MULTIPLE-MODES OF SPECIATION INVOLVED IN THE PARALLEL EVOLUTION OF SYMPATRIC MORPHOTYPES OF LAKE WHITEFISH (COREGONUS-CLUPEAFORMIS, SALMONIDAE)

We performed a phylogenetic analysis of mtDNA variation among seven sy mpatric pairs of dwarf and normal morphotypes of whitefish from northe rn Quebec and the St. John River drainage to address three questions r elevant to understanding their radiation. Are all sympatric pairs repr oductively isolated? Do phylogenetic analyses confirm that sympatric w hitefish morphotypes found in eastern North America represent the outc ome of polyphyletic evolutionary events? If so, did all sympatric pair s from the St. John River drainage originate from the same scenario of allopatric divergence and secondary contact? The hypothesis of geneti c differentiation was supported for all sympatric pairs from the St. J ohn River drainage, whereas lack of mtDNA diversity precluded any test of reproductive isolation for northern Quebec populations. Patterns o f mtDNA variation confirmed that dwarf and normal morphotypes evolved in parallel among independent, yet closely related, lineages, thus pro viding indirect evidence for the role of natural selection in promotin g phenotypic radiation in whitefish. Patterns of mtDNA diversity among sympatric pairs of the St. John River indicated a complex picture of whitefish evolution that implied sympatric divergence and multiple all opatric divergence/secondary contact events on a small geographic scal e. These results suggests that ecological opportunities, namely trophi c niche availability, may promote population divergence in whitefish.