雌雄同体植物的性别干扰及其进化意义

雌雄同体植物在传粉和交配过程中两性功能存在潜在的冲突和妥协。除自交和近交衰退外,人们近年来更加强调导致配子浪费和适合度减少的繁殖代价——性别干扰。性别干扰潜在地存在于雌雄同体植物中,尤其是花粉和柱头空间位置接近而又同时成熟的两性花中。该文首先介绍了雌雄同体植物性别干扰的含义及其各种形式,进而用性别干扰理论来解释各种花部性状的适应意义,同时还回顾了植物中关于性别干扰的少数实验证据。该文强调,通常被解释为避免自交的花部机制实际上更大可能是为了避免性别干扰。从更广泛意义上,自交也可以看成是一种形式的性别干扰。

SEXUAL INTERFERENCE IN COSEXUAL PLANTS AND ITS EVOLUTIONARY IMPLICATIONS

The fundamental sexual condition of the vast majority of flowering plant species is hermaphroditism. Hermaphroditic individuals both receive and disperse pollen and may ultimately function as both maternal and paternal parents to the next generation of individuals. Such dual sex roles can result in conflicts and compromise the parental roles of plants during pollination and mating. Our aim in this review is to introduce the key concepts and various forms of sexual interference in flowering plants. Sexual interference can potentially take several distinct forms with contrasting reproductive consequences and has been recognized as occurring within flowers and between flowers. Intra-floral interference includes physical interference between sex functions, pollen clogging, and ovule discounting, while inter-floral interference refers to geitonogamous pollen discounting. The adaptive significance of floral diversity such as dichogamy, herkogamy, unisexuality, and self-incompatibility has largely been regarded in the literature as resulting only from selection to avoid selfing and the harmful effects of inbreeding, but without regard to the possibly important role that sexual interference has played. We review the limited experimental evidence for interference between sex functions and evaluate the hypothesis that some floral adaptations may serve an alternative function in reducing mating costs. In a broader sense, selfing also may be regarded as a form of sexual interference, or more specifically, male function (pollen dispersal) interfering with female function (seed production). Through imaginative experiments involving floral manipulations, it is possible to evaluate various forms of sexual interference in plants and their potential ecological and evolutionary significance.