Phylogenetic systematics, biogeography and diversification patterns in cowries

I use mitochondrial molecular sequence data to construct the first rigorous, comprehensive phylogenetic hypothesis for the gastropod group cowries, a well-known, diverse member of reef-associated communities. Analysis of sequence data from the Cytochrome Oxidase subunit I and large ribosomal subunit 16S from 151 taxa reconstruct divergences stretching from the Paleogene to the Recent. This phylogeny is consistent with the fossil record, biogeography, morphology and recognized major species complexes.; The effect of transversion bias on estimates of relationships is explored. Phylogenies produced by a range of transition:transversion (Ti:Tv) correction factors are pooled and evaluated using maximum likelihood criteria. These topologies follow a smooth curve through likelihood space, with increasingly complex models of molecular evolution providing significantly better fit to the data. For these data, a 4:1 Ti:Tv ratio applied during parsimony produces the most likely topologies. Heuristic shortcomings are addressed when analyzing large data set.; This comprehensive sequence database is used to examine the effect that exemplar strategies have on recovering relationships. Both consensus approaches and comparison to the topology with all taxa included were used to assess the effectiveness of subsampling the dataset. Transversion bias again had a significant effect on tree topologies: increased Ti:Tv ratios performed better at recovering deeper divergences, while lower Ti:Tv ratios performed better at recovering shallow divergences. Branch length evenness in the tree significantly improved results.; The biogeographic history of the Indo-Pacific is deconstructed into its component evolutionary units by identifying endemic Indo-Pacific clades. Major concordant breaks occur between taxa approximately 10 million years ago, when the surface circulation between the Indian and Pacific basins was severed. The diversity spike in the Indo-West Pacific is due to a single Indo-Pacific clade containing many paraphyletic taxa that contain young, nested, geographically restricted species potentially formed during sea level lowstands. Evidence of introgression between a peripheral endemic species and a widespread IP species is presented.; Simulations based on the phylogeny and fossil record demonstrate that no differential speciation or extinction is required to produce the frequency distribution of present clade size. Speciation must exceed extinction by 2.51 to produce standing diversity. Wide-ranging taxa exhibit resilience to extinction and morphologic inertia.