Abstract
AbstractPremise of the ResearchThe prevalence of sexual dimorphisms, which evolve due to contrasting strategies to maximize reproductive success in males and females, is variable among dioecious plant species. In theSalicaceae, many traits have been assessed across many studies, but direct or indirect associations between these traits and reproductive allocation are often neglected. Given the dynamic evolution of sex determination systems and the strong interest in wood production in the family, we wondered whether sexual dimorphisms related to reproduction may have gone unreported. Here, we assess sexual dimorphism in reproductive traits in two species ofSalix. Recognition of reproductive sexually dimorphic traits will contribute to understanding the evolution of sex determination systems in the Salicaceae.MethodologyWe conducted observational studies in natural populations to assess the presence of sexual dimorphisms in early spring bud density, catkin number, and flower number per catkin across four sampling periods inSalix exigua. We also analyzed flower number and catkin number per flower inSalix nigra.Pivotal ResultsWe observed no sexual dimorphism in pre-season buds per branch inS. exiguabut did find that males produced more flowers per catkin and more catkins per branch than females in bothS. exiguaandS. nigra.ConclusionsHigher flower numbers in males compared to females is consistent with expectations from intra-sexual selection among males. The presence of reproductive sexual dimorphisms inSalixsuggests that sexual selection may affect the evolution of mating strategies inSalixspecies, and the evolution of the sex determination system within this genus.
Publisher
Cold Spring Harbor Laboratory