Current Research Focus:
1) Phylogenetic Community Ecology
Phylogenetic community ecology emphasizes the relevance of species evolutionary history for understanding species interactions and patterns of community structure, and has become an exciting field of research that improves our understanding of mechanisms regulating the structure of natural communities. Existing phylogenetic community ecology studies, however, have been mostly observational. Experimental manipulations, as a dominant and powerful form of ecological research, are lacking in this emerging field. In this context, we have completed experiments that found support for two related hypotheses of Darwin: the phylogenetic limiting similarity hypothesis (the struggle for existence is greater between more closely related species, Violle et al. in press, Ecology Letters) and the naturalization hypothesis (the naturalization of alien species becomes more difficult in the presence of their more closely related natives, Jiang et al. 2010, American Naturalist). We deem the experimental approach as a necessary means of moving the field forward, and will continue to link phylogeny with species interactions in our future work.
2) The relationship between biodiversity and ecosystem functioning (BEF)
An emerging BEF pattern is that ecosystem functioning tends to increase with biodiversity. This pattern, however, is largely based on studies with aggregated community biomass as the focal ecosystem variable. The positive biodiversity-biomass relationship occurs due frequently to positive selection effects that arise from positive correlations between species competitive ability and biomass production (i.e., competitively dominant species are most productive). An interesting hypothesis is that neutral and negative BEF relations may be common for other functions for which species competitive abilities are poor indicators of their functional impacts, where negative selection effects may dominate (Jiang et al. 2008, Oikos). Our recent work with bacteria-mediated organic matter decomposition (Jiang 2007, Ecology) provided support for this hypothesis. We are conducting meta-analyses of BEF relations for some non-biomass ecosystem variables to further evaluate this idea. We are also conducting experiments to explore how biodiversity affects population and ecosystem stability in systems of varying trophic diversity.
3) Community assembly
Natural communities do not come to existence all of a sudden, but are typically assembled through sequential species colonization events. Using microbial microcosms, we have investigated the influences of species dispersal within meta-communities and disturbance regimes on the structuring role of the history of community assembly. We are in the process of exploring the significance of community assembly for ecosystem functioning and other aspects of the context dependency of community assembly.