Evolution of Dioecy from Gynodioecy: Artificial Selection for Sex Allocation Patterns

项目摘要。植物生殖系统的知识对于农业和濒危物种的管理以及对基本进化过程的理解至关重要。 植物通常是雌雄同体的，在同一朵花中具有雄性和雌性功能。 然而，在许多不同的植物类群中，进化导致了两性异形的繁殖系统，包括gynodiopathy（种群中的雌性和雌雄同体）和diopathy（种群中的雄性和雌性植物）。 这种分离与分配给男性和女性职能的资源的变化有关。 很少有研究探讨分配模式向雄性和雌性功能转变的遗传潜力，并考虑到具有各种生殖系统的物种的已知进化关系。 拟议的研究将探讨性别分配的遗传潜力与人工选择分配到男性和女性的功能在两个密切相关的夏威夷物种Schiedea（嘉鱼科）。 考虑到属内分配模式的范围，在雌雄同体动物中更大分配给雄性功能和在雌性动物中更大分配给雌性功能的人工选择程序应表现出显著的遗传变化潜力。在第一个试验中，将估计性别分配性状的加性遗传方差及其与其他生殖性状的遗传协方差。 在第二个试验中，将进行人工选择，以增加雌雄同体的雄蕊生物量和增加雌性的心皮和果实生物量。 这些性状的直接反应和相关性状的间接反应都将被测量，因为性状相关性可能会增强或阻碍雄性和雌性功能专业化的选择。S. salicaria被预测会变得更像雄性，因此更类似于性二型的S。adamantis雌雄同体。比较研究经常被用来预测进化的进程。 拟议中的研究将这种方法向前推进，通过确定是否可以使用人工选择产生基于比较研究假设的进化趋势。

Project Summary. Knowledge of plant reproductive systems is critical for agriculture and management of endangered species as well as for an understanding of basic evolutionary processes. Plants are usually hermaphroditic, with both male and female function in the same flowers. In many different plant groups, however, evolution has led to sexually dimorphic breeding systems including gynodioecy (females and hermaphrodites in populations) and dioecy (populations with separate male and female plants). This separation has been associated with changes in allocation of resources to male and female function. Few studies examine the genetic potential for shifts in allocation patterns to male and female function, and have taken into account known evolutionary relationships of species with various reproductive systems. The proposed study will examine the genetic potential for sex allocation shifts with artificial selection on allocation to male and female function in two closely related Hawaiian species of Schiedea (Caryophyllaceae). Given the range of allocation patterns within the genus, an artificial selection program for greater allocation to male function in hermaphrodites and to female function in females should demonstrate significant genetic potential for change. In the first experiment, additive genetic variances of sex allocation traits and their genetic covariances with other reproductive characters will be estimated. In the second experiment, artificial selection will be performed for increased biomass of stamens in hermaphrodites and increased carpel and fruit biomass in females. Both direct responses of these traits and indirect responses of correlated traits will be measured, as trait correlations may enhance or impede selection for specialization in male and female function. S. salicaria is predicted to become more male-like and therefore more similar to the sexually dimorphic S. adamantis hermaphrodites. Comparative studies have often been used to predict the course of evolution. The proposed research takes this approach forward, by determining whether evolutionary trends hypothesized on the basis of comparative studies can be produced using artificial selection.