Spider Species Richness Research Articles

Sampling effort and species richness assessment: a case study on Brazilian spiders

The knowledge on the geographical distribution of species is essential for building biogeographical and macroecological hypotheses. However, information on this regard is not distributed uniformly in space and usually come from biased sampling. The aim of this study is to quantify the influence of spatial distribution of sampling effort on the assessment of spider species richness in Brazil. We used a database of spider distribution records in Brazil, based on the taxonomic and biodiversity survey literature. The results show that the Atlantic Forest was better sampled and had the highest spider species richness among the Brazilian biomes. The Amazon, though having large collecting gaps and high concentration of records around major cities and rivers, showed the second highest number of species. The Pampa had a large number of records, but these are concentrated near a major city in the transition zone with the Atlantic Forest. The Cerrado, Caatinga and Pantanal had shown to be poorly sampled and, consequently, were among the lesser known biomes regarding the spider fauna. A linear regression analysis showed that the spider species richness in Brazil is strongly correlated to the number of records. However, we have identified areas potentially richest in species, which strongly deviate from the predicted by our analyses. Our results show that it is possible to access the spatial variation in species richness, as long as the variation in sampling effort is taken into account.

Trait composition and functional diversity of spiders and carabids in linear landscape elements

Agricultural intensification is a cause of global biodiversity decline. Seminatural linear landscape elements (LLE) within agricultural landscapes can considerably mitigate these declines, but their effects on functional properties of biodiversity are poorly known. We analyzed trait composition and functional diversity (functional dispersion) of spiders and carabids in woody and herbaceous LLE. We expected that species assemblages of woody LLE are more diverse and K-selected compared to herbaceous LLE, and that effects of environmental parameters vary between LLE types. We selected 58 LLE in an agricultural landscape in Northwest Germany. We sampled carabids and spiders by pitfall trapping and measured landscape connectivity, landscape-wide land-use diversity, local land-use diversity, and local plant richness as explanatory variables. The trait composition of arthropods in woody LLE was more K-selected (lower dispersal ability, a higher food specialization or trophic level) than in herbaceous LLE. Moreover, spider functional diversity was higher in woody LLE. Spider functional diversity and proportion of predatory carabids in woody LLE increased with increasing connectivity of the habitats. In contrast, in herbaceous LLE local plant richness and landscape-wide land-use diversity were most important drivers for spider and carabid diversity and traits. Our results show that species richness and functional diversity of spiders and carabids were differently affected by landscape and local factors. Therefore, the importance of landscape connectivity was higher in woody LLE, suggesting that their inhabitants are more sensitive to habitat fragmentation than the highly mobile generalist species living in herbaceous habitats.

Advances in the Study of the Spider Fauna (Aranei) of Russia and Adjacent Regions: A 2015 Update

Abstract Recent (2015) calculations of spider species richness in the boundaries of Russia and other former Soviet Union countries, as well as between physiographical regions of these territories, are provided in comparison with earlier data. By December 31st, 2015, 3,374 and 2,397 spider species have been reported from the FSU territories and Russia, respectively.

Effects of tree species diversity on a community of weaver spiders in a tropical forest plantation

AbstractThe effects of producer diversity on predators have received little attention in arboreal plant communities, particularly in the tropics. This is particularly true in the case of tree diversity effects on web‐building spiders, one of the most important groups of invertebrate predators in terrestrial plant communities. We evaluated the effects of tree species diversity on the community of weaver spiders associated with big‐leaf mahogany (Swietenia macrophylla) in 19, 21 × 21‐m plots (64 plants/plot) of a tropical forest plantation which were either mahogany monocultures (12 plots) or polycultures (seven plots) that included mahogany and three other tree species. We conducted two surveys of weaver spiders on mahogany trees to evaluate the effects of tree diversity on spider abundance, species richness, diversity, and species composition associated with mahogany. Our results indicated that tree species mixtures exhibited significantly greater spider abundance, species richness, and diversity, as well as differences in spider species composition relative to monocultures. These results could be due to species polycultures providing a broader range of microhabitat conditions favoring spider species with different habitat requirements, a greater availability of web‐building sites, or due to increased diversity or abundance of prey. Accordingly, these results emphasize the importance of mixed forest plantations for boosting predator abundance and diversity and potentially enhancing herbivore pest suppression. Future work is necessary to determine the specific mechanisms underlying these patterns as well as the top‐down effects of increased spider abundance and species richness on herbivore abundance and damage.

The role of plant fidelity and land-use changes on island exotic and indigenous canopy spiders at local and regional scales

Understanding the processes that lead to successful invasions is essential for the management of exotic species. We aimed to assess the comparative relevance of habitat (both at local and at regional scale) and plant features on the species richness of local canopy spiders of both indigenous and exotic species. In an oceanic island, Azores archipelago, we collected spiders in 97 transects belonging to four habitat types according to the degree of habitat disturbance, four types of plants with different colonisation origin (indigenous vs. exotic), and four types of plants according to the complexity of the vegetation structure. Generalised linear mixed models and linear regressions were performed separately for indigenous and exotic species at the local and regional landscape scales. At the local scale, habitat and plant origin explained the variation in the species richness of indigenous spiders, whereas exotic spider richness was poorly correlated to habitat and plant structure. The surrounding landscape matrix substantially affected indigenous spiders, but did not affect exotic spiders, with the exception of the negative effect exerted by native forests on the richness of exotic species. Our results revealed that the local effect of habitat type, plant origin and plant structure explain variations in the species richness observed at a regional scale. These results shed light on the mechanistic processes behind the role of habitat types in invasions, i.e., plant fidelity and plant structure are revealed as key factors, suggesting that native forests may act as physical barriers to the colonisation of exotic spiders.

Understory spider assemblages from a cloud forest in Chiapas, Mexico, and their relationships to environmental variables

Cloud forests have high ecological complexity, but their reduced area and exploitation by human communities, make them one of the most endangered ecosystems in Mexico. The spider assemblages of a cloud forest reserve in Chiapas, Mexico, were studied to analyze influence of environmental variables (forest stand structure, temperature and relative humidity) and their temporal variation, on the distribution, abundance, species richness and assemblage structure of spiders. Ten parcels were established for the sampling of spiders and the recording of forest and climatic variables. Spider sampling took place during the dry and rainy seasons. Vegetation data were recorded at the end of the study (except canopy cover, which was registered at the end of each season). Some differences were found among parcels in forest stand structure, but only the density of seedlings showed a high correlation with spider abundance, seemingly seedlings (by its size and architecture) offered numerous supports for the understory spiders’ webs and then promote the settlement of weaver spiders. Also there were some correspondences between the similarity patterns of forest structure and spider assemblages, giving some evidence of a forest structure influence on the integration of spiders’ assemblages. Spider abundance was notoriously higher in the dry season. Other environmental variables had only weak effects on spider variables (abundance and species richness) and assemblage structure. The most abundant families were Tetragnathidae, Theridiidae and Linyphiidae, which were also among the dominant families in other tropical cloud forests, with the latter two also being among the most diverse. As complex ecosystems, tropical cloud forests seem to have complicated interactions with their inhabitant animals, not easy to elucidate.

Effects of local and landscape factors on spiders and olive fruit flies

Conservation biological control uses naturally occurring enemies to limit pest populations and to increase agricultural sustainability. The olive is an important perennial crop in Mediterranean countries and there is a high demand for alternative solutions to pesticide applications. As spiders are the most abundant predators in olive trees, they could be effective against the olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), the main pest of this crop. In order to optimise the effectiveness of spiders, it is essential to understand their relationship with environmental factors at both the local and landscape scales. We studied spiders and their potential prey in the canopies of 18 olive orchards in different landscapes of the Monte Pisano (central Italy). The abundance and species richness of spiders as well as the abundance of sheet web spiders were lower in conventional orchards than in organic orchards. The composition of spider communities was affected by the amount of Mediterranean garigue in the surrounding landscape, and the abundance of flies increased with increasing percentage of wood in the landscape. Olive fruit fly densities were negatively correlated with cursorial and sheet web spiders⿿ abundance, suggesting that spiders may be involved in pest suppression. As the response of spiders to local and landscape factors was family and guild specific, tailored management for biological control requires further clarification of the individual and interactive effects of the different spider families and guilds on B. oleae.

Diverse Effects of a Seven-Year Experimental Grassland Fragmentation on Major Invertebrate Groups.

Habitat fragmentation is a major driver of biodiversity loss, but observed effects vary and may depend on the group examined. Time since fragmentation may explain some differences between taxonomical groups, as some species and thus species composition respond with a delay to changes in their environment. Impacts of drivers of global change may thus be underestimated in short-term studies. In our study we experimentally fragmented nutrient-poor dry calcareous grasslands and studied the response of species richness, individual density and species composition of various groups of invertebrates (gastropods, ants, ground beetles, rove beetles, orthoptera, spiders, woodlice) in 12 small (1.5 m * 1.5 m) and 12 large (4.5 m * 4.5 m) fragments and their corresponding control plots after 7 years. We further examined responses to fragmentation in relation to body size and habitat preferences. Responses to fragmentation varied between taxonomical groups. While spider species richness and individual density were lower in fragments, the opposite was true for an orthopteran species and woodlice. Species composition and β-diversity differed between fragments and control plots for some groups. However, the interaction treatment*plot size was rarely significant. Species with high occupancy rates in undisturbed control plots responded more negatively to the fragmentation, while species with large body size were relatively more abundant in fragments in some groups. No effect of the fragmentation was found for ants, which may have the longest lag times because of long-lived colonies. However, relationships between abundance and the species’ preferences for environmental factors affected by edge effects indicate that ant diversity too may be affected in the longer-term. Our results show the importance of considering different groups in conservation management in times of widespread fragmentation of landscapes. While species richness may respond slowly, changes in abundance related to habitat preferences or morphology may allow insights into likely long-term changes.

The influence of vegetation structure on spider species richness, diversity and community organization in the Apšuciems calcareous fen, Latvia

La influencia de la estructura de la vegetacion en la riqueza de especies, la diversidad y la organizacion de las comunidades de aranas en el pantano en terreno calcareo de Apsuciems, en Letonia Se considera que los pantanos en terrenos calcareos son uno de los ecosistemas mas amenazados de Europa. Asimismo, son uno de los habitats con mayor diversidad, puesto que albergan una variedad de especies de plantas y animales increiblemente rica y diversa. No obstante, a pesar de su diversidad, los pantanos en terrenos calcareos se han estudiado poco, especialmente por lo que hace a los invertebrados, como las aranas. Debido a que son buenos indicadores, es interesante conocer su ecologia en habitats singulares y amenazados. Este estudio tiene como finalidad documentar la composicion y diversidad de las especies, familias y gremios de alimentacion de aranas en los estratos edafico y herbaceo del pantano calcareo de Apsuciems, y evaluar la influencia de la estructura de la vegetacion en la organizacion de las comunidades de aranas. En verano de 2012, recogimos aranas que habitan en el suelo utilizando trampas de caida y aranas que habitan en la hierba con redes entomologicas. En total, en el pantano de Apsuciems se recogieron 2.937 aranas pertenecientes a 19 familias y 80 especies. Nuestros resultados indican que las especies y familias de aranas tienden a estratificarse a lo largo de la estructura vertical del habitat; la composicion de aranas en el estrato edafico diferia de la del estrato herbaceo. Por el contrario, la estructura de los gremios de alimentacion era parecida en el estrato edafico y el estrato herbaceo. Cada uno de los dos estratos estudiados presentaba gremios parecidos en proporciones similares. Nuestros resultados tambien pusieron de manifiesto que la composicion de aranas diferia considerablemente entre distintas partes del gremio y que gran parte de esta variabilidad se podia explicar por las propiedades arquitectonicas del habitat. En general, cuanto mas diversa era la vegetacion, mayor era el numero de aranas.

Bahasa Indonesia

Spiders are the main predators in paddy ecosystem. Application of entomopathogenic fungus, such as Beauveria bassiana (Balsamo) is not expected to have any negative effect on spiders in the paddy field. This research was aimed to compare species composition, abundance, and species richness of spiders in ratoon paddy. The research was done on three hectares of rice fields that were treated with the following treatment, (i) 2 L/ha/application of liquid B. bassiana, (ii) 2 L/ha/application compost extract (without liquid B. bassiana), and (iii) a combination of liquid B. bassiana and compost extract with each using the same 2L/ha/application dose. The result of this research showed that B. bassiana bioinsecticide application did not affect the abundance and species richness of spiders in ratoon paddy. The treatments did not significantly affect species richness and abundance of the canopy-inhabiting spiders. The species richness and abundance of the soil-dwelling spiders on the paddy field applied by the bioinsecticide was not different from those without the bioinsecticide. The treatments did not effect species composition of the canopy-inhabiting and the soil-dwelling spiders. Application of B. bassiana bioinsecticide was not harmful for the spiders in the rice field.

Local and Landscape Correlates of Spider Activity Density and Species Richness in Urban Gardens.

Urbanization is a major threat to arthropod biodiversity and abundance due to reduction and loss of suitable natural habitat. Green spaces and small-scale agricultural areas may provide habitat and resources for arthropods within densely developed cities. We studied spider activity density (a measure of both abundance and degree of movement) and diversity in urban gardens in Santa Cruz, Santa Clara, and Monterey counties in central California, USA. We sampled for spiders with pitfall traps and sampled 38 local site characteristics for 5 mo in 19 garden sites to determine the relative importance of individual local factors. We also analyzed 16 landscape variables at 500-m and 1-km buffers surrounding each garden to determine the significance of landscape factors. We identified individuals from the most common families to species and identified individuals from other families to morphospecies. Species from the families Lycosidae and Gnaphosidae composed 81% of total adult spider individuals. Most of the significant factors that correlated with spider activity density and richness were local rather than landscape factors. Spider activity density and richness increased with mulch cover and flowering plant species, and decreased with bare soil. Thus, changes in local garden management have the potential to promote diversity of functionally important spiders in urban environments.

Optimizing arthropod predator conservation in permanent grasslands by considering diversity components beyond species richness

Grasslands host large parts of Europe’s agricultural arthropod diversity. Considering the adverse effects of ongoing land use changes on many grassland taxa, there is an urgent need to establish measures that allow for optimizing the conservation of permanent grassland habitats and their climatic, environmental and ecological benefits. Here, data from 42 permanent grasslands were used to quantify the effect of individual management practices on different diversity components in spider and ground beetle communities. Intensive fertilization and frequent cutting reduced the species richness of spiders and the number of threatened spider species, but increased the average taxonomic distinctness of communities. Moreover, high grazing intensity reduced the average body size of individuals in local spider communities. Frequent cutting led to a higher abundance of predaceous and omnivorous ground beetles but a lower abundance of herbivorous species. These opposing responses of both different biodiversity components and different taxa to individual grassland management practices confirm that no single management practice maximizes the biodiversity of arthropod predators in permanent grasslands at the local scale. Rather, our study suggests that arthropod predator diversity can only be conserved by promoting a landscape-scale combination of different management practices and intensities in permanent grasslands. When considering conservation measures, conservation goals should not only be formulated in terms of local species richness, but also need to address other components of diversity such as taxonomic or functional diversity.

In stable, unmanaged grasslands local factors are more important than landscape-level factors in shaping spider assemblages

Previous studies reported that landscape-level factors are vital to support diversity of spiders in strongly modified arable lands and disturbed habitats such as managed semi-natural grasslands. Cropland management (ploughing, fertilization, and pest management) and agricultural practices (mowing and grazing) destroy and/or modify regularly the spider assemblages; thus, continuous recolonization from the surrounding landscape is vital to sustain the species pool. On the contrary, we hypothesized that in unmanaged grasslands, the spider assemblages are stable and the importance of recolonization is limited, the local factors become much more important drivers in shaping spider assemblages than landscape-level factors. We tested the importance of local and landscape-level factors on the abundance and species richness of spiders in unmanaged grasslands. At the landscape-level, we found that only the isolation had significant effect on the total abundance, on the abundance of hunting and habitat specialist species, and on the abundance of a frequent species (Gnaphosa mongolica). At the local scale, however, four out of five studied factors influenced significantly the species richness and abundance of spider assemblages and the abundance of two frequent species (Alopecosa psammophila, Berlandia cinerea). Species richness and abundance increased by plant cover, litter cover, and patch size, while decreased by bare ground cover. We found that in unmanaged grasslands, the local factors had vital role in maintaining the spider species richness; this is just the opposite conclusion that was earlier reported for agricultural ecosystems, where landscape-level effects had crucial role providing the species for continuous recolonization.

Strikingly high effect of geographic location on fauna and flora of European agricultural grasslands

Wild bees, spiders, earthworms and plants contribute considerably to biodiversity in grasslands and fulfil vital ecological functions. They also provide valuable services to agriculture, such as pollination, pest control and maintenance of soil quality. We investigated the responses of wild bees, spiders, earthworms and plants to geographic location, agricultural management and surrounding landscape variables using a dataset of 357 grassland fields within 88 farms in six European regions. Regions and taxonomic groups were selected to have contrasting properties, in order to capture the multiple facets of European grasslands. Geographic location alone had a dominant effect on the fauna and flora communities. Depending on the taxonomic group, various agricultural management and surrounding landscape variables alone had an additional significant effect on observed species richness, rarefied species richness and/or abundance, but it was always small. Bee species richness and abundance decreased with increasing number of mechanical operations (e.g. cutting). Observed spider species richness and abundance were unrelated to measured aspects of agricultural management or to surrounding landscape variables, whereas rarefied species richness showed significant relations to nitrogen input, habitat diversity and amount of grassland habitats in the surroundings. Earthworm abundance increased with increasing nitrogen input but earthworm species richness did not. Observed plant species richness decreased with increasing nitrogen input and increased when there were woody habitats in the surroundings. Rarefied plant species richness decreased with mechanical operations. Investigating multiple regions, taxonomic groups and aspects of fauna and flora communities allowed identifying the main factors structuring communities, which is necessary for designing appropriate conservation measures and ensuring continued supply of services.

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.

Effects of non-nativeEucalyptusplantations on epigeal spider communities in the northern Negev desert, Israel

Abstract Plantation forests are being planted at an increasing rate and account for 7% of the global forested area. The majority of planted forests are composed of exotic tree species, and Eucalyptus trees have become the most widely planted hardwood species in the world. While Eucalyptus plantations have economic importance, their role in native biodiversity conservation, especially in areas without naturally occurring forests, is little explored. In the present study, we assessed the impact on biodiversity of replacing natural semi-deserts with Eucalyptus camaldulensis plantations. The impact was evaluated by comparing epigeal spider communities of seven plantations with previously sampled communities of seven natural habitats in the northwestern Negev, Israel. In contrast to our assumptions, spider species richness was higher in Eucalyptus plantations compared to natural semi-deserts. However, substantial differences in species composition between the two habitat types were observed. Few species found ...

Predator body sizes and habitat preferences predict predation rates in an agroecosystem

Top-down control of pest populations by their natural enemies is a crucial ecosystem service supporting agricultural production. The relationship between predator community composition and predation rates of pests remains poorly investigated. A deeper understanding of the processes shaping interaction strength in agroecosystems is needed if we are to accurately predict natural pest control services. Functional traits in a community can provide insights into processes shaping community assembly and ecosystem functioning. Functional diversity indices can be constructed from a single trait, such as body length, or from the integration of multiple traits, such as body length, hunting mode and habitat preference. However, their performance in predicting ecosystem functioning and services remains largely unexplored. We used empirical data replicated at landscape scales to examine which component of ground-dwelling predator community structure (activity-density, species richness, evenness, taxonomic distinctness and functional diversity) of spiders, carabids and staphylinids best predicted predation rates of aphids in spring cereals. Functional diversity explained a greater part of variation in predation rates than any other taxonomic or activity-density component. Among the indices for functional diversity, single-trait indices better predicted variation in aphid predation rates compared with multiple-trait indices. In particular, we found that the community-average value of body-size of ground-dwelling predators was negatively related to predation rates of aphids, whereas the proportion of spiders with a preference for arable land was positively related to predation rates. Additional analyses of body-size distributions of ground-dwelling predators suggested that intraguild predation was a key process shaping the relationship between predator community composition and the level of aphid pest control. Considering the functional trait composition of communities provides a more mechanistic understanding of the processes shaping the strength of trophic interactions in terrestrial ecosystems, thus improving predictive power. Body-size distribution and habitat preference appear to be particularly valuable in predicting the level of natural pest control by ground-dwelling predators in an agroecosystem.

Importance of core and linear marsh elements for wetland arthropod diversity in an agricultural landscape

Abstract The importance of linear habitat elements connecting core habitat patches for biodiversity conservation is still poorly understood. We surveyed reed strips along drainage ditches and reed marshes in an agricultural landscape to assess how both the density of linear habitat elements and the area of core habitat affect diversity and community composition of spiders, ground beetles, and long‐legged flies. For each taxonomic group, species composition of both ‘all’ and ‘typical wetland’ species, but not species richness was different between ditches and marshes. Overall local species richness and richness of species of conservation interest were affected at a landscape scale both by the density of ditches and by the area of core wetland. Strength and direction of these effects differed among groups. An increase in the density of reed ditches positively affected the total species richness of spiders and ground beetles and the species richness of typical wetland ground beetles, but not for long‐legged flies and typical wetland spiders. The positive effects were explained by improved network functionality, rather than by increase in available habitat area at landscape level. The number of red list spiders and long‐legged flies increased only with increasing core wetland area, while no significant effects were found for the number of red list ground beetles. Our study revealed that preserving or increasing the density of habitat corridors (more reed ditches) can be beneficial for the species richness of particular predatory arthropods, including species of conservation concern (especially ground beetles). Other groups react indifferently or are only positively impacted by an increase of core wetland area.

A Case Study of the Herb-Dwelling Spider Assemblages (Aranei) in a Meadow Under the Power Transmission Lines in Ukrainian Carpathians / Исследование сообществ хортобионтных пауков (Aranei) мезофитного луга под высоковольт- ной линией электропередачи в Украинских Карпатах

Abstract The fauna and structure of herbdwelling spider assemblages in mesophitic meadow under the high voltage power line near Irliava village (Uzhhorod District, Transcarpathian Region) were analyzed on the material collected by sweep netting. Th e counts were held at five sampling sites: 1) under the wires; 2) at a distance of 50 m; 3) 100 m; 4) 150 m; 5) 200 m. In total, 41 spider species of 14 families were collected. Erigonoplus globipes (L. Koch, 1872) and Hylyphantes nigritus (Simon, 1881) were recorded in the Carpathians for the first time. Th e reduction of total number and species richness of spiders was registered as the approaching to the high voltage power line. Except single finds, no species avoided the wire nearest sites (0-50 m). Abundance of most spider families (except Araneidae) was not significantly influenced by distance from the high voltage power line.

Influence of Crop Management and Environmental Factors on Wolf Spider Assemblages (Araneae: Lycosidae) in an Australian Cotton Cropping System.

Wolf spiders (Lycosidae) are the most abundant ground-hunting spiders in the Australian cotton (Gossypium hirsutum L.) agroecosystems. These spiders have potential in controlling pest bollworms, Helicoverpa spp. (Lepidoptera: Noctuidae) in minimum-tilled fields. A study was carried out during a wet growing season (2011-2012) in Narrabri, New South Wales, Australia, to determine how different crop rotations and tillage affect wolf spider assemblages in cotton fields. Spider abundance and species richness did not differ significantly between simple plots (no winter crop) and complex plots (cotton-wheat Triticum aestivum L.-vetch Vicia benghalensis L. rotation). However, the wolf spider biodiversity, as expressed by the Shannon-Weaver and Simpson's indices, was significantly higher in complex plots. Higher biodiversity reflected a more even distribution of the most dominant species (Venatrix konei Berland, Hogna crispipes Koch, and Tasmanicosa leuckartii Thorell) and the presence of more rare species in complex plots. T. leuckartii was more abundant in complex plots and appears to be sensitive to farming disturbances, whereas V. konei and H. crispipes were similarly abundant in the two plot types, suggesting higher resilience or recolonizing abilities. The demographic structure of these three species varied through the season, but not between plot types. Environmental variables had a significant effect on spider assemblage, but effects of environment and plot treatment were overshadowed by the seasonal progression of cotton stages. Maintaining a high density and even distribution of wolf spiders that prey on Helicoverpa spp. should be considered as a conservation biological control element when implementing agronomic and pest management strategies.