Mitochondrial phylogeography of the European ground squirrel, Spermophilus citellus, yields evidence on refugia for steppic taxa in the southern Balkans

Abstract

The spatial genetic structure of the European ground squirrel, a species characteristic of the short-grass steppe, was investigated on the basis of a 1140-bp cyt b gene sequence. The phylogeographical architecture of this species is expected to shed light on the putative long-term presence of the steppic ecosystem in south-eastern Europe and the evolutionary consequences of glacial cycles as forcing factors in speciation. Among 31 haplotypes, three highly divergent phylogenetic lineages (Southern, Northern and Jakupica) were recognized. This result suggests the past existence of an allopatric fragmentation event caused by effective biogeographical barriers. The Southern lineage consisted of the southernmost populations, those from Greece, Macedonia and European Turkey, and showed the highest divergence from all other samples. Haplotypes of the Northern lineage showed little geographical structure, with dispersal on both sides of the Danube River and in both of the two main geographical fragments of the species. The Jakupica lineage is a geographical isolate on a high plateau in central Macedonia. The estimated time for divergence of the Southern lineage (ca. 0.58 Mya) suggests the long-term persistence of a short-grass steppic refugium in the southern Balkans. Although the divergence between the Northern and Jakupica lineages occurred more recently (ca. 0.3 Mya), it still putatively predates two glacial cycles. The three phylogeographical lineages of the European ground squirrel should be regarded as independent units for conservation management purposes. © 2009 Macmillan Publishers Limited All rights reserved.