Sex expression in the clonal gynodioecious herbGlechoma hederacea(Lamiaceae)

Abstract

The frequency of sex morphs of the clonal plant, Glechoma hederacea L., was recorded at ramet, clone, and population levels in the province of Skåne, South Sweden. In a random sample of 748 ramets at 31 sites, 68% of the ramets possessed only hermaphrodite flowers, 22% possessed only female flowers, and 10% were partially male sterile with both hermaphrodite and female flowers. At one-third of the sites, only one sex morph was found (mostly hermaphrodites). At the other sites, the proportion of female ramets and partially male-sterile ramets ranged from 3 to 100%. Multilocus genotypes were established using isozyme electrophoresis to study sex expression (stamen fertility) at different levels (among flowers within ramets, among ramets within genets, and among genets) in the field and for transplants raised under uniform greenhouse conditions. Sex expression was found to be genotype specific. Some genets were stable females or stable hermaphrodites, others being partially male sterile with a specific level of stamen fertility both in the field and in cultivation. Some multilocus genotypes showed great variation in stamen fertility among plots both in the field and in cultivation, indicating that sex expression in these genets was greatly influenced by environmental conditions. Stamen fertility varied temporally and spatially in ramets of the partially male-sterile sex types. Flower size was positively correlated with stamen fertility.