Arthropod Species Richness Research Articles

Forest disturbance and arthropods: small‐scale canopy and understory disturbances alter movement of mobile arthropods

AbstractDispersal of ground‐dwelling arthropods is understudied in forest ecosystems, which hinders understanding of effects of disturbances on population dynamics. The objective of the study was to quantify movement of ground‐dwelling arthropods in response to a factorial combination of canopy gap formation via girdling and understory vegetation removal, which was shown in a companion study to alter arthropod abundance and species richness. Arthropod movement was quantified using a self‐mark–capture technique where arthropods were marked as they crossed three concentric bands of different colored fluorescent powders located 3, 8, and 15 m from the center of 30 × 30 m experimental quadrats. The number of colors found on an individual was considered representative of dispersal such that the more colors detected, the more an individual moved. The likelihood that arthropods were marked with fluorescent powder and the number of colors detected differed among taxonomic groups. Most taxa were marked with one color and a high proportion of those individuals were collected adjacent to the band in which they were marked, suggesting limited dispersal. Canopy gaps and understory vegetation removal influenced movement of three taxa of highly mobile arthropods: Parajulidae and Paradoxosomatidae (detritivores), and Opiliones (scavengers). Opiliones were less likely to be marked with fluorescent powder in canopy gaps than under closed canopy in July, but more likely to be marked in August. Paradoxosomatidae were less likely to be marked in canopy gaps than under closed canopy in August, but their movement was unaffected in July. Parajulidae were more likely to be marked with fluorescent powders when understory vegetation was removed in July and August. Limited dispersal of most other ground‐dwelling arthropods suggests that these more sessile taxa may experience decreased survival and reproduction if they are unable to cope with environmental change in response to natural and anthropogenic disturbances. Understanding how disturbances mediate arthropod movement can inform biodiversity conservation strategies and sustainable forest management.

Urban green roofs promote metropolitan biodiversity: A comparative case study

Urban green spaces can provide habitat and resources for urban dwelling fauna. Suburban green spaces occur most commonly as parks and roadside vegetation, but as human populations grow and space in cities becomes increasingly limited, space-efficient green solutions like green roofs and walls in metropolitan areas are becoming increasingly common. However, the efficacy of these forms of green infrastructure in attracting and promoting biodiversity remains limited. To address this, we compared arthropod, gastropod, and avian species richness and diversity between green and conventional roofs on neighbouring and identical buildings in metropolitan Sydney, Australia. By monitoring local biodiversity using motion sensing camera traps and regular insect surveys, we found that the green roof supported four times the avian, over seven times the arthropod, and twice the gastropod diversity of the conventional roof. Only the green roof attracted locally rare species including blue banded bees (Amegilla Cingulata) and metallic shield bugs (Scutiphora pedicellata). Our results suggest that green roofs, like other urban green spaces, can have ecological significance by attracting and supporting urban fauna that may then add important functional capacities to previously depauperate spaces. This study demonstrates the potential for the widespread adoption of green roofs to create more biologically diverse cities.

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.

Temperature and productivity distinctly affect the species richness of ectothermic and endothermic multitrophic guilds along a tropical elevational gradient.

The diversity of endotherms and ectotherms may be differently affected by ambient temperature and net primary productivity (NPP). Additionally, little is known about how these drivers affect the diversity of guilds of different trophic levels. We assessed the relative role of temperature and NPP in multitrophic guilds of ectothermic (arthropods: ants, ground beetles, spiders, and harvestmen) and endothermic (large mammals) animals along a tropical elevational gradient. We sampled arthropods at eight elevation belts and large mammals at 14 elevation belts in Atlantic rainforest (ranging from 600 to 2450m.a.s.l.) of Itatiaia National Park, Southeast Brazil. Overall arthropod species richness was more associated with temperature than overall large-mammal species richness, while the latter was more associated with NPP. When separated into trophic guilds, we found that the species richness associated with NPP increased across arthropod trophic levels from herbivores to predators. Conversely, although NPP influenced large-mammal herbivore species richness, its effects did not seem to accumulate across large-mammal trophic levels since the species richness of large-mammal omnivores was more associated with temperature and none of the variables we studied influenced large-mammal predators. We suggest that thermal physiological differences between ectotherms and endotherms are responsible for the way in which arthropods and large mammals interact with or are constrained by the environment. Furthermore, the inconsistency regarding the role of temperature and NPP on species richness across multitrophic guilds of ectotherms and endotherms could indicate that thermal physiological differences might also interfere with energy use and flux in the food web.

Re-established grasslands on farmland promote pollinators more than predators

Agricultural intensification is among the major threats to farmland biodiversity and associated ecosystem services. Agri-environment schemes in Europe aim to counteract the continuous decrease of permanent grassland habitat and related decline of biodiversity in agricultural landscapes. We established new grasslands adjacent to permanent old grasslands to study effects on arthropod pollinators and predators. Over three years, we assessed the effects of newly established grasslands on activity density, species richness and assemblages of pollinators (syrphids, bumblebees, solitary bees) and ground-dwelling predatory arthropods (carabids, spiders, ants). Pollinator activity density and species richness of all three pollinator groups approximately doubled in newly established grasslands compared to old grasslands, indicating suitability of new grasslands as pollinator feeding habitat. Predator responses were less consistent. Species richness and activity density of carabids and ants did not increase in new grasslands, indicating slower adaptation to new habitats. Spider activity density increased in the newly established grasslands and in adjacent cereal fields, but no significant differences in species richness compared to old grasslands were observed. Bumblebees and solitary bees showed distinct distance decays in cereal fields. Syrphid activity density declined in cereal fields far away from the newly established grasslands, but not nearby. Carabids increased and ants decreased in species richness and activity density with increasing distance from old grasslands in cereal fields and newly established grasslands alike. In contrast, spider species richness and activity density decreased with increasing distance from old grasslands in cereal fields only, but there was no distance decay in newly established grasslands. While pollinators utilized the additional floral resources within the whole area of newly established grassland quickly, predators reacted much slower. Even after three years, there was no measurable response of carabid and ant activity density and only a minor response of spiders. This clearly shows that short-term measures are not sufficient to sustainably conserve farmland biodiversity. The conservation of permanent grassland and landscape heterogeneity should be prioritized. However, the restoration of new grassland should also be encouraged by agri-environment schemes as a supplement, to enhance functional biodiversity in agricultural landscapes.

Small-scale traditional maize farming fosters greater arthropod diversity value than conventional maize farming

Globally insects are in decline, with the transformation of natural areas for agriculture one of the most important drivers of this decline. Yet, insects play an important role in regulating ecosystem services such as pollination, soil fertility and pest suppression, so their conservation within agricultural areas is critical. We examined comparative impacts of traditional small-scale low input farming versus large-scale conventional farming systems, and mono-cropped versus inter-cropped systems in Kenyan maize fields on predator, ant and herbivore arthropod species richness and composition. We also considered the value of hedgerows and percentage of surrounding maize cover for arthropod conservation. As expected, traditional farming retained higher herbivore species richness, evenness and abundance, as well as higher predator abundance compared to conventional farming. Percentage maize cover was positively correlated to ant species richness, predator and herbivore abundance, as well as determining species assemblage composition for ants and herbivores. Hedgerow volume and the comparison of mono- vs inter-cropping were important predictors for predator evenness. These results suggest that the low input farming systems retain far higher arthropod numbers, although this does not seem to be due to the use of intercropping on the farms. Rather it seems that hedgerows play an important role in maintaining arthropods. While higher maize coverage surrounding the farm increases the species and abundance of arthropods in the fields, this is most likely due to the high biotope fidelity of arthropods that specialize in open cropping systems such as maize fields.Implications for insect conservationThe results here are encouraging as the retention of culturally important farming techniques (i.e., the traditional Kenyan farmers) and small improvements, such as the retention of hedgerows, greatly promotes biodiversity in the farmlands.

Field Borders Provide Winter Refuge for Beneficial Predators and Parasitoids: A Case Study on Organic Farms.

Semi-natural field borders are frequently used in midwestern U.S. sustainable agriculture. These habitats are meant to help diversify otherwise monocultural landscapes and provision them with ecosystem services, including biological control. Predatory and parasitic arthropods (i.e., potential natural enemies) often flourish in these habitats and may move into crops to help control pests. However, detailed information on the capacity of semi-natural field borders for providing overwintering refuge for these arthropods is poorly understood. In this study, we used soil emergence tents to characterize potential natural enemy communities (i.e., predacious beetles, wasps, spiders, and other arthropods) overwintering in cultivated organic crop fields and adjacent field borders. We found a greater abundance, species richness, and unique community composition of predatory and parasitic arthropods in field borders compared to arable crop fields, which were generally poorly suited as overwintering habitat. Furthermore, potential natural enemies tended to be positively associated with forb cover and negatively associated with grass cover, suggesting that grassy field borders with less forb cover are less well-suited as winter refugia. These results demonstrate that semi-natural habitats like field borders may act as a source for many natural enemies on a year-to-year basis and are important for conserving arthropod diversity in agricultural landscapes.

Land use and climate change affects butterfly diversity across northern Austria

ContextBiodiversity is severely decreasing at a global scale since several decades. There are significant changes in species community compositions, reductions of species richness and abundances of arthropods, as well as of arthropod biomass. Land use intensification and climate change are assumed to be main drivers causing biodiversity change and loss. However, proximate effects of land use, landscape configuration, topography and climate on species richness and species community composition were only rarely analysed.ObjectiveWe study the effects of current land cover, landscape structures and climate on butterfly and burnet moth species diversity and community composition across northern Austria (i.e. the federal state of Salzburg).MethodsWe compiled observation data of butterflies and burnet moths for the past 40 years. We divided faunal data, land cover data and data on climate into 5 × 5 km2 grid cells. We classified all lepidopterans assessed into groups according to their distribution, behaviour, ecology and life-history.ResultsWe found higher species richness and temporal community shifts in higher elevations, and where topographic heterogeneity is high. Habitat connectivity has a positive impact on ecologically specialised, sedentary, and endangered species. Mean temperature and precipitation positively influenced species richness. ConclusionsBoth, land-use and climate strongly shape biodiversity structures. In particular, landscape heterogeneity promotes the diversity of ecological niches, which subsequently accelerates species diversity, including specialist species. Agricultural intensification in higher elevations and at steep slopes is more difficult and therefore less attractive, and thus the level of biodiversity is still high. In addition, climate warming might lead to the accumulation of species in higher elevations. Our study further underlines the relevance of habitat conservation at lower elevations, where not all habitat types are conserved sufficiently.

Using Locally Adapted Seeds to Restore Native Plants and Arthropods After Plant Invasion and Drought

Non-native plants alter conditions and can reduce the effectiveness of restoration tools. Under these conditions, adding native, locally adapted seeds to favor establishment of native plant communities may provide a potential restoration strategy. We explored the efficacy of soil disturbance and the addition of native seed to restore native plant and arthropod communities in landscapes dominated by Kleberg bluestem (Dichanthium annulatum [Forssk.] Stapf, Old World bluestem grasses, OWB) in summers 2011−2013; our study coincided with severe drought. We compared vegetation and arthropods on disked plots with and without seed (experimental plots), as well as plots within adjacent, undisturbed OWB monocultures. Adding seeds increased cover of native plants and reduced cover of OWBs relative to unseeded plots and undisturbed OWB monocultures. Most of the plants we recorded in seeded plots were not included in the seed mix; we hypothesize that arthropods may have been consuming the added seed rather than the seed bank, permitting native plants in the seed bank to establish. Adding seed also increased arthropod species richness, which was more pronounced as drought severity decreased. During severe drought, arthropod abundance in experimental plots was comparable with undisturbed OWB monocultures, despite the absence of vegetation after disking. However, as drought subsided, undisturbed OWB monocultures had more arthropods than experimental plots. Non-native arthropods, particularly herbivores, were positively associated with OWBs; adding seed was associated with reduced dominance of both OWBs and nonnative arthropods. Reducing dominance of OWBs by adding seed was also associated with reduced dominance of some predators that consume non-native arthropod prey. Understanding how communities respond to multiple disturbances seems especially important to inform restoration strategies given that changes in climate patterns and establishment of invasive species are likely to be more common and widespread.

Accounting for species interactions is necessary for predicting how arctic arthropod communities respond to climate change

Species interactions are known to structure ecological communities. Still, the influence of climate change on biodiversity has primarily been evaluated by correlating individual species distributions with local climatic descriptors, then extrapolating into future climate scenarios. We ask whether predictions on arctic arthropod response to climate change can be improved by accounting for species interactions. For this, we use a 14‐year‐long, weekly time series from Greenland, resolved to the species level by mitogenome mapping. During the study period, temperature increased by 2°C and arthropod species richness halved. We show that with abiotic variables alone, we are essentially unable to predict species responses, but with species interactions included, the predictive power of the models improves considerably. Cascading trophic effects thereby emerge as important in structuring biodiversity response to climate change. Given the need to scale up from species‐level to community‐level projections of biodiversity change, these results represent a major step forward for predictive ecology.

Soil Biodiversity as Affected by Different Thinning Intensities in a Pinus laricio Stand of Calabrian Apennine, South Italy

Forest soil biodiversity, which drives natural ecosystem multifunctionality, can be altered by incorrect forestry management practices. Pinus laricio is the most representative and widespread conifer species in Calabria, South Italy, and appropriate management is needed to maintain Pinus laricio forest for its great economic and natural value. In Europe, thinning is considered the most effective silvicultural treatment to maintain/increase the ecological value of coniferous stands. In this study, moderate thinning (MT), intense thinning (HT), and clear cut (CC) treatments were used to manage Pinus laricio stands with the aim of identifying the thinning intensity that is less detrimental to soil biodiversity. The effects of the different thinning intensities were evaluated, in two contrasting seasons (summer and winter), on the abundance, and diversity of arthropods, fungi, and bacteria colonies as well as on selected soil properties (organic matter, humification index, bulk density, pH) related to soil habitability. Results evidenced that the abundance, species richness, and diversity of arthropods, as well as fungi, bacteria colonies, and soil properties, changed with the treatments and seasons. Under HT, the greatest biodiversity and the highest amounts of arthropods, fungi, and bacteria were found in both seasons. This study finds evidence for Connell’s intermediate disturbance hypothesis, highlighting that the greatest organic carbon content and humification index, as well as the lowest bulk density, found in HT reduced the likelihood of competitive exclusion between occurring species, thereby promoting high species richness and diversity. This study gives insights into ecological relationships between understory composition related to tree species abundance and soil community.

Cross-taxon congruence between predatory arthropods and plants across Mediterranean agricultural landscapes

Although arthropods are among the most diverse, abundant and ecologically important animals in terrestrial ecosystems, they are generally neglected in most biodiversity inventories due to their complex systematics and overwhelming diversity, coupled with the current decline in the number of taxonomists. For this reason, several surrogate groups for arthropod diversity have been proposed, with plants being identified as a good putative cross-taxon indicator. By sampling plants and three groups of ground-dwelling arthropods (rove beetles, ground beetles and spiders) in 300 sites across 15 landscapes including multiple semi-natural and agricultural habitats, we tested for habitat-dependence and scale-dependence in the cross-taxon congruence. Plant species richness was a poor predictor of the species richness of predatory arthropods. Among the predator groups, ground beetles appeared as the best potential surrogate for the other ground-dwelling predators. This is backed by the fact that ground beetles were extremely diverse and abundant in all habitats and are usually easier to identify than both rove beetles and spiders. Decreasing the scale at which the cross-taxon congruence was tested improved the strength of the cross-taxon congruence. Although plant species richness was not a suitable indicator for the diversity of predatory arthropods, vegetation structure played a significant role in influencing cross-taxon congruence in both natural and agricultural habitats. Our results highlight the need to explore the cross-taxon relationships at a fine habitat resolution scale, as strong correlations were obtained only by taking into account habitat identity.

Organic farming promotes arthropod predators, but this depends on neighbouring patches of natural vegetation

Current global declines in insect populations emphasise the need for biodiversity appropriate farming. Organic farming can promote in-field biodiversity, yet this may depend on surrounding vegetation, which acts as a source habitat for arthropod predators that promote pest suppression. Here we assess the role that natural vegetation plays in relation to farm management type (conventional versus organic farming) for arthropod predator diversity in a perennial cropping system (citrus orchards). We also determine how environmental variables, specifically plant species richness, flower abundance, cover crop height, litter depth, as well as grass, herbaceous, woody plant and rock cover, influence arthropod predators across the orchard – natural vegetation landscape mosaic. Arthropod species richness and abundance were significantly higher on organic farms, but species composition varied with biotope (natural vegetation, orchards with associated natural vegetation and those without associated natural vegetation). There was an interesting interaction between farming type and surrounding biotope. Organic farms had greater arthropod predator species richness and abundance than conventional farms in the absence of natural vegetation, but there was no difference between organic and conventional orchards in the presence of natural vegetation. Thus, patches of remnant natural vegetation improve the biodiversity of arthropod predators within conventional orchards. The environmental variables sampled here were all significant drivers for some focal taxa in most biotopes, emphasising the need to conserve heterogeneity in agricultural systems. The value of organic farming depends on landscape context, particularly proximity of natural vegetation. It is therefore recommended that to improve predator species richness and abundance, farmers should aim to diversify both local- and landscape-level environmental heterogeneity.

Ecosystem Engineering Effects of Mongolian Marmots (Marmota sibirica) on Terrestrial Arthropod Communities

The Mongolian marmot (Marmota sibirica) is a large, endangered rodent species that ranges across the steppe regions of Mongolia, and parts of China and Russia. Marmot lives colonially and creates extensive burrow systems that change the soil nutrient profiles and influence plant and animal community composition and productivity. We examined the role of marmots on the diversity and abundance of ground-dwelling and flying insects. We hypothesize that the arthropod communities differ between marmot colonies and surrounding grasslands in diversity and abundance. We trapped 4765 individuals of arthropods representing 178 species of insects and 12 families of spiders. Marmot colony sites differed significantly from off colony sites by communities of ground-dwelling and flying insects. Our findings indicate that abundance and species richness of arthropods are largely associated with marmot burrows, which might be a reason for increased habitat heterogeneity, such as bare ground, specific vegetation structure, and thermoregulatory site by ecosystem engineering. Our results demonstrate that the marmots are keystone species in arid ecosystems, and have complementary, additive effects on steppe arthropod communities.

Arthropod facilitation mediated by abandoned dead domatia

AbstractIn ant–plant mutualistic interactions, plants provide shelter (domatia) and/or food to ants and in exchange, and ants provide protection against herbivores. After plant tissue senescence, ants are expected to abandon dead domatia, leaving these empty spaces available for other arthropods. In this study, we tested for the role of the mutualistic interaction between Cordia alliodora and Azteca pittieri in promoting new habitats for arthropods through abandoned dead domatia. We predicted that species richness, abundance, and colonization frequency of secondary arthropods would be greater in dead branch domatia (dead domatia) compared with live branch domatia (live domatia). During March 2019, we selected 38 C. alliodora trees in a Mexican tropical dry forest. For each tree, we collected five live and five dead domatia, for 380 domatia in total. We found six morphospecies of secondary arthropods colonizing live domatia, while 42 were present in dead domatia. Ants were the most species‐rich group (10 species) in abandoned dead domatia and utilized them as nesting sites (25 nests). Secondary arthropod species richness, abundance, and colonization frequency were greater in dead domatia compared with live domatia. We concluded that the Azteca–Cordia mutualistic interaction is an important habitat facilitator by promoting new habitats for arthropods through abandoned dead domatia.

Anticipated or delayed responses to rainfall: Effects of rainfall on arthropods assemblage in an enclave of evergreen forest

In northeast Brazil, the most part of vegetation is a deciduous seasonally dry tropical forest called of “Caatinga”. Despite the semi-arid areas correspond to most of the caatinga vegetation, there are some areas 500 m above sea level with an annual rainfall up to 1200 mm forming evergreen forest enclaves. Macroarthropod abundance and fauna composition differences in Caatinga are related to seasonal rainfall effects but, this difference is unclear in the enclaves of evergreen forests. Thus, the aim of this study was to measure the effects of rainfall on insect, arachnid, and centipede assemblages in an enclave of evergreen forest within the Caatinga vegetation. We tested the following hypotheses: 1) rainfall changes arthropod abundance and species richness; 2) predator abundance correlate with prey, and 3) abundance arthropod abundance and species richness exhibit a delayed or anticipated response to rainfall. No effects of rainfall on insects and arachnids abudance were observed. There was a significant correlation between prey and predator abundance with changes in dominant species between the rainy and dry seasons. The insects and arachnids can show some anticipated responses to rainfall. The abundance and richness of centipedes were influenced by rainfall whith a delayed response. Our findings indicate that, in evergreen forest enclaves within Caatinga vegetation, the soil arthropods show different responses compared to rainfall than the most common areas of the Caatinga domain and an increase in the detection of insects and arachnids just before the beginning of the rainy season.

Selective extinctions resulting from random habitat destruction lead to under-estimates of local and regional biodiversity loss in a manipulative field experiment.

Land-use change is a significant cause of anthropogenic extinctions, which are likely to continue and accelerate as habitat conversion proceeds in most biomes. One way to understand the effects of habitat loss on biodiversity is through improved tools for predicting the number and identity of species losses in response to habitat loss. There are relatively few methods for predicting extinctions and even fewer opportunities for rigorously assessing the quality of these predictions. In this paper, we address these issues by applying a new method based on rarefaction to predict species losses after random, but aggregated, habitat loss. We compare predictions from three rarefaction models, individual-based, sample-based, and spatially clustered, to those derived from a commonly used extinction estimation method, the species-area relationship (SAR). We apply each method to a mesocosm experiment, in which we aim to predict species richness and extinctions of arthropods immediately following 50% habitat loss. While each model produced strikingly accurate predictions of species richness immediately after the habitat loss disturbance, each model significantly underestimated the number of extinctions occurring at both the local (within-mesocosm) and regional (treatment-wide) scales. Despite the stochastic nature of our small-scale, short-term, and randomly applied habitat loss experiment, we found surprisingly clear evidence for extinction selectivity, for example, when abundant species with low extinction probabilities were extirpated following habitat loss. The important role played by selective extinction even in this contrived experimental system suggests that ecologically driven, trait-based extinctions play an equally important role to stochastic extinction, even when the disturbance itself has no clear selectivity. As a result, neutrally stochastic null models such as the SAR and rarefaction are likely to underestimate extinctions caused by habitat loss. Nevertheless, given the difficulty of predicting extinctions, null models provide useful benchmarks for conservation planning by providing minimum estimates and probabilities of species extinctions.

Historical, local and landscape factors determine the success of grassland restoration for arthropods

In Europe, extensively managed grasslands have undergone large-scale declines due to intensive agriculture and abandonment. Their restoration supports arthropod biodiversity within farming systems. We investigated limiting factors for arthropod establishment during grassland restoration across a chronosequence of 52 restoration sites established by either natural regenerating or direct seeding. Our study covered 363 arthropod species of 10 orders, including detritivores, herbivores, predators and pollinators. These were sampled using pitfall traps, suction sampling and transect walks. The similarity of plant communities on restoration sites to target species rich grasslands was positively correlated with the similarity of the arthropod communities to these same grasslands. There was evidence that restoration sites located in landscapes suffering from historic large-scale loss of species rich grassland (1930–2015) had lower success in replicating the composition of arthropod communities and supported the lowest levels of species richness. The age of the restoration site was a predictor of restoration success for some trophic levels. For example, predator species richness was greatest in the oldest restoration sites. However, this was only the case were sites were either of large size or located in landscapes with the lowest historic loss of species rich grassland. Impacts of within site management also affected arthropod communities. The annual frequency of cutting negatively affected detritivores species richness, and selected against traits including herbivore monophagy. Overall arthropod species richness was positively correlated with sward height. These results emphasise the relative importance of the success with which the floral community is replicated, as well as landscape and management factors, during grassland restoration. This has implications for future agri-environmental schemes. In particular, achieving high quality within-site management that maximises establishment of the plant communities needs to be the initial focus of any restoration program.