REU: The Genetic and Ecological Bases of Dioecy in Schiedea

不像大多数动物的个体有单独的雄性和雌性，植物在繁殖系统中表现出很大的范围。大多数植物是雌雄同体的，在同一花中具有雄性和雌性的功能。但是许多其他物种，包括一些重要的农作物，在同一株植物上有单独的雄花和雌花，或者由单独的雄花和雌花组成（雌雄异株）。人们提出了许多假说来解释植物育种系统的多样性和雌雄异株的进化。一个主要的论点认为，雌雄异株的进化是为了避免近亲繁殖的衰退。近亲繁殖衰退发生在近亲交配的个体（或者在极端情况下，雌雄同体发生自花授粉），由此产生的后代表现出活力和繁殖能力下降。本研究将探讨近交抑制在夏威夷石竹属植物雌雄异株进化中的作用。这个群体显然是在进化雌雄异株，并在非常密切相关的物种中表现出一系列的繁殖系统。由于栖息地被破坏、被引进的食草动物放牧以及与引进的植物竞争，许多来自脆弱的夏威夷生态系统的重要中间物种濒临灭绝，因此这项研究具有特殊的紧迫性。众所周知，近交抑制也会影响许多重要经济作物的产量，如玉米（Zea mays）。了解导致雌雄异株的因素可能会提高控制植物性别比例的能力，在许多作物品种的产量取决于雌性的果实或种子产量的情况下，这种知识具有巨大的价值。

Unlike most animals which have individuals with separate male and female sexes, plants exhibit a great range in breeding systems. Most plant species are hermaphroditic with male and female function in the same flower. But many other species, including a number of important crop plants, have separate male and female flowers on the same plant or consist of populations of separate male and female plants (dioecy). Many hypotheses have been proposed to explain the diversity of breeding systems in plants and the evolution of dioecy. One major argument suggests that dioecy has evolved to avoid inbreeding depression. Inbreeding depression occurs when closely-related individuals mate (or in the extreme case, self-pollination occurs in hermaphrodites) and the resulting offspring show reduced vigor and ability to reproduce. In this research role of inbreeding depression in the evolution of dioecy in the Hawaiian plant genus Schiedea (Caryophyllaceae) will be examined. This group is apparently evolving dioecy and exhibits a range of breeding systems in very closely related species. This research is of special urgency because many of the important intermediate species from the fragile Hawaiian ecosystems are near extinction because of habitat destruction, grazing by introduced herbivores, and competition with introduced plants. Inbreeding depression is also well known to influence yield in many economically important crop plants, such as corn (Zea mays). Knowledge of factors causing dioecy may lead to greater ability to manipulate sex ratios in plants and is of tremendous value where yield depends upon the production of fruit or seed by the females as in the case of many crop species.