Oceanic Island (Terceira, Azores)

A Small-Scale Analysis of Elevational Species Richness and Beta Diversity Patterns of Arthropods on an Oceanic Island (Terceira, Azores)

A Small-Scale Analysis of Elevational Species Richness and Beta Diversity Patterns of Arthropods on an Oceanic Island (Terceira, Azores).

Simple SummaryWe studied the diversity of arthropods in native forests along a 1000 m elevation gradient on Terceira Island, Azores (Portugal). These forests form an isolated and threatened habitat with unique endemic species. We analysed the change in alpha and beta diversity of arthropod species with elevation and if the diversity of endemic, native non-endemic and introduced species responds differently to elevation. Resident arthropods were sampled using SLAM (Sea, Land and Air Malaise) traps between 2014 and 2018. Spiders (Araneae), beetles (Coleoptera), true bugs (Hemiptera) and barklice (Psocoptera), as well as endemic, native and introduced species, were analysed separately. Total species richness decreases with elevation for all species, Coleoptera and Psocoptera, and particularly so for introduced species, but peaks at mid-high elevation for Araneae and endemic species. These patterns are probably driven by unfavourable climatic conditions at higher elevations while being influenced by human disturbance at lower elevations. Total species diversity along the whole elevation gradient is shaped by this decreasing richness as well as the replacement of species at different elevations.We present an analysis of arthropod diversity patterns in native forest communities along the small elevation gradient (0–1021 m a.s.l.) of Terceira island, Azores (Portugal). We analysed (1) how the alpha diversity of Azorean arthropods responds to increasing elevation and (2) differs between endemic, native non-endemic and introduced (alien) species, and (3) the contributions of species replacement and richness difference to beta diversity. Arthropods were sampled using SLAM traps between 2014 and 2018. We analysed species richness indicators, the Hill series and beta diversity partitioning (species replacement and species richness differences). Selected orders (Araneae, Coleoptera, Hemiptera and Psocoptera) and endemic, native non-endemic and introduced species were analysed separately. Total species richness shows a monotonic decrease with elevation for all species and Coleoptera and Psocoptera, but peaks at mid-high elevation for Araneae and endemic species. Introduced species richness decreases strongly with elevation especially. These patterns are most likely driven by climatic factors but also influenced by human disturbance. Beta diversity is, for most groups, the main component of total (gamma) diversity along the gradient but shows no relation with elevation. It results from a combined effect of richness decrease with elevation and species replacement in groups with many narrow-ranged species.

Level of urbanization and habitat type, and not patch size, influence predacious arthropod diversity patterns of urban grasslands in South Africa

Abstract. Greyvenstein B, Botha M, van den Berg J, Siebert SJ. 2021. Level of urbanization and habitat type, and not patch size, influence predacious arthropod diversity patterns of urban grasslands in South Africa. Biodiversitas 22: 4078-4094. Predacious arthropods provide a valuable ecosystem service within urban environments by suppressing pest numbers. However, urban ecological studies largely ignore this functional group and its diversity and species composition patterns. Some studies have been published regarding these patterns, however they were mostly done in Australia, Europe and America, thus an African perspective is lacking. Our aim was to address the gap in African literature by quantify the differences in predacious arthropod species richness and diversity within urban green space in varying urbanization intensities, habitat types of grassland and patch sizes in South Africa. Various indices were considered to examine the effect of urbanization on the diversity patterns of Chrysopidae (Neuroptera), Mantodea, Araneae and Coccinellidae (Coleoptera). Study sites included three levels of urbanization represented by population density, two types of urban grasslands (i.e., ruderal and fragmented grassland) and a peri-urban rangeland grassland as control, and a wide range of patch sizes. Our results indicated that an increase in urbanization intensities was associated with increased abundance of predacious arthropod taxa. Also, that urban and peri-urban grasslands had similar predacious arthropod species richness and diversity, but differed in species composition. No relationship was found between patch size and arthropod diversity or composition. Thus, predacious arthropod abundances are influenced by the level of urbanization and their species composition is influenced by the type of urban grassland (ruderal or fragmented), which are important considerations for future urban planning/management and conservation strategies. This study gives a South African perspective and indicates that despite the lack of assigned function of urban green spaces, they sustain diverse and distinct predacious arthropod communities, which in turn fulfill various roles in a functioning ecosystem.

The shrub Ephedra californica facilitates arthropod communities along a regional desert climatic gradient

AbstractArthropods underpin arid community dynamics and provide many key ecosystem services. In arid ecosystems, the key habitat components that influence arthropod community structure are relatively understudied. Ephedra californica is a locally abundant shrub now restricted to highly fragmented populations with established positive effects on plant and vertebrate animal communities within the drylands of Southern California. The capacity for these positive effects to further support ground arthropod communities has not been examined. We tested the hypothesis that the physical structure and cover vegetation enhance key measures of arthropod community assembly at nine Californian desert sites that comprise an extensive regional aridity gradient. We contrasted the effects of shrub canopies with ground‐covering vegetation on structuring ground‐active arthropod communities by surveying ground‐active arthropods with pitfall traps and collecting vegetation on the soil surface in the form of residual dry matter (RDM). We collected a total of 5820 individual arthropod specimens for a total of 159 morphospecies. Arthropod abundance and morphospecies richness and RDM biomass and cover were significantly greater beneath the canopy of E. californica throughout the region. Total biomass of RDM did not significantly influence arthropod communities, but cover of RDM on the soil surface negatively influenced arthropod abundance. Neither climatic aridity nor downscaled evaporative stress estimates were significant mediators of the arthropod‐vegetation association patterns. Vegetation thus likely has direct and indirect physical effects on arthropod communities. These canopy vs. soil surface vegetation differences will refine sampling of fine‐scale patterns of arthropod diversity in drylands. Regional land managers can support arthropod diversity by maintaining populations of foundation shrub species such as E. californica.

Tree canopy arthropods have idiosyncratic responses to plant ecophysiological traits in a warm temperate forest complex

Biodiversity studies on forest canopies often have narrow arthropod taxonomic focus, or refer to a single species of tree. In response, and to better understand the wide range of drivers of arthropod diversity in tree canopies, we conducted a large-scale, multi-taxon study which (a) included effect of immediate surroundings of an individual tree on plant physiological features, and (b), how these features affect compositional and functional arthropod diversity, in a warm, southern Afro-temperate forest. We found that tree species differed significantly in plant physiological features and arthropod diversity patterns. Surprisingly, we found negative correlation between surrounding canopy cover, and both foliar carbon and arthropod diversity in host trees, regardless of tree species. Subtle, tree intraspecific variation in physiological features correlated significantly with arthropod diversity measures, but direction and strength of correlations differed among tree species. These findings illustrate great complexity in how canopy arthropods respond to specific tree species, to immediate surroundings of host trees, and to tree physiological features. We conclude that in natural forests, loss of even one tree species, as well as homogenization of the crown layer and/or human-induced environmental change, could lead to profound and unpredictable canopy arthropod biodiversity responses, threatening forest integrity.

Seasonal changes in arthropod diversity patterns along an Alpine elevation gradient

Deciphering patterns in species distributions and species interactions along ecological gradients are fundamental topics in ecology. Theory holds that species diversity is greater and interactions are stronger under warmer and more stable environments, such as low elevations and latitudes. However, recent findings have shown conflicting evidence, potentially due to seasonal effects. We aimed to address this gap by studying seasonal changes in arthropod communities over an elevation gradient in the Swiss Alps, as well as herbivore‐predator interactions and their resulting consequences on plant herbivory levels. Overall, we found hump‐shaped patterns in arthropod abundance, richness and diversity with increasing elevation, with all factors peaking below the tree line. However, these patterns varied seasonally, with strong mid‐elevation peaks at the beginning of the summer, shifting to a pattern of linear decrease at the beginning of the fall. In searching for mechanisms explaining these changes, we found that shifts in arthropod communities over elevation and seasons usually followed shifts in vegetation productivity estimates. Other factors, such as top‐down control by natural enemies, which was generally stronger at low elevations, and plant species‐specific resistance rates along elevation gradients were also implicated as drivers of diversity and herbivory rates. These results highlight the complexity of arthropod communities' responses to environmental gradients, which vary during the season in response to relative changes in both bottom‐up and top‐down forces.

How are arthopod communities structured and why are they so diverse? Answers from Mediterranean mountains using hierarchical additive partitioning

Mountains are complex ecosystems supporting a great variety of taxa. Here, we explored the diversity patterns of arthropods in two mountains, pinpointing the spatial scale that accounts most for overall diversity variation, using an additive partitioning framework. Butterflies and Orthoptera were sampled in Rodopi (2012) and Grammos (2013) mountains. Diversity was partitioned into five hierarchical levels (mountain, elevational zone, habitat, transect and plot). We compared the estimated diversity values for each level to the respective permuted values expected by chance, for all species, as well as for species identified as “rare” or “common”. At broader spatial levels, the variation in total diversity was attributed to the beta diversity component: mountains accounted for 20.94 and 26.25% of butterfly and Orthoptera diversity, and elevational zones accounted for 28.94 and 35.87% respectively. At finer spatial scales, beta diversity was higher than expected by chance in terms of the Shannon index. The type of habitat was found to play a significant role only for rare orthopterans. Finally, common species were recognized for shaping overall species diversity. We highlight the importance of the spatial levels of elevation zone and then mountain position in conservation planning, due to the greater beta diversity recorded at this scale as compared to habitat or more finite scales. Monitoring programs might need to adapt different strategies with respect to the focal organisms, and consider patterns of common rather than rare species that found to drive the patterns of the entire community.

Historical arthropod diversity patterns direct rehabilitation targets for Robben Island, South Africa, a continental island in a biodiversity hotspot

Island species are susceptible to extinction through disturbances such as habitat transformation. Due to the small size and isolation of islands, species have limited options for refuges and recolonization, making their rehabilitation a conservation priority. Robben Island is a continental island, isolated from the mainland ca. 15 000 years ago, and has been degraded by humans and alien species for nearly 400 years. Mainland areas with similar vegetation should be good reference sites for the biological restoration of the island due to historical connectedness. However, very little information exists as to which species were lost. Here we aim to identify the best mainland sites to use as reference sites for Robben Island based on remaining arthropod diversity on the island. Sites found to be most similar in terms of arthropod diversity to Robben Island were sites north of Robben Island (Elandsbaai and Dwarskersbos) rather than the geographically closest locations. These sites therefore represent ideal reference sites for biological restoration of the island. We do not suggest the reintroduction of species from these localities, but rather Robben Island should be restored to match their vegetation height and cover.

The utility of DNA metabarcoding for studying the response of arthropod diversity and composition to land-use change in the tropics.

Metabarcoding potentially offers a rapid and cheap method of monitoring biodiversity, but real-world applications are few. We investigated its utility in studying patterns of litter arthropod diversity and composition in the tropics. We collected litter arthropods from 35 matched forest-plantation sites across Xishuangbanna, southwestern China. A new primer combination and the MiSeq platform were used to amplify and sequence a wide variety of litter arthropods using simulated and real-world communities. Quality filtered reads were clustered into 3,624 MOTUs at ≥97% similarity and the taxonomy of each MOTU was predicted. We compared diversity and compositional differences between forests and plantations (rubber and tea) for all MOTUs and for eight arthropod groups. We obtained ~100% detection rate after in silico sequencing six mock communities with known arthropod composition. Ordination showed that rubber, tea and forest communities formed distinct clusters. α-diversity declined significantly between forests and adjacent plantations for more arthropod groups in rubber than tea, and diversity of order Orthoptera increased significantly in tea. Turnover was higher in forests than plantations, but patterns differed among groups. Metabarcoding is useful for quantifying diversity patterns of arthropods under different land-uses and the MiSeq platform is effective for arthropod metabarcoding in the tropics.

Plant and arthropod diversity patterns of maize agro-ecosystems in two grassy biomes of South Africa

Intensive, large-scale cultivation has led to a postulated decrease in biodiversity worldwide, which has been ascribed to fragmentation and degradation of natural habitat bordering crop fields. Maize is the most widely planted grain crop in Grassland and Savanna Biomes of South Africa, but the effect that crop production has on surrounding species diversity and composition is unknown. This study intends to address this knowledge gap by comparing diversity patterns and species assemblages between maize fields and margins of six localities in South Africa across two biomes for plants and associated arthropods. A total of 15,019 individuals and 824 native and exotic plant species were recorded and 39 497 individuals and 1 629 morpho-species for arthropods. Although biodiversity loss was apparent in maize fields, plant and arthropod diversity remained the same for rangeland at shorter (30–100 m) and longer (100–400 m) distances from maize fields, suggesting that distance from maize fields had no effect on biodiversity patterns beyond 30 m. Plant species assemblages were best correlated with agricultural disturbance while arthropod communities were mainly correlated with biome. Our results suggest that the crop field margins (30–100 m from field edge) were not species poor ecosystems, but were surprisingly rich in plant and arthropod diversity. Field margins may therefore be of conservation value in the agricultural landscape with a diversity of species supporting important ecosystem services.

Agricultural landscape structure affects arthropod diversity and arthropod-derived ecosystem services

Knowledge of how landscape structure impacts the diversity and abundance of beneficial and harmful arthropods, pest regulation, and ultimately crop yield has the potential to significantly improve management of agricultural landscapes. We examined how landscape structure in southern Québec affected soybean herbivores, predators of aphids, pest regulation including aphid and herbivory regulation, and crop production. Local-scale field characteristics and landscape structure at distances less than 2km around each field were the most important predictors for these variables. Increasing field width consistently decreased arthropod diversity and abundance for both predators of aphids and soybean herbivores, but the effects of these changes on pest regulation were inconsistent. Increased field width resulted in less damage to soybean plants from herbivores; but in contrast, aphid numbers were greatest in more complex landscapes where fields were generally narrower. Distance-from-forest within fields and no-till planting methods also decreased pest regulation. Despite these results, soybean yield was not strongly related to pest regulation and instead varied most with distance-from-forest. Thus, patterns of arthropod diversity and abundance may not necessarily coincide with those of pest regulation or crop yield.

The Role of Spatial Aggregation in Forensic Entomology: Table 1.

A central concept in forensic entomology is that arthropod succession on carrion is predictable and can be used to estimate the postmortem interval (PMI) of human remains. However, most studies have reported significant variation in successional patterns, particularly among replicate carcasses, which has complicated estimates of PMIs. Several forensic entomology researchers have proposed that further integration of ecological and evolutionary theory in forensic entomology could help advance the application of succession data for producing PMI estimates. The purpose of this essay is to draw attention to the role of spatial aggregation of arthropods among carrion resources as a potentially important aspect to consider for understanding and predicting the assembly of arthropods on carrion over time. We review ecological literature related to spatial aggregation of arthropods among patchy and ephemeral resources, such as carrion, and when possible integrate these results with published forensic literature. We show that spatial aggregation of arthropods across resources is commonly reported and has been used to provide fundamental insight for understanding regional and local patterns of arthropod diversity and coexistence. Moreover, two suggestions are made for conducting future research. First, because intraspecific aggregation affects species frequency distributions across carcasses, data from replicate carcasses should not be combined, but rather statistically quantified to generate occurrence probabilities. Second, we identify a need for studies that tease apart the degree to which community assembly on carrion is spatially versus temporally structured, which will aid in developing mechanistic hypotheses on the ecological factors shaping community assembly on carcasses.

A systematic review of arthropod community diversity in association with invasive plants

Invasive plants represent a significant financial burden for land managers and also have the potential to severely degrade ecosystems. Arthropods interact strongly with plants, relying on them for food, shelter, and as nurseries for their young. For these reasons, the impacts of plant invasions are likely strongly reflected by arthropod community dynamics including diversity and abundances. A systematic review was conducted to ascertain the state of the literature with respect to plant invaders and their associated arthropod communities. We found that the majority of studies did not biogeographically contrast arthropod community dynamics from both the home and away ranges and that studies were typically narrow in scope, focusing only on the herbivore feeding guild, rather than assessing two or more trophic levels. Importantly, relative arthropod richness was significantly reduced on invasive plant species. Phylogenetic differences between the invasive and local plant community as well as the plant functional group impact arthropod diversity patterns. A framework highlighting some interaction mechanisms between multiple arthropod trophic levels and native and invasive plants is discussed and future research directions relating to these interactions and the findings herein are proposed.

Patterns of Arthropod Diversity in Contrasting Habitats of El Pedregal de San Angel, a Preserve in Mexico City

We studied the community of arthropods inhabiting the ecological preserve El Pedregal de San Angel, in Mexico City. We estimated morphospecies richness, abundance, and diversity patterns in two contrasting habitats, open and closed, during four seasons of the year. Because closed-habitat sites have greater net primary productivity than open habitats, we predicted arthropod diversity would be greater in closed than in open habitats. Morphospecies richness of Acari and Arachnida was similar in both types of habitats throughout the year, whereas richness of some orders of Insecta such as Coleoptera, Diptera, Hemiptera, and Hymenoptera was greatest in open habitats. Mites were the most abundant arthropods and were always more abundant in open than closed habitats. Diversity of arthropods was greater in closed habitats during fall and spring, suggesting that habitat characteristics related to primary productivity might affect this community. We suggest that studies of patterns of arthropod diversity and factors associated with the maintenance of such diversity should be considered in the preservation of these organisms and of their natural habitats.

Conservation of arthropod diversity in montane wetlands: effect of altitude, habitat quality and habitat fragmentation on butterflies and grasshoppers

1. The patterns of arthropod diversity were investigated in 24 montane wetlands in Switzerland. These differed in altitude, management regime (cattle‐grazing vs. mowing), vegetation structure (index combining vegetation height and density) and degree of habitat fragmentation. 2. The general arthropod diversity was determined by net sampling at 10 sampling points per site. The diversity of grasshoppers and butterflies was measured by counting species richness at the site and species density (species richness per unit area) on transects. The species richness of grasshoppers and butterflies was found to be more sensitive to the geographical attributes of the site whereas species density was more affected by the habitat quality. 3. Grasshopper diversity decreased within the observed altitudinal range (800–1400 m) and was higher at grazed sites, whereas butterfly diversity was higher at mown sites. Arthropod diversity but not abundance of arthropods was positively related to the vegetation structure. 4. The species richness of butterflies was negatively influenced by the degree of habitat fragmentation: both the size of habitat as well as the area of wetland habitats within 4 km were related positively to the number of specialist wetland butterflies. 5. Late mowing as well as low‐density cattle‐grazing are appropriate management actions to maintain arthropod diversity in montane wetlands. In order to establish site‐specific management plans, the biology of the present target species as well as the historical context should be considered. 6. We suggest that the best protection for the species examined in this study would be a network of wetland sites managed using a variety of traditional, non‐intensive methods. This can only be achieved by coordinated planning of conservation measures among sites.