Spider Species Richness Research Articles

Vibration as a New Survey Method for Spiders.

Spiders have important ecological roles as generalist predators, are a significant source of food for many other species, and are bioindicators of environmental health. However, spiders are poorly studied. Given their importance, a comparison of spider survey methods used to determine differences in spider diversity and abundance is required to understand their limitations and biases. A new survey method to attract spiders, based on vibration from an idling diesel tractor, was tested and compared to the traditional methods of pitfall trapping and hand collection of spiders at night. Across the three survey methods, there were, in total, 2294 spiders in 34 families, 138 genera, and 226 species identified. Spider species diversity and richness were significantly greater for spiders collected at night than from the other two methods (spiders collected in pitfall traps and attracted to vibration). The collection of spiders using the night collection and vibration-based methods were very similar in terms of labor required and material costs. Of all spider species identified, 80% were captured during hand collection, 30% through pitfall trapping, and 30% from vibration-based collection. Most species of spiders caught in pitfall traps were species known to be primarily ground-dwelling, whereas both arboreal and ground-dwelling spiders were collected at night and as a result of being attracted and collected using the vibration-based method.

Local and landscape drivers of natural enemy communities in Indonesian oil palm plantation

Abstract Oil palm plantations are typically managed in a monoculture system over large areas. This system contributes to biodiversity loss and promotes pest outbreaks by reducing natural enemies. However, ecosystem functions in oil palm plantations vary spatially and temporally and can still support biodiversity under certain conditions. We conducted a study on the species richness, abundance and species composition of natural enemies in oil palm plantations and investigated the factors influencing natural enemy communities in oil palm plantations at both local and landscape scales. We selected 12 sites in an oil palm plantation in Central Borneo, Indonesia, which were grouped into 4 sub‐areas based on the presence of natural habitats, which varied in local and landscape characteristics. Arthropods were sampled using canopy knockdown fogging with a pyrethroid insecticide. Different taxa of natural enemies responded differently to changes in habitat characteristics within oil palm plantations. Species richness of spiders was not affected by either local or landscape scale, but their species composition was affected by oil palm tree age (local scale) and the total edge of dominant oil palm tree age (landscape scale). Ant species richness was influenced by the class area of natural habitat (landscape scale), whereas their species composition was not influenced by either local or landscape scale. On the other hand, species richness of parasitoid wasps was influenced by light intensity (local scale) and the variation of oil palm tree age within a landscape (landscape scale). However, their species composition was only affected by light intensity. The results suggest that oil palm management practices need to consider both local and landscape scales to maintain biodiversity and biological control and to achieve sustainable management of oil palm plantations.

Local Habitat Complexity and Its Effects on Herbivores and Predators in Urban Agroecosystems.

In urban community gardens, cultivated vegetation provides variable levels of habitat complexity, which can suppress pests by promoting predator diversity and improving pest control. In this study, we examine three components of the structural complexity of garden vegetation (cover, diversity, and connectivity) to investigate whether higher garden vegetation complexity leads to fewer herbivores, more predators, and higher predation. We worked in eight community gardens where we quantified vegetation complexity, sampled the arthropod community, and measured predation on corn earworm eggs. We found that plots with high vegetation cover supported higher species richness and greater abundance of predatory insects. High vegetation cover also supported a greater abundance and species richness of spiders. In contrast, high vegetation diversity was negatively associated with predator abundance. While high predator abundance was positively associated with egg predation, greater predator species richness had a negative impact on egg predation, suggesting that antagonism between predators may limit biological control. Community gardeners may thus manipulate vegetation cover and diversity to promote higher predator abundance and diversity in their plots. However, the species composition of predators and the prevalence of interspecific antagonism may ultimately determine subsequent impacts on biological pest control.

Spider diversity in different habitats at District Mardan, Khyber Pakhtunkhwa Pakistan.

Spider species are important for maintaining ecological balance, controlling insect populations, and providing potential sources of medicinal compounds. Highlighting the importance of spider species, the present study was aimed at exploring the diversity of spider fauna and species richness in various habitats in District Mardan, Khyber Pakhtunkhwa, Pakistan, from March 2021 to December 2021. Spiders were collected through different methods: pitfall traps, cryptic searching, ground hand collection, aerial hand collection, and vegetation beating. Then, the captured spiders were washed in alcohol and preserved in a combination of 80% alcohol and 20% glycerol for further observation. Identification was carried out with the help of available spider identification keys and literature. A total of 578 specimens representing 29 species from 17 families and 26 genera were collected and identified. Family Lycosidae was the most dominant family (13.49%), followed by Salticidae (10.2%), Araneidae (8.47%), Tetragnathidae (7.61%), Pholicidae (6.4%), Oxyopidae (5.88%), Thomisidae (5.7%), Clubionidae (5.53%), Sicariidae (5.19%), Scytodidae (5.01%), Corinnidae (4.67%), Agelenidae (4.32%), Cheiracanthiidae and Sparassidae (4.15%), Oecobiidae and Hersiliidae (3.97%) and Theridiidae was the rarest among all (1.21%). The most commonly identified species are Hippasa partita, Lycosa poonaesis, Lycosa terrestris, Draposa oakleyi, Plexippus paykulli, Menemerus nigli, Thyene imperialis, Thyene bivittate and Hasarius adansoni. Argiope versicolor, Neoscona theisi, Tetragnatha extensa, Crossopriza lyoni, and Oxyopes Javanus. During the present study, it was observed that spider species were abundantly found in warm areas from May to August, which demonstrates that the spider fauna of the study area is very rich but has yet to be explored.

Differential patterns of taxonomic and functional diversity for two groups of canopy arthropods across spatial scales

AbstractArthropod diversity is often linked to variation in resource use, dispersal ability, habitat connectivity, and climate factors that differ across spatial scales. The aim of this research was to examine how species richness, functional diversity, and community composition of two taxa differing in functional roles and dispersal ability are structured across spatial scales and to identify the importance of vegetation, climate, and landscape in explaining these patterns at different scales. Organisms were collected from tree canopies using insecticidal fogging in the summer of 2000 from 96 trees in 24 stands of 6 deciduous forest sites in 2 ecoregions of the eastern United States. Taxonomic and functional beta diversity of ants (Hymenoptera: Formicidae) and spiders (Araneae) were partitioned across four hierarchical spatial scales (individual tree, forest stand, site, and ecoregion). The contributions of climatic, landscape, and vegetation variables were determined using model selection. Ant and spider species richness, functional diversity, and community composition differed between taxa and across spatial scales. Alpha diversity (within trees) was lower than expected for both taxa and types of diversity, with host tree species supporting different species of ants and spiders. While the beta components of species diversity among trees and forest stands were greater than expected for both taxa, spiders also showed significant levels of beta diversity among sites. Functional beta diversity was less scale‐dependent than taxonomic beta diversity. Stand‐level patterns of beta diversity were significantly predicted by variation in climate and landscape connectivity. The effects of climate and landscape fragmentation on the diversity and community structure of both taxa indicate that anthropogenic climate change and land use change will alter canopy arthropod communities. Results also suggest that patterns of diversity among fragmentation metrics are influenced by differences in dispersal ability.

Seasonal Diversity of Spiders (Arachnida: Araneae) and Collection Methods in Barpeta District, Assam, India

Barpeta district, Assam, India covers an area of 2754 square kilometers. The Spider specimens were collected by visual search method and the collection methods adopted were Aerial hand collection, Ground hand collection and Beat sheet method. 70 spider species from the different habitats of Barpeta District were documented. The study shows the difference in quantity and quality of spider fauna concerning the seasons and collection method. The spider species were more active in the post-monsoon season and some were inactive during winter. Almost 75% of spider species were collected by the beat sheet method which shows that it is more significant than all other trapping techniques. The spider species richness and spider abundance were significantly affected by seasons, studied by Simpson’s diversity index and Shannon – Weiner’s diversity index. However, further study needs to be carried out for the effective conservation of these species.

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.

Plant invasion and fragmentation indirectly and contrastingly affect native plants and grassland arthropods

Plant invasion and habitat fragmentation have a detrimental effect on biodiversity in nearly all types of ecosystems. We compared the direct and indirect effects of the invasion of the common milkweed (Asclepias syriaca) on biodiversity patterns in different-sized Hungarian forest-steppe fragments. We assessed vegetation structure, measured temperature and soil moisture, and studied organisms with different ecological roles in invaded and non-invaded sites of fragments: plants, bees, butterflies, flower-visiting wasps, flies, true bugs, and spiders. Temperature and soil moisture were lower in invaded than in non-invaded area. Milkweed had a positive effect on plant species richness and flower abundance. In contrast, we mainly found indirect effects of invasion on arthropods through alteration of physical habitat characteristics and food resources. Pollinators were positively affected by native flowers, thus, milkweed indirectly supported pollinators. Similarly, we found higher species richness of herbivores in invaded sites than control sites, as species richness of true bugs also increased with increasing plant species richness. Predators were positively affected by complex vegetation structure, higher soil moisture and lower temperature. Furthermore, increasing fragment size had a strong negative effect on spider species richness of non-invaded sites, but no effect in invaded sites. Especially, grassland specialist spiders were more sensitive to fragment size than generalists, whereas generalist spider species rather profited from invasion. Although milkweed invades natural areas, we did not identify strong negative effects of its presence on the diversity of the grassland biota. However, the supportive effect of milkweed on a few generalist species homogenises the communities. The rate of invasion might increase with increasing fragmentation, therefore we recommend eliminating invasive plants from small habitat fragments to preserve the native biota. Focusing also on generalist species and revealing the indirect effects of invasions are essential for understanding the invasion mechanisms and would support restoration efforts.

Spider diversity (Arachnida: Araneae) in two different coffee management systems and surrounding tropical forest during two contrasting seasons in Oaxaca, Mexico

This study focuses on species richness, abundance, diversity, and seasonal variation of spiders in two coffee plantations with different crop management and a portion of tropical forest in two municipalities of La Costa region of Oaxaca, Mexico, using manual collection, foliage beating and pitfall traps. We collected 2,210 spiders belonging to 35 families, 100 genera and 146 species. The inventory includes 51 new species records for Oaxaca. Completeness values for two estimators indicate that the level of representation of inventories range from 68.25% to 78.44%, and the proportion of singletons range from 33.72% to 38.14%. Spider abundance in the rainy season was significantly lower than during the dry season. Spider abundance in the Tropical Forest was significantly lower than Monoculture site with the foliage beating method. Polyculture was the site with the lowest spider abundance with the pitfall traps. Rarefaction curves did not show significant differences in species richness between the sites and seasons. Hutcheson t-test showed that spider diversity was significantly lower in Monoculture than Tropical Forest during the rainy season. This study contributes to the knowledge of the arachnofauna of Mexico and particularly of the state of Oaxaca.

The analysis of the influence of grazing intensity on the diversity and abundance of plants and spiders (Arachnida: Araneae)

In restoration projects, low stock grazing has become a popular means of management. However, an accurate understanding of the effects of grazing on plants and spiders is often lacking. Although spiders and plants are not closely related evolutionarily or genetically, the relationship between them can be complex and diverse. Many species of spider build their webs or nests on plants, using the leaves, stems, or flowers as anchoring points. This provides them with protection from predators, access to prey and a stable habitat. On the other hand, spiders can provide a number of benefits to grassland ecosystems, such as helping to control populations of insects and other arthropods that can damage or consume grassland plants. This study addresses the effects of different grazing regimes on plant and spider diversity in siliceous grasslands. Plant and spider diversity was studied for four months in the Sharri Mountains (Kosovo) in order to determine the biodiversity in ungrazed, moderately grazed and overgrazed siliceuous grasslands. The responses of plant height, plant biomass, plant species diversity and spider species diversity to three grazing intensities at 12 sites were recorded. Vegetation structure (plant height and plant biomass) was significantly higher in ungrazed grasslands compared to grazed and overgrazed grasslands. This was not the case, however, for spider species richness and diversity, as these were higher in moderately grazed than ungrazed grassland. On overgrazed grasslands, spider diversity was extremely low, as only one species of spider (Pardosa saltuaria) was recorded. Plant and spider diversity increased in the following order: overgrazed grasslands < ungrazed grasslands < moderately grazed grasslands, in all the habitats studied. Different grazing intensities significantly affected the abundance of particular plants on siliceous grasslands, for example, Deschampsia cespitosa, one of the most dominant plants on siliceous grasslands had an abundance of 4.77% in ungrazed grasslands., but only 4.94% in moderately grazed grasslands and was absent in overgrazed grasslands. There were other species of plants that were most abundant in intensively grazed silicate grasslands. One of them was Nardus stricta, whose percentage in ungrazed, moderately grazed and overgrazed grasslands was characterized by a multiple exponential increase in % (s1 – ungrazed grasslands = 0.99%, s2 – moderately grazed grasslands = 1.25% and s3 – overgrazed grasslands = 10.50%). It is concluded that the intensity of grazing of natural grasslands directly affects biodiversity and that this information may be valuable for long-term management and conservation programs in similar habitats in SE Europe and beyond.

Inconsistent responses of carabid beetles and spiders to land-use intensity and landscape complexity in north-western Europe

Reconciling biodiversity conservation with agricultural production requires a better understanding of how key ecosystem service providing species respond to agricultural intensification. Carabid beetles and spiders represent two widespread guilds providing biocontrol services. Here we surveyed carabid beetles and spiders in 66 winter wheat fields in four northwestern European countries and analyzed how the activity density and diversity of carabid beetles and spiders were related to crop yield (proxy for land-use intensity), percentage cropland (proxy for landscape complexity) and soil organic carbon content, and whether these patterns differed between dominant and non-dominant species. <17 % of carabid or spider species were classified as dominant, which accounted for >90 % of individuals respectively. We found that carabids and spiders were generally related to different aspects of agricultural intensification. Carabid species richness was positively related with crop yield and evenness was negatively related to crop cover. The activity density of non-dominant carabids was positively related with soil organic carbon content. Meanwhile, spider species richness and non-dominant spider species richness and activity density were all negatively related to percentage cropland. Our results show that practices targeted to enhance one functionally important guild may not promote another key guild, which helps explain why conservation measures to enhance natural enemies generally do not ultimately enhance pest regulation. Dominant and non-dominant species of both guilds showed mostly similar responses suggesting that management practices to enhance service provisioning by a certain guild can also enhance the overall diversity of that particular guild.

Ground-dwelling arthropods as biodiversity indicators in maize agroecosystems of Northern Italy

Reliable monitoring of arthropod diversity in a given agroecosystem is essential for the conservation of the related ecosystem services, such as biological control. The often daunting complexity of arthropod collection and identification, however, highlights the need for surrogate taxa that can be easily sampled and be representative of a number of other taxa in term of diversity, general community features and specific composition.In this study, we used pitfall traps to sample three ground-dwelling arthropod taxa important as biocontrol agents (ground beetles, rove beetles and spiders) in 9 conventionally managed maize agroecosystems of Northern Italy over the course of two years, with the goal of characterizing their assemblages and evaluating their reciprocal potential as indicators of activity density, species richness, community turnover and species co-occurrence.Although dominated by few generalist species, sampled arthropod communities were relatively species-rich, and included the first Italian record of the spider Zelotes metellus (Roewer) (Araneae: Gnaphosidae). Ground beetles as a group were confirmed as promising indicators for the species richness and community composition turnover of rove beetles and spiders. Additionally, several abundant arthropod species acted as indicators of the species richness of their respective groups, and the ground beetle Pterostichus macer (Marsham) also worked as an indicator of overall rove beetle activity density. While the co-occurrence of individual arthropod species was limited for the studied taxa, a few species such as the ground beetle Parophonus maculicornis (Duftschmid) did show promise as species-specific bioindicators. Our results could be useful in improving the monitoring and management of these important natural enemies in maize-growing regions.

Commercial banana and macadamia plantations in a savanna matrix support high levels of arthropod diversity

Expansion and intensification of agroecosystems is one of the major causes of habitat loss in the savanna biome in South Africa. As such, this study sought to determine the influence of commercial subtropical fruit plantations (banana and macadamia) on species richness, abundance, and composition of surface-active arthropods compared to the savanna biome. Given that pesticides and herbicides are applied from spring to early autumn in banana and macadamia plantations, we sampled in winter to reduce the potential impact of pesticides and herbicides. Surface-active arthropods were sampled using pitfall traps. Habitat type did not affect species richness and abundance of ants and spiders, as well as species richness of beetles. However, significantly greater abundance of beetles was recorded in the macadamia plantation compared to the banana and savanna. This could have been due to greater abundance of herbivorous beetles and other insects, which would have increased the diversity of predatory beetles. Furthermore, unlike the banana plantation, the macadamia plantation was characterised by a deep leaf litter layer and the presence of weeds and grasses, which probably increased abundance of beetles. Species composition indicated that the studied arthropod taxa associate with specific habitats, as demonstrated by the three habitats supporting different species composition. Despite savanna habitat not supporting high species richness or abundance of surface-active arthropods, we recorded the highest number of unique species of ants and spiders in the savanna rather than in the plantations. These results highlight the importance of natural landscapes in conservation of surface-active arthropods.

A relict subterranean spider (Araneae: Linyphiidae: Troglohyphantes) reveals a unique component of the biogeography of Corsica

Abstract Spiders of the genus Troglohyphantes (Araneae: Linyphiidae) exemplify one of the largest subterranean adaptive radiation across European mountain ranges, counting over 130 species and representing about one fifth of total species richness of cave spiders in Europe. Despite the emerging potential of Troglohyphantes as a biogeographical model, no attempt has been made to reconstruct the geological events underlying the current distribution patterns of the genus. By coupling traditional taxonomy with target gene sequence data and comparative functional trait analyses, we describe a new species of Troglohyphantes, the first reported from the island of Corsica (France). The species is characterized by a high level of subterranean adaptation and distinct morphological affinities with geographically distant congenerics. By means of time-stamped phylogenies, we tested contrasting hypotheses about the origin of the new species. The most parsimonious explanation suggests that the species diverged from an ancestral group of species originating in the Adriatic plate in the lower Miocene (~19 Ma), colonizing Corsica from the east. In the absence of relevant fossil records, the well-known geochronology of Corsica and the Western Mediterranean basin can be used in future studies to reconstruct the biogeography of the whole genus and for inferring the timeline of its diversification.

Urban wildflower meadow planting for biodiversity, climate and society: An evaluation at King's College, Cambridge

Abstract The biodiversity and climate crises are critical challenges of this century. Wildflower meadows in urban areas could provide important nature‐based solutions, addressing the biodiversity and climate crises jointly and benefitting society in the process. King's College Cambridge (England, UK) established a wildflower meadow over a portion of its iconic Back Lawn in 2019, replacing a fine lawn first laid in 1772. We used biodiversity surveys, Wilcoxon signed rank and ANOVA models to compare species richness, abundance and composition of plants, spiders, bugs, bats and nematodes supported by the meadow, and remaining lawn, over 3 years. We estimated the climate change impact of meadow vs lawn from maintenance emissions, soil carbon sequestration and reflectance effect. We surveyed members of the university to quantify the societal benefits of, and attitudes towards, increased meadow planting on the collegiate university estate. In spite of its small size (0.36 ha), the meadow supported approximately three times more plant species, three times more spider and bug species and individuals, and bats were recorded three times more often over the meadow than the remaining lawn. Terrestrial invertebrate biomass was 25 times higher in the meadow compared with the lawn. Fourteen species with conservation designations were recorded on the meadow (six for lawn), alongside meadow specialist species. Reduced maintenance and fertilising associated with meadow reduced emissions by an estimated 1.36 Mg CO2‐e per hectare per year compared with lawn. Relative reflectance increased by 25%–34% for meadow relative to lawn. Soil carbon stocks did not differ between meadow and lawn. Respondents thought meadows provided greater aesthetic, educational and mental wellbeing services than lawns. In open responses, lawns were associated with undesirable elitism and social exclusion (most colleges in Cambridge restrict lawn access to senior members of college), and respondents proved overwhelmingly in favour of meadow planting in place of lawn on the collegiate university estate. This study demonstrates the substantial benefits of small urban meadows for local biodiversity, cultural ecosystem services and climate change mitigation, supplied at lower cost than maintaining conventional lawn.

Seasonal changes in spider diversity in subtropical riparian forests: what drives the seasonality of the araneofauna?

Spiders are usually found through all seasons in the subtropics, but little is known about their seasonality patterns and how they respond to abiotic factors, especially in species-rich regions such as Brazil. We investigated the seasonal variation in spider communities and the possible influence of abiotic factors (e.g., temperature, rainfall) on spider abundance, species richness and composition in subtropical riparian forest in four river basins. Changes in spider abundance among seasons differed between ontogenetic stages: there were more spiderlings in the autumn, and similar numbers of adults year round. Species richness, on the other hand, was highest in spring and summer. Species composition differed between seasons and river basins. Several factors may be behind diversity changes in the araneofauna among seasons, however, none of the abiotic factors evaluated showed a strong direct influence. Seasonal patterns varied, with different species having peaks in all three seasons but autumn. Seasonality is clear in these spider communities but not all patterns follow predictions from simple temperature changes.

Does habitat type in no‐tillage agroecosystems influence ground‐dwelling macroarthropod community structure? A case study in KwaZulu‐Natal, South Africa

AbstractLoss of biodiversity in agroecosystems has negative implications for crop production and the functioning of the ecosystem. As such, agroecologists advocate minimum tillage practices in order to conserve biological diversity. To establish the influence of agricultural practices on biodiversity, we compared the species richness, abundance and composition of beetles, ants, spiders and small groups of ground dwelling arthropods in a veld and three agroecosystems (maize, sugarcane and multispecies pasture) under minimum tillage. Sampling was by pitfall trapping during the summer rainfall season in December 2019. Although ants were the most abundant (47%), followed by beetles (31%); beetles were the most speciose making up 40% of the morphospecies followed by spiders (31%). The veld had significantly greater relative proportion of species richness of spiders (54%) than the three agroecosystems, while significantly low relative proportion of species richness of ants was in the pasture (6%) compared to the veld (63%). Species richness and abundance of beetles were similar across habitat types. The four habitats supported different assemblages of ants, beetles and spiders. The differences in species composition among the habitats support the notion that agricultural practices with minimum soil disturbance enhance conservation of biological diversity, particularly, specialist species.

Response of ants, beetles and spiders to disturbance varies among taxa in a South African savannah biome

Savannahs are structurally complex ecosystems consisting of a diverse community of plants and animals such as arthropods. Arthropods are essential in many ecosystem processes that help maintain life on Earth. The anthropogenic conversion of natural landscapes into croplands, residential and industrial areas has a negative impact on surface-active arthropods that have limited dispersal abilities and narrow habitat preferences. This study investigated the effect of disturbance on assemblages of ants, beetles and spiders in the savannah vegetation in Mpumalanga province, South Africa. We compared species richness, abundance and composition of these three taxa between the pristine savannah and the savannah that is exposed to a variety of anthropogenic activities (disturbed savannah). Arthropods were collected using pitfall traps in 15 sites in pristine savannah and 15 sites in disturbed savannah. We found that disturbance affects species richness and abundance of these taxa differently. Disturbance did not affect species richness of spiders and abundance of beetles, while greater species richness of ants and beetles, as well as abundance of ants and spiders was in disturbed than in pristine savannah. Furthermore, the species compositions of all taxa were different between disturbed and pristine savannah. The disturbed savannah had twice more unique indicator species than the pristine savannah. Differences in assemblages of arthropods between pristine and disturbed habitats suggest that it may be important to consider habitats in and outside protected areas in the conservation of arthropods, particularly in areas with greater percentage of natural and semi-natural landscapes occurring outside protected areas.

Agricultural spider decline: long-term trends under constant management conditions

There is widespread evidence for a worldwide trend of insect decline, but we have much fewer data about recent temporal trends in other arthropod groups, including spiders. Spiders can be hypothesised to similarly decline because of trophic dependence on insects and being equally sensitive to local and global environmental changes. Background trends in arthropod populations can be verified if we decouple large-scale environmental transitions, such as climate change, from local factors. To provide a case study on baseline spider community trends, we observed changes in the spider community of an unsprayed alfalfa field and its margin 23 years apart under largely unchanged local conditions. We aimed to determine whether there are changes in spider abundance, species richness and mean species characteristics. Spider abundance per unit effort decreased dramatically, by 45% in alfalfa and by 59% in the margin, but species richness and most characteristics remained unchanged. Community composition in both habitats shifted and became more similar by the current study period. The population decline was especially marked in certain farmland species. We propose that in the absence of local causative factors, spider abundance decline in our study indicates a reduction of spider populations at landscape and regional scales.

Can Gap-Cutting Help to Preserve Forest Spider Communities?

Continuous cover forestry maintains many characteristics of uneven-aged natural forests and aims to preserve biodiversity. Gap-cutting is a management option that may create a balance between timber production and continuous forest cover. We investigated the effect of newly created gaps on ground-dwelling spider assemblages in a managed oak forest, in the Pilis Mts., Hungary. Between 2018–2021 we sampled newly created elongated and circular-shaped gaps of two different sizes in a six-times replicated randomised complete block design. Pitfall samples of ~4600 spiders indicated that spider species richness was moderately higher in the gaps than in control stands. Spider assemblages did not respond in a specific way to the different gap implementations, but their variation in species composition was considerably higher in gaps than in the control plots. The excess spider abundance and species number in gaps, as compared to control, increased over the observation period, as did the dissimilarity of gap assemblages to control. Species responses imply that gaps create a variation in microhabitats and microclimatic conditions, resulting in spiders’ diversification. The overall effect of gaps on spider assemblages suggests that gap-cutting is a suitable management option that preserves forest spider assemblages.