Clima atual e passado como condutor da diversidade beta funcional e filogenética de aranhas ao longo do gradiente latitudinal

Abstract

Climatic gradients can affect spatial and temporal distribution, as well as the morphological differentiation of organisms. The theory predicts that phylogenetically close species have larger body sizes in colder regions because of the need for heat storage; this explanation has been attributed to Bergmann's rule. However, the applicability of this rule to arthropods is still a challenge. Our objective was to test whether the spatial (over 2,000 km latitudinal gradient) and temporal (over 120,000 years) climate variability affect the phylogenetic and functional diversity of spiders. We used data from the literature (Gonçalves-Souza et al., 2014) that were collected in Restinga areas from southern Bahia to Santa Catarina in an extension of 12° 34'10 'at 27° 37'9' latitude. The functional attributes obtained were: height, length and width of the prossome and the length of the opistossoma. The phylogenetic tree was constructed from topologies at family and gender level. To test the effect of recent and past climate on functional and phylogenetic diversity, we used a Principal Coordinate Analysis (PCoA) combined with a Distance Based Redundancy Analysis (dbRDA) with the climate being the independent variable. Our results demonstrated that phylogenetically close spiders do not share similar morphological attributes (i.e., low phylogenetic signal). In addition, we found that stability favors the occurrence of smaller spiders. The maximum temperature of the hottest month of the past was the variable that most explained the variations of the functional and phylogenetic diversity of the spiders. The variables that indicate extreme temperature values and the annual precipitation of both the recent climate and the past were those that affected the body size most strongly. In this way, we can affirm that the seasonality and climatic extremes are dictating the variation of the body size and that this also reflects in the kinship relations of the spiders. Given the global climatic variations expected over the next 50 years, our results may help to understand possible future patterns of spatial distribution of arthropods.