In this dissertation, I combine phylogenetics, comparative methods, and studies of morphology and ecological performance to understand the evolutionary and biogeographical factors that lead to the community structure we see today in frogs. In Chapter 1, I first summarize the conceptual background of the entire dissertation. In Chapter 2, I address the historical processes influencing body-size evolution in treefrogs by studying body-size diversification within Caribbean treefrogs (Hylidae: Osteopilus). In this chapter I combine analyses of resource use, community assembly, phylogenetics, and rates of body-size evolution within Osteopilus to examine support for the influence of past competition on body-size evolution within the genus. In Chapter 3, I develop an approach to quantify the relative importance of in situ evolution (ISE) within a region and ecologically conservative dispersal (ECD) from outside that region to better understand the evolutionary and biogeographical processes that influence community structure in Middle American hylid treefrogs. I also test whether colonization of the region (Middle America) is related to climatic similarity of invaded areas to ancestral areas of colonizers, and whether temporal staggering of colonization is related to subsequent evolution within the region. Last, I determine whether species that are ecologically similar can co-occur in communities and whether ecological differences are necessary for a species or lineage to colonize the region. Finally, in Chapter 4 I examine the evolution of microhabitat use, morphology, and performance in three assemblages of frogs to ask whether these processes (ISE and ECD) are important on a worldwide scale across a large clade. I examine the consequence for morphological and performance evolution of both cross-continental, ecologically conservative dispersal of lineages, as well as microhabitat diversification within a single clade in a single geographic location. Overall, these studies suggest that the ecological, morphological, and performance diversity we see in a given location is a mixture of both ISE and ECD, even at the global scale.