Mitochondrial phylogeography of the black rat supports a single invasion of the western Mediterranean basin

The black rat Rattus rattus is recognized as one of the world's most harmful invasive species. It has spread across the globe by passive human transport and the dynamics of colonization have been investigated in several areas of the world. However, data for the Mediterranean basin are still lacking. We investigated the black rat colonization of the western Mediterranean basin by means of mitochondrial genes. Mitochondrial control region and cytochrome b gene were sequenced in order to quantify genetic diversity of western Mediterranean black rats. Maximum likelihood phylogenetic analysis based on cytochrome b was used to assign specimens to a specific lineage of the R. rattus species complex. The mitochondrial control region was used to reconstruct phylogeographic pattern by statistical parsimony network and to asses historical demography of western Mediterranean black rats. The results show an unexpectedly low diversity considering that the Mediterranean basin has been a trade route since very ancient times. The results mtDNA analysis are compatible with a single event of invasions of western Mediterranean by R. rattus.