Past and recent climate drive functional and phylogenetic beta diversity of Neotropical spiders
Studies testing the processes that drive beta diversity patterns represent one of the most debated issues in the ecological literature. Besides metric properties, the contingent behavior of beta diversity in relation to taxonomic group, the nature of environmental variables and the spatial grain received much attention. It has been advocated that beta diversity patterns are driven by multiple interacting processes acting at different spatial and temporal scales affect. However, most studies have examined beta diversity solely in response to similar sets of environmental variables within similar spatial and/or temporal scale. Furthermore, these studies have mainly used species identity, whereas functional and phylogenetic components of beta diversity are barely investigated. We studied Neotropical spiders that live on vegetation of 12 sites along a latitudinal gradient in Brazil (latitude -12.6 to -27.6, ca. 2.000 km). We used different sets of environmental variables, i.e., past (last glacial maximum) and recent climate, as potential drivers of spider functional and phylogenetic beta diversity. Specifically, we asked (1) whether past climate is a better predictor of deep phylogenetic patterns in beta diversity, and (2) whether recent climate are better predictors of shallower phylogenetic patterns and functional beta diversity.
We found that the minimum temperature of coldest month (both from past and recent climate) and annual precipitation were the main drivers of functional and phylogenetic beta diversity. Past and present climate affected similarly phylobetadiversity of basal and recent nodes in the phylogenetic tree. The deepest phylogenetic gradient (~200 million years ago) separates Araneoidea (web builders) from other clades that prey-capture web were lost, such as RTA clade (e.g. Salticidae). The functional gradient separated salticids (hunting spiders) from other spiders, and large-bodied hunters from small-bodied web building spiders. Our results shown that past climate events and recent changes in precipitation and temperature are interactively affecting functional and phylogenetic beta diversity of spiders. Functional beta diversity was jointly affected by past and present climate, which suggest morphological and life history traits of spiders are more labile and thus could be driven by habitat and microhabitat characteristics. The last glaciation event had strong effects on the deepest pattern of phylogenetic beta diversity, but recent changes in temperature and precipitation is also playing a role in this pattern. Taken together, our results reinforce the need of selecting environmental variables from different spatial and temporal scales to improve our understanding of beta diversity patterns.