Population genetic consequences of geographic disjunction: A prairie species isolated on Great Lakes alvars

I investigated broad-scale geographic variation in population genetic structure using microsatellites in the allopolyploid plant, Geum triflorum Pursh. (Rosaceae, prairie smoke), examining the population genetic consequences of geographic disjunction. G. triflorum is widespread throughout the midwestern prairies, with a disjunct distribution within the Great Lakes region where populations are isolated on alvar habitat. Disjunct 'alvar' populations had significantly lower genetic diversity (H') than core 'prairie' populations, containing only a subset of the alleles found within 'prairie' populations that were embedded within the more continuous range. My data are consistent with patterns of isolation by distance within both alvar and prairie regions, although isolated alvar populations exhibited significantly greater among population differentiation (F' ST) than prairie populations, suggesting that long-term isolation has had a greater impact on population genetic structure than the more recent fragmentation of prairie populations. (Abstract shortened by UMI.)...