Estudo das comunidades de aranhas (Arachnida: Araneae) em ambiente de Mata Atlântica no Parque Metropolitano de Pituaçu - PMP, Salvador, Bahia

Abstract

The Pituaçu Metropolitan Park (PMP) is a secondary Atlantic rainforest remnant with 425ha. New studies on ecology dynamics can help its management plan implementation and conservation. This paper analyses the border effect over the composition, diversity and richness of spider species in the PMP. The methods used were: nocturnal manual collection (CMN), and beating trays (GE). Twelve sampling units were randomly chosen (6 on the border and 6 on the interior) totalling an effort of 24 hours and 240 shrubs. Spider richness was estimated using Bootstrap, diversity using Shannon - Wiener (H). The similarity index of Jaccard was used to estimate the level of equality between the species composition in each unit. The statistical analysis were carried out using EstimateS©, Biostat 2.0© and Diversity© packages. Comparisons betwenn spider richness were made using ANOVA. A total of 948 specimens were collected. Of these, 272 were adults, belonging to 80 species and 20 families. Bootstrap estimated 32 species for GE in the center and 34 on the border. Concerning CMN, estimates were of 45 species in the center and 53 on the border, verifying that for both sampling methods there was no significant difference between the areas (ANOVA p>0,05). In relation to diversity, Shannon-Wiener index found that for both sampling methods the diversity was higher on the border than in the center. These results show that there is a significant difference between the habitats located on the border and in the center. Jaccard similarity index resulted in 32,2% for CMN and 20,9% for GE between the border and centre, indicating that there is a low level of similarity between the species composition of these areas. Among the dominant species in the center habitat, the orbweaving spiders were dominant, which was not observed on the remnant's border, where the runner spiders were dominant. The presence of a higher diversity of spider species on the border of the fragment is an unexpected result, since the majority of the studies indicate a higher diversity in the center, considering it a more preserved natural environment.