Spider Species Richness Research Articles

No detrimental effects of soil disturbance resulting from grassland restoration operations on aboveground‐dwelling invertebrate communities

Active grassland restoration requires soil disturbance by harrowing or plowing prior to seeding to create favorable conditions for plant germination. Yet, it is still unknown if these soil interventions are detrimental to the local ground‐dwelling invertebrate fauna. We evaluated how ground beetle (Carabidae) and spider (Araneae) communities, two important grassland bioindicators, respond to three common grassland restoration methods, differing in soil disturbance intensity and seed application method. The study was carried out in 47 extensively managed mesic meadows using a before‐after‐control‐intervention design. It was applied at the field scale and replicated 12 times across selected Swiss lowland sites. We did not detect any significant differences in abundance and species richness of ground beetles and spiders between restored and control meadows 1 year after restoration. At the community level we observed a slight shift towards a preference for wetter habitat (for both invertebrate groups), and restored meadows harbored a smaller weighted mean body size of spiders than control meadows. The latter was mainly driven by a higher abundance of some small pioneer species typically found in frequently disturbed habitats, notably in arable fields. Our results suggest that 1 year after restoration action, the ground‐beetle and spider communities recovered almost entirely to their predisturbance state, indicating that, with respect to above ground‐dwelling invertebrates, harrowing or plowing can be applied when restoring plant species‐poor grasslands.

Composition, abundance and biodiversity of terrestrial arthropods in pastures and their relationship with landscaping plants

We investigated the association of landscaping plants with the communities of ground-dwelling arthropods within pastures and tested the hypothesis that arthropod biodiversity increases with vegetation heterogeneity. The community characterization and biodiversity of arthropods in a pasture were compared with those within communities with landscaping plants, including forest remnants, Forsythia koreana and Prunus serotina. The total abundance of mites was greater within the forest remnants than within the pasture; however, the abundance of insects and spiders did not differ. Nonmetric multidimensional scaling and the multiresponse permutation procedure revealed that the community composition of insects and spiders differed according to vegetation type. The abundance of Teleogryllus emma was highest within the forest remnant community, which suggested the species’ dependency on vegetation type. Species richness and the Shannon index of insects increased within F. koreana but not within P. serotina compared with the pasture. This suggested that belts of shrubs might have a greater promoting effect on insect biodiversity than belts of trees. Species richness of spiders did not differ by vegetation type. The total number of insect and spider species within the study area increased by 2.8 and 3.5 times, respectively, by establishing three types of vegetation. These results suggested that increasing vegetation heterogeneity by establishing landscaping plants is a good option for conserving insect and spider biodiversity in pastures.

The Effect of Sampling Bias on Evaluating the Diversity and Distribution Patterns of Iranian Spiders (Arachnida: Araneae)

Although spiders constitute a highly diversified group of animals, the knowledge regarding their geographic distribution (i.e., the so-called Wallacean shortfall) and diversity patterns is incipient on a global scale; while attempts to explore such patterns have been made for the highly diversified Neotropical fauna, several Old World regions are historically neglected. Aiming to close this gap, the present study provides the most comprehensive review of spatial variation in the diversity patterns of the spider fauna of Iran. We also examined the effects of sampling biases on the results. We gathered a database with 4434 non-duplicate records of 935 species of spiders from Iran, 215 of which are currently considered endemic to the country. We showed that, despite a significant improvement in state-of-the-art taxonomic research regarding this fauna in the past 20 years, the Iranian spider fauna suffers from a highly uneven distribution of records throughout the country and its ecoregions. Additionally, highly sampled areas are typically near large cities. We also found a high correlation between the number of records and species of spiders and the number of records of plants and other animals in Iran, suggesting that the biodiversity shortfalls herein described for spiders are corroborated by other taxa. The biases reported herein are likely to be observed for other countries, as the area alone explained only 33.24% of the spider species richness among 171 compared countries. We hope that the present study stimulates further sampling and research aiming to explore this fauna and the underlying biological processes related to its patterns of diversity and distribution.

Landscape-scale connectivity and fragment size determine species composition of grassland fragments

As a consequence of agricultural intensification and habitat fragmentation since the mid-20th century, biological diversity has declined considerably throughout the world, particularly in Europe. We assessed how habitat and landscape-scale heterogeneity, such as variation in fragment size (small vs. large) and landscape configuration (measured as connectivity index), affect plant and arthropod diversity. We focused on arthropods with different feeding behaviour and mobility, spiders (predators, moderate dispersal), true bugs (mainly herbivores and omnivores with moderate dispersal), wild bees (pollinators with good dispersal abilities), and wasps (pollinators, omnivores with good dispersal abilities). We studied 60 dry grassland fragments in the same region (Hungarian Great Plain); 30 fragments were represented by the grassland component of forest-steppe stands, and 30 were situated on burial mounds (kurgans). Forest-steppes are mosaics of dry grasslands with small forests in a matrix of plantation forests. Kurgans are ancient burial mounds with moderately disturbed grasslands surrounded by agricultural fields. The size of fragments ranged between 0.16–6.88 ha (small: 0.16–0.48 ha, large: 0.93–6.88 ha) for forest-steppes and 0.01–0.44 ha (small: 0.01–0.10 ha and large: 0.20–0.44 ha) for kurgans. Fragments also represented an isolation gradient from almost cleared and homogenous landscapes, to landscapes with relatively high compositional heterogeneity. Fragment size, connectivity, and their interaction affected specialist and generalist species abundances of forest-steppes and kurgans. Large fragments had higher species richness of ground-dwelling spiders, and the effect of connectivity was more strongly positive for specialist arthropods and more strongly negative for generalists in large than in small fragments. However, we also found a strong positive impact of connectivity for generalist plants in small kurgans in contrast to larger ones. We conclude that besides the well-known effect of enhancing habitat quality, increasing connectivity between fragments by restoring natural and semi-natural habitat patches would help to maintain grassland biodiversity.

Differences in arthropod communities between grazed areas and grazing exclosures depend on arthropod groups and vegetation types

Livestock grazing is one of the most common management practices for grasslands and can greatly affect their biodiversity. However, arthropod diversity response patterns to grazing regimes are difficult to predict. We conducted a short-term grazing exclusion experiment in traditionally managed alkali grasslands in Hungary to investigate differences between grazed and ungrazed vegetation for different arthropod groups. The experiment was laid out in a full factorial design, with twelve 50 × 100 m short-term grazing exclosures in vegetation types with high (alkali wet meadow) and low productivity (alkali steppe). We sampled ground beetles and spiders with pitfall traps and true hoppers by sweep netting. We used vegetation type (wet meadow vs dry steppe), management (grazed vs ungrazed) and their interaction as fixed effects in mixed models. We found higher species richness and activity density of spiders and ground beetles in the more productive wet meadow vegetation, where the community structure of each arthropod group also shifted toward hygrophilous species. Significant interactions between vegetation type and management indicated a dependence of management effects on vegetation types: arthropod community structure shifted towards hygrophilous species in ungrazed meadows, but not in ungrazed steppe sites. True hopper abundance was higher in grazed meadow sites, but lower in grazed steppe sites, compared to ungrazed sites. True hopper community structure shifted toward generalist herbivores in ungrazed sites, regardless of vegetation type. We concluded that vegetation types determine arthropod communities and modulate the effects of grazing on arthropods. Our results suggest that moderate disturbance from low-intensity grazing has a positive or neutral effect in wetter, more productive vegetation, but a negative or neutral effect in drier, less productive vegetation, depending on the arthropod group. Herbivorous insects that dwell on plants are particularly affected by management because they are more susceptible to direct impacts, such as unintentional predation by grazing cattle, and because of asymmetrical competition between mammalian and insect herbivores.

Rainforest conversion to rubber and oil palm reduces abundance, biomass and diversity of canopy spiders.

Rainforest canopies, home to one of the most complex and diverse terrestrial arthropod communities, are threatened by conversion of rainforest into agricultural production systems. However, little is known about how predatory arthropod communities respond to such conversion. To address this, we compared canopy spider (Araneae) communities from lowland rainforest with those from three agricultural systems in Jambi Province, Sumatra, Indonesia, i.e., jungle rubber (rubber agroforest) and monoculture plantations of rubber and oil palm. Using canopy fogging, we collected 10,676 spider specimens belonging to 36 families and 445 morphospecies. The four most abundant families (Salticidae N = 2,043, Oonopidae N = 1,878, Theridiidae N = 1,533 and Clubionidae N = 1,188) together comprised 62.2% of total individuals, while the four most speciose families, Salticidae (S = 87), Theridiidae (S = 83), Araneidae (S = 48) and Thomisidae (S = 39), contained 57.8% of all morphospecies identified. In lowland rainforest, average abundance, biomass and species richness of canopy spiders was at least twice as high as in rubber or oil palm plantations, with jungle rubber showing similar abundances as rainforest, and intermediate biomass and richness. Community composition of spiders was similar in rainforest and jungle rubber, but differed from rubber and oil palm, which also differed from each other. Canonical Correspondence Analysis showed that canopy openness, aboveground tree biomass and tree density together explained 18.2% of the variation in spider communities at family level. On a morphospecies level, vascular plant species richness and tree density significantly affected the community composition but explained only 6.8% of the variance. While abundance, biomass and diversity of spiders declined strongly with the conversion of rainforest into monoculture plantations of rubber and oil palm, we also found that a large proportion of the rainforest spider community can thrive in extensive agroforestry systems such as jungle rubber. Despite being very different from rainforest, the canopy spider communities in rubber and oil palm plantations may still play a vital role in the biological control of canopy herbivore species, thus contributing important ecosystem services. The components of tree and palm canopy structure identified as major determinants of canopy spider communities may aid in decision-making processes toward establishing cash-crop plantation management systems which foster herbivore control by spiders.

Spiders in canopy and ground microhabitats are robust to changes in understory vegetation management practices in mature oil palm plantations (Riau, Indonesia)

Conversion of natural habitats to oil palm agriculture has caused declines in biodiversity and changes in ecosystem functions. To preserve biodiversity we must protect natural habitats, but once oil palm plantations are established, developing more-environmentally friendly management strategies could support higher levels of within-plantation biodiversity and boost the delivery of ecosystem services, possibly increasing oil palm productivity. In this study, we use a before-after control-impact (BACI) experiment to test whether three understory vegetation management strategies affect spider abundance, species richness, and species-level community composition in canopy and ground microhabitats in mature oil palm plantations. Our treatments encompassed the range of current management practices and included heavy applications of herbicides to eliminate all understory vegetation, maintaining some understory vegetation using business-as-usual herbicide applications, and enhancing understory vegetation by not applying any herbicides. We focussed on spiders, as they are both biologically and economically important in oil palm plantations, owing to their important pest control services. We identified more than 1000 spiders, representing 20 families and 83 morphospecies. The treatments did not affect any aspects of spider biodiversity, although the abundance and species richness of canopy-dwelling spiders changed between pre- and post-treatment sample periods, independent of treatment. Our findings indicate that differences in understory vegetation management practices do not affect spiders, or the pest management services that they provide, in mature oil palm plantations. As such, more extreme changes in management would probably be required to enhance spider biodiversity in oil palm plantations in the long-term. Further studies are needed to determine the practicalities of such approaches, to assess how changes in vegetation management practices affect spiders in additional microhabitats, and how the impacts of such approaches vary across the 20–30 year oil palm commercial life cycle.

A preliminary survey of the ground-dwelling spider assemblages of the Ndumo Game Reserve, South Africa (Arachnida: Araneae)

Ground-dwelling spider assemblages were sampled by pitfall trapping in four contrasting biotopes in the Ndumo Game Reserve, South Africa, situated in the Maputaland-Pondoland-Albany biodiversity hotspot. Over two years (2006 and 2007) in two seasons (mid-summer and winter, 10 days each) 1261 spiders were collected, representing 31 families and 121 species. Twenty-five taxa were recorded from Ndumo for the first time. Spider activity densities and species richness were highest in the deciduous broadleaf woodland (BW, n = 538, S = 106), followed by Albizia adianthifolia-Vachellia tortilis woodland (AW, n = 358, S = 70), sand forest (SF, n = 188, S = 74), and Mahemane thicket (MT, n = 177, S = 53). The four most abundant species were Asemesthes ceresicola Tucker, 1923 (Gnaphosidae, 27.8%), Arctosa sp. (Lycosidae, 8.4%), Pardosa crassipalpis Purcell, 1903 (Lycosidae, 7.4%), and Stenaelurillus guttiger (Simon, 1901) (Salticidae, 5.2%). Species richness and activity densities were strongly seasonal, with sharp decreases in winter. Conservation assessments could not be carried out on a sizable proportion of the species collected, as they represent new taxa or were only represented by immatures (30.6%), but of the remainder the majority had a conservation status of Least Concern (64.5%), with very few being Data Deficient (4.1%) and a single vulnerable species being collected, Massagris natalensis Wesołowska & Haddad, 2009. However, among the new taxa not assessed there may be several Maputaland endemics.

Preliminary patterns of seasonal changes in species composition of surface‐active arthropods in a South African savannah

AbstractSurface‐active arthropods have limited dispersal abilities and their abundances are responsive to changes in the environment. Their sensitivity allows for the identification of aspects of environmental variation that are responsible for changes in community assemblages of these arthropods. Limited dispersal abilities allow for changes in the populations of surface‐active arthropods to be linked reliably to changes in their local environment. In this study, we tested the hypothesis that seasonal variation in resource availability drives assemblages of three groups of surface‐active arthropods (ants, beetles and spiders). Ten study sites were selected, where sampling was carried out continually during the wet, austral summer season (December 2018–February 2019) and then repeated at the same sites in the dry winter season (June 2019–August 2019) in a mesic savannah of Mpumalanga province, South Africa. Pitfall trapping was used to sample the surface‐active arthropods. We found 89 morphospecies of ants, 48% of which were members of the Myrmicinae, while 32% of the 163 morphospecies of beetles were the Scarabaeidae. There were 262 morphospecies of spiders, of these, 22% were from the Salticidae. We found similar abundance and species richness of ants between seasons but significantly greater abundance and species richness of beetles and spiders in summer than in winter. These results show that the impact of seasonal variation in resource availability differs among arthropod taxa. However, the species compositions of all three taxa were significantly different between summer and winter. These results can be explained by the ‘niche differentiation hypothesis’ coupled with the ‘resource‐ratio hypothesis’. Additionally, these results highlight the role that temporal and dietary niche differentiation play in driving the assemblage composition of surface‐active arthropods in a mesic savannah.

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

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

Prescribed fire and other fuel-reduction treatments alter ground spider assemblages in a Southern Appalachian hardwood forest

Prescribed burns and understory thinnings are forest management practices aimed at reducing fuel loads to lessen wildfire threat in the Southern Appalachians, USA. Spiders play a critical role in forest ecosystems by controlling insect populations and providing an important food source for vertebrates. We used pitfall and colored pan traps to investigate how abundance, species richness, and diversity of spiders differed among three fuel reduction treatments administered repeatedly over a 15-year period and untreated controls. Additionally, we examined how spiders responded to one round (before and after) of fuel reduction treatments. We established treatments within the 15-year period as follows: mechanical understory removal (twice; M), prescribed burning (four times; B), mechanical understory removal followed one year later by high-severity prescribed burns and three subsequent burns (MB), and untreated controls (C). Our study period (2014–2016) occurred after multiple prescribed burns and two rounds of mechanical understory removal had occurred. Salticidae and Lycosidae were the two most commonly collected spider families in Southern Appalachian hardwood forests. Generally, we found increased spider abundances within all fuel-reduction treatments compared to controls. Individual spider families and species showed variable responses to treatments, but abundance of several spider families was greater in one or more fuel-reduction treatments than in controls. Additionally, abundance of several spider families and hunting/web building guilds (webs built for hunting purposes or defense) exhibited yearly differences to the last round of fuel-reduction treatments. Overall, our results suggest that changes in the overstory and understory of a forest are important drivers of regional spider abundance and assemblages, and forest management practices that modify forest structure can dramatically alter spider abundance and richness, usually in a positive manner.

Different components of landscape complexity are necessary to preserve multiple taxonomic groups in intensively-managed rice paddy landscapes

Increase in pesticide use and landscape homogenization are two key drivers of the decline in farmland biodiversity. The effects of these two drivers are often complex, interactive and vary among taxonomic groups. Our study tested the hypothesis that pesticide use influences the effect of different components of landscape complexity on different taxonomic groups. We sampled 32 rice paddy landscapes of 1 * 1 km in the Camargue (south of France), a wetland internationally recognized as an exceptional biodiversity hotspot. We assessed the abundance and diversity of 7 taxa (plants, bees, butterflies, hoverflies, carabids, spiders and birds) in 3 or 4 crop fields per landscape. For each landscape, we measured the length of different field margins (ditch, grass strip, hedgerow), the proportion of semi-natural areas and crop diversity. For each field, we measured management intensity by the treatment frequency index (TFI) of pesticides. We then tested our hypothesis across 118 fields. Our results show that different components of landscape complexity influence different taxonomic groups: crop diversity and the length of ditches influence bee abundance and species richness, the proportion of semi-natural areas influence spider abundance and species richness, and the length of grass strips influences bird abundance. Moreover, we show that local pesticide use modulates these effects, with more positive effects of landscape complexity in intensively-managed fields. However, we found no interactive effect between landscape complexity and field management for plants, butterflies, hoverflies and carabids. Our study therefore suggests that different components of landscape complexity need to be maintained in order to preserve multiple taxonomic groups. Moreover, it suggests that increasing landscape complexity is particularly relevant to restore biodiversity in intensively-managed fields. Agricultural policies should therefore support the simultaneous increase in semi-natural areas, field margins length and crop diversity to conserve a wide range of taxonomic groups in intensively-managed rice paddy landscapes.

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.

Diversity and abundance of Spider population (Arachnida: Araneae) in some selected localities in and around Madurai city, India

A study of spider species diversity was conducted in some selected localities of in and around Madurai city from October 2019 to March 2020. A total of 29 species of spiders belonging to 22 genera from 6 families were identified from the study sites. Araneidae and Salticidae were found to be the most dominant family with species from 6 and 7 genera respectively. Based on guild structure analysis, Orb-web builders and stalkers were the most dominant feeding guilds. There were considerable disparities in spider species diversity and distribution across all study sites during the study period, with Vadipatti (23 species) having the highest spider species diversity and Kelavasal (7 species) having the lowest diversity. Spider species diversity (Shannon’s index), richness (Margalef’s index) and evenness (Pielou’s index) indices were higher on Vattipatti (2.23; 3.37; 0.46), and least in the Kelavasal (1.11; 1.06; 0.23). Among 29 species, Argiope anasuja, Cyrtophara cicatrosa, Cyrtophora citricola, Gasteracantha geminata and Myrmarachne bengalensis were the most dominant species in Vatipatti and Arasakulam due to the existence of their prey and diverse range of plants, which influenced that these species were more dominant. The present study revealed that spider diversity was higher in rural areas (Vatipatti and Arasakulam) with superior ecological settings, but lower in urban areas (Thiagarajar College campus and Kelavasal) with the most intact ecological environment

Landscape- and time-dependent benefits of wildflower areas to ground-dwelling arthropods

Wildflower areas are a popular agri-environment scheme to counteract agro-biodiversity loss. Yet, their benefits are controversially discussed. Since inconsistent benefits may be owed to landscape context and temporal dynamics, we applied a multi-year study to unravel effects of permanent and transient habitats on ground-dwelling arthropods in wildflower areas and cereal fields.Across three consecutive years, we studied activity density, species richness and community composition of rove beetles, carabid beetles and spiders in ten pairs of wildflower areas and cereal fields along independent gradients of proportions of permanent semi-natural habitats or transient wildflower areas.Arthropod responses to the proportions of permanent semi-natural habitats often followed a hump-shaped pattern, whereas transient wildflower areas seemed to drive linear responses. An interactive effect on rove beetle richness in wildflower areas implies that benefits were highest either at intermediate proportions of permanent semi-natural habitats or at lower proportions, but with additional availability of transient wildflower areas or in landscapes with low proportions of permanent semi-natural habitats, but high proportions of wildflower areas. However, ground-dwelling arthropod activity density or species richness did not systematically increase over the three study years.Our results suggest that both permanent and transient habitats differ in how they affect biodiversity, possibly due to different temporal continuity and resource diversity. Benefits of permanent semi-natural habitats seemed highest at an equilibrium between an increasing resource-related species pool and an increasing diversity dilution, whereas benefits of transient wildflower areas seemed to increase with resource complementarity and connectivity at the landscape scale. Nevertheless, both habitats seem to complement each other and considered in concert, seem to be most effective in promoting benefits of wildflower areas to ground-dwelling arthropods at intermediate landscape complexity. The substantial variation in diversity patterns among years with weather extremes, suggests that optimizing benefits of wildflower areas requires further multi-year studies.

Resilience of spider communities affected by a range of silvicultural treatments in a temperate deciduous forest stand

To secure the ecosystem services forests provide, it is important to understand how different management practices impact various components of these ecosystems. We aimed to uncover how silvicultural treatments affected the ground-dwelling spider communities during the first five years of a forest ecological experiment. In an oak-hornbeam forest stand, five treatments, belonging to clear-cutting, shelterwood and continuous cover forestry systems, were implemented using randomised complete block design. Spiders were sampled by pitfall traps, and detailed vegetation, soil and microclimate data were collected throughout the experiment. In the treatment plots spider abundance and species richness increased marginally. Species composition changes were more pronounced and treatment specific, initially diverging from the control plots, but becoming more similar again by the fifth year. These changes were correlated mostly to treatment-related light intensity and humidity gradients. The patchy implementation of the treatments induced modest increase in both gamma and beta diversity of spiders in the stand. Overall, spiders gave a prompt and species specific response to treatments that was by the fifth year showing signs of relatively quick recovery to pre-treatment state. At the present fine scale of implementation the magnitude of changes was not different among forestry treatments, irrespective of their severity.

Invasive Plants Differentially Impact Forest Invertebrates, Providing Taxon-Specific Benefits by Enhancing Structural Complexity

Exotic plant species often negatively affect native herbivores due to the lack of palatability of the invading plant. Although often unsuitable as food, certain invasive species may provide non-nutritional ecological benefits through increased habitat structural complexity. To understand the potential for common invasive forest plant species of the eastern United States to benefit invertebrate communities, we examined the functional and taxonomic community composition of forest insects and spiders in long-term monitoring plots that contained invasive plant species. The extent of invasive plant species ground cover significantly altered spider community composition as categorized by hunting guild. Areas with higher invasive herbaceous and grass cover contained a higher abundance of space web-weaving and hunting spiders, respectively. Spider species richness and total invertebrate abundance also increased with greater invasive grass cover. Still, these trends were driven by just two invasive plant species, garlic mustard and Japanese stiltgrass, both of which have previously been shown to provide structural benefits to native invertebrate taxa. While these two species may improve the structural component of understory forest habitat, many invertebrate groups were not significantly correlated with other prevalent invasive plants and one species, mock strawberry, negatively affected the abundance of certain insect taxa. Particularly in forests with reduced native plant structure, invasive plant management must be conducted with consideration for holistic habitat quality, including both plant palatability and structure.

Taxon- and functional group-specific responses of ground beetles and spiders to landscape complexity and management intensity in apple orchards of the North China Plain

Agricultural intensification has caused severe declines in ground-dwelling arthropods and associated ecosystem services. The conservation and re-establishment of semi-natural habitats in agricultural landscapes represent widely accepted measures to counter these declines. The effectiveness of these measures nonetheless varies between target taxa and their functional traits, while also being affected by local management. Here, we studied how species richness and abundance of different functional groups of carabid beetles and spiders in apple orchards were affected by landscape complexity (% semi-natural habitat) and local management intensity (mowing and soil total nitrogen (STN) content). Both abundance and species richness of non-carnivorous carabids and carabids overall were negatively affected by STN, while the abundance of carnivorous carabids and carabids overall was affected by interactive effects of mowing and landscape complexity, showing a positive response to mowing where semi-natural habitats are scarce, but negative responses in landscapes with a higher proportion of semi-natural habitats. The abundance of ground-hunting spiders and spiders overall was generally positively related to % semi-natural habitats, while the abundance of web-building spiders and the species richness of ground-hunting spiders showed a positive correlation with STN at landscapes with a low or medium abundance of semi-natural habitats, but a negative correlation where semi-natural habitats were more abundant. Non-carnivorous carabid diversity benefitted from low nitrogen application, while carnivorous carabid abundance benefitted from mowing intensity especially in simple and structurally homogenous agricultural landscapes. Both web-building and ground-hunting spiders positively responded to low nitrogen applications and intermediate landscape complexity. Overall, a low local management intensity promoted carabid beetles, while spiders were favored by increasing landscape complexity. We conclude that taxon- and functional group-specific, multi-scale conservation strategies are therefore required to conserve invertebrate predators in apple orchards.

Re-established grasslands on farmland promote pollinators more than predators

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

Impact of pool design on spider and dytiscid recolonization patterns in a restored fen

Peatland pools present unique fauna and flora and contribute significantly to peatland biodiversity. The ecological functionality of artificial pools in restored peatlands is poorly documented. In this study, we investigated arthropod assemblages of 21 artificial pools in a restored fen in southeastern Canada and 16 pools from four pristine fens as reference ecosystems. Three years following restoration, predacious diving beetles (Coleoptera: Dytiscidae) and spiders (Araneae) were sampled within and around pools using minnow traps and pitfall traps, respectively. We used Bayesian community occupancy models to document arthropod recolonization. Twenty‐one dytiscid species were captured in pools. Dytiscid species richness was higher in artificial pools than in reference pools. Three dytiscid species were more likely to occur in deeper pools. Dytiscid species composition in artificial pools differed from reference pools. Seventy‐seven spider species were captured around pools. Spider species richness was higher around artificial pools than around reference pools. Seventeen spider species responded to vegetation cover, either positively or negatively. In contrast, spider species composition was similar between artificial and reference pools. We conclude that artificial pools should be along a gradient of pool depth, but also that fast‐growing vegetation should be introduced on pool margins to foster a quicker return of arthropod assemblages similar to reference ecosystems.