Patterns of Allocation to Reproductive Structures in Natural Populations of the Gynodioecious Wild Geranium (Geranium maculatum)

Dorothy A. Christopher^1,* and Shu-Mei Chang^2,†

¹Department of Biology, Western Connecticut State University, 181 White Street, Danbury CT 06810.² Department of Plant Biology, University of Georgia, 120 Carlton Street, Athens GA 30602.^†Deceased. *Corresponding author.

Southeastern Naturalist, Volume 25, Issue 2 (2026): 222–236

First published early online: 31 May 2026

Abstract
Plants with separate sexes often exhibit variation between sexes in allocation to reproductive structures. Gynodioecy, in which female and hermaphrodite individuals co-occur in a species, is thought to be an intermediate stage in the evolution of separate male and female sexes from a hermaphroditic ancestor. Though this is a major transition in angiosperms, we do not fully understand the evolution of dioecy. The objective of this study was to investigate allocation to reproductive structures in females and hermaphrodites of Geranium maculatum (Wild Geranium). In 10 natural populations in which females and hermaphrodites co-occur at varying frequencies, we measured flower number, fruit set, seed number, and rhizome length. In hermaphrodites, we measured pollen production and pollen size. We found females increased seed production relative to hermaphrodites in 4 out of 7 dimorphic populations. We found females had larger rhizomes than hermaphrodites, suggesting females may experience higher lifetime fitness. These results highlight the importance of incorporating measures of sexual and asexual reproduction into studies of sexual variation in plants.

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