A central question in ecology is how ecologically similar species are able to coexist. In other words, why do some species occur together in some ecological communities, but not others? The classical theory in ecology is that species cannot coexist if they are functionally too similar. This and newer theories can be tested in plant communities. Some ecologists have proposed that plant communities are structured by habitat filtering -the idea that plants with similar resource requirements will share similar habitats. In the last few years, some ecologists have even proposed the radical idea of neutrality and ecological equivalence-all species, at least to a first approximation, are equivalent from a functional perspective.
This research will test these hypotheses in tree communities that differ in species richness, ranging from about 40 species in a temperate forest to over 300 in a tropical forest. The tests involve measuring the degree of similarity in leaf traits important to photosynthesis, and the variability of these traits within and among the tree species. Each of the three hypotheses listed above has different predictions for the degree of similarity and overlap to expect in these leaf traits among co-occurring tree species. Because light is one of the primary limiting resources in forests, leaf traits important in photosynthesis, such as leaf chemistry, leaf size and shape, and leaf density, have been chosen for study. Broader impacts of this research include potential applicability to conservation and understanding invasive species, as well as educational and collaborative opportunities.
