Bottlenose Dolphins Didn't Colonize the Mediterranean Until After the Last Ice Age

The bottlenose dolphin didn't always live in the Mediterranean. Scientists have found that this charismatic marine mammal only moved to the region after the last Ice Age, about 18,000 years ago.

In order to find a bit more about the population structure and history of the bottlenose dolphin, scientists took tissue samples from 194 bottlenose dolphins between 1992 and 2011. These dolphins lived in five main eastern Mediterranean basins.

The Mediterranean basin is a global biodiversity hotspot. In fact, there are several marine species that exhibit complex population structure patterns over relatively short geographic distances. It's therefore a particularly interesting region for scientists to investigate.

In the end, the researchers found that the bottlenose dolphin only colonized the area after the last Ice Age. Because of this, the population structure in the Mediterranean mainly arises from the different colonization routes that the various early colonizers took, and the genetic varieties they carried.

"Similar to the North Atlantic, two ecological types are likely to exist, one occupying deep 'pleagic'-or away from the coast-waters, and another occupying 'coastal' shallow water areas," said Andre Moura, one of the researchers, in a news release. "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 are likely to represent a single metapopulations-this is a particular type of population structure, when a single population is subdivided into regional subgroups that exchange individuals at varying rates."

The findings have important implications for conservation efforts in the Mediterranean.

The findings are published in the journal Evolutionary Biology.

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