Sexual strategies in plants IV. The distributions of gender in two monomorphic shrub populations

Abstract

The gender of plants of populations of two New Zealand montane shrub species during two flowering seasons isdescribed:Discaria toumatou has hermaphrodite flowers and Leptospermum scoparium is andromonoecious. Individuals in such species that are monomorphic for their sexual type are often considered to behave equally as pollen and ovule parents in sexual reproduction. Counts of the numbers of pollen- and fruit-bearing flowers on a sample of plants demonstrate, however, that in one season individuals within each population span the range from exclusively pollen- to predominantly ovule-contributors in functional gender (the proportions of genes that are likely to be transmitted through pollen and ovules, based on parental investments). The distribution of gender within a population changes somewhat between years but is basically consistent. Gender in successive years is not correlated among individuals within a population, indicating that the environment influences femaleness. Femaleness is not correlated with the number of flowers per plant, but in D. toumatou gender is positively correlated with the peak flowering date of a plant in one of the two seasons. © 1980 Taylor & Francis Group, LLC.