Influência de variáveis abióticas sobre a comunidade de aranhas (Araneae) em serapilheira coletadas pelo extrator de Winkler em duas fisionomias vegetais na Restinga da Marambaia

Abstract

The Restinga da Marambaia is located in the Brazilian Southeast. This work aimed to evaluate whether there is any relationship between the richness and abundance concerning the time of exposition of the Winkler extractor. Thirty samples from leaf litter were collected and kept in laboratorial conditions, remaining in this extractor for 144 hours. In the first 24 h, the samples were exchanged for each three hours. After which, the samples were exchanged every six hours until the end of the experiment. Each content of litter leaf was taken out of Winkler extractor and the spiders were manually collected during 15 minutes. This allowed us record those spiders that had not been captured. A total of 737 spiders were sampled. Of these, 462 were immature and 275 were adults, composing of 24 families. During the first 3h of working of Winkler extractor, 247 samples were recorded (33.6% of the total), representing 15 morphospecies (55.5% of the total). After 24h, 516 samples were recorded (69.9% of the total) and 22 morphospecies (81.4% of the total). After 48h only two additional mophospecies were recorded.. Finally, during the 96h, 148 samples were recorded (20.1% of the total) and they represented only three species. Throughout manual captures, 98 samples were recorded distributed among 15 families with 10 morphospecies. Of these, there were six families, being represented by juveniles from leaf litter. This work allowed us to detect throughout a rapid surviey ~ 70% of total sampled and 91% of the species in 24h (KW: P< 0,05) of working of this tool. In this same ecosystem another study was developed. This last work aimed to investigate whether abiotic factors, such as soil temperature and humidity, covering by litter and litter depth and seasonality the two different vegetation types. Samples were taken between 2005-2007 in close thicket of Mirtaceae physiognomy (FN.1) and in restinga forest physiognomy (FN.2). Seasonal samplings were performed when 30 samples of leaf litter were analyzed for each physiognomy, totalizing 480 sampled units. During this work abiotic information was also collected. The Winkler extractor was used for 48h. A total of 4,460 spiders were collected, representing an average of 9.29 samples per sampling (1m2). These spiders were distribuited among 35 families. A total of 1.835 adult spiders were distribuited among 35 families and 68 morphospecies. For the FN.1, 46 species were recorded and 30 families, comprising 13 unique species. When the total abundance was analyzed for the two physiognomies, the FN.2 exhibited 2,333 samples, representing 52.3% of total captured. Oonopidae represented the richest family within FN.1 with 13 species, whereas only seven were observed within FN2. Salticidae was the second richest with 11 species. Of these, 10 species were recorded in FN.1 and seven in FN.2. Theridiidae represented nine, of which seven were recored for FN.2 and five for FN.1. Linyphiidae represented seven, six in FN.2 and five in FN.1. These four morphospecies represented 58.8% of the species sampled. After analyzing, the overall results with the community of spiders of Restinga da Marambaia it was possible to infer that the autumn and spring are the best seasons to capture adults. This study also corroborated the hypothesis that some abiotic factors interfere on the community of spider, especially the depth of leaf litter, as well as the soil humidity. Despite the fact that some of these variables are not significant for a specific season or physiognomy, it is thought that when they act together there is an influence in the ix distribuition of spiders in the two plant physiognomies studied. The two types vegetation exhibited species showing that they can be similar or distinct if the FN.1 and FN.2 are compared.