Spider Species Diversity Research Articles

Targeting a portion of central European spider diversity for permanent preservation.

Given the limited success of past and current conservation efforts, an alternative approach is to preserve tissues and genomes of targeted organisms in cryobanks to make them accessible for future generations. Our pilot preservation project aimed to obtain, expertly identify, and permanently preserve a quarter of the known spider species diversity shared between Slovenia and Switzerland, estimated at 275 species. We here report on the faunistic part of this project, which resulted in 324 species (227 in Slovenia, 143 in Switzerland) for which identification was reasonably established. This material is now preserved in cryobanks, is being processed for DNA barcoding, and is available for genomic studies.

Abundance and diversity of spiders (Araneae) in barley and young leys

The fauna of surface-active spiders was studied in 12 cereal fields, with two types of subcrop, and in four young (17 months old) perennial leys (grass/clover). The fields were located in the southeastern (A), central (B) and western (C) parts of Norway. In total, 3945 spiders were caught from May to September 2004, using pitfall traps. Linyphidae was the most numerous family, with Erigone atra Blackwall 1833 representing 56% of all trapped individuals. The total numbers of spider species and individuals were significantly higher in leys than in barley at sites where both crops were present (sites A and B), with on average 11 species and 93 specimens in barley, and 20 species and 393 specimens in leys. Thus, young perennial leys appeared to provide a better habitat for spiders than did cereal fields, as has previously been documented for older perennial leys. The use of multi-species crops instead of a single crop species undersown in cereals, tended to result in higher spider species diversity, but it did not influence the total number of specimens. An ordination (DCA) showed a clustering of the spider fauna from the same site, but no clear separation between main crop types (ley vs. barley) was apparent. The main crops, subcrops, and the surrounding environs of the cropped field seem to affect the diversity and abundance of spiders.

Diversity of Spider Fauna in Upland Rice Agroecosystem at Gudalur Valley in Tamilnadu

The diversity of spiders and impact of pest population on spider density has been studied in the upland rice agroecosystem in Bharathy variety at Hybrid Rice Evaluation Centre, Tamil Nadu Agricultural University, Gudalur, The Nilgiris during Kharif 2010 and 2011. Three aspects, population of spiders and pests in different rice establishment techniques, diversity of spider species in different rice establishment techniques and impact of pest density on the population of spiders were studied. A total of 11 species of spider from 7 different families were observed from all the three different techniques of upland rice crop at different days after transplantation. Among the spider species, Lycosa pseudoannulata was higher in early growth stage and Tetragnatha javana was predominant in later stages of the crop. Population of brown plant hopper, green leaf hopper and stem borer showed significant positive impact on L. pseudoannulata and Oxyopes javanus population. Regression analysis revealed that 97 percent of L. pseudoannulata , 72 percent of O. javanus , 94 percent of T. javana and 80 percent of Clubiona sp. population depends on the incidence of pests in the upland rice ecosystem. Diversity indices revealed that diversity of spider was more in the direct sown method than transplanting and seedling throwing method.

An experimental study of spiders in a shrub-steppe ecosystem: the effects of prey availability and shrub architecture

Habitat structure is of great importance for the distribution and abundance of various organisms. Spiders are especially sensitive to structural features of their environment. Although spiders are influenced by habitat structure, it remains unclear whether spiders respond to architecture, to differences in prey availability associated with different architectures, or both. Here, we investigated the effects of shrub architecture and prey availability and their interactions on a spider community in a shrub-steppe environment in northern Utah, USA. Big sagebrush shrubs, matched by size, were randomly assigned to six experimental treatments: two levels of prey attractant (shrubs were either baited or not baited) and three levels of foliage density (low, natural/control, or high). We found that spider abundance and species richness were affected by both prey availability and shrub architecture, while variation in spider species diversity (Shannon-Wiener index) was governed by changes in shrub architecture. Spider species and family compositions were also associated with changes in shrub architecture, although guild composition was not. We discuss the implications and limitations of these findings and present suggestions for future research.

Results and prospects of the study of spiders (Aranei) in Russia and around the world

Data on the species diversity of spiders in the world fauna and in Russia are presented. Advance in the knowledge of the species diversity is discussed. The most productive arachnologists who described over 1000 species are listed, as well as all the Russian specialists who described over 30 species. A brief historical summary of classification of spiders is given. Based on the prevalent methodology, the history of the spider classification can be conventionally subdivided into four partly overlapping periods: “ecological” (1678–1886), morphological (1864–2009), synthetic (since 1967), and cladistic (since 1976).

Decoupling Fragmentation from Habitat Loss for Spiders in Patchy Agricultural Landscapes

Habitat loss reduces species diversity, but the effect of habitat fragmentation on number of species is less clear because fragmentation generally accompanies loss of habitat. We compared four methods that aim to decouple the effects of fragmentation from the effects of habitat loss. Two methods are based on species-area relations, one on Fisher's alpha index of diversity, and one on plots of cumulative number of species detected against cumulative area sampled. We used these methods to analyze the species diversity of spiders in 2, 3.2 × 4 km agricultural landscapes in Southern Judea Lowlands, Israel. Spider diversity increased as fragmentation increased with all four methods, probably not because of the additive within-patch processes, such as edge effect and heterogeneity. The positive relation between fragmentation and species diversity might reflect that most species can disperse through the fields during the wheat-growing season. We suggest that if a given area was designated for the conservation of spiders in Southern Judea Lowlands, Israel, a set of several small patches may maximize species diversity over time.

Effects of cover crops on spider communities in tea plantations

In agroecosystems, spiders are important predators that play a role in the control of agricultural pests. Modifying the vegetation around crops is an effective measure that can increase plant diversity and enhance the abundance and diversity of spider species. In this study, spiders were sampled monthly from May 2006 through April 2008 from tea canopies and ground covers in four tea plantation treatments in Xingchun (27°38′51.4″ N and 117°54′29.9″ E), which is in the Wuyi Mountains, Fujian Province, Southeastern China. The first tea plantation was intercropped with Paspalum notatum, the second with Cassia rotundifolia, and the third with natural ground cover. All ground cover was removed by hand in the fourth tea plantation. The spiders collected in the tea canopies numbered 21,170 individuals, representing 21 families and 158 species, whereas a total of 978 individual spiders, representing 16 families and 74 species, were collected in the ground cover treatments. Subsequent analysis revealed that Coleosoma octomacutatum (Boesenberg et Strand, 1906), Telamonia bifurcilinea Bosenberg et Strand, 1999, and Erigone sp. 1 were the dominant spider species in these tea plantations. There were no significant differences among cover crop treatments with respect to the species richness, species abundance, or absolute abundance of spiders in either study year. In this work, all fourteen communities sampled had similar types of species abundance distributions, which followed bell-shaped and left-truncated lognormal distributions, with an almost identical modal octave on a log 2 scale and a missing zero class. The results of the present study do not support the natural enemy hypothesis, but rather indicate that ground covers do not have adverse effects on the tea plantations.

Effects of Grassland Succession on Communities of Orb-Weaving Spiders

Native grasslands are among the most imperiled of the North American ecosystems, but abandoned agricultural areas may provide suitable habitat for animal taxa that are endemic to grasslands. We studied how species diversity of orb-weaving spiders was influenced by secondary succession of a grassland plant community by monitoring the abundance and species diversity in study plots that were cultivated at 6-yr intervals and left uncultivated in the interim. We tested the hypothesis that local abundance and species diversity of spiders would be positively associated with time since cultivation because plant communities in older habitats would be more architecturally complex. Local abundance of spiders in general was not associated with time since cultivation, but abundance of Mangora gibberosa (Hentz) was positively associated with the abundance of perennial plants. Species richness and diversity of spiders also were positively associated with the abundance of perennial plants and reached a threshold a few years after cultivation. Species diversity of orb-weaving spiders seems to be strongly influenced by species composition of the plant community. Therefore, effective restoration of the structure and function of endemic communities of orb-weaving spiders may depend on preserving endemic grassland plant communities.

Regional patterns in the invasion success of Cheiracanthium spiders (Miturgidae) in vineyard ecosystems

Invasions have often been linked to reduced biodiversity, but the role of non-native species in the decline of native species is ambiguous. In a 2003 survey of four California vineyard regions, exotic spiders (Cheiracanthium spp.) were more dominant in vineyards with lower spider species diversity and reduced spider abundance. There was no evidence for the role of species interactions in the invasion of Cheiracanthium spiders, however, as native spiders from the same feeding guild were most abundant in regions with high Cheiracanthium levels. Comparison with a survey conducted 10 years earlier indicated that the recent invader C. mildei simply represented an addition to the spider community, with no apparent change in proportions of the congener C. inclusum. Invasion success is discussed with respect to agricultural habitat, as results suggest that disturbed conditions in many vineyards may favor Cheiracanthium spp. and native wandering spiders while decreasing overall spider diversity.

The role of dispersal from natural habitat in determining spider abundance and diversity in California vineyards

Many generalist predators do not persist in crops year-round, and must colonize crops on a seasonal basis from natural vegetation. We monitored the spider community in the air, on the ground, and in the foliage of California vineyards and neighboring oak-woodlands, to assess whether dispersal from natural habitats influences the abundance and species diversity of spiders in agroecosystems. Early in the growing-season, low spider numbers in vineyard foliage indicated that few spiders overwintered in the vineyard. Aerial dispersal did not, however, occur primarily in the spring when generalist predators are likely to be important in pest suppression, but in mid-summer, while dispersal activity on the ground did not change over time. Aerial collection traps showed greater similarity to spider composition in vineyard foliage than ground collection traps, indicating that spiders in vineyards disperse more by air than over ground. Dwarf spiders (Linyphiidae) dominated spider composition on aerial traps but were not abundant on the vine, while other spider species showed an opposing pattern, suggesting that while spiders may have entered vineyards by air, other factors may have also contributed to spider composition in vineyards. These results are discussed with respect to control of vineyard pests and the establishment of spiders in vineyard agroecosystems.

Does the microarchitecture of Mexican dry forest foliage influence spider distribution

Spider species diversity has been associated with vegetation structure and stratification but there are few studies comparing the spider distribution in different shrubs and trees. In this study we analyzed the species distribution of the spider community of 11 shrub and tree species in two different study sites in a Mexican tropical dry forest. We present results from multivariate analyses that explain their distribution. A classification analysis based on spider abundances separated one shrub, Croton ciliatoglanduliferus, from the rest of the plant species. This was explained by the presence of large numbers of the oxyopid Peucetia viridans (Hentz 1832) on this plant. A second cluster segregated broad-leaved from small-leaved, bipinnate species. This was mainly due to higher spider abundances in the latter type of plants. Four vegetation variables were estimated and their influence on the species distribution was assessed by means of a principal components and regression analysis. With the exception of P. viridans, all spiders were positively associated with number of leaves and number of branchlets per 50 cm branch and negatively with foliage area.

Spider biodiversity patterns and their conservation in the Azorean archipelago, with descriptions of new species

In this contribution, we report on patterns of spider species diversity of the Azores, based on recently standardised sampling protocols in different habitats of this geologically young and isolated volcanic archipelago. A total of 122 species is investigated, including eight new species, eight new records for the Azorean islands and 61 previously known species, with 131 new records for individual islands. Biodiversity patterns are investigated, namely patterns of range size distribution for endemics and non‐endemics, habitat distribution patterns, island similarity in species composition and the estimation of species richness for the Azores. Newly described species are: Oonopidae ‐ Orchestina furcillata Wunderlich; Linyphiidae: Linyphiinae ‐ Porrhomma borgesi Wunderlich; Turinyphia cavernicola Wunderlich; Linyphiidae: Micronetinae ‐Agyneta depigmentata Wunderlich; Linyphiidae: Erigoninae ‐ Acorigone gen. nov. with its type species Acorigone zebraneus Wunderlich; Clubionidae ‐ Cheiracanthium floresense Wunderlich; Cheiracanthium jorgeense Wunderlich; Salticidae ‐ Neon acoreensis Wunderlich. Other major taxonomic changes are: Diplocentria acoreensis Wunderlich, 1992 (Linyphiidae) is transferred to Acorigone (comb. nov.), Leucognatha Wunderlich 1995 (Tetragnathidae) is not an endemic genus of the Azores but an African taxon and synonymous with Sancus Tullgren, 1910; Leucognatha acoreensis Wunderlich, 1992 is transferred to Sancus. Minicia picoensis Wunderlich, 1992 is a synonym of M. floresensis Wunderlich, 1992. For each species additional information is presented about its known distribution in the islands, its colonisation status, habitat occurrence and biogeographical origin.

The Impact of Different Agricultural Land-uses on Epigeal Spider Diversity in Scotland

Detailed knowledge of the biodiversity of spider communities on agricultural land is important both in terms of enhancing pest control and understanding the driving forces influencing nature conservation value. Pitfall traps were used to assess spider species diversity at 71 Scottish agricultural sites between May and September during 1996 and 1997. Land-use varied from intensive arable fields, grasslands and extensive heather (Calluna vulgaris) moorland. Spider species richness (S) was found to decrease significantly as farm management intensity increased. Several linear regression models based on the 1996 data (50 sites) and a selection of plant, soil and landscape variables explained up to 88% of the variation in species richness. Four of these models were used to estimate 1997 species richness (36 sites: 15 repeat and 21 new) and up to 58% of sites were correctly predicted to within ± four species of the actual number caught. As only 60% of the repeat 1997 sites had values of S within four units of their 1996 score, this suggested a relatively high level of model accuracy. Model accuracy increased to 64% when all four models were used for each site, suggesting the individual models should be targeted at specific land-use types. We discuss the relevance of these models for predicting the consequences of changes in agricultural land-use for spider diversity.

Influence of ground cover on spider populations in a table grape vineyard

1. Cover crops and/or resident ground vegetation have been used in California vineyards to increase the number of predators and decrease the number of pestiferous herbivores. The most common resident predators in vineyards are spiders (Araneae). Several observational studies suggest that the addition of cover crops results in an increase in spider density and a decrease in insect pest densities.2. To test experimentally the effects of cover crops and/or resident ground vegetation (hereafter collectively referred to as ground cover) on spider populations, a 3‐year study was undertaken in a commercial vineyard. Large, replicated plots were established with and without ground cover during the growing season. Spider species diversity was analysed on the vines and on the ground cover.3. On the vines, there was no significant difference in spider species richness or the total number of spiders in plots with and without ground cover. There were differences in the relative abundance of two spiders between treatments, with one species (Trachelas pacificus [Chamberlin & Ivie]) more abundant in plots with ground cover and another (Hololena nedra Chamberlin & Ivie) more common on vines in plots with no ground cover. Annual variation in spider abundance was greater than variation due to ground cover treatment.4. On the ground cover, the spider species diversity was considerably different from that found on the vines above, suggesting that there is little movement of spiders between the ground cover and the vines. Enhancement of T. pacificus populations on vines with ground covers may be a result of prey species movement between the ground cover and the vines. Spider abundance was sparse on the bare ground.5. The maintenance of ground cover increased spider species diversity in the vineyard as a whole (vine and ground cover). However, the relatively small changes in spider abundance on the vines indicate there are limitations in the use of ground covers for pest management with respect to generalist predators.

Structure and abundance of arachnid communities in Scots and lodgepole pine plantations

Between April and September 1994, six plots within Aberfoyle Forest in Scotland, three of Scots ( Pinus sylvestris) and three of lodgepole pine ( Pinus contorta), were surveyed for spiders and harvestmen, as these are predators of several forest invertebrate pests. A total of 64 species of spider were trapped in Scots and lodgepole pine; 56 in Scots pine and 32 in Lodgepole pine. The most abundant spiders, both in Scots and Lodgepole pine, were Linyphiidae. Scots pine plots were floristically more diverse and structurally more complex than lodgepole pine plots. More species of spiders and harvestmen (midsummer only) were found at ground level in Scots pine than lodgepole pine plots. More species and a greater numbers of spiders were found in the canopy of Scots pine than in that of lodgepole pine. However, no differences in the abundance of harvestmen were found between the canopies of Scots and lodgepole pine. Spider species diversity was greatest in Scots pine.

Determinants of web spider species diversity: Vegetation structural diversity vs. prey availability.

The hypotheses that vegetation structural diversity and prey availability determine alpha diversity were examined for scrub- and meadow-inhabiting web spider species assemblages along elevational gradients in Costa Rica and California. Prey availabilities were estimated by sticky trap catches, using only the orders and size classes of insects actually captured by the spiders. The measured component of vegetation structural diversity was the maximum tip height in 20 cm increments from 0 to 2.0 m. Spider species diversity and vegetation tip height diversity were both expressed by the Inverse Simpson Index. Web spider species diversity is highly significantly correlated with vegetation tip height diversity. Prey availability is not a significant predictor of web spider species diversity in these habitats.

Spider Community Organization: Seasonal Variation and the Role of Vegetation Architecture

The relationships between vegetation architecture and spider community attributes were examined in a big sage ( Artemisia tridentata ) community. Spiders were separated into guilds using similarities of species' hunting behavior. Shrub architecture was experimentally manipulated in the field by either clipping 50% of a shrub's foliage to decrease foliage density or tying together a shrub's branches to increase foliage density. Shrub perturbations resulted in changes in the number of spider species, spider guilds and guild importance values. The number on spider species and guilds in the tied shrubs were significantly higher than those in the clipped or control shrubs sampled. Spider species diversity and the number of species and guilds were positively correlated with indicators of shrub volume and shrub foliage diversity. This suggests that structurally more complex tied shrubs can support a higher number of spider Species and species diversity. Temporal patterns of the number of spider species, and species diversity (H') showed midsummer peaks m both 1974 and 1975. Evenness (J') remained relatively constant through both seasons. The data suggest that architectural properties of habitat may be an important determinant of the distribution and species diversity of predatory invertebrates.