Populations of gynodioecious >Teucrium polium, Rosmarinus officinalis, Polygonum equisetiforme, and Hirschfeldia incana have been found to consist of hermaphrodite (H), female (F), and partially male sterile (PMS) plants. In this study the degree of maleness of hermaphroditic flowers was assessed by pollen stainability. In the first three species, H plants devoid of non-stainable pollen were a minority. High percentages of H flowers were partially male sterile. In T. polium and R. officinalis, 59% and 89% respectively, of flowers examined were partially male sterile, producing 20-80% aborted pollen grains. In P. equisetiforme and H. incana, 89% and 83%, respectively, of flowers examined produced up to 20% aborted grains. These findings support the assumptions that, in many gynodioecious species, PMS individuals represent a part of a continuum, from fully male fertile hermaphrodites to totally male sterile plants, and that partial male sterility may be a normal feature of gynodioecy. In T. polium, R. officinalis, and P. equisetiforme, high variation in numbers of pollen grains produced by H flowers showed no correlation to variation in pollen abortion. Morphologically, PMS flowers were distinguishable from H flowers only in R. officinalis. It appears that, for estimating maleness, use of morphological criteria may be inadequate, while tests of pollen stainability are pertinent. Partial male sterility may have an inherent advantage. In pollen loads on stigmas, PMS pollen reduces the potential paternal pool, but concurrently also reduces gametophytic competition, thereby increasing the chances of PMS genotypes to sire offspring.

Key words: Gynodioecy, Hirschfeldia incana, partial male sterility, Polygonum equisetiforme, Rosmarinus officinalis, Teucrium polium