According to a new study, bottlenose dolphin colonized the Mediterranean after the last Ice Age, about 18,000 years ago. Leading marine biologists collaborated in the study, the most detailed ever conducted into the genetic structure of the Mediterranean’s bottlenose dolphin population to date.

The team’s goal was to investigate the population structure and historical processes that may be accountable for the species’ geographic distribution in the area. Until now, no other study has compared the genetic structure within the Mediterranean population with the genetic structure in the North Atlantic. Tissue samples from 194 adult bottlenose dolphins were collected between 1992 and 2011 from the five main eastern Mediterranean basins.

"As a consequence of the bottlenose dolphin only colonizing the Mediterranean after the last glacial maximum or Ice Age, population structure in the Mediterranean mainly arises from the different colonization routes the various early colonizers took, and the genetic varieties they carried, “ said lead study authors Dr Andre Moura, from the School of Life Sciences, University of Lincoln, UK.

Two ecological types

"Similar to the North Atlantic, two ecological types are likely to exist, one occupying deep 'pelagic' -- or away from the coast -- waters, and another occupying 'coastal' shallow water areas. By comparing our results with genetic data from previous studies on Atlantic bottlenose, we concluded that bottlenose dolphin in the North Atlantic, Mediterranean and North Sea likely represent a single metapopulation.

"This is a particular type of population structure when a single population is subdivided into regional subgroups that exchange individuals at varying rates. These results have important implications for the understanding and conserving Mediterranean biodiversity," he added.

The Mediterranean basin in particular is a global biodiversity hotspot and several marine species exhibit complex population structure patterns over relatively short geographic distances.