The influence of demography and local mating environment on sex ratios in a wind-pollinated dioecious plant

Pickup, Melinda and Barrett, Spencer C H (2013) The influence of demography and local mating environment on sex ratios in a wind-pollinated dioecious plant. Ecology and Evolution, 3 (3). pp. 629-639. ISSN 2045-7758

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Negative frequency-dependent selection should result in equal sex ratios in large populations of dioecious flowering plants, but deviations from equality are commonly reported. A variety of ecological and genetic factors can explain biased sex ratios, although the mechanisms involved are not well understood. Most dioecious species are long-lived and/or clonal complicating efforts to identify stages during the life cycle when biases develop. We investigated the demographic correlates of sex-ratio variation in two chromosome races of Rumex hastatulus, an annual, wind-pollinated colonizer of open habitats from the southern USA. We examined sex ratios in 46 populations and evaluated the hypothesis that the proximity of males in the local mating environment, through its influence on gametophytic selection, is the primary cause of female-biased sex ratios. Female-biased sex ratios characterized most populations of R. hastatulus (mean sex ratio = 0.62), with significant female bias in 89% of populations. Large, high-density populations had the highest proportion of females, whereas smaller, low-density populations had sex ratios closer to equality. Progeny sex ratios were more female biased when males were in closer proximity to females, a result consistent with the gametophytic selection hypothesis. Our results suggest that interactions between demographic and genetic factors are probably the main cause of female-biased sex ratios in R. hastatulus. The annual life cycle of this species may limit the scope for selection against males and may account for the weaker degree of bias in comparison with perennial Rumex species.

Item Type: Article
DOI: 10.1002/ece3.465
Uncontrolled Keywords: dioecy, female-biased sex ratios, gametophytic competition, local mating environment, plant density, sex ratios, wind pollination
Subjects: 500 Science > 570 Life sciences; biology > 576 Genetics and evolution
Research Group: Barton Group
SWORD Depositor: Sword Import User
Depositing User: Sword Import User
Date Deposited: 05 Jan 2016 09:19
Last Modified: 05 Sep 2017 14:29

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