Mitochondrial gene diversity in the common voleMicrotus arvalisshaped by historical divergence and local adaptations.

The phylogeography of the common vole (Microtus arvalis) was examined by analysing mitochondrial DNA (mtDNA) sequence variation in 1044 base pairs (bp) of the cytochromeb(cytb) gene and in 322 bp of the control region (ctr) among 106 individuals from 58 locations. The geographical distribution of four previously recognizedcytbevolutionary lineages in Europe was refined and a new lineage was found in southern Germany. All lineages were distributed allopatrically, except in one sample that was probably located in a contact zone. The occurrence of several lineages in the Alps is in keeping with their recent recolonization from distinct sources. The translation of 84cytbDNA sequences produced 33 distinct proteins with relationships that differed from those of the DNA haplotypes, suggesting that the mtDNA lineages did not diverge in response to selection. In comparison withM. agrestis, a neutrality test detected no overall evidence for selection in thecytbgene, but a closer examination of a structural model showed that evolutionarily conserved and functionally important positions were often affected. A new phylogeographical test of random accumulation of nonsynonymous mutations generated significant results in three lineages. We therefore conclude that the molecular diversity ofcytbinM. arvalisis overall the result of the demographic history of the populations, but that there have been several episodes of local adaptation to peculiar environments. [ABSTRACT FROM AUTHOR]