Densidades de aranhas errantes (Ctenidae e Sparassidae, Araneae) em uma floresta fragmentada

Abstract

The wandering spiders of the families Ctenidae and Sparassidae are nocturnal and can be found mainly on the leaf litter, and in sites close to each other in the Amazon. The coexistence of these spiders suggests that they compete for food, shelters and, as a generalist predator, the intraguild predation can also limit the abundance of their populations. In this study, we investigated the forest fragmentation effects on the density of spiders, whose populations are under the influence of isolation and reduction of their habitats. The densities of Ctenidae and Sparassidae species in seven forest fragments (£10 ha) and nine areas of continuous forest (>1000 ha) in a "terra-firme" (non-flooded) forest of Central Amazon were compared. ANOVA tests revealed that ctenid spiders are more susceptible to the forest fragmentation by having their populations reduced in fragments where, on the other hand, sparassid spiders were more abundant. Therefore, the studied fragments were considered to be disturbed environments since they are not capable of maintaining these spider populations at the same levels as that observed in continuous forest. Besides, the negative correlation between the density of ctenid and sparassid spiders in the study area (Pearson, r = -0,527; n = 16) indicates that, probably the competition for resources and perhaps, the intraguild predation are important factors for the size of these populations. Nevertheless, a better knowledge on the interactions between Ctenidae and Sparassidae species (interspecific competition and intraguild predation) is fundamental to understand how the coexistence between them influences the susceptibility of these spiders to the forest fragmentation.