Goldberg Emma E, Otto Sarah P, Vamosi Jana C, Mayrose Itay, Sabath Niv, Ming Ray, Ashman Tia-Lynn
Department of Ecology, Evolution, and Behavior, University of Minnesota, Saint Paul, Minnesota, 55108.
Department of Zoology, University of British Columbia, Vancouver, BC, V6J 3S7, Canada.
Evolution. 2017 Apr;71(4):898-912. doi: 10.1111/evo.13181. Epub 2017 Feb 8.
Sexual system is a key determinant of genetic variation and reproductive success, affecting evolution within populations and within clades. Much research in plants has focused on evolutionary transitions away from the most common state of hermaphroditism and toward the rare state of dioecy (separate sexes). Rather than transitions predominantly toward greater sexual differentiation, however, evolution may proceed in the direction of lesser sexual differentiation. We analyzed the macroevolutionary dynamics of sexual system in angiosperm genera that contain both dioecious and nondioecious species. Our phylogenetic analyses encompass a total of 2145 species from 40 genera. Overall, we found little evidence that rates of sexual system transitions are greater in any direction. Counting the number of inferred state changes revealed a mild prevalence of transitions away from hermaphroditism and away from dioecy, toward states of intermediate sexual differentiation. We identify genera in which future studies of sexual system evolution might be especially productive, and we discuss how integrating genetic or population-level studies of sexual system could improve the power of phylogenetic comparative analyses. Our work adds to the evidence that different selective pressures and constraints act in different groups, helping maintain the variety of sexual systems observed among plants.
性别系统是遗传变异和繁殖成功的关键决定因素，影响着种群内部和进化枝内部的进化。植物学领域的许多研究都聚焦于从最常见的雌雄同体状态向罕见的雌雄异株状态（两性分离）的进化转变。然而，进化并非主要朝着更大的性别分化方向进行，而是可能朝着较小的性别分化方向发展。我们分析了包含雌雄异株和非雌雄异株物种的被子植物属中性别系统的宏观进化动态。我们的系统发育分析涵盖了40个属的总共2145个物种。总体而言，我们几乎没有发现证据表明性别系统在任何方向上的转变速率更高。计算推断的状态变化数量发现，从雌雄同体和雌雄异株向中等性别分化状态的转变略有普遍。我们确定了未来性别系统进化研究可能特别有成效的属，并讨论了整合性别系统的遗传或种群水平研究如何能够提高系统发育比较分析的效力。我们的工作进一步证明了不同的选择压力和限制在不同群体中起作用，有助于维持植物中观察到的性别系统的多样性。
