Comparative phylogeography of the ants Myrmica ruginodis and Myrmica rubra
Correspondence: Jenni Leppänen, Department of Biosciences, PO Box 65, 00014 University of Helsinki, Finland.
Here we compare the phylogeographies of the ants Myrmica ruginodis and Myrmica rubra. We test the hypotheses that owing to differences in their cold tolerance and life-history traits, M. ruginodis has less differentiated populations, a weaker phylogeographical structure and some Pleistocene refugia further north than M. rubra.
The Palaearctic region, from western Europe to Siberia and from Fennoscandia to the northern parts of the Mediterranean peninsulas and Turkey.
We sequenced mitochondrial DNA from M. ruginodis samples collected in 53 localities, and used the GenBank sequences of M. rubra individuals from 95 localities, presented in previous work. We studied the genetic diversity of M. ruginodis, the differentiation of its populations, and the geographical distribution and expansion of its haplogroups.
Populations of M. rubra were genetically slightly more differentiated than those of M. ruginodis, but we did not obtain differences in their phylogeographical structures. Both species had a west–east phylogeographical structure with secondary contact zone in between, and many haplogroups were widely distributed.
The different life histories of the species (monogyne–monocalic versus polygyne–polycalic) seem to have affected population differentiation on a local rather than a phylogeographical scale. Myrmica ruginodis survived the last glaciation in several refugia in the Mediterranean peninsulas and probably in Siberia – as did M. rubra – but also in Turkey. Circumstantial evidence supported the hypothesis of additional, more northerly refugia of the cold-tolerant M. ruginodis close to the southern edge of the permafrost of the Last Glacial Maximum, whereas for M. rubra a northern refugium in western Europe may have also existed. Post-glacial recolonization of both species took place from both the south-west and south-east, and probably also from the east. The origins of the eastern lineages of M. ruginodis were, however, difficult to localize, which stresses the importance of extensive sampling in the east when studying the phylogeography of European taxa.