How does environmental variation maintain biodiversity within an ecosystem?

Species-specific, asynchronous recruitment at BCI

Studies have identified numerous mechanisms that can promote coexistence in diverse tropical forests. Yet, until recently, few explanations for the diversity of tropical forests could explain how such dramatic variation in species-specific responses to yearly climate variation — evidenced by the dramatic temporal fluctuations in species’ flowering, reproduction, and seedling recruitment — might contribute to coexistence. By using a unique long-term data set from Barro Colorado Island, Panama, colleagues and are able to apply coexistence theory to quantify the potential for these fluctuations to promote coexistence.

Habitat heterogeneity can also shape species coexistence, and may interact with temporal variation. For example, the clustering of individuals resulting from limited dispersal can reduce the potential for coexistence via the storage effect. Because dispersal limitation is a frequent phenomenon, especially among primary producers, this conclusion has major implications for future studies of temporal variability and diversity. Current work is seeking to extend this research into the spatial dimension, and ask what contribution environmental heterogeneity in seedling recruitment makes to coexistence. 

This study, and many others, are testament to the value of long-term field studies and monitoring efforts to advance our understanding of biodiversity. My contribution is to demonstrate the utility of using long-term data  in combination with mathematical models based on key knowledge of population dynamics to explore the biodiversity consequences of observed patterns.

Representative publications: 

Usinowicz, J., S. J. Wright, and A. R. Ives. 2012. Coexistence in tropical forests through asynchronous variation in annual seed production. Ecology 93:2073–2084. PDF  (See Appendix A for a brief review of coexistence concepts). 

Usinowicz, J. 2015. Limited Dispersal Drives Clustering and Reduces Coexistence by the Storage Effect. The American Naturalist 186:634–648. PDFAppendix A, Appendix B, Appendix CLink to code on GitHub.

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