Pre-dispersal seed predation reduces the reproductive compensatory advantage of thrum individuals in Erythroxylum havanense (Erythroxylaceae)
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Male-sterility mutations in hermaphroditic species represent the first step in the evolution of gender specialization. Male-sterile individuals commonly compensate the loss of the male function by increasing the number or quality of seeds. Because the magnitude of compensation determines the maintenance of females within populations and the evolution of sexual specialization, plant-animal interactions may affect these evolutionary processes if animals are sensitive to such reproductive asymmetries. Here we explore the effect of seed predation on the reproductive compensation of Erythroxylum havanense, a distylous shrub with morph-biased partial male sterility, during two consecutive years. Seed predation reduced the compensatory advantage of thrums in 1987, but not in 1988. Annual differences in the intensity of seed predation seem to be accounted for differences in the onset and synchrony of flowering. Thus, although seed predators may reduce the compensatory advantage of thrums, their impact is modulated by the environmental cues triggering flowering and insect emergence.
KeywordsErythroxylum havanense Heterostyly Pre-dispersal seed predation Reproductive compensatory advantage Tropical dry-forest
The authors thank María del Carmen Vázquez, Germán Ávila-Sakar, Rubén Pérez-Ishiwara and Gustavo Verduzco for their assistance in the field. They also thank Juan Fornoni for its valuable comments to improve previous versions of this manuscript. This research was supported by grants from UNAM and CONACyT, Mexico.
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