Composition Of Spider Assemblages Research Articles

Response of Spider and Epigaeic Beetle Assemblages to Overwinter Planting Regimes and Surrounding Landscape Compositions.

The rotation patterns of summer rice-winter oil seed rape and summer rice-winter fallow are the main planting regimes in the rice ecosystem in southern China. However, the impact of local rotation patterns and landscape factors on the overwintering conservation of predators in spider and epigaeic beetle assemblages remains poorly understood. Here, we investigate the diversity and density of spiders and beetles over two consecutive winters (2019/2020 and 2020/2021), focusing on the impact of two rotation patterns (rice-fallow and rice-oilseed rape) and surrounding landscape compositions on predator diversity. The main findings of our research were that spiders were more abundant and had a higher activity density in the fallow rice fields (FRs) compared to the oilseed rape fields (OSRs), whereas ground beetles exhibited the opposite pattern. Specifically, fallow rice fields supported small and ballooning spiders (e.g., dominant spider: Ummeliata insecticeps), while OSRs supported larger ground beetles (e.g., dominant beetles: Agonum chalcomus and Pterostichus liodactylus). Moreover, the composition of spider assemblages were impacted by semi-natural habitats (SNHs) during overwintering, while ground beetle assemblages were influenced by overwinter planting patterns. Overall, our results suggest that different planting regimes and preserving semi-natural habitats are a strategic way to enhance species diversity and functional diversity of ground predators. It is, therefore, recommended that to conserve and improve predator diversity during overwintering, land managers and farmers should aim to maintain diverse planting regimes and conserve local semi-natural habitats.

Effects of Natural Habitat and Season on Cursorial Spider Assemblages in Mediterranean Vineyards.

Natural habitats adjacent to vineyards are presumed to have a positive effect on the diversity of natural enemies within the vineyards. However, these habitats differ in vegetation structure and seasonal phenology and in turn could affect the species composition of natural enemies. Here, we compared the species richness and diversity and the composition of spider assemblages in several locations within three commercial vineyards and the nearby natural habitats in a Mediterranean landscape in northern Israel. We sampled spiders by means of pitfall traps in early and in late summer. Both the time in the season and the habitat (natural versus vineyard) affected spider species richness and diversity. More species were found in early summer (47) than in late summer (33), and more occurred in the natural habitat (34 species) than in the vineyards (27-31 species). Fifteen species were found exclusively in the natural habitat, and only 11 species were shared by the vineyards and natural habitat, four of which were the most abundant and geographically widely distributed species in the samples. In late summer, spider diversity in the natural habitat was higher than within the vineyards: the spider assemblages in the vineyards became dominated by a few species late in the crop season, while those of the natural habitat remained stable. Overall, the natural habitat differed in assemblage composition from all within-vineyard locations, while the three locations within the vineyard did not differ significantly in assemblage composition. Season (early vs. late summer), however, significantly affected the spider assemblage composition. This study documents the large diversity of spiders in a local Mediterranean vineyard agroecosystem. Over 60% of the known spider families in the region occurred in our samples, highlighting the importance of this agroecosystem for spider diversity and the potential for conservation biocontrol, where natural habitats may be a source of natural enemies for nearby vineyards.

Multiple Factors at Regional, Landscape, and Local Scales Determine Spider Assemblage Composition in Pomegranate Orchards

Orchards may support high spider diversity relative to annual crops due to their structural complexity and relative stability. Multiple environmental conditions at the landscape, regional, and local scales may influence the assemblage composition of spiders in orchards. We asked which environmental variables best explains spider assemblage composition and the similarity of the assemblages of pomegranate orchards located along a latitudinal gradient in Israel? Spiders were sampled from twelve pomegranate orchards along a climatic gradient from north to south. Orchards located at higher latitudes had richer assemblages than orchards located at lower latitudes. The assemblage composition was influenced at the large scale by latitude and annual crop cover in the surrounding landscape but not by local factors. By contrast, functional groups based on foraging strategies were affected by local scale factors, such as vegetation within the orchards. This study demonstrates the importance of considering environmental variables at different scales to understand the factors affecting the assemblage composition of naturally occurring predators in the orchard.

Multiple Factors at Regional, Landscape, and Local Scales Determine Spider Assemblage Composition in Pomegranate Orchards

Multiple Factors at Regional, Landscape, and Local Scales Determine Spider Assemblage Composition in Pomegranate Orchards

Comparisons of the composition of spider assemblages in three vegetation habitats in Bogor, West Java, Indonesia

Abstract. Lia M, Rauf A, Hindayana D. 2021. Comparisons of the composition of spider assemblages in three vegetation habitats in Bogor, West Java, Indonesia. Biodiversitas 23: 244-255. Vegetation structures are known to influence the microclimate and consequently the invertebrate assemblages. This study, therefore, aims to compare the species composition of assemblages of ground- and foliage-dwelling spiders in three vegetation habitats: undisturbed urban forest, oil palm plantation, and cornfield, in Bogor, West Java. To ensure a thorough representation of all spider guilds, spiders were collected using pitfall traps, sweep net, and through a direct search on ground and vegetation from January to July 2016. A total of 2299 individual spiders, representing 28 families and 207 species/morphospecies were collected. The spider species richness, abundance, and diversity were higher in the forest and oil palm plantation, compared to the cornfield. Furthermore, the dominant guild in the forest habitat was orb weavers, while the oil palm and corn habitats were dominated by ground runners. The non-metric multidimensional scaling exhibited that the composition of spider assemblages varied among the three vegetation habitats, with spider assemblages in forest habitat associated with higher RH, while the corn habitat was correlated with high light intensity and air temperature. The indicator species analysis revealed that Tetragnathidae has high potential as indicators of the dense, complex vegetation structure of the forest, while Lycosidae is indicators of the more open vegetation of oil palm plantation and cornfield habitats.

Spider Assemblages of Tree Branches in Managed and Primeval Deciduous Stands of the Białowieża Forest

The Białowieża Forest is an important biodiversity hotspot on a European scale, and therefore its preservation should have a high priority. However, forest management conducted over a large area of the forest, intensive logging, and elimination of dead trees pose serious threats to many species in the forest. The main aim of this study was to determine the species composition of spider assemblages inhabiting tree branches of the Białowieża Forest and to compare their species richness and the abundance of individuals (adults and juveniles) between managed and primeval stands. Between April and November 2000, we sampled three forest types (oak–lime–hornbeam forest, ash–alder riparian forest, and alder carr) in protected primeval stands within the Białowieża National Park and in managed stands. We collected 1761 specimens from 14 families and identified 41 species. Tree branches were inhabited mainly by juveniles. Species richness was smaller in managed stands compared to primeval stands. The highest number of species was found in primeval alder carr. Our study shows a negative effect of forest management on spider assemblages in terms of species richness. We emphasize the important role of alder carr forests as potential biodiversity hotspots.

It’s All about the Zone: Spider Assemblages in Different Ecological Zones of Levantine Caves

Caves possess a continuum of ecological zones that differ in their microhabitat conditions, resulting in a gradient of nutrients, climate, and illumination. These conditions engender relatively rapid speciation and diverse assemblages of highly specialised spider fauna. It is unclear, however, how zonation of these caves affects spider assemblage composition and structure. Surveys of 35 Levantine caves were conducted to compare the assemblages of spiders between their different ecological zones. The diverse spider assemblages of these caves differed between the entrance, twilight, and dark zones, with troglophiles and accidental species occupying the cave entrance, endemic troglobites occupying the dark zones, and hybrid assemblages existing in the twilight zones. The progression of assemblage composition and divergence throughout cave zones is suggestive of processes of ecological specialisation, speciation, and adaptation of cave-endemic troglobites in the deepest zones of caves, while cave entrance assemblages are composed of relatively common species that can also be found in epigean habitats. Moreover, the cave entrance zone assemblages in our study were similar in the different caves, while the cave dark zone assemblages were relatively distinct between caves. Cave entrance assemblages are a subset of the regional species pool filtered by the cave conditions, while dark zone assemblages are likely a result of adaptations leading to local speciation events.

Massive spider web aggregations in South American grasslands after flooding

1. Major floods of riparian and grassland habitats may lead to a shift in the availability of resources (e.g., food, space) that produces cascading effects on the organisms that rely on it. After flooding occurs, particularly in natural grasslands or agricultural fields, massive aggregative spider webs are occasionally observed. However, given it is an infrequent and unpredictable event, it is seldom reported in detail.2. We characterise two instances of massive web aggregations that followed major floods in grasslands and agricultural fields in Argentina and Uruguay in 2015. In the Argentinean event, we compare the composition of spider assemblages on the webs, in grasses below the webs, and in grasses from nearby habitats, with samples taken in the same location but when the fields were not flooded.3. The assemblage of spiders in the massive web aggregations largely consisted of immature Diapontia uruguayensis (Lycosidae). In the grass below the webs, we recorded an impressive density of 1007 specimens m−1 belonging to several spider species, 6–15 times the density of similar samples without aggregated webs, co‐occurring and showing low levels of aggression among them.4. Our observations and review of the literature support the idea massive webs produced by lycosids are a byproduct of an unusually high density of spiders simultaneously attempting to disperse through the air via ballooning and escaping from floods.

Farming system shapes traits and composition of spider assemblages in Mediterranean cherry orchards.

Habitat properties, including crop type, farming system, management practices, or topographic features such as the hillside aspect, may act as environmental filters that select organisms sharing traits compatible with those conditions. The more environmentally-friendly management practices implemented in organic farming seem to benefit a range of taxa, but the extent of those benefits is not well understood. In cherry orchards of the Jerte Valley (Extremadura, western Spain), we explored the response of spider assemblages to the farming system (organic and conventional) and the hillside aspect (sunny or shady) from a taxonomical, behavioral, and morphological perspective. Spiders from both the canopy and soil surface were collected and identified to family. According to their foraging strategy, spiders were sorted in guilds and, for a selected family in each guild, body size was measured on each captured individual. Spider traits and composition were determined by local factors derived from farming system, and by climate conditions associated to the hillside aspect. In taxonomical terms, spiders benefit from organic farming and by the shady aspect. However, from a behavioral perspective, spiders with different foraging strategies exhibit strong variations in their response to the evaluated factors. From a morphological perspective, body size within guilds is differently conditioned by management practices that constitute conditioning disturbance events for each guild, resulting in selecting small individuals. The observed differences in taxonomical, behavioral, and morphological responses of spider communities to habitat properties highlight the importance of examining their assemblages from different perspectives when assessing how they respond to changes in management practices and topographic features.

The spider diversity and plant hopper control potential in the long-term organic paddy fields in sub-tropical area, China

Previous studies showed that organic farming augmented natural enemies and enhanced pest control in the agroecosystem, but the effect may change over time, as long-term application of different cultivation methods would gradually affect the agricultural systems. In this paper, spider diversity and its plant hopper control potential were assessed in paddy fields cultivated organically for 5 (OR5), 10 (OR10) and 15 (OR15) years and in conventional paddy fields (CR). The results showed that the abundance, richness and Pilou evenness of spiders in organic paddy fields were significantly higher than those in conventional paddy fields were, but no significant difference found between OR5, OR10 and OR15. There was no significant difference between Shannon Wiener index (H') of spiders in organic and conventional paddy fields. There was no distinct difference in spider assemblage composition between conventional and organic paddy fields, and a considerable overlap between the organic paddy fields with different organic farming period. Plant hopper was less abundant in organic paddy fields than conventional ones in rice blooming stage, but there was no difference in other rice growth stages. A higher number of the spider species in organic paddy fields had large temporal overlap with plant hopper than that in conventional fields. Adopting organic practices in paddy fields can maintain a high diversity of spiders across rice paddy ecosystems, although there was not significant increase of spider diversity over time after five years since transition.

Field survey of foliage-dwelling spiders (Arachnida, Araneae) in Peninsular Malaysia

Diversity of spider groups have received less research attention and there are limited published references for spiders from Peninsular Malaysia. The current survey was conducted to locate and identify foliage-dwelling spiders (Arachnida, Araneae) at five different sites in Peninsular Malaysia. Spider specimens were collected using manual search and sweep-netting between September 2012 and November 2012. A total of 92 morpho-species from 65 genera that belong to 15 families have been successfully recorded and identified. The greatest proportion of specimens captured (40%) were Foliage-runners (Clubionidae, Miturgidae, Oxyopidae, Pisauridae, Salticidae, Scytodidae, Thomisidae), followed by orb-weavers (Araniedae, Nephilidae, Tetragnathidae, Uloboridae) (36.5%), space-weavers (Pholcidae, Psechridae Theridiidae) (21.5%) and ground-dwellers (Sparassidae) (2.0%). Cluster analysis has revealed that the same habitat types share a more similar diversity composition compared to different habitat types, which indicates that spider assemblage composition was partly co-dependent on vegetation structure. However, no significant difference in spider assemblage composition was found between all the five sites which follows that these diurnal group of spiders are actually adaptable to various habitat types.

Forest type interacts with milkweed invasion to affect spider communities

Abstract Non‐native tree plantations constitute a large part of forestation worldwide. Plantations are prone to invasion by exotic herbaceous plant species due to habitat properties, including understory vegetation structure. We established 40 sampling sites in 10 plantation forests. Sites were selected according to tree species (native poplar forests and exotic pine plantations) and common milkweed (Asclepias syriaca) density (invaded and non‐invaded sites) in a full factorial design. We collected spiders with pitfall traps. We found a significant effect of A. syriaca invasion on spider functional diversity (Rao's quadratic entropy), with invaded sites having a lower functional diversity than non‐invaded sites. A larger effect of invasion with A. syriaca on the RaoQ of spiders was observed in pine compared to poplar plantations. Spider species were larger, and web‐building spiders were more frequent in poplar forests than in pine plantations. We found no effect of A. syriaca invasion on species richness or abundance of spiders. Species composition of spider assemblages in the two forest types was clearly separated according to non‐metric multidimensional scaling. We identified seven species associated with pine plantations and six species associated with poplar plantations. The similar species richness and the higher functional diversity of non‐invaded sites suggested that these trait states were less similar than invaded sites and that functionally different species were present. In contrast, the invaded sites had lower functional diversities and thus more uniform trait state compositions, suggesting that environmental filtering played an important role in species sorting, making invaded plantations low‐quality secondary habitats for the original spider fauna.

Body size mediates the relationship between spider (Arachnida: Araneae) assemblage composition and prey consumption rate: results of a mesocosm experiment in the Yukon, Canada.

Many ecological assemblages are undergoing rapid changes in composition and diversity, and changes at one trophic level can have direct and cascading effects on other trophic levels. Prey consumption typically increases with predator diversity due to niche complementarity and sampling effects. However, the effect of functional traits and interactions between predator species mean that the relationship is far from simple. In July 2016, we performed a series of experiments in the Yukon, Canada, to investigate the relationship between spider assemblage composition and prey consumption, with a focus on the wolf spider Pardosa lapponica (Thorell 1872). We carried out feeding trials, in which P. lapponica and other spider species were offered potential prey, as well as mesocosm experiments, in which we varied spider assemblage composition within small enclosures. We confirmed that P. lapponica is a generalist consumer, individual consumption rate increased with spider body size, and that intraguild predation is present. We found that prey consumption was greatest in the least diverse assemblage but consumption did increase with predator functional trait variation and biomass. The best model of prey consumption included predator assemblage composition, variation in body mass, biomass, and all interactions. The body size of a spider affects its trophic niche, energy requirements, and its interactions with other spiders. As a result, body size mediates the relationship between spider assemblage composition and prey consumption. A deeper understanding of the relationships between traits and functions will allow us to better predict the effect of species loss or gain on ecosystem functions.

Arthropod assemblages and functional responses along an urbanization gradient: A trait-based multi-taxa approach

Urbanization causes considerable alteration across a wide range of ecosystem functions at regional and global scales. These changes could be key drivers of habitat stability and ecosystem services in urban greenspaces. The aim of this study was to test the influence of urbanization on taxonomic and functional diversities of arthropods of different trophic levels. We collected predator spiders, polyphagous rove beetles, and decomposer woodlice along a rural-suburban-urban gradient by litter sifting. Neither the taxonomic, nor the functional diversity (Rao’s quadratic entropy) using a morphological trait (body size) and ecological traits (habitat affinity, humidity preference, and disturbance sensitivity) of the spiders were significantly different along the urbanization gradient. For rove beetles, taxonomic diversity was significantly higher in rural sites compared to suburban and urban ones, while functional diversity did not differ significantly between sites. Both the taxonomic and the functional diversities of woodlice were significantly higher in the rural sites than in the suburban or urban sites. Detrended canonical correspondence analysis also showed that urbanization did not cause considerably changes in composition of spider assemblages, while rove beetle and woodlouse assemblages showed clear separation between rural and urban sites. This study pointed out that trophic levels may be a crucial driver of the responses to urbanization. Our results suggest that urbanization has a less harmful effect on predator spiders, as they can easily recolonize the managed urban greenspaces. Contrarily, recolonization of arthropods at lower trophic levels (rove beetles and woodlice) into the urban habitats is considerably restricted.

Environmental heterogeneity, not distance, structures montane epigaeic spider assemblages in north-western Patagonia (Argentina)

There is considerable controversy around the patterns and processes that influence spatial variation in taxonomic composition in mountain environments. We analysed elevational variation in the taxonomic composition of epigaeic spider assemblages across five mountains in north-western Patagonia (Argentina) to examine the relative importance of dispersal (distance) limitation and environmental heterogeneity on a regional scale. The distance limitation hypothesis predicts greater taxonomic similarity between sampling sites separated by short geographical distances than between mountain peaks separated by longer distances, a lack of indicator species of macro-habitats, and weak associations between spider species composition and environmental gradients. Alternatively, the environmental heterogeneity hypothesis predicts that taxonomic differentiation will occur over short distances along elevation gradients in association with the turnover in major habitats and change in environmental conditions, and that indicator species will be present. We collected spiders using 486 pitfall traps arranged in fifty-four 100-m2 grid plots of nine traps separated by ~ 100 m of elevation, from the base to the summit of each mountain. Multivariate analyses identified spider assemblages that were associated with macro-habitats rather than with mountains. Local environmental variation (mainly in vegetation cover), precipitation and soil characteristics influenced the spatial variation in species composition. Characteristic indicator species showed high specificity and fidelity to macro-habitats, whereas vulnerable species showed high specificity and low fidelity to mountains or macro-habitats. We conclude that, on a regional scale, species adaptation to environmental gradients plays a more important role than dispersal limitation in structuring the taxonomic composition of spider assemblages. Moreover, the presence of indicator species suggests that spiders have a great potential as ecological indicators for evaluating the response of montane biodiversity to future climatic change.

Invasive plants induce the taxonomic and functional replacement of dune spiders

Understanding the impacts caused by invasive plants on higher trophic levels is fundamental to predict future changes to native communities. Invasive plants like Acacia longifolia can change habitat structure and thereby alter the taxonomic and functional diversity and composition of predator communities. This work aims to evaluate the effect of this invasive plant species on spider assemblages, at both taxonomic and functional levels, in grey dunes. Spiders were sampled in six native and six invaded sites, in northwestern Portugal. Individuals were identified to species level and their functional features were quantified. Generalized Linear Models (GLM) were used to compare differences of species richness, abundance, functional diversity (FDQ) and trait proportions between native and invaded dunes. We also assessed the relative contribution of replacement and richness differences to overall taxonomic and functional dissimilarity between native and invaded dunes. GLMs showed that there was no change in species richness between dune types, but there was a significant increase in FDQ in invaded dunes. Significant shifts in the proportion of trait categories were observed. Native dunes favoured ambush hunters and myrmecophagous species. On the contrary, invaded dunes favoured species that inhabit leaf litter, web builders and crustaceophagous species. The proportion of diurnal species was higher in native dunes, contrary to invaded dunes, where both diurnal and nocturnal species dominated. Taxonomic and functional dissimilarity was mainly determined by the replacement, not the net loss, of species and traits. These results showed that functionally different spider species were favoured by the invasion of Acacia longifolia. The invasion of Acacia longifolia certainly attenuated the extreme habitat conditions normally found in grey dunes, allowing the immigration of more generalist species from neighbouring habitat types into invaded dunes. Thus, it can be concluded that there was no homogenization, taxonomic or functional, but changes in the composition of spider assemblages and the replacement of functions after dune invasion.

Spider Assemblages of Hummocks and Hollows in a Primeval Alder Carr in the Białowieża National Park — Effect of Vegetation Structure and Soil Humidity

We studied the species richness, diversity, abundance and guild composition of spider assemblages on the hummocks and in the hollows of the alder carr in the Bialowieza National Park. We also assessed the effect of vegetation structure and soil humidity on spiders settled in these two microhabitats. The spiders were collected from 10 May until 27 October 2001 by pitfall trapping. The main factor which differed between the hummocks and the hollows was soil humidity. In the case of vegetation cover we found some differences between the microhabitats but it was particularly evident in the case of litter, which was higher on the hummocks. Spider species diversity was significantly higher on the hummocks than in the hollows, but the number of individuals captured in both microhabitats was similar. The collected spiders belonged to six guilds and the proportion of spider individuals in particular guilds was significantly different between the hummocks and the hollows. The most abundant guild in both microhabitats was ‘ground hunters’ and the most numerous species was Piratula hygrophila. Our analyses showed that soil humidity positively affected the number of spider species and the number of individuals. Sampling date strongly influenced the number of collected species and spider individuals. Vegetation and litter cover did not have a significant impact on the spider assemblages. Our findings suggest that research conducted only on hummocks in the alder carr does not reveal the real structure of spider assemblages.

Spider species composition in the tree-shrub strata of riparian forests and its microhabitats in southern Brazil

The composition of the spider fauna of riparian forests is insufficiently known. These forests, adjacent to both aquatic and terrestrial environments, are recognised as having important ecosystem functions. We compare the composition of spider assemblages of four riparian forests in different drainage basins, along with their microhabitats (edges and forest interior), in the state of Rio Grande do Sul, southern Brazil. Sampling was carried out in the riparian forests of the following rivers: Piratini, municipality of Arroio Grande; Camaqua, municipality of Cristal; Sinos, municipality of Parobe, and Maquine, municipality of Maquine. Two samples per season were collected in two years, by sampling the tree-shrub strata with a beating tray, following fixed transects. There were six transects per drainage basin, two per microhabitat: grassland edge, forest interior and river edge. Overall, 42,057 spiders were sampled (juveniles: 79%; adults: 21%). Among the adults (8,851 individuals), we identified 440 species. Similarity analyses (ANOSIM) indicated that the araneofauna composition of the four drainage basins differ in their quantitative (Morisita) and qualitative (Simpson) similarity indexes. There were no differences in composition among microhabitats. The composition of the Maquine River basin was the most distinct, possibly due to a greater influence of the Atlantic forest on it and a greater dominance of the Linyphiidae Sphecozone personata (Simon, 1894) (SIMPER analysis, contribution to dissimilarity: 12.15%). Differences in spider composition on large spatial scales most likely reflect regional variations in a number of environmental factors, and result in each area having in increased importance in terms of conservation.

Tree Species Richness Strengthens Relationships between Ants and the Functional Composition of Spider Assemblages in a Highly Diverse Forest

AbstractIn species‐rich ecosystems, such as subtropical and tropical forests, higher trophic level interactions are key mediators of ecosystem functioning. Plant species loss may alter these interactions, but the effects of plant diversity might be modified by intraguild interactions, particularly among predators. We analyzed the relationships between spiders and ants, two dominant predatory arthropod taxa, on tree saplings across a gradient from medium to high woody plant species richness in a subtropical forest in Southeast China. Neither ant nor spider total biomass was significantly related to plant species richness. By contrast, the biomass distribution of web‐building and hunting spiders changed and spider family richness increased in the presence of ants, resulting in more web builder‐dominated assemblages. However, these relationships depended on the plant communities, and were stronger in plots with higher plant species richness. Our results indicate that in addition to potential effects of ants on hunting spiders in particular, ants could indirectly influence intraguild interactions within spider assemblages. The observed shifts in the spider assemblages with increasing ant presence and plant species richness may have functional consequences, as web‐building and hunting spiders have distinct prey spectra. The relationships among ants, spiders, and plant species richness might contribute to explaining the non‐significant relationship between the overall effects of predators and plant diversity previously observed in the same forest plots. Our findings thus give insight into the complexity of biotic interactions in such species‐rich ecosystems.

Effects of reconstruction of a pre-European vertebrate assemblage on ground-dwelling arachnids in arid Australia.

Species loss can result in changes in assemblage structure and ecosystem function through ecological cascades. Australian vertebrate assemblages changed significantly following European colonisation, which resulted in the establishment of invasive vertebrates and the loss of native marsupials, many of which consume invertebrates. Conservation focusses on the removal of invasive carnivores and the reintroduction of regionally extinct species to fenced sites, resulting in what could be considered a reconstruction of pre-European vertebrate assemblages. In semi-arid Australian spinifex mallee ecosystems, we asked: (1) what is the effect of reconstructed pre-European vertebrate assemblages on native arachnid assemblages? and (2) what direct or indirect mechanisms (predation, disturbance and/or competition) could plausibly be responsible for these effects? We compared sites with reconstructed vertebrate assemblages with paired control sites. Arachnids were sampled using pitfall trapping and direct searching. Hypotheses regarding mechanisms were tested using scat analysis (predation) and by comparing burrow depth (disturbance) and scorpion mass (competition) between control and reconstructed sites. The dominant dune scorpion, Urodacus yaschenkoi, was less abundant and a wolf spider (Lycosa gibsoni species group) more abundant in reconstructed sites. Differences in spider assemblage composition were marginally non-significant. Scat analysis confirmed native vertebrate predation on scorpions and we found no evidence that competition or disturbance affected scorpions. We, thus, suggest that changes in spider assemblages may have resulted from ecological cascades via decreases in dune scorpions. The loss of omnivorous mammals and other changes associated with the invasion of carnivores may, therefore, have had broad-reaching consequences for native arachnid assemblages in Australian ecosystems.