In a paper published in mid-February in the Journal of Evolutionary Biology researchers tried to identify the processes and factors that led to the emergence of regional population structure in bottlenose dolphins inhabiting the Adriatic Sea and the eastern part of the Mediterranean Sea using DNA analysis and phylogeography. So far the most comprehensive analysis of the genetic structure of populations of bottlenose dolphins in the Mediterranean and Adriatic included analysis of 194 tissue samples of common bottlenose dolphins collected in five regions of the Mediterranean (the Adriatic, the Tyrrhenian, Ionian, Aegean and Levantine basin).

One of the authors of this scientific article, Dr. Drasko Holcer from the Blue World Institute says: “We started the study of the genetic structure of bottlenose dolphins in 2012. with the primary goal of determining the population structure in common bottlenose dolphins of the Adriatic Sea. The analysis was based on the material that Blue World Institute and several other organisations collected during ten years of work in the Adriatic. We published the results of this analysis in 2014 in an article titled “Population genetic structure of common bottlenose dolphins (Tursiops truncatus) in the Adriatic Sea and contiguous regions- implications for international conservation”. The results of that work have shown that there is a clear structuring within the population of common bottlenose dolphins in the Adriatic and that there are differences between the parts of the Adriatic basin and adjacent regions of the Mediterranean. Also, we found that females are the main mediators in the process of gene mixing in the Adriatic, while the main “colonization” routes within the area are from the north to other parts of the Adriatic Sea and from the west to the east. These results showed that despite the seemingly homogeneous distribution of common bottlenose dolphins in the Adriatic Sea, there are regional “units” which need particular conservation effort in order to prevent possible negative impacts of anthropogenic activities.

Cooperation with colleagues from other regions of the Mediterranean and the inclusion of their samples in our next analysis resulted in the publication of a new article, “Drivers of population structure of the bottlenose dolphin (Tursiops truncatus) in the Eastern Mediterranean Sea.” The new results showed that bottlenose dolphins in the Mediterranean area settled relatively recently – after the last glaciation, some 18.000 years ago, from the North Atlantic. Physiographic and oceanographic characteristics of different parts of the Mediterranean have significant impact on the development of sub-structuring within populations. This characteristics affected colonization routes leading to development of local units among common bottlenose dolphins within different areas. Also, bottlenose dolphins inhabiting the oceans have two distinct ecotypes – pelagic (inhabiting the open sea) and coastal (inhabits coastal shelf areas). In the Mediterranean Sea pelagic ecotype was previously not known. The results of our research for the first time recognise that in the Mediterranean Sea both ecotypes are present, and that pelagic ecotype serve as a “source” from which coastal areas are being (re)populated. Also, the results show that the bottlenose dolphins in the Mediterranean are part of a larger meta-population of the North Atlantic.”
The research team was led by Dr. Stefania Gaspari of the University of Florence. Articles can be viewed at the web-page of the publisher or author or you can request it from us