Species richness and community structure of arboreal spider assemblages in fragments of three vegetational types at Banhado Grande wet plain, Gravataí River, Rio Grande do Sul, Brazil

Abstract

ABSTRACT. The taxonomic composition, observed and estimated species richness, and patterns of community structure of arboreal spider assemblages in eleven sites surrounding the "Banhado Grande" wet plain in the state of Rio Grande do Sul, Brazil, are presented. These sites represent three different vegetational types: hillside (four sites), riparian (five sites) and flooded forests (two sites). The spiders were captured by beating on foliage and "aerial litter". A sample was defined as the result of beating on twenty bushes, tree branches or "aerial litter" clusters, which roughly corresponds to one-hour search effort per sample. Fifty five samples (five per site) were obtained, resulting in an observed richness of 212 species present as adult or identifiable juveniles. The total richness for all samples was estimated to be between 250 (Bootstrap) to 354 species (Jackknife 2). Confidence intervals of both sample and individual-based rarefaction curves for each vegetation type clearly indicated that flooded forest is the poorest vegetation type with respect to spider species richness, with hillside and riparian forests having a similar number of species. The percentage complementarity between the eleven sites indicated that all sites contain a distinct set of species, irrespective of their vegetation types. Nevertheless, the spider assemblages in riparian and hillside forests are more similar with respect to each other than when compared to flooded forest. Both cluster and nonmetric multidimensional scaling analyses showed no strong correspondence between the spider arboreal fauna and the three vegetation types. Moreover, a Mantel test revealed no significant association between species composition and geographic distance among sites. KEYWORDS.Arboreal spiders, taxonomic composition, species richness, wet plain, southern Brazil. RESUMO. Riqueza de espécies e estrutura da comunidade de assembléias de aranhas arbóreas em fragmentos de três tipos de vegetação na planície inundável do Banhado Grande, rio Gravataí, Rio Grande do Sul, Brasil. Apresenta-se a composição taxonômica e a riqueza de espécies, tanto observada quanto estimada, de aranhas arborícolas em onze fragmentos florestais nos arredores do Banhado Grande, Rio Gravataí, Rio Grande do Sul, Brasil. Estes fragmentos representam três tipos de vegetação: floresta de encosta (quatro áreas), floresta ripária (cinco áreas) e floresta paludosa (duas áreas). As aranhas foram capturadas em folhagem e "serapilheira suspensa" com auxílio de um guarda-chuva entomológico. Cada amostra foi definida como o resultado da coleta em vinte arbustos, galhos de árvores ou aglomerado de serapilheira suspensa, o que correspondeu a aproximadamente uma hora de coleta contínua por amostra. Cinqüenta e cinco amostras (cinco por área) foram obtidas, resultando em uma riqueza observada de 212 espécies representadas por adultos ou jovens identificáveis. A riqueza total para todas as amostras foi estimada entre 250 (Bootstrap) a 354 (Jackknife 2) espécies. Intervalos de confiança das curv...

A structured inventory of spiders (Arachnida, Araneae) in natural and artificial forest gaps at Porto Urucu, Western Brazilian Amazonia

“…Scharff et al, 2003, Denmark, SI = 132). However, low sampling intensity values are common in inventories carried out in tropical sites, such as those reported by Coddington et al (1991) (Bolivia, three localities, SI < 5), and even in some sub-tropical sites, as reported by Bonaldo et al (2007) (State of Rio Grande do Sul, Brazil; SI = 10.4, but inflated by the inclusion of identifiable juveniles in the calculation; SI = 8.8, excluding the identifiable juveniles and few species identified only by juveniles). The number of species represented by singletons was 167.…”

Diversity, composition and phenology of araneid orb-weavers (Araneae, Araneidae) associated with riparian forests in southern Brazil

“…Among those, more than 60% were shared with two spider fauna lists for Rio Grande do Sul State: indRusiak & Buss (1998), in Santa Maria, in the centre of the State, where one of the sites studied was a riparian forest as well, and with (2005) in Capão do Leão, south of the State, studying a restinga (sandy soil sclerophyllous) forest. A comparison with Bonaldo et al (2007), studying various environments, among them five sites in riparian forests, yields 53% similarity for the Araneidae fauna.…”

“…Spiders in this family are generally among the most abundant and speciose of those sampled from the treeshrub plant strata in faunal inventories in southern Brazil, even from distinct ecosystems (indRusiak & kotzian, 1998;BaldisseRa et al, 2004;RodRigues, 2005;silva & aRaujo, 2005;Bonaldo et al, 2007;podgaiski et al, 2007;BaldisseRa et al, 2008;RodRigues et al, 2014). A species list was presented by indRusiak & Buss (2003) for the central region of Rio Grande do Sul State, and in the list of spiders species of Rio Grande do Sul State (Buckup et al, 2010) cite Araneidae as the family with the highest number of species to the State (210 species).…”

Composição e diversidade da fauna de aranhas (Arachnida, Araneae) da Fazenda Nazareth, Município de José de Freitas, Piauí, Brasil

“…Isto indica que, embora os valores de riqueza observada sejam similares, há grande substituição de espécies (turnover) entre as formações vegetais amostradas, evidenciando sua especificidade ao hábitat. Valores baixos de similaridade entre áreas próximas também foram observados em diversos outros estudos como Coddington et al (1996), Toti et al (2000), Bonaldo et al (2007), entre outros.…”