Can phylogenetic diversity predict ecosystem functioning? A synthesis

Background/Question/Methods

Two decades of “biodiversity-ecosystem function” research have led to the realization that community composition largely influences ecosystem functions through determining functional traits, niches and species interactions.  However, it has been challenging to condense information about these forms of ecological complexity. Given that there is evidence that traits, niches and species interactions often have a phylogenetic signal, a useful unified measure of all of these diversities may be phylogenetic diversity (PD): the combined phylogenetic distance between all species in a community. Although there has been substantial research on the factors that determine community PD, exploration of the consequences of community PD for ecosystem functioning is just beginning. In this talk, we critically examine the evidence for and against the utility of PD in predicting ecosystem functions. Our examples span a range of communities, from single-trophic to complex networks, and from microbial to plant and animal.

Results/Conclusions

Very few studies have examined the relationship between PD and ecosystem function, but those that have been conducted are generally consistent with PD being a useful predictor. However, we caution that the utility of PD depends critically on the strength of phylogenetic signals to both traits and interactions, and the influence of community assembly process on the community-level phylogenetic signal. Furthermore, interpreting patterns in the absence of a direct test of the underlying mechanism cannot lead to strong inference. We advocate for a more mechanistic approach that includes an understanding of how traits, niches and interactions are shaped by evolution, such that phylogeny is viewed as an explanation  for these state variables, rather than yet another diversity index. If future research can meet these challenges, then studying the effects of community PD on ecosystem function may lead us to a conceptual unification of evolutionary biology with ecosystem ecology.