Phylogeography of the pool frog (Rana lessonae Camerano) in Europe:: evidence for native status in Great Britain and for an unusual postglacial colonization route

The pool frog, Rana lessonae, has historically been considered an introduction into Britain, with Italy the most likely source. Recently, the possibility of native status for a Norfolk pool frog population was raised. We used random amplified DNA (RAPD) analyses to clarify the status issue. Nine arbitrarily designed primers detected 160 polymorphisms in 174 pool frogs from 11 European locations. Polymorphism levels varied widely, being lowest in the northern populations and highest in the south. As with many isolated populations, the peninsular and insular populations of Sweden, Norway and Britain showed relatively little polymorphism. Principal component and cluster analysis showed clear geographical groupings. The Norfolk, Norwegian and Swedish individuals formed a closely related group - a northern clade, substantiating native status for the Norfolk population, which, interestingly, had idiosyncratic features suggestive of a distinctive evolutionary history. Phylograms constructed from RAPD data were consistent with an unexpected postglacial colonization route, in which the northern clade derived from migration out of Italy, via Hungary and Poland, though cryptic glacial refagia in Eastern Europe are an alternative explanation. Our RAPD analyses concur with a parallel microsatellite investigation. Both genetic studies and bioacoustic and archaeozoological findings support native status for Norfolk pool frogs and have prompted a programme for re-establishing the northern clade in England. (c) 2005 The Linnean Society of London.