Phylogenetic diversity stabilizes community biomass

Aims The relationship between biodiversity and ecological stability is a long-standing issue in ecology.Current diversity–stability studies,which have largely focused on species diversity,often report an increase in the stability of aggregate community properties with increasing species diversity.Few studies have examined the linkage between phylogenetic diversity,another important dimension of biodiversity,and stability.By taking species evolutionary history into account,phylogenetic diversity may better capture the diversity of traits and niches of species in a community than species diversity and better relate to temporal stability.In this study,we investigated whether phylogenetic diversity could affect temporal stability of community biomass independent of species diversity.Methods We performed an experiment in laboratory microcosms with a pool of 12 bacterivorous ciliated protist species.To eliminate the possibility of species diversity effects confounding with phylogenetic diversity effects,we assembled communities that had the same number of species but varied in the level of phylogenetic diversity.Weekly disturbance,in the form of short-term temperature shock,was imposed on each microcosm and species abundances were monitored over time.We examined the relationship between temporal stability of community biomass and phylogenetic diversity and evaluated the role of several stabilizing mechanisms for explaining the influence of phylogenetic diversity on temporal stability.Important Findings Our results showed that increasing phylogenetic diversity promoted temporal stability of community biomass.Both total community biomass and summed variances showed a U-shaped relationship with phylogenetic diversity,driven by the presence of large,competitively superior species that attained large biomass and high temporal variation in their biomass in both low and high phylogenetic diversity communities.Communities without these species showed patterns consistent with the reduced strength of competition and increasingly asynchronous species responses to environmental changes under higher phylogenetic diversity,two mechanisms that can drive positive diversity–stability relationships.These results support the utility of species phylogenetic knowledge for predicting ecosystem functions and their stability.

Stochastic processes play more important roles in driving the dynamics of rarer species

Aims One major goal of modern community ecology is to understand how deterministic and stochastic processes combine to drive community assembly.However,little empirical knowledge is known about how their relative importance varies between common and rare species.Methods We exploited two 30-year data sets of plant communities in a temperate steppe using two different methods.One is a null model method,and the other is a recently developed direct-calculation method.Important Findings We found that stochastic processes tended to be more important in influencing rare than common species.This finding suggests that stochastic forces may play a more important role in structuring communities with more rare species,providing a possible solution to the debate on the varied importance of deterministic and stochastic processes among different communities.