Hybrid ecosystems can contribute to local biodiversity conservation

Calcareous grasslands have become severely threatened habitats in Europe. The aim of this study was to investigate the changes in plant species richness, and functional and phylogenetic diversity in northern Estonian calcareous (alvar) grasslands resampled after 90 years of land-use change. Functional traits characterizing species that have benefited most from decreased habitat area and altered environmental conditions, and additional species that can potentially inhabit the remaining grassland patches were identified. Also changes in the relative amount of habitat-specific species were studied to detect a possible decrease in habitat integrity. Although grasslands in the studied region had lost most of their original area (~90 %), species richness had substantially increased due to invasion by more competitive, nutrient-demanding native species. Functional diversity generally increased, whereas phylogenetic diversity showed no response to altered conditions. Overall, these grasslands have lost their integrity as calcareous grassland habitat type in the region, because the relative amount of habitat-specific characteristic species has declined significantly. However, although the grasslands have transformed to a ‘hybrid’ habitat type and restoration to their previous state is likely not reasonable, such degraded species-rich grassland fragments can still be recognized as important habitats to preserve high local biodiversity and several characteristic species of calcareous grasslands. As current landscapes consist of an increasing number of hybrid and novel communities, new tools to supplement traditional conservation or restoration practices are necessary to recognize and maintain regions and habitats of high local biodiversity.     

Landscape structure and management regime as indicators of calcareous grassland habitat condition and species diversity

This study investigates the importance of spatial landscape characteristics and habitat management on the condition of calcareous grassland in the North Down Natural Area, Kent UK. We used a digitised map of the study area containing shapefiles of all the habitats including 82 patches of calcareous grassland together with management information for each patch and data on the presence and abundance of a range of calcareous grassland indicator plant species. We defined habitat condition by presence of indicator species and used classification trees to generate models with rules for predicting habitat condition from the landscape spatial characteristics and management information. We also applied the same method to investigate the factors affecting presence or diversity of three ecological groups of positive indicator species and dominance of a negative indicator species. All the models except one showed good classification accuracy and high kappa statistic. Favourable habitat condition was predicted by presence of different types of grazing management, presence of woodland around patches of calcareous grassland and shape complexity. These results indicate that calcareous grassland in favourable condition is management-dependent but also located in less intensively managed landscapes. Unfavourable habitat condition was predicted by threat factors such as lack of management and high incidence of arable or improved grassland around patches of calcareous grassland, indicating nutrient enrichment and habitat degradation. Some of these factors also predicted high diversity of the different ecological species groups. The value of this method for predicting habitat condition and species diversity from baseline ecological data for conservation monitoring at the landscape level is emphasised.     

Habitat Diversity in the Conservation of the Grassland Auchenorrhyncha (Homoptera: Cercopidae,Cicadellidae, Cixidae,Delphacidae) of Northern Britain

Definition of northern British grassland Auchenorrhyncha habitats was carried out using a classification based on analysis of data from 351 sites, involving 121 species, located between Greater Manchester and northern Scotland. Ten habitats were identified showing little influence of geographical position and exhibiting a basic upland-lowland trend. Other factors influencing habitat and species assemblage distribution were soil water, vegetation structure and land cover. An analysis of the species data with satellite-derived land cover data indicated that the lowland covers of tilled land, coast and urban and the upland covers of heath grassland and shrub heath were most important in affecting both species and assemblage distribution. The large-scale survey of grassland sites provided new information on both the ecology and distribution of individual Auchenorrhyncha species. Some were limited to specific habitat types but a considerable number were generalist species found in most or all of the 10 habitat types but showing preferences within upland to lowland or wet to dry site gradients. The ability to generate a subtle grassland Auchenorrhyncha habitat classification with large-scale survey results from standardised and reproducible sampling increases the potential for using habitat diversity for the conservation of grassland Auchenorrhyncha. Habitat preservation would also ensure that species richness (biodiversity) is maintained and that the habitats of rare species are conserved.     

Asymmetric carabid beetle spillover between calcareous grasslands and coniferous forests

Central European calcareous grasslands are considered biodiversity hotspots, but are severely threatened by the change in land-use and by habitat fragmentation. Coniferous forests are typical adjacent habitats to calcareous grasslands, as abandoned calcareous grasslands are often afforested or develop into coniferous forests by succession. To investigate spillover between calcareous grasslands and coniferous forests, a total of 144 pitfall traps for carabid beetles were placed at three different distances (1, 5, 20 m) from the edge in both habitats at eight locations from April to late August. We found that both habitats had a distinct species assemblage and a decrease in spillover with increasing distance from the habitat edge into the adjacent habitat. Calcareous grasslands were more affected by spillover from the adjacent coniferous forests than vice versa because more forest specialists penetrated into calcareous grasslands than grassland specialists penetrated into coniferous forests. We conclude that spillover into small and isolated habitats can severely change species assemblages, which has to be considered in conservation measures. The protection of large sites with small edge-interior ratios can reduce negative effects on species assemblages in endangered calcareous grasslands.     

Naturally recruited herbaceous vegetation in abandoned Belgian limestone quarries: towards habitats of conservation interest analogues?

We examined if naturally recruited herbaceous vegetation in abandoned Belgian limestone quarries tend towards plant communities analogous to semi-natural habitats of conservation interest. We studied taxon-based assemblages (using two-dimensional non-metric multidimensional scaling ordination) and functional patterns (relative to Grime’s competitor, stress tolerator and ruderal plant strategies (CSR) classification) of plant communities (n = 360 plots) among three different time periods after quarry abandonment (< 3 y, 3–20 y, >?20 y). We compared those successional assemblages with those of habitat of conservation interest plant communities (n = 53 plots): lowland hay meadows and rupicolous, xerophilous and mesophilous calcareous grasslands. Our results indicate that naturally recruited herbaceous vegetation compositionally resembled mesophilous grassland, even though initial substrate conditions were more similar to rupicolous or xerophilous grasslands. The specific successional pathway we found in CSR state-space differs from Grime's predictions because there was a functional shift in plant assemblages from dominance by ruderals to dominance by stress-tolerant species. The differences in successional trajectories we found on different types of rock substrate suggest that conservation management should adopt a site-specific approach, recognizing that the highest probabilities of success on hard limestone will be restoration to calcareous grassland analogues.     

Spatial structure, rock type, and local environmental conditions drive moss and lichen distribution on calcareous boulders

Although mosses and lichens are a relevant component of the biota of rock habitats targeted for biodiversity conservation in Europe, the ecological factors driving their distribution are still poorly known. In this work, we examined the epilithic moss and lichen assemblages colonizing boulders of different types of calcareous rocks co-occurring in the same area in the Italian Alps. The goals were: (1) to evaluate if and to what extent different calcareous rocks host different assemblages; (2) to identify species associated to each rock type; (3) to quantify the relative importance of rock type, local environmental factors, and habitat spatial structure in explaining species distribution. Our results demonstrated that different calcareous rocks host different moss and lichen assemblages with some typical species, indicating that each rock type contributes to the total diversity of both mosses and lichens. Local environmental conditions influenced mosses and not lichens whose distribution is mainly associated to rock type. The patterns of both organism groups were also significantly related to habitat spatial structure, species assemblages tending to have a patchy distribution, which may reflect dispersal dynamics. Our results have implications for conservation: (1) each rock type may play a relevant role in maintaining the overall diversity contributing with unique assemblages and typical species; (2) the patchy distribution of both moss and lichen assemblages should warn from considering rock patches as a monotonous repetition of the same habitat across space.     

Environmental drivers of spider community composition at multiple scales along an urban gradient

Broad-scale modification of natural ecosystems associated with urbanisation often leads to localised extinctions and reduced species richness. Despite this, habitats within the urban matrix are still capable of supporting biodiversity to varying degrees. As species have different responses to anthropogenic habitat modification, the species composition of urban areas can depend greatly on the habitat characteristics of the local and surrounding areas. The aim of this study was to compare the community composition of spiders in private gardens, urban parks, patches of remnant vegetation and continuous bushland sites, so as to identify habitat variables associated with variation in spider populations along and within the urban gradient and matrix. Overall spider abundances and richness were highest in remnant vegetation patches and were associated with increased vegetation cover at microhabitat and landscape-scales. While gardens were not as diverse as remnant patches, they did support a surprisingly high diversity of spiders. We also found that species composition differed significantly between gardens and other urban green spaces. Higher richness within gardens was also associated with greater vegetation cover, indicating the importance of private management decisions on local biodiversity. Differences in community composition between land-use types were driven by a small number of urban-tolerant species, and spider guilds showed different responses to habitat traits such as vegetation cover and human population densities. This study demonstrates that urban land-uses support unique spider communities and that maintaining vegetation cover within the urban matrix is essential in order to support diverse spider communities in cities.     

The value of the trackway system within a lowland plantation forest for ground-active spiders

European forest management guidelines include conservation and enhancement of biodiversity. Within plantation forestry, trackways provide contiguous permanent open-habitat with potential to enhance biodiversity. We examined the ground-active spider assemblage in the trackway network of Thetford Forest, Eastern England, the largest lowland conifer forest in the UK, created by afforestation of heathland and farmland. Results are relevant to other forests in heath regions across Europe. We used pitfall trapping to sample the spider assemblage of trackways within thicket-aged stands (n = 17), mature stands (n = 13) and heathland reference sites (n = 9). A total of 9,314 individuals of 71 species were recorded. Spider assemblages of the trackway network were distinct from those of the heathland reference sites; however, trackways were found to support specialist species associated with grass-heath habitats, including nationally scarce species. Richness of grass-heath species was similar for trackways in thicket-aged forest and heathland reference sites, although the abundance of individuals was three times greater in the reference sites. Trackways in mature stands had lower grass-heath species richness and abundance than both thicket trackways and heath reference sites. Wide trackways within thicket stands contained greater richness and abundance of specialist xeric species than narrower trackways. However, fewer xeric individuals were found in trackways compared to heathland reference sites. Either inferior habitat quality in trackways or poor dispersal ability of specialist xeric species may largely restrict these to relict areas of heathland. Targeted widening of trackways to allow permanent unshaded habitat and creating early successional stages by mechanical disturbance regimes could improve trackway suitability for specialist species, helping to restore connectivity networks for grass-heath biodiversity.     

Forest Loss and the Biodiversity Threshold: An Evaluation Considering Species Habitat Requirements and the Use of Matrix Habitats

Habitat loss is the main driver of the current biodiversity crisis, a landscape-scale process that affects the survival of spatially-structured populations. Although it is well-established that species responses to habitat loss can be abrupt, the existence of a biodiversity threshold is still the cause of much controversy in the literature and would require that most species respond similarly to the loss of native vegetation. Here we test the existence of a biodiversity threshold, i.e. an abrupt decline in species richness, with habitat loss. We draw on a spatially-replicated dataset on Atlantic forest small mammals, consisting of 16 sampling sites divided between forests and matrix habitats in each of five 3600-ha landscapes (varying from 5% to 45% forest cover), and on an a priori classification of species into habitat requirement categories (forest specialists, habitat generalists and open-area specialists). Forest specialists declined abruptly below 30% of forest cover, and spillover to the matrix occurred only in more forested landscapes. Generalists responded positively to landscape heterogeneity, peaking at intermediary levels of forest cover. Open area specialists dominated the matrix and did not spillover to forests. As a result of these distinct responses, we observed a biodiversity threshold for the small mammal community below 30% forest cover, and a peak in species richness just above this threshold. Our results highlight that cross habitat spillover may be asymmetrical and contingent on landscape context, occurring mainly from forests to the matrix and only in more forested landscapes. Moreover, they indicate the potential for biodiversity thresholds in human-modified landscapes, and the importance of landscape heterogeneity to biodiversity. Since forest loss affected not only the conservation value of forest patches, but also the potential for biodiversity-mediated services in anthropogenic habitats, our work indicates the importance of proactive measures to avoid human-modified landscapes to cross this threshold.     

Biodiversity in agricultural landscapes: different non-crop habitats increase diversity of ground-dwelling beetles (Coleoptera) but support different communities

Agricultural intensification poses a major threat to the conservation of biodiversity and associated ecosystem services. Since non-crop habitats are regarded as important refuges for farmland biodiversity, various greening measures have been proposed to halt biodiversity loss. However, the effectiveness of these measures for biodiversity conservation is still under debate. Therefore, we here compared ground-dwelling beetle (Coleoptera) assemblages of different non-crop habitats (field margins, set-aside fields sown with wildflowers, and permanent grassland fallows) and wheat fields within an intensively used agricultural landscape in western Germany. Taxonomic diversity of Carabidae, Staphylinidae and other coleopteran families and their conservation value were higher in all non-crop habitats than on wheat fields. Surprisingly, though, different types of non-crop habitats did not differ in species richness or the number of threatened species. Thus, field margins and sown wildflower fields were as effective in promoting beetle diversity as grassland fallows. However, different non-crop habitats supported different species assemblages, and several species, in particular especially large ones, were restricted to grassland fallows. These results suggest that different greening measures are effective in promoting the biodiversity of beetles, and that permanent grassland fallows are essential for nature conservation. The fact that habitat types harbored different assemblages stresses the need to combine a variety of greening measures to yield the highest benefit for biodiversity.

     

Trait-Specific Responses of Wild Bee Communities to Landscape Composition,Configuration and Local Factors

Land-use intensification and loss of semi-natural habitats have induced a severe decline of bee diversity in agricultural landscapes. Semi-natural habitats like calcareous grasslands are among the most important bee habitats in central Europe, but they are threatened by decreasing habitat area and quality, and by homogenization of the surrounding landscape affecting both landscape composition and configuration. In this study we tested the importance of habitat area, quality and connectivity as well as landscape composition and configuration on wild bees in calcareous grasslands. We made detailed trait-specific analyses as bees with different traits might differ in their response to the tested factors. Species richness and abundance of wild bees were surveyed on 23 calcareous grassland patches in Southern Germany with independent gradients in local and landscape factors. Total wild bee richness was positively affected by complex landscape configuration, large habitat area and high habitat quality (i.e. steep slopes). Cuckoo bee richness was positively affected by complex landscape configuration and large habitat area whereas habitat specialists were only affected by the local factors habitat area and habitat quality. Small social generalists were positively influenced by habitat area whereas large social generalists (bumblebees) were positively affected by landscape composition (high percentage of semi-natural habitats). Our results emphasize a strong dependence of habitat specialists on local habitat characteristics, whereas cuckoo bees and bumblebees are more likely affected by the surrounding landscape. We conclude that a combination of large high-quality patches and heterogeneous landscapes maintains high bee species richness and communities with diverse trait composition. Such diverse communities might stabilize pollination services provided to crops and wild plants on local and landscape scales.     

Even the Smallest Non-Crop Habitat Islands Could Be Beneficial: Distribution of Carabid Beetles and Spiders in Agricultural Landscape

Carabid beetles and ground-dwelling spiders inhabiting agroecosystems are beneficial organisms with a potential to control pest species. Intensification of agricultural management and reduction of areas covered by non-crop vegetation during recent decades in some areas has led to many potentially serious environmental problems including a decline in the diversity and abundance of beneficial arthropods in agricultural landscapes. This study investigated carabid beetle and spider assemblages in non-crop habitat islands of various sizes (50 to 18,000 square metres) within one large field, as well as the arable land within the field, using pitfall traps in two consecutive sampling periods (spring to early summer and peak summer). The non-crop habitat islands situated inside arable land hosted many unique ground-dwelling arthropod species that were not present within the surrounding arable land. Even the smallest non-crop habitat islands with areas of tens of square metres were inhabited by assemblages substantially different from these inhabiting arable land and thus enhanced the biodiversity of agricultural landscapes. The non-crop habitat area substantially affected the activity density, recorded species richness and recorded species composition of carabid and ground-dwelling spider assemblages; however, the effects were weakened when species specialised to non-crop habitats species were analysed separately. Interestingly, recorded species richness of spiders increased with non-crop habitat area, whereas recorded species richness of carabid beetles exhibited an opposite trend. There was substantial temporal variation in the spatial distribution of ground-dwelling arthropods, and contrasting patterns were observed for particular taxa (carabid beetles and spiders). In general, local environmental conditions (i.e., non-crop habitat island tree cover, shrub cover, grass cover and litter depth) were better determinants of arthropod assemblages than non-crop habitat island size, indicating that the creation of quite small but diversified (e.g., differing in vegetation cover) non-crop habitat islands could be the most efficient tool for the maintenance and enhancement of diversity of ground-dwelling carabids and spiders in agricultural landscapes.     

Perennial Agroenergy Feedstocks as En Route Habitat for Spring Migratory Birds

Increased production of bioenergy crops in North America is projected to exacerbate already heavy demands upon existing agricultural landscapes with potential to impact biodiversity negatively. Grassland specialist birds are an imperilled avifauna for which perennial-based, next-generation agroenergy feedstocks may provide suitable habitat. We take a multi-scaled spatial approach to evaluate the ability of two candidate second-generation agroenergy feedstocks (switchgrass, Panicum virgatum, and mixed grass–forb plantings) to act as spring migratory stopover habitat for birds. In total, we detected 35 bird species in mixed grass–forb plantings and switchgrass plantings, including grassland specialists and species of state and national conservation concern (e.g., Henslow’s Sparrow, Ammodramus henslowii). Some evidence indicated that patches with higher arthropod food availability attracted a greater diversity of migrant bird species, but species richness, total bird abundance, and the abundance of grassland specialist species were similar in fields planted with either feedstock. Species richness per unit area (species density) was relatively higher in switchgrass fields. The percent land cover of forest in landscapes surrounding study fields was negatively associated with bird species richness and species density. Habitat patch size and within-patch vegetation structure were unimportant in predicting the diversity or abundance of spring en route bird assemblages. Our results demonstrate that both switchgrass and mixed grass–forb plantings can attract diverse assemblages of migrant birds. As such, industrialized production of these feedstocks as agroenergy crops has the potential to provide a source of en route habitat for birds, particularly where fields are located in relatively unforested landscapes. Because industrialization of cellulosic biomass production will favor as yet unknown harvest and management regimes, predicting the ultimate value of perennial-based biomass plantings for spring migrants remains difficult.     

Bird assemblages in fragmented agricultural landscapes: the role of small brigalow remnants and adjoining land uses

Agricultural intensification typically leads to changes in bird diversity and community composition, with fewer species and foraging guilds present in more intensively managed parts of the landscape. In this study, we compare bird communities in small (2–32 ha) brigalow (Acacia harpophylla) remnants with those in adjacent uncultivated grassland, previously cultivated grassland and current cropland, to determine the contribution of different land uses to bird diversity in the agricultural landscape. Twenty remnant brigalow patches and adjacent agricultural (‘matrix’) areas in southern inland Queensland, Australia were sampled for bird composition and habitat characteristics. The richness, abundance and diversity of birds were all significantly higher in brigalow remnants than in the adjacent matrix of cropping and grassland. Within the matrix, species richness and diversity were higher in uncultivated grasslands than in current cultivation or previously cultivated grasslands. Forty-four percent of bird species were recorded only in brigalow remnants and 78% of species were recorded in brigalow and at least one other land management category. Despite high levels of landscape fragmentation and modification, small patches of remnant brigalow vegetation provide important habitat for a unique and diverse assemblage of native birds. The less intensively managed components of the agricultural matrix also support diverse bird assemblages and thus, may be important for local and regional biodiversity conservation.     

Bark-dwelling spider assemblages (Araneae) in the boreal forest: dominance,diversity, composition and life-histories

We collected spiders from tree-bark, foliage and litter habitats in deciduous and conifer dominated stands in NW Alberta (Canada) to define these assemblages and consider their conservation significance. To establish habitat associations, we used Indicator Species Analysis (ISA) together with a species dominance metric (DV′) newly proposed here. Of the 116 species collected, 78 were collected from bark. Results support categorizing 16 species as true bark-dwellers, 16 as facultative bark-dwellers and 46 as accidental bark-dwellers or species of unknown association. Species that were strong indicators of particular microhabitats in analyses restricted to bark habitats lost their indicator value when foliage and ground habitats were also considered, suggesting that bark habitats are critical for specific life-history functions. Clubiona canadensis Emerton 1980, Callobius nomeus (Chamberlin 1919), Pocadicnemis americana Millidge 1976 and Enoplognatha intrepida (Sørensen 1888) were the most common bark-dwelling species but their dominance varied among forest cover-types and trapping techniques. Collecting period, forest cover-type, habitat, and trapping technique were generally important environmental variables influencing composition of bark-dwelling assemblages. Although less important in structuring assemblages, tree status (dead or alive) and decay class were important for particular species. Bark habitats are crucial for boreal forest spider assemblages and must be considered central to maintenance of spider diversity.     

The role of habitat patches on mammalian diversity in cork oak agroforestry systems

Habitat patches, depending on the degree of differentiation from the matrix, can add few or many elements to the species pool of a particular landscape. Their importance to biodiversity is particularly relevant in areas with complex landscapes, where natural, naturalized, or managed habitats are interspersed by small patches of habitat types with very different biophysical characteristics; e.g., fruit orchards and riparian areas. This is the case of the montado landscape, a cork oak agroforestry system that largely covers south-western Portugal. We evaluated whether the high mammalian biodiversity found in this system is, in part, the cumulative result of the species found in the non-matrix habitats. Our results indicate that in areas where there are inclusions of orchards/olive yards and riparian vegetation in the cork oak woodland, a significantly higher number of mammalian species are present. We further detected a positive effect of low human disturbance on mammal diversity. Ultimately, our results can be used by managers to augment their management options, since we show that the inclusion and maintenance of non-matrix habitat patches in cork oak agro-silvo-forestry systems can help to maximize mammal biodiversity without compromising services associated with agriculture and forestry.     

使用陷阱采样在蜘蛛生态学研究中的应用

介绍1种国外常用的研究地面活动蛛知生态学的采样的方法，即陷阱采样。对如何制作和排布陷阱做了比较详细的说明，并对使用陷阱研究的生境以及通过陷阱所获得的类群做了介绍，同时，通过举例对如何使用陷阱及由陷阱得到的数据的数学处理作了说明。     

Non‐cropped fragments as important spider reservoirs in a Pampean agro‐ecosystem

Agricultural landscapes include patches of cropped and non‐cropped habitats. Non‐cropped fragments are often source habitats for natural pest predators which colonise less suitable agricultural fields. The goals of the present study were: (a) to evaluate the contribution of non‐cropped fragments to agro‐ecosystems as biodiversity reservoirs and ecosystem service providers, by assessing the abundance of spider species and their diversity and (b) to quantify the spatial variation in spider communities across different non‐cropped fragments and crops. We hypothesised that non‐cropped fragments function as spider diversity reservoirs with better conditions for reproduction than crops. We collected spiders from 10 restored fragments having had no disturbance for 20 years and four field edges, along a gradient inside the crop adjacent to each fragment. Overall, we collected 3,591 spiders belonging to 49 species/morphospecies in 14 families. Non‐cropped fragments had a central role in the spider community, as estimated through species–habitat networks. We found differences in the diversity and abundance of spiders between non‐cropped and cropped fragments. However, these differences were only for immature spiders, whose abundance decreased from non‐cropped fragments towards the inside of crops. Our results highlight the importance of non‐cropped fragments in agro‐ecosystems as important source habitat patches, reservoirs of biodiversity and sites where spider reproductive success is possibly higher.     

Adjacent woodlands rather than habitat connectivity influence grassland plant,carabid and bird assemblages in farmland landscapes

One response to biodiversity decline is the definition of ecological networks that extend beyond protected areas and promote connectivity in human-dominated landscapes. In farmland, landscape ecological research has focused more on wooded than open habitat networks. In our study, we assessed the influence of permanent grassland connectivity, described by grassland amount and spatial configuration, on grassland biodiversity. We selected permanent grasslands in livestock farming areas of north-western France, which were sampled for plants, carabids and birds. At two spatial scales we tested the effects of amount and configuration of grasslands, wooded habitats and crops on richness and abundance of total assemblages and species ecological groups. Grassland connectivity had no significant effects on total richness or abundance of any taxonomic group, regardless of habitat affinity or dispersal ability. The amount of wooded habitat and length of wooded edges at the 200 m scale positively influenced forest and generalist animal groups as well as grassland plant species, in particular animal-dispersed species. However, for animal groups such as open habitat carabids or farmland bird specialists, the same wooded habitats negatively influenced richness and abundance at the 500 m scale. The scale and direction of biodiversity responses to landscape context were therefore similar among taxonomic groups, but opposite for habitat affinity groups. We conclude that while grassland connectivity is unlikely to contribute positively to biodiversity, increasing or maintaining wooded elements near grasslands would be a worthwhile conservation goal. However, the requirements of open farmland animal species groups must be considered, for which such action may be deleterious.     

Environmental and spatial drivers of spider diversity at contrasting microhabitats

The relative importance of environmental and spatial drivers of animal diversity varies across scales, but identifying these scales can be difficult if a sampling design does not match the scale of the target organisms' interaction with their habitat. In this study, we quantify and compare the effects of environmental variation and spatial proximity on ground‐dwelling spider assemblages sampled from three distinct microhabitat types (open grassland, logs, trees) that recur across structurally heterogeneous grassy woodlands. We used model selection and multivariate procedures to compare the effects of different environmental attributes and spatial proximity on spider assemblages at each microhabitat type. We found that species richness and assemblage composition differed among microhabitat types. Bare ground cover had a negative effect on spider richness under trees, but a positive effect on spider richness in open grassland. Turnover in spider assemblages from open grassland was correlated with environmental distance, but not geographic distance. By contrast, turnover in spiders at logs and trees was correlated with geographic distance, but not environmental distance. Our study suggests that spider assemblages from widespread and connected open grassland habitat were more affected by environmental than spatial gradients, whereas spiders at log and tree habitats were more affected by spatial distance among these discrete but recurring microhabitats. Deliberate selection and sampling of small‐scale habitat features can provide robust information about the drivers of arthropod diversity and turnover in landscapes.