Data from: Post-glacial habitat release and incipient speciation in the genus Delphinus

The role of ecological and changing environmental factors in the radiation
of species diversity is a fundamental question in evolutionary biology. Of
particular interest is the potential for these factors to determine the
boundary between what we would consider differentiation among populations
and incipient speciation. Dolphins in the genus Delphinus provide a useful
test case, exhibiting morphological variation in beak length, coloration
and body size across their wide geographic distribution, and in particular
among coastal and more pelagic habitats. Two species have been proposed,
D. delphis and D. capensis, but morphologically similar allopatric
populations are not monophyletic, indicating that the mostly coastal
‘long-beaked’ D. capensis form is not a single globally distributed
species. However, the sympatric populations in the Eastern North Pacific
currently designated as these two species are both morphologically and
genetically differentiated. Here we use microsatellite DNA and
mitochondrial DNA markers to investigate the evolutionary mechanisms that
led to this incipient speciation event. We used coalescent and assignment
methods to investigate the timing and extent of reproductive isolation.
Our data indicate that although there is some level of on-going gene flow,
the putative species found in the Eastern North Pacific are reciprocally
monophyletic. The timing of isolation appears to be associated with
regional changes in paleoceanographic conditions within the Holocene
timeframe.