Journal Article

Ecological context and metapopulation dynamics affect sex-ratio variation among dioecious plant populations

David L. Field, Melinda Pickup and Spencer C. H. Barrett

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 111, issue 5, pages 917-923
Published in print May 2013 | ISSN: 0305-7364
Published online February 2013 | e-ISSN: 1095-8290 | DOI:
Ecological context and metapopulation dynamics affect sex-ratio variation among dioecious plant populations

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  • Plant Ecology
  • Plant Reproduction and Propagation


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Background and Aims

Populations of dioecious flowering plants commonly exhibit heterogeneity in sex ratios and deviations from the equilibrium expectation of equal numbers of females and males. Yet the role of ecological and demographic factors in contributing towards biased sex ratios is currently not well understood.


Species-level studies from the literature were analysed to investigate ecological correlates of among-population sex-ratio variation and metapopulation models and empirical data were used to explore the influence of demography and non-equilibrium conditions on flowering sex ratios.

Key Results

The survey revealed significant among-population heterogeneity in sex ratios and this was related to the degree of sampling effort. For some species, sex-ratio bias was associated with the proportion of non-reproductive individuals, with greater male bias in populations with a lower proportion of individuals that were flowering. Male-biased ratios were also found at higher altitudes and latitudes, and in more xeric sites. Simulations and empirical data indicated that clonal species exhibited greater heterogeneity in sex ratios than non-clonal species as a result of their slower approach to equilibrium. The simulations also indicated the importance of interactions between reproductive mode and founder effects, with greater departures from equilibrium in clonal populations with fewer founding individuals.


The results indicate that sex-based differences in costs of reproduction and non-equilibrium conditions can each play important roles in affecting flowering sex ratios in populations of dioecious plants.

Keywords: Biased sex ratios; costs of reproduction; dioecy; stress gradients; non-equilibrium conditions; metapopulations

Journal Article.  4862 words.  Illustrated.

Subjects: Plant Ecology ; Plant Reproduction and Propagation

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