Beyond genetic differences: epigenetic variation in common bottlenose dolphins Tursiops truncatus from contrasting marine ecosystems

Abstract

Recent genetic and morphological studies have indicated an incipient ecological divergence between 2 ecotypes of common bottlenose dolphin Tursiops truncatus in the Southwestern Atlantic. However, genetic variation is not the only molecular mechanism that alters the phenotype of these animals: epigenetics can also influence phenotypic plasticity, as well as the ecological adaptation and divergence of natural populations. Nevertheless, very little is known about the role that epigenetics plays in the population ecology of marine mammals. In this work, we tested whether there are differences in DNA methylation patterns between a coastal and an offshore ecotype of common bottlenose dolphin. Methylation patterns were analyzed using the methylation-sensitive amplified polymorphism technique on biopsy samples collected from animals of both ecotypes. We found consistent differences in DNA methylation patterns between coastal and offshore individuals. We also confirmed the genetic differences described in previous studies, indicating that the divergence between ecotypes has both genetic and epigenetic components. Our data show that it is possible to differentiate animals from the coastal and offshore ecotypes using DNA methylation markers, supporting the hypothesis that contrasting environments—which are decisive for the ecological divergence of these populations—lead to epigenetic modifications in common bottlenose dolphins.