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.
New Phytol. 2012 Aug;195(3):676-687. doi: 10.1111/j.1469-8137.2012.04191.x. Epub 2012 Jun 12.
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.
个体间生殖成功率的差异被认为是驱动植物性二态性进化的主要过程，例如雌雄同体中雌性和雌雄同体共存。在雌雄同体的 Beta vulgaris ssp. maritima 中，性别决定涉及细胞质雄性不育（CMS）基因和雄性育性的核恢复基因。同时存在恢复 CMS 和非 CMS 雌雄同体。理论上，基因型特异性的雄性适合度差异有望解释细胞质核多态性的维持。利用两个复合种群中幼苗和开花植物的基因型信息，我们调查了雄性繁殖力是否受到生态、表型和遗传因素的影响，同时考虑了花粉扩散的形状和规模。除了空间限制的花粉流动外，我们还表明，雄性繁殖力受到开花同步性、繁殖投资、花粉产生和潜在父亲细胞质身份的影响。非 CMS 雌雄同体的 sire 成功率高于恢复 CMS 雌雄同体。然而，这种繁殖力差异的幅度取决于非 CMS 雌雄同体携带恢复基因的可能性。我们的结果表明，沉默恢复基因存在成本，这种情况得到了稀缺的经验证据的支持，但从理论上讲，这是维持雌雄同体物种稳定性二态性所必需的。
