Glacial refuges for three‐spined stickleback in theIberianPeninsula: mitochondrialDNAphylogeography

Abstract

SummaryAnalyses of the mtDNAof 183 three‐spined sticklebacks (Gasterosteus aculeatus), from freshwater Iberian populations, were performed to reconstruct the phylogeography of this species and to inform conservation recommendations on the basis of genetic diversity and the geographical distribution of variation.A high degree of population structure, with high overall genetic diversity but very low intrapopulation variation, was observed. Haplotypes were distributed according to a geographical pattern with most samples fixed by a unique haplotype.Phylogenetic analyses supported two independent lineages in the Mediterranean region, highly divergent from Atlantic (Portuguese) haplotypes. Analyses of the historical demography confirmed that the Iberian Mediterranean three‐spined stickleback diverged prior to the last glaciation.Phylogeographic reconstruction, together with 114 representative sequences of the European three‐spined stickleback, revealed eight mtDNAlineages and related our Iberian Mediterranean haplotypes to those previously described in the lower Rhône (southern France). Multiple ancient Pleistocene lineages were described through the Adriatic, Black Sea and Mediterranean regions. The highly structured network fits well with a freshwater habit of the three‐spined stickleback in the ancient colonisation of southern Europe.Results suggested a Middle Adriatic and Black Sea origin of the European post‐glacial three‐spined stickleback, but additional colonisation from the northern Adriatic and even from Atlantic marine refuges cannot be discarded. Mediterranean three‐spined sticklebacks probably did not contribute to this post‐glacial colonisation.Conservation priorities should be established in the Iberian Mediterranean, where the three‐spined stickleback has many endemic genotypes whose habitats are threatened. On the basis of the genetic data, we recommend that each river system is considered as an independent conservation unit.