Date of Award
Doctor of Philosophy (PhD)
Schnitzer, Stefan A.
Ecology seeks to explain the mechanisms that allow multiple species to coexist in the same habitat without one species outcompeting or driving others to extinction. Niche differentiation is a mechanism that has been proposed to allow species to coexist through specialization on different resources or habitats, which reduces competition and the probability of competitive exclusion. Species can reduce competition by using different combinations of resources and thus partitioning available resources in time and space. Differences in resource use is hypothesized to be influenced by species’ morphological and physiological adaptations, known as functional traits. Links between functional traits and abiotic factors are well established in the literature, however, whether functional traits explain species interactions and coexistence remains poorly understood. For my doctoral dissertation research, I used a combination of key functional traits to test whether a trait-based approach can explain species coexistence in tropical woody plants. For my first chapter, I investigated whether functional traits differ between co-occurring lianas and trees. Previous studies have shown that these two plant groups compete intensely for resources, and thus they may differ in trait space. I found that four functional traits related to rapid resource acquisition strategy were particularly important in defining differences in resource acquisition between lianas and trees. For my second chapter, I tested whether temporal changes in resource availability could explain resource partitioning in lianas and trees. I measured functional traits in liana and tree species grown in a seasonal common garden. Two key functional traits, turgor loss point and photosynthetic capacity, explained temporal partitioning of resources between lianas and trees. In my third chapter, I tested how liana species partition resources among themselves by comparing functional trait differences in a highly diverse community of lianas in a tropical forest in Panama. Functional traits varied widely in liana species, demonstrating that lianas have many different strategies to compete for resources. Turgor loss point, wood density and specific leaf area were particularly important predictors of liana life history strategies. Taken together, my findings increase our understanding of the role of functional traits to explain plant species interactions and coexistence in tropical forests.
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