Sex-specific fitness variation in gynodioecious Beta vulgaris ssp. maritima: do empirical observations fit theoretical predictions?

Authors

  • I. DE CAUWER,

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    • Present address: Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.

  • J.-F. ARNAUD,

    1. Laboratoire de Génétique et Évolution des Populations Végétales, FRE CNRS 3268, Bâtiment SN2, Université des Sciences et Technologies de Lille – Lille 1, Villeneuve d’Ascq Cedex, France
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  • A. COURSEAUX,

    1. Laboratoire de Génétique et Évolution des Populations Végétales, FRE CNRS 3268, Bâtiment SN2, Université des Sciences et Technologies de Lille – Lille 1, Villeneuve d’Ascq Cedex, France
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  • M. DUFAY

    1. Laboratoire de Génétique et Évolution des Populations Végétales, FRE CNRS 3268, Bâtiment SN2, Université des Sciences et Technologies de Lille – Lille 1, Villeneuve d’Ascq Cedex, France
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Isabelle De Cauwer, Laboratoire de Génétique et Évolution des Populations Végétales, FRE CNRS 3268, Bâtiment SN2, Université des Sciences et Technologies de Lille – Lille 1, F-59655 Villeneuve d’Ascq Cedex, France.
Tel.: +44 0 1142220112; fax: +44 0 1142220002; e-mail: i.decauwer@sheffield.ac.uk

Abstract

In gynodioecious species, in which hermaphroditic and female plants co-occur, the maintenance of sexual polymorphism relies on the genetic determination of sex and on the relative fitness of the different phenotypes. Flower production, components of male fitness (pollen quantity and pollen quality) and female fitness (fruit and seed set) were measured in gynodioecious Beta vulgaris spp. maritima, in which sex is determined by interactions between cytoplasmic male sterility (CMS) genes and nuclear restorers of male fertility. The results suggested that (i) female had a marginal advantage over hermaphrodites in terms of flower production only, (ii) restored CMS hermaphrodites (carrying both CMS genes and nuclear restorers) suffered a slight decrease in fruit production compared to non-CMS hermaphrodites and (iii) restored CMS hermaphrodites were poor pollen producers compared to non-CMS hermaphrodites, probably as a consequence of complex determination of restoration. These observations potentially have important consequences for the conditions of maintenance of sexual polymorphism in B. vulgaris and are discussed in the light of existing theory on evolutionary dynamics of gynodioecy.

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