Mechanisms of community assembly in plant communities

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The overarching goal of my research is to uncover the mechanistic nature of existing variation in the distribution and abundance of species in natural systems. I use a combination of field and glasshouse investigations to explore how competition, predation, dispersal, and adaptation to environmental conditions contribute to community structure. ***Null models have undergone significant development and exploration to better understand the influence of processes, competition in particular, on patterns of species organization within communities. However, a recent review indicates that such models rarely find significant evidence of deterministic community assembly rules related to competition (e.g., trait divergence and negative co-occurrence). In combination with this, several avenues of research suggest that multiple processes may produce conflicting patterns within a community that are not picked up by community-scale null models. As such, there are significant concerns about whether the current collection of null modelling tools available can address the questions we wish them to. Furthermore, most research to date has not adequately matched null model analyses with experimental manipulation and glasshouse research to better link patterns with processes. ***The above issues are compounded by gaps in our understanding of how competition plays out within communities. For example, simple competition experiments that identify pair-wise competitive hierarchies related to plant species maximum size do not clearly align with analogous field experiments, and are poorly integrated with the potential for size differences to drive niche differentiation and thus the avoidance of competition. Finally, while the potential exists for intransitive competition to promote diversity within natural systems, the simple nature of competition experiments, particularly on plant species, makes it difficult to assess the potential for intransitivity to promote species diversity, particularly when assessments of competitive relationships generally rely on poor evidence that the species in question do in fact compete within natural communities.***My students and I will address the above issues by developing and refining null model analyses and through the use of field and glasshouse experiments. This work will expand our understanding of the relative contributions of competition, predation, and dispersal, to community structure and further our understanding of the link between competitive ability and patterns of abundance observed in natural communities. Additionally, understanding the relative impact of different mechanisms that can augment (e.g., dispersal, facilitation) or reduce diversity (e.g., competition, predation) will greatly inform conservation and restoration initiatives, and aid in the management of invasive species.********