Gynodioecy inCampanula trachelium(Campanulaceae)

Abstract

Male sterility was observed in nine populations of Campanula trachelium in Ireland, with hermaphrodite and functionally female plants present in each population. As far as the authors are aware, this represents the first documented instance of gynodioecy in the species. The mean frequency of females in nine surveyed populations was 0·099 with a standard error of 0·0029. The frequency of females was not significantly correlated with population size during the year of survey but the variance in female frequency increased with decreasing population size. Observations of twenty hermaphrodite and twenty female individuals in one population over a 3-year period suggested that male sterility is likely to be a constant, heritable sex state in Campanula trachelium, although confirmation of heritability was outside the scope of this study. The information presented here will be important in the consideration of conservation strategies for the species and sets the scene for further investigation of the evolutionary benefits and costs of gynodioecy and the impact of interactions between population size and sex ratio on the extinction risk of populations.