Disentangling the causes of heterogeneity in male fecundity in gynodioecious Beta vulgaris ssp. maritima.
Variation among individuals in reproductive success is advocated as a major process driving evolution of sexual polymorphisms in plants, such as gynodioecy where females and hermaphrodites coexist. In gynodioecious Beta vulgaris ssp. maritima, sex determination involves cytoplasmic male sterility (CMS) genes and nuclear restorers of male fertility. Both restored CMS and non-CMS hermaphrodites co-occur. Genotype-specific differences in male fitness are theoretically expected to explain the maintenance of cytonuclear polymorphism. Using genotypic information on seedlings and flowering plants within two metapopulations, we investigated whether male fecundity was influenced by ecological, phenotypic and genetic factors, while taking into account the shape and scale of pollen dispersal. Along with spatially restricted pollen flow, we showed that male fecundity was affected by flowering synchrony, investment in reproduction, pollen production and cytoplasmic identity of potential fathers. Siring success of non-CMS hermaphrodites was higher than that of restored CMS hermaphrodites. However, the magnitude of the difference in fecundity depended on the likelihood of carrying restorer alleles for non-CMS hermaphrodites. Our results suggest the occurrence of a cost of silent restorers, a condition supported by scarce empirical evidence, but theoretically required to maintain a stable sexual polymorphism in gynodioecious species.
Laboratoire de Génétique et Évolution des Populations Végétales, UMR CNRS 8198, Bâtiment SN2, Université des Sciences et Technologies de Lille - Lille 1, F-59655 Villeneuve d'Ascq Cedex, France.|Present address: Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.
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De Cauwer
Laboratoire de Génétique et Évolution des Populations Végétales, UMR CNRS 8198, Bâtiment SN2, Université des Sciences et Technologies de Lille - Lille 1, F-59655 Villeneuve d'Ascq Cedex, France.
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Arnaud
INRA, UR 546, Biostatistique et Processus Spatiaux, Domaine St Paul, Site Agroparc, F-84914 Avignon Cedex 9, France.
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Klein
Laboratoire de Génétique et Évolution des Populations Végétales, UMR CNRS 8198, Bâtiment SN2, Université des Sciences et Technologies de Lille - Lille 1, F-59655 Villeneuve d'Ascq Cedex, France.
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Dufay
D027461:Beta vulgaris / Q000235:genetics* / Q000502:physiology; D003593:Cytoplasm / Q000235:genetics / Q000502:physiology; D017753:Ecosystem; D056084:Genetic Fitness; D018740:Genetic Heterogeneity; D005838:Genotype; D057850:Hermaphroditic Organisms; D008954:Models, Biological; D010641:Phenotype; D051479:Plant Infertility; D011058:Pollen / Q000502:physiology; D012639:Seeds / Q000235:genetics* / Q000502:physiology; D012641:Selection, Genetic; D057945:Self-Fertilization