| Summary: | It has been predicted that small, isolated populations will contain less genetic diversity and be genetically distinct from neighboring populations due to genetic drift. These predictions were tested for the flowering plant species Campanula rotundifolia by comparing three disjunct Missouri populations and eighteen non-disjunct, non-Missouri populations for patterns of isozyme variation in two enzyme systems (LAP and EST). The 21 populations are significantly differentiated from each other, with an estimated Fst of 0.173. Nei's genetic distance between populations is only weakly correlated with geographic distance (r + 0.145), and Fst estimates for local clusters of populations are as high as the total Fst, indicating that differentiation is mostly on a local scale. The median genetic distance between Missouri and non-Missouri populations was not significantly different from the median genetic distance between different non-Missouri populations, so there is no evidence that the disjunct Missouri populations have diverged to a greater extent than have non-disjunct populations. The median gene diversity (Nei) within the disjunct Missouri populations was not significantly less than that within non-Missouri populations, so there is likewise no evidence that the disjunct populations are genetically depauperate.
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