Diversification in the marine realm is driven by poorly understood processes
including vicariance, dispersal and ecological specialization. To test the role of these
processes, I construct the first comprehensive molecular phylogenies of the Rapaninae
and Ergalataxinae, two cosmopolitan, ecologically important but taxonomically
complex subfamilies of carnivorous neogastropods (four genes: 12S rRNA, 28S
rRNA, 16S rRNA, cytochrome c oxidase I). I sampled more than 50% of the
described species in both subfamilies: 66 species and 19 genera of Ergalataxinae, 82
species and 26 genera of Rapaninae, and used fossils to calibrate the phylogenies.
Unlike previously studied gastropod groups, the rapanine genus Stramonita has long
lived pelagic larvae with a potentially trans-oceanic scale of dispersal, raising the
question of how allopatric speciation has proceeded. To delimit species, I use
statistical methods of phylogenetic tree analysis and show that the S. haemastoma
species complex diversified in response to barriers operating at both large and small
geographic scales; habitat specialization may also have played a role in this radiation.
Dietary specialization has also been implicated in marine radiations. The ergalataxine
genus Drupella was previously thought to consist of five species of obligate
corallivores. I show that this monophyletic genus includes the facultative coral-feeder
‘Ergalatax margariticola’, which is itself composed of two cryptic species. Genetic
structure within this species complex does not relate to feeding mode, but instead
seems to correspond to broad patterns of habitat ecology found in other gastropod
taxa. Drupella diversified following the major expansion of coral reefs in the early
Miocene. If dietary specialization has permitted sympatric speciation, it is predicted
that sympatric sister species should be specialized on different food resources. I test
this prediction in the rapanine genus Drupa. Contrary to expectation, the sympatric
sister species D. ricinus and D. arachnoides have similarly generalist diets.