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Physiology and distributions of tropical plants – Drs. Kursar and Coley  One of the central questions in ecology is “what influences the distributions of organisms?” We are applying this question to the well recognized but poorly understood change in species composition across rainfall gradients within the tropics. We are testing the hypothesis that habitat restrictions arise from the combined constraints of herbivores, drought and perhaps light. Because the benefits of adaptations to herbivores, light and drought will vary across a rainfall gradient, this should select for species with different combinations of traits in dry and wet forests. High herbivory and low light are predicted to limit survival of many species in wet forests; interplay between drought and defensive costs should restrict many species from dry forests. To determine if drought, herbivore pressure and light enforce habitat specialization thereby leading to species turnover across rainfall gradients, we are carrying out reciprocal transplants across the rainfall gradient of the Isthmus of Panama, manipulating water and herbivores, and evaluating survival and growth. |
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