Evolutionary Ecology

, Volume 14, Issue 3, pp 195–211

A hypothesis for the evolution of androdioecy: the joint influence of reproductive assurance and local mate competition in a metapopulation

  • John R. Pannell


In a subdivided population with recurrent local extinction and re-colonisation, competition amongst related pollen or sperm to fertilise ovules or eggs (‘local mate competition’) is expected to select for female-biased sex allocation. Population turnover should also select against unisexuality in favour of self-fertile cosexuality, because males and females are unable to establish new populations on their own (‘Baker's Law’). Here I argue that androdioecy, a rare breeding system in which males co-occur with hermaphrodites, may evolve in a metapopulation under the joint action of local mate competition and Baker's Law if rates of self-fertilisation decrease with increasing population size. The hypothesis makes several predictions regarding patterns of life-history and sex allocation that are borne out by recent observations of androdioecious species in several unrelated lineages of plants and animals.

Baker's Law colonisation dioecy dispersal extinction gain curve gynodioecy local mate competition sex ratio 


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© Kluwer Academic Publishers 2000

Authors and Affiliations

  • John R. Pannell
    • 1
  1. 1.Department of Plant SciencesUniversity of OxfordOxfordUnited Kingdom

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