The effect of females on genetic diversity and population structure in a gynodioecious species, Geranium maculatum

Gynodioecy, the coexistence of females and hermaphrodites within populations, is predicted to affect genetic variation and thereby evolution on the individual and population level. Genetic variation is predicted to be higher in females and in populations containing a higher proportion of females. Additionally, genetic structure within populations is expected to be lower in populations with females. This study is the first to test these predictions by examining heterozygosity on the individual, area and population level and comparing population structure between populations with and without females. Four populations were chosen, two with females and two without, and the location and multilocus genotypes determined for approximately 200 or 100 individuals, respectively, using six allozyme markers. Contrary to the predictions, females and hermaphrodites did not significantly differ in heterozygosity. Also contrary to predictions, a higher proportion of females in an area or population was associated with lower heterozygosity and more inbreeding. Our results support the prediction of less genetic structure in populations with females. The heterozygosity results suggest that hermaphrodites outcross less often when in populations containing females. Additionally, our results suggest that females biparentally inbreed. Combining the two types of evidence suggests that while there may be more selfing in populations with females, overall, there is more gene movement.