Efeitos do clima sobre padrões de tamanho corporal e riqueza de aranhas na Mata Atlântica.

Abstract

What determines the distribution patterns of richness and morphological attributes of species have been studied for decades and most explanations are based on climatic gradients. However, to ectotherms, there is still controversy about the mechanisms that determine these patterns. Here we investigated how climate determines the body size and richness of spiders in the Atlantic Forest. Our hypothesis is that both temperature and precipitation affect both spider body-size and richness. We found a positive relationship between average body size of spiders and annual mean temperature and temperature seasonality. On the other hand, the same variables had a negative relationship with spider richness, while annual precipitation had a positive effect on richness. The negative relationship of temperature and richness denotes high sensitivity of the spiders to heat, which seems to limit the distribution of these ectotherms. Furthermore, larger spider species appear to occur at intermediate latitudes, where is warm and temperature varies considerably, unlike what is predicted for endotherms. Besides investigating the effects of climatic factors, we suggest future studies to assess the role of evolutionary processes when studying what determines spider body size distributions in the Atlantic Forest.