COLLABORATIVE RESEARCH: MODELING SUCCESSIONAL VEGETATION DYNAMICS IN WET TROPICAL FORESTS AT MULTIPLE SCALES: INTEGRATING NEIGHBORHOOD EFFECTS, FUNCTIONAL TRAITS, AND PHYLOGENY

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Several mechanisms have been proposed to explain the high number of species present in tropical forests. The outcome of these processes, which could include random or non-random elements, may be reflected in the evolutionary history and distribution of functional traits (plant size, leaf size, flowering pattern, etc.) in a community. Because they reflect "community assembly in action", successional tropical forests (developing after a disturbance) provide an ideal natural laboratory for testing the power of an integrated multi-faceted approach to community assembly. Using data collected in secondary and mature forests in Costa Rica and Puerto Rico, the proposed research will develop a novel approach to understanding community assembly that will integrate detailed forest inventory data. This approach will be used to assess the relative importance of habitat differences, niche differences, and lack of seedlings in driving tropical forest community assembly at different spatial scales and across life history stages. Coordinated data collection will allow for comparisons of functional traits across successional stages within a context of the plants' evolutionary history, which will be reconstructed using DNA bar-coding technology.The major objectives of this research are to (1) compare patterns of species-level phylogenetic (evolutionary) relationships and functional similarity of plants between successional and mature forest communities; (2) link functional traits and phylogenetic structure with population and community dynamics through sophisticated models of tree mortality and growth, and (3) assess the role of recruitment limitation and the relative importance of functional and phylogenetic relatedness in predicting species- and stage-specific population dynamics during succession.Secondary forests now cover more area than remaining old-growth forests in many tropical countries and are increasingly important components of tropical landscapes for biodiversity conservation and provision of ecosystem services. A mechanistic understanding of how these forest communities are assembled is urgently needed. The evolutionary relationships among plants that will be discovered as part of this project will contribute to a deepening understanding of the angiosperm evolutionary history. Two doctoral graduate students, one postdoctoral researcher, and undergraduate students from the University of Puerto Rico, the largest Hispanic institution in the US federal system, will be trained.