I study how species assemble into ecological communities. For the past 15 years, I have been particularly interested in understanding historical contingency, or when and why the structure and function of communities are contingent on the past history of species immigration.
Some current topics
Ecological communities were once thought to tend towards a single "climax" state, with a deterministic composition of species that can be predicted from environmental conditions. More recently, it is increasingly recognized that, even given the same environmental conditions, the ways species affect one another and their consequences for species composition can differ greatly depending on the history of community assembly, or the order and timing in which different species immigrate--the phenomenon known as priority effects. With this recognition, communities are no longer considered deterministic, but sometimes historically contingent, as depicted below (for an application of this diagram to the human microbiome, see Fig. 1 in Costello et al. 2012).
© 2011 T. Fukami, modified from Fukami 2010The extent of historical contingency due to priority effects is difficult to quantify because immigration history is impossible to reconstruct in sufficient detail for most natural communities. Nevertheless, theory suggests that priority effects can be substantial, with profound implications for understanding and conserving species diversity. For example, priority effects may lead to unexpectedly high variation in community structure among similar sites, collectively enhancing regional species diversity. Further, if priority effects are strong, restoring native diversity in degraded sites may require specific sequences of species removal and introduction.
Despite these implications, the field of ecology currently lacks a coherent framework in which to explain when, why and how strongly historical contingency affects community assembly. The goal of my research is to build such a framework. In my past research, I found that historical contingency could be strong enough to affect major patterns of community structure, including productivity-biodiversity relationships, species-area relationships, and local-regional species richness relationships. In my current research, I seek to improve and integrate ecological concepts from a historical perspective on community assembly.