Within- and between-population variation in ramet behaviour in the gynodioecious clonal herb, Glechoma hederacea (Labiatae)

Abstract

Clones of the gynodioecious herb Glechoma hederacea L. produce ramets which flower and bear seed, ramets which flower but fail to bear seed, and sterile ramets. Performance and survivorship of these subsets of ramets were compared for hermaphrodite and male sterile clones in contrasting grassland and woodland habitats for 2 consecutive years. For all clones, ramet densities on given dates were comparable between years. Winter survival of ramets exceeded 95% and mortality during the growing season was exponential. No genet recruitment was recorded throughout the study. For all clones, flowering ramets were larger than nonflowering ramets. Both flowering and nonflowering ramets of hermaphrodite clones, from grassland and woodland, were significantly larger than corresponding types of ramets from male sterile clones. A higher proportion of ramets of hermaphrodite clones flowered and set seed than ramets of male sterile clones. Flowering ramets of hermaphrodite clones produced more flowers than flowering ramets of male sterile clones. For all clones, half-lives of subsets of ramets declined in the order: seed-bearing > flowering but not seed-bearing > nonflowering. Within the grassland habitat, ramet subsets from hermaphrodite clones had longer half-lives than corresponding subsets from the male sterile clones. In the absence of greater flowering and seed set by male sterile clones, self-incompatibility of hermaphrodite flowers, which has been reported previously for G. hederacea, is crucial for the maintenance of clones of both sexes in populations.