Phylogenetic turnover and diversity in tropical forests through space and time

Background/Question/Methods The diversity and dynamics of communities are two of most analyzed patterns in ecology. A myriad of mechanistic hypotheses have been derived to explain the patterns. Strong tests of these hypotheses require refined information pertaining to the evolutionary history and function of the species in the community. Recent work has advanced our understanding of phylogenetic and functional similarity of coexisting species at discrete points in time, but less focus has been placed on examining the ability of phylogeny and function to explain the temporal dynamics of communities. Perhaps one of the most intriguing aspects of community dynamics is that they often experience what has been termed ‘ecological drift'. To date, the degree of ecological drift in communities has been determined by examining the rate of temporal decay in species compositional similarity through time. If communities are truly drifting, it is expected that the rate of temporal decay in the phylogenetic and functional compositional similarity through time should at a comparable rate. In this seminar, I provide the results of a study that quantified the relative rates of decay in the species, phyogenetic and functional composition of assemblages through space and time in multiple tropical forest dynamics plots. Results/Conclusions The results show that the rates of decay in the species, phylogenetic, and functional compositions of tropical tree assemblages are often unequal. In particular, the rate of decay of the species similarity is often the fastest followed by the phylogenetic similarity and the functional similarity respectively. This finding suggests that the phylogenetic and functional compositions of the studied tropical tree communities are drifting at a slower rate. The observed slower rates of decay may be indicative of a propensity for closely related and functional similar species to replace one another in communities through time and a lack of invasion by distantly related and functionally dissimilar species through time.