The online early section of Molecular Phylogenetics and Evolution this week has the first comprehensive phylogeny of a rather important genus of ants: Myrmica.

Myrmica is ubiquitous in the colder climates of North America and Eurasia, with a few seemingly incongruous species inhabiting the mountains of tropical southeast Asia. The genus contains about 200 species, many that are common soil-nesting ants in lawns and gardens, and at least one damaging invasive species, M. rubra. The taxonomy ranks among the most difficult of any ant genus, as workers of different species tend to be numbingly similar to each other. And there are a lot of species.

Summary cladogram of the ant genus Myrmica, redrawn from Jansen et al 2010, depicting a parsimony reconstruction of the geographic distribution of the genus.

This phylogeny- part of Gunther Jansen‘s Ph.D. thesis- finally sets the systematics of Myrmica on a firm evolutionary footing. Jansen used genetic data from several loci and 106 specimens to infer the history of the genus, recovering a well-supported phylogeny spanning roughly half of the extant species. Considering the difficulties posed by a monotonous worker morphology, these molecular data provide a needed infusion of new information.

Jansen’s primary findings are:

  • In spite of the difficulty posed by morphology, most of the morphology-based species groups are recovered as clades.
  • Much of the deeper history of Myrmica is preserved in North America, with what appears to be several independent dispersals across Beringia to Eurasia.
  • Most social parasites are closely related to their hosts (see Emery’s rule), but the exceptions suggest that socially parasitic lineages can persist beyond subsequent speciation events in their host lineage.
  • Modern Myrmica shared a common ancestor about 30 to 45 million years ago, and the diversification appears to coincide with a global cooling around the Oligocene-Eocene boundary.

It’s a solid paper, and a very welcome advance to the systematics of an important ant genus.

Source: Jansen, G., Savolainen, R., Vepsalainen, K., 2010. Phylogeny, divergence-time estimation, biogeography and social parasite–host relationships of the Holarctic ant genus Myrmica (Hymenoptera: Formicidae). Molecular Phylogenetics and Evolution, doi: