PHYLOGENETIC-RELATIONSHIPS AMONG PALEARCTIC AND NEARCTIC WHITEFISH (COREGONUS SP) POPULATIONS AS REVEALED BY MITOCHONDRIAL-DNA VARIATION

We recently documented the existence of two highly distinct mitochondr ial DNA (mtDNA) phylogenetic groups of Coregonus sp. in Beringia in th e absence of geographic separation. To test whether this resulted from secondary intergradation of two groups that evolved in allopatry in E urasia and Beringia, mtDNA restriction-fragment-length polymorphisms o f 210 whitefish representing 22 populations from Europe and Siberia we re compared with mtDNA variation observed among 581 fish from North Am erica. Results confirmed that Beringia represents a zone of secondary contact among endemic whitefish and a group of Eurasian origin. All Be ringian populations clustered much more closely to Eurasian population s than other North American ones. We also compared mtDNA variation amo ng Palearctic populations with that observed in North America. Europea n populations clustered into two major mtDNA groups that exhibited a s trong geographic pattern of distribution, independent of the morpholog ical Variation observed among populations: one dominated all the more northern populations and extended to Alaska-Yukon; the second largely dominated samples from central alpine lakes, and was absent from Berin gia. These results suggest that central alpine lakes and northern Euro pe were postglacially recolonized by two genetically distinct whitefis h groups that most likely evolved in allopatry followed by limited int ergradation.