Web Weavers Research Articles

Composition and Diversity of Spiders in the Lian-huo Highway (Shangqiu Section) Shelter Forest and Campus Habitat of Henan Province, China

Background: Spider assemblages, which are easily sampled, are useful indicators that can be used to compare the biodiversity of various environments and assess the effects of disturbances on diversity. Because spiders are generally found in forests in high abundance, they form some good model taxa for biodiversity studies. Methods: The present study compares the composition and diversity of spiders in the Lian-Huo highway (Shangqiu section) shelter forest (HS) and campus habitat (CH) of Henan province, China. Sampling were collected from April to June 2018 and fourth time a month, a total of twenty-four samples were collected. Within each habitat type there were eight sites surveyed which represented a wide geographical spread of the habitats. Result: A total of 3725 individual spiders were collected from the two sites, representing 14 families and 23 species. Guild structure analysis of the collected spiders revealed 4 feeding guilds viz, web weavers, Sheet web weavers, Foliage hunter’s spider and Ambush hunters. The abundance of spiders in the campus habitat is significantly higher than that in Lian-Huo highway (Shangqiu section) shelter forestand the Shannon-Wiener index (H’) (HS=3.3827, CH=2.2007), Simpson index (D) (HS=0.8710, CH=0.7391), Evenness index (J) (HS=2.8391, CH=1.7088) and Richness index (E) (HS=0.7462, CH=0.6362) are significantly higher in the campus habitat than in the Lian-Huo highway (Shangqiu section) shelter forest. These results suggest that increasing the complexity of habitat structure and reducing anthropogenic disturbance is a meaningful way to conserve and restore Spiders diversity.

Chromosome-level genome of spider Pardosa pseudoannulata and cuticle protein genes in environmental stresses

Spiders are representative arthropods of adaptive radiation. The high-quality genomes have only been reported in several web weaver spider species, leaving the wandering spiders’ genomic information scarce. The pond wolf spider, Pardosa pseudoannulata, is a representative species in the retrolateral titial apophysis (RTA) clade. We present a chromosome-level P. pseusoannulata genome assembly of 2.42 Gb in size with a scaffold N50 of 169.99 Mb. Hi-C scaffolding assigns 94.83% of the bases to 15 pseudo-chromosomes. The repeats account for 52.79% of the assembly. The assembly includes 96.2% of the complete arthropod universal single-copy orthologs. Gene annotation predicted 24,530 protein-coding genes with a BUSCO score of 95.8% complete. We identified duplicate clusters of Hox genes and an expanded cuticle protein gene family with 243 genes. The expression patterns of CPR genes change in response to environmental stresses such as coldness and insecticide exposure. The high-quality P. pseudoannulata genome provides valuable information for functional and comparative studies in spiders.

Characteristics of spider assemblages of subtropical rice paddy fields in the Yaeyama Islands, Japan

Spiders are important natural enemies of rice pests in paddy fields. To estimate their roles, it is essential to understand their functional diversity. However, little is known about the spider fauna of paddy fields in subtropical regions. Here, we investigated spider diversity and species composition in paddy fields in the Yaeyama Islands, in subtropical Japan. We collected 1489 individuals of at least 42 species in 13 families and 7 guilds from rice paddies on Ishigaki, Iriomote, and Yonaguni islands by net sweeping during the first and second crops from 2013 to 2015. The Tetragnathidae (39%), Araneidae (35%), and Thomisidae (18%) were the most abundant families, comprising > 90% of total abundance. Orb web weavers (73%) and ambush hunters (19%) were the most abundant guilds. The most common species were Neoscona theisi (Walckenaer, 1841) (Araneidae) (n = 352), Tetragnatha javana (Thorell, 1890) (Tetragnathidae) (n = 294), and Tetragnatha nitens (Audouin, 1826) (Tetragnathidae) (n = 94). The results show that the species composition of spiders in subtropical paddy fields is more similar to that in tropical paddy fields in Asia than to that in temperate paddy fields in mainland Japan. Ordination analysis showed that the composition of spiders on Ishigaki island varies greatly with season and year. This study makes a valuable contribution to knowledge of the comprehensive diversity of subtropical spiders associated with rice paddy fields in Japan.

Assessing the impact of fire on spiders through a global comparative analysis.

In many regions fire regimes are changing due to anthropogenic factors. Understanding the responses of species to fire can help to develop predictive models and inform fire management decisions. Spiders are a diverse and ubiquitous group and can offer important insights into the impacts of fire on invertebrates and whether these depend on environmental factors, phylogenetic history or functional traits. We conducted phylogenetic comparative analyses of data from studies investigating the impacts of fire on spiders. We investigated whether fire affects spider abundance or presence and whether ecologically relevant traits or site-specific factors influence species' responses to fire. Although difficult to make broad generalizations about the impacts of fire due to variation in site- and fire-specific factors, we find evidence that short fire intervals may be a threat to some spiders, and that fire affects abundance and species compositions in forests relative to other vegetation types. Orb and sheet web weavers were also more likely to be absent after fire than ambush hunters, ground hunters and other hunters suggesting functional traits may affect responses. Finally, we show that analyses of published data can be used to detect broad-scale patterns and provide an alternative to traditional meta-analytical approaches.

Seasonal diversity of spider assemblages (Araneae: Arachnida) in the “Guillermo Piñeres” Botanical Garden, Turbaco–Colombia

ABSTRACT Climatic seasons have been shown to determine the temporal fluctuations in species communities of different ecosystems. Here, we assessed the diversity of spider assemblages in dry, transition and rainy seasons in the “Guillermo Piñeres” Botanical Garden (GPBG), Turbaco, Colombia. We collected spider assemblages between June 2018 and April 2019 through standardized day and night sampling methods for tropical ecosystems: looking up, looking down, beating and leaf litter sieving. In total, we collected 1585 individuals, belonging to 28 families and 112 (morpho) species. We calculated the effective species richness (Hill numbers) to evaluate the changes in diversity across seasons and used clustering and ordination methods (Jaccard index-based nMDS) to identify differences in the composition of the assemblages. Also, we compared the abundance and species richness of predatory guilds of the three seasons. The transition season showed the highest diversity with 94 morphospecies, an effective number of species of 48.7 and a dominance of 32.4 effective species. The clustering and ordination methods grouped the sampling events into three groups, each corresponding to a climatic season. The most abundant guild was the orb web weavers, with the highest value in the rainy season, while “other hunters” were the most species rich. Our results indicate that the spider assemblages in GPBG present a seasonal variation in diversity, probably influenced by climatic conditions. Understanding how these seasonal changes occur is necessary to develop forest management strategies for monitoring and management projects on the conservation of species assemblages according to the Convention on Biological Diversity.

Combining organic and conservation agriculture to restore biodiversity? Insights from innovative farms in Belgium and their impacts on carabids and spiders

Conservation and organic agriculture are two alternative crop management strategies associated with environmental impact reduction, leading theoretically to more biodiversity and higher ecological functioning, underpinning better ecosystem service delivery. The combination of these two farming strategies is increasingly seen as an opportunity to mitigate shortcomings of each of them taken individually. However, combining organic and conservation agriculture is undeniably challenging, since it leaves nocurativeoption (neither synthetic pesticides nor soil plowing) for pest control (phytophagous, pathogens, and weeds). Hence, the latter must be ensured by effective restoration of predatory communities. The present research investigated the potential of combining organic and conservation agriculture to support two major ground-dwelling natural enemy communities: carabids and spiders. We used pitfall traps to sample these two communities in paired adjacent cereal fields conducted under organic-conservation (OC) and conventional (CV) agriculture in Belgium. Community assemblages were significantly different across system types, both in terms of species diversity and functional trait diversity. OC parcels showed higher alpha and beta species diversities for both carabids and spiders and species composition differed between OC and CV parcels. OC systems were associated with higher variation of species assemblages among parcels than CV systems Functional traits also differed across system types for both groups. We found more herbivorous and granivore carabids in OC parcels, and more predator species in CV parcels. We found larger spiders, more hunting spiders and more wetland spiders in OC parcels, whereas we found more web weavers and more forest spiders in CV ones. Functional diversity was higher in OC parcels for carabids, but not for spiders. In brief, OC parcels supported more diverse communities, both taxonomically and functionally. These outcomes show that OC systems are promising systems to support these natural enemy communities. Further studies should assess whether combining organic and conservation agricultural enables sufficient pest control levels to achieve high levels of food production and farmers income.

Seasonal diversity, distribution and abundance of Araneae in the Thattekkad Bird Sanctuary, Kerala, India

The aim of the present study was to analyze the diversity of spiders across various parts of the Thattekkad Bird Sanctuary, Kerala, a tropical, semi evergreen, low-land forest located between the tributaries of the Periyarriver. Survey of the spider fauna was carried out for a period of twelve months. In total, 3286 individuals were collected from the sanctuary, which consist of 89 species of spiders under 59 genera and 18 families. Araneidae was the most abundant family. The most abundant species was Hippasa agelenoides of Lycosidae family. Spiders belonging to six feeding guilds, i.e., orb - web weavers, stalkers, ground runners, scattered line weaver foliage runners and ambushers were identified. Relative abundances of spider community strongly differed with the pre-monsoon, monsoon and post monsoon seasons. Seasonal diversity indices of Margalef richness index, Pielou’s evenness index, Shannon-Wiener and Simpson index were calculated.

Checklist of spiders from Vallakadavu range of Western Ghats, Kerala, India

In the preliminary study conducted to document the spider fauna in Vallakadavu range, Idukki district, Kerala, a total of 33 species of spiders belonging to 29 genera from 12 families were recorded. Among the 12 families recorded, Araneidae was the most predominant with orb web weavers. From the guild analysis, the recorded families were categorized into seven principle types of web patterns.The study extends the range of Poecilotheriastriata Pocock, 1895 in the state to the east.

Are spider communities influenced by urbanisation? An approach using species and guilds resolutions and their interaction with the anthropogenic environment

ABSTRACT Spiders, natural enemies of several insects of economical and sanitary relevance, are sensitive to anthropogenic disturbances. Urban habitats, home to nearly half of the world’s human population, are growing in number and size. Consequently, natural habitats are lost and impervious surfaces increase. We compared the overall spider species and guilds assemblage characteristics associated with vegetation, between sites located within different urbanisation levels (urban and suburban) and in relation to local and landscape traits. The most abundant guilds were sheet web weavers and ambush hunters. The overall richness of spiders and richness and abundance of two guilds (space web weavers and stalker hunters) were higher in suburban than urban sites. The overall spider abundance, Shannon-Weaver diversity and the Shannon evenness index did not change between urban and suburban sites. While the species composition differed between urban and suburban sites, comprising the urban spider species a subset of those found in the suburban pool. Species abundances were negatively related with the percentage of bare ground, canopy cover, and urban level. Richness was positively related to low vegetation. Guilds’ responses differed concerning their life histories. At a landscape level, high consolidation (impervious surface) degree surrounding the green patches had negative effects while medium values had positive effects. Higher diversity was associated with intermediate mixtures of vegetation and impervious cover. In conclusion, the spider’s community and guild characteristics were associated with environmental, landscape and local factors through the urbanised landscape.

Relationship between agricultural pesticides and the diet of riparian spiders in the field

BackgroundExamining the effects of pesticides is difficult in regions such as Western Europe because of the relatively ubiquitous use of agrochemicals and the lack of unaffected areas. To study a wide gradient of agrochemical stress, we conducted a study in Central Romania, where traditional agriculture, which is assumed to use less agrochemicals, exists adjacent to intensive agriculture. We investigated potential effects of land use related stressors including pesticides on aquatic–terrestrial predator–prey relationships using stable isotope analysis. Therefore, we sampled spiders, as well as their aquatic and terrestrial prey along streams with a pesticide pollution gradient and determined spider and prey stable carbon and nitrogen signals.ResultsAquatic prey contributed 40.8–55.4% to the diet of the orb web weaving spider Tetragnatha sp. and 34.0–53.0% to the diet of the ground-hunting Pardosa sp. The biomass of potential aquatic prey increased along a gradient of increasing riparian habitat conditions and water quality and decreasing agriculture (e.g. arable land) in the catchment. The proportion of aquatic prey in the orb web weavers diet responded positively to the biomass of potential aquatic prey and negatively to this gradient. Increasing potential prey biomass resulted in an increasing proportion of aquatic prey for the orb web weaver. The proportion of aquatic prey in the ground hunters diet increased with in-stream pesticide toxicity and along a gradient of increasing pastoralism in the catchment as well as increasing riparian habitat and water quality.ConclusionThe diet of two riparian predators responded to complex gradients of catchment land use, stream and riparian habitat quality as well as to in-stream pesticide toxicity. The responses to the different environmental variables can be attributed to direct (e.g. change in spider community) and indirect (e.g. changes in aquatic prey and terrestrial prey) effects. Future manipulative field studies or experiments on aquatic–terrestrial food webs are required to examine the causality of our findings and should also consider the quality of prey organisms to foster mechanistic understanding of cross-ecosystem effects.

The spider fauna from Uruguay River islands: understanding its role in a biological corridor.

Biological corridors are connections which link habitats in a regional scale, allowing the gene flow between populations. The Uruguay River comprises riverside and insular riparian forests along subtropical to temperate zones passing through different biogeographic provinces. The aim of this study was to characterise the spider fauna from the Uruguay River islands highlighting their connection role for the spider community of riparian forest. Spiders were studied from surveys in a fluvial island of the southern course of the river with nine campaigns being carried out from September 2007 to September 2009. Three complementary collecting methods were used: G-Vac, night hand collecting and pitfall traps. A total of 58 samples were taken in each campaign. A total of 33 families, 145 species/morphospecies and 8 guilds were registered. Theridiidae and space web weavers showed the highest abundance and species richness. Web weavers were predominant in the spider community evidencing the importance of the forest vegetation heterogeneity in spider diversity. Fifteen species have been recorded for the first time for Uruguay. Additional data of previous surveys in the northern islands of the river were analysed and compared. Several species confirm the role of the Uruguay River as a biological corridor from the upper to lower course of the river. The riparian forests from the islands constitute a southernmost intromission of Paranaense biota between Chaco and Pampa regions along the river. The results obtained are an important input for the conservation of these areas. Knowing the biodiversity, as well as its dynamics and the flow of biota that exists in these environments, would allow planning the management from a regional point of view.

Spider assemblages associated with different crop stages of irrigated rice agroecosystems from eastern Uruguay.

The rice crop and associated ecosystems constitute a rich mosaic of habitats that preserve a rich biological diversity. Spiders are an abundant and successful group of natural predators that are considered efficient in the biocontrol of the major insect pests in agroecosystems. Spider diversity in different stages of the rice crop growth from eastern Uruguay was analysed. Field study was developed on six rice farms with rotation system with pasture, installed during intercropping stage as cover crop. Six rice crops distributed in three locations were sampled with pitfall and entomological vaccum suction machine. Sixteen families, representing six guilds, were collected. Lycosidae, Linyphiidae, Anyphaenidae and Tetragnathidae were the most abundant families (26%, 25%, 20% and 12%, respectively) and comprised more than 80% of total abundance. Other hunters (29%), sheet web weavers (25%) and ground hunters (24%) were the most abundant guilds. Species composition along different crop stages was significantly different according to the ANOSIM test. The results showed higher spider abundance and diversity along the crop and intercrop stages. This study represents the first contribution to the knowledge of spider diversity associated with rice agroecosystem in the country.

Spider communities in two plant architectures of epiphytic cacti in the Brazilian Atlantic forest

ABSTRACTThe vegetative architecture of the Cactaceae provides sites used by spiders as hideout, foraging, mating and oviposition. We found more web weavers in plants with cylindrical cladodia and more hunters in plants with flat cladodia. Between February 2014 and January 2015 1551 spiders distributed in 20 families were collected: one of these families, Palpimanidae, had only juvenile individuals collected; of the other 19 families, 80 species/morphospecies were identified. This work aims to contribute to the knowledge of biodiversity in the canopy of the Atlantic Forest, especially the relationship between cacti and spiders.

Effects of agricultural practices and fine-scale landscape factors on spiders and a pest insect in Japanese rice paddy ecosystems

We examined the effects of environmentally friendly (EF) farming and landscape factors on the abundances of major spider guilds and a rice pest, the small brown planthopper (SBPH), Laodelphax striatellus (Fallen), in a Japanese rice paddy ecosystem. The abundances of all spider guilds increased by EF farming, whereas different spider guilds showed contrasting responses to the size of the forest within 200 m of the fields. The abundances of ground spiders and horizontal web weavers increased with increasing forest area, unlike small ground spiders, whose abundance decreased. The abundances of SBPH nymphs and adults decreased by EF farming but responded differently to landscape: nymphs decreased with increasing forest area, but adults did not. Further analysis indicated a potential negative relationship between web-weaving spiders and SBPH nymphs. Our findings suggest that the size of the forest adjacent to fields is an important determinant of spider guild composition and pest abundance.

Ants (Hymenoptera: Formicidae) and Spiders (Araneae) Co-occurring on the Ground of Vineyards from Douro Demarcated Region

This study, held in vineyards from Douro Demarcated Region, aimed to: a) identify the communities and main functional groups of spiders and ants; b) check patterns of co-occurrence between the two communities; and c) evaluate the impact of ground cover and adjacent non-crop habitats in the proximity of vineyards, on the two communities. Samplings were done using pitfall trapping. Twenty species of ants and 44 species of spiders were identified, which included respectively three and nine Iberian endemic species. Aphaenogaster gibbosa (Latreille 1798), Aphaenogaster iberica Emery 1908, Cataglyphis hispanica (Emery 1906), Cataglyphis iberica (Emery 1906), Messor barbarus (L. 1767) and Tapinoma nigerrimum (Nylander 1856) totalized 71.21% of ants. Alopecosa albofasciata (Brullé 1832), Callilepis concolor Simon 1914, Eratigena feminea Simon 1870, Zodarion alacre (Simon 1870) and Zodarion styliferum (Simon 1870) accounted for 38% of spiders. Abundance of both ant-mimicking and ant-eating spiders were positively correlated with Formicinae, while only ant-eating spiders showed positive correlation with Myrmicinae ants. All genera/ species of ant-associated spider were associated with one or more genera/ specie of ants. The abundance of specialist spiders was higher in areas where abundance of ants was also higher. Sheet web weavers spiders were found to be positively correlated with the percentage of ground cover. The present study a) stresses that vineyard agroecosystem support a rich assemblage of ants and spiders evincing that wine production and species conservation is possible and b) the co-occurrence between some species of this two groups is not determined by random patterns.

Diversidad de arañas del suelo y su relación con ambientes heterogéneos del Parque General San Martín, Entre Ríos, Argentina

The spider community associated to the ground in different environments and its relationship with environmental heterogeneity in the Parque General San Martín was analyzed. Spiders were captured with pit-fall traps in 3 representative environments of the park, for 2 seasons (2011-2012): native forest (BN), exotic forest (BE) and grasslands (P), characterized by graminiform plants. 1,398 spiders were collected (26 families and 120 species/morphospecies). The highest spider abundance was registered in P (678 individuals), followed by BE (501) and BN (219), while species richness was higher in BN. Diversity indexes showed statistically significant differences among the environments sampled. Heterogeneity variables used in this study showed a higher heterogeneity in BN, followed by P and BE as the most homogenous. Eight guilds were registered. All of the guilds were present in BN, while the sensing web weavers were not recorded in the BE, as well as the ambush hunters in P. This work constitutes the first approach about the importance and changes undergone by the diversity of ground spiders in environments with different degrees of heterogeneity, as a result of the advance of exotic species in a park from Entre Ríos.

Abiotic factors and biotic interactions jointly drive spider assemblages in nest-boxes in mixed forests

Although spiders are common inhabitants of tree cavities, factors that drive their community structure in these microhabitats are little known. Here we investigated whether bark type, season, intraguild predation (IGP) among spiders, and presence of vertebrate predators can influence the spider community structure in tree cavities. We examined spider abundance and the taxonomic and functional composition of spiders in nest-boxes within two mixed forest stands in central Slovakia in 2012–2013. In total, 1211 spiders belonging to 31 species were sampled from 60 nest-boxes at two sites over three seasons. Spider abundance peaked in autumn as spiders sought wintering sites. Guilds and taxonomic composition changed seasonally with spring and autumn communities dominated by “Other hunters” (Anyphaenidae, Clubionidae, Philodromidae) while during summer the community was dominated by “Sheet web weavers” (Linyphiidae). The guild and taxonomic turnover may be partly explained by the interaction between spiders' phenology and IGP exerted by winter-active spiders on smaller spiders from autumn until spring. Bark type influenced the guild composition as dominance of “Space web weavers” was higher in trees with rough bark than in trees with smooth bark. The rough bark also reduced the intensity of IGP by Anyphaena accentuata (Sundevall, 1833) on philodromids. The presence of insectivorous birds reduced the abundance of spiders by 67%. The presence of bird predators altered the guild composition as they affected mostly the web spiders. The results show that the biotic interactions and abiotic factors interactively determined the spider community structure in the nest-boxes depending on spiders' functional traits.

Diversidad taxonómica y funcional de arañas (Araneae) epigeas en bosques nativos de las Yungas (Salta, Argentina)

El estudio de la araneofauna en las Yungas argentinas es escaso. Sin embargo, es relevante debido a la alta diversidad ambiental y biológica que posee esta ecorregión, principalmente en los sistemas forestales amenazados por el avance de la frontera agropecuaria. El objetivo de este trabajo es comparar la diversidad y la composición de los ensambles de arañas epigeas en la Selva Pedemontana (SP), Selva Montana (SM) y Bosque Montano (BM) de las Yungas de la provincia de Salta. Se tomaron muestras mediante trampas de caída durante el otoño, la primavera 2006 y el verano 2007 en tres sitios de la SP, cinco en la SM, y tres en el BM. Se recolectaron 643 arañas pertenecientes a 75 especies/morfoespecies. Los ensambles de SP reportaron la mayor riqueza de especies sumado a una composición de especies muy disímil en relación con las de SM y BM. Las tejedoras espaciales, otras cazadoras y cazadoras de suelo representaron más del 95 % de la abundancia en cada comunidad. Ellas mostraron patrones semejantes de abundancia en la SM y BM, mientras que en la SP las tejedoras espaciales redujeron marcadamente su abundancia. El cambio en la configuración del paisaje debido al uso del suelo es la principal fuerza que estaría estructurando los ensambles locales de la SP. Este estudio constituye el primero en analizar la diversidad de arañas epigeas y sus gremios en las Yungas del norte argentino siendo un punto de partida para futuros monitoreos de biodiversidad en la región.

Trophic Niche Differences in Arachnid Predators Between Field and Forest Ecosystems

ABSTRACT: Arachnids are important predators in arthropod assemblages that occur from early successional old fields to mature forests. As generalist predators, they may occupy varying trophic niches in different environments that have different prey available. Given that trophic niche can be quantified by the enrichment of 15N in an organism, we tested the null hypothesis that the trophic niche is invariant between old fields and forests in three groups of arachnids: cursorial and web weaving spiders (Araneae), and harvestmen (Opiliones), by comparing the stable isotope ratios of nitrogen (δ15N) in specimens of each group collected from field and forest. Cursorial spiders fed at the highest trophic level in both habitats, and likely consumed other predators as well as herbivores in the field. Web weavers showed slightly higher δ15N in the field than in the forest. Harvestmen and cursorial spiders had significantly lower δ15N in the forest, indicating a trophic shift downward during later succession when th...

Wandering and web spiders feeding on the nectar from extrafloral nectaries in neotropical savanna

AbstractDespite their essentially carnivorous habits, spiders can supplement their diets with other food sources, such as extrafloral nectar. The extrafloral nectar can constitute an excellent complementary energy source for spiders because it is rich in mono and disaccharides besides other compounds. We investigate the presence of fructose and its concentration in the bodies of wandering and web weaver spiders collected on extrafloral nectary‐bearing plants from a neotropical savanna area by means of cold anthrone test. The tested spiders belonged to seven families: Anyphaenidae, Araneidae, Oxyopidae, Pisauridae, Salticidae, Theridiidae and Thomisidae. A total of 265 (88.04%) of all tested individuals were fructose intake positive. In general, there was no difference in the percentage of positive spiders between wandering and web weaver spider species or between adult and immature individuals. Results found in this study corroborate those from other studies that suggest that nectar feeding is a common activity among spiders and it includes a new family (Theridiidae) in the nectivory spiders list.