Anthropogenic global change has led to the decline and fragmentation of countless natural populations throughout the tree of life and across the globe. Understanding how these fragmented populations evolve and interact with their environments is a fundamental question in ecology and evolution with potential applications for biodiversity conservation. In this dissertation, I researched how dispersal, inbreeding, and mutualisms affect fitness in two systems: Poecilia reticulata (the Trinidadian guppy) and Chamaecrista fasciculata (the partridge pea). Using observations and experiments, I aimed to answer three main questions: (Chapter 2) What are the effects of dispersal on fitness in the Trinidadian guppy?; (Chapter 3) What are the individual and population-level drivers of dispersal in the Trinidadian guppy?; (Chapter 4) How do inbreeding and mutualisms interact to affect fitness in Chamaecrista fasciculata? I found that dispersal behavior in guppies is driven by complex interactions between population, individual, and seasonal conditions; that dispersal and inbreeding are important drivers of fitness in guppies and C. fasciculata; that mutualisms are affected by inbreeding in C. fasciculata; and that the expression of inbreeding depression in C. fasciculata is altered by the loss of mutualistic interactions.
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