Résumé
Environmental conditions can shape genetic and morphological divergence.
Release of new habitats during historical environmental changes was a
major driver of evolutionary diversification. Here, forces shaping
population structure and ecotype differentiation (‘pelagic’ and ‘coastal’)
of bottlenose dolphins in the North-east Atlantic were investigated using
complementary evolutionary and ecological approaches. Inference of
population demographic history using approximate Bayesian computation
indicated that coastal populations were likely founded by the Atlantic
pelagic population after the Last Glacial Maxima probably as a result of
newly available coastal ecological niches. Pelagic dolphins from the
Atlantic and the Mediterranean Sea likely diverged during a period of high
productivity in the Mediterranean Sea. Genetic differentiation between
coastal and pelagic ecotypes may be maintained by niche specializations,
as indicated by stable isotope and stomach content analyses, and social
behaviour. The two ecotypes were only weakly morphologically segregated in
contrast to other parts of the World Ocean. This may be linked to weak
contrasts between coastal and pelagic habitats and/or a relatively recent
divergence. We suggest that ecological opportunity to specialize is a
major driver of genetic and morphological divergence. Combining genetic,
ecological and morphological approaches is essential to understanding the
population structure of mobile and cryptic species.