| This thesis evaluates timing, tempo, and patterns of ecological and taxonomic diversification in Cephaloleia (Chrysomelidae: Cassidinae), a species rich genus of herbivorous Neotropical leaf beetles. We first report the results of a species-level molecular phylogenetic study employing mitochondrial DNA sequences, designed to clarify relationships among species and to document contemporary patterns of host affiliation. We then use nuclear and mitochondrial DNA sequences, fossils, and other data to evaluate (1) whether the evolutionary history of Cephaloleia diversification departs significantly from a constant rate model, (2) whether Cephaloleia has experienced unusually rapid shifts in diversification rate during its evolutionary history, and (3) whether temporal patterns of Cephaloleia diversification are consistent with relatively recent and rapid diversification ('cradle' models), and/or the slow accumulation of species over time ('museum' models). Finally, we use molecular phylogenetic and ecological data to (1) help clarify the numbers and kinds of transitions in host tissue and host taxon affiliation over the reconstructed evolutionary history of Cephaloleia, (2) test whether such transitions are under phylogenetic constraints, and (3) evaluate Cephaloleia diversification in light of evolutionary transitions in host affiliation proposed to be symptoms of preadaptations or key innovations.; Phylogenetic analyses recovered a monophyletic Cephaloleia provided a few Cephaloleia-like species currently placed in other cassidine genera were included. Analyses evaluating the evolutionary history of Cephaloleia diversification recovered evidence for Paleocene-Eocene adaptive radiation, Oligocene codiversification with hosts, and Miocene-Pliocene diversification associated with the formation of the Isthmus of Panama. These and other observations suggest that for Cephaloleia, tropical forests are at the same time both evolutionary 'cradles' and 'museums' of diversity.; Overall, reconstructed ancestral states of host affiliation showed that evolutionary transitions in host usage were conservative and highly correlated with phylogeny. These results also suggested that the leaf roll feeding habit has a single origin in Cephaloleia, and that tissue specialization plays an important role in transitions to novel host taxa. Taken as a whole, these data and analyses provide considerable insight into the ecological and evolutionary radiation of Cephaloleia, and establish a foundation and protocol for further such macroevolutionary studies of the genus, and of other groups of organisms. |
