Contrasts in the phylogeography of two migratory lampreys in western Europe

The ways that organisms respond to climatic oscillations depend on a wide range of factors, including life-history, behaviour, thermal preferences and physiology, and ecology. To investigate these processes, we compared the phylogeographic patterns found in Lampetra fluviatilis and Petromyzon marinus in Europe. We reanalysed all molecular data available for the mitochondrial non-coding region subunit I for both species. For L. fluviatilis, we also analyzed new and existing data for ATPase subunits 6 and 8, which cover a wider geographic range. In L. fluviatilis, both gene diversity and nucleotide diversity are at least three times higher than in P. marinus in Europe. L. fluviatilis shows population differentiation in Europe and displays a deeper haplotype network, with no predominance of an ancestral haplotype, which contrasts with a star-like pattern for P. marinus. Bayesian skyline plots for the two species fit exponential models and, with estimates of the times to the most recent common ancestor in each species, indicate that P. marinus has much younger populations in Europe, supporting the hypothesis of its relatively recent migration from North America. The differences in phylogeographic structures of these two species are discussed considering the likely effects of differences in their thermal preferences, migration abilities, and times available for diversification.