Examining the Relationship between Functional Gender and Gender Specialization in Hermaphroditic Plants

Abstract

Functional gender, as measured by relative success in fruit or seed production, may not indicate the true extent of gender specialization of individual plants. We propose our measure of "relative quality" as a more appropriate indicator of gender specialization, provided that the data arise from a fully crossed experimental mating series. Relative quality does not lead to an artifactual inverse correlation of gender abilities, whereas relative success can do so when true variation exists in at least one gender ability. The difference in the performance of these two indexes arises because quality, unlike success, separates an individual plant's contribution from that of its mating partners. Data on functional gender based on uncontrolled observations in natural populations cannot be used for any inferences about gender abilities. The observed correlation between male and female success reflects the net effects of the variance among individuals in genderspecific abilities, the degree of genetic incompatibilities among the plants, and the specific distribution of matings. The observed correlation between our indexes of male and female quality reflects the net effects of the last two influences.