DISSERTATION RESEARCH: Geographic Variation in Pollinators, Outcrossing, and the Incipient Evolution of Dioecy in Echinocereus coccineus (Cactaceae)

生物学中的一个基本问题是：为什么有不同的性别？拥有不同的性别可以避免最糟糕的近亲繁殖：自花受精。在动物授粉的植物中，假设在某些区域（例如，山顶，沙漠），因为那里的不太专业的传粉者主要是这些植物的自花受精。另一种假设是，不同的性别进化是因为资源（例如，性功能所需的水资源（如水）稀缺，如果两性分开，可以更有效地分配。红葡萄酒杯仙人掌提出了一个独特的机会，同时测试这两个假设，因为他们拥有两性（性别在一起）和雌雄异株（性别分开）人口。该物种由雌雄异株种群中和周围的不太专业的蜜蜂授粉，这支持了避免近亲繁殖的假设。然而，雌雄异株种群也往往出现在干旱地区。这支持了资源分配假说。在植物、种群和景观尺度上进行的遗传分析将确定蜜蜂产生的自花受精率是否足以产生dioclonal。传粉者，降雨量和其他环境因素的直接和间接的影响，对diophyll的演变将使用结构方程模型进行评估。这项研究的资助将提供在自然种群中对近亲繁殖回避假说的首次检验。为该项目开发仙人掌的第一个微卫星标记导致了三个机构的合作，并对少数民族大学生进行了现代遗传技术的培训。

One of the fundamental questions in biology is: Why have separate sexes? Having separate sexes avoids the worst type of inbreeding: self-fertilization. In animal-pollinated plants it is hypothesized that separate sexes evolve in certain areas (e.g., mountain-tops, deserts) because the less specialized pollinators there predominantly self-fertilize these plants. An alternative hypothesis is separate sexes evolve because resources (e.g., water) needed for sexual function are scarce, and can be allocated more efficiently if the sexes are separated. Claret-cup cacti present a unique opportunity to concurrently test these two hypotheses because they possess both hermaphroditic (sexes together) and dioecious (sexes separated) populations. This species is pollinated by less-specialized bees in and around dioecious populations, which supports the inbreeding-avoidance hypothesis. However, dioecious populations also tend to occur in arid areas. This supports the resource-allocation hypothesis. Genetic analyses at the plant, population and landscape scale will determine if the rate of self-fertilization produced by bees is sufficient to produce dioecy. The direct and indirect effects of pollinators, rainfall and other environmental factors on the evolution of dioecy will be assessed using Structural Equation Modeling. Funding of this research will provide the first test of the inbreeding-avoidance hypothesis in natural populations. Developing the first microsatellite markers for cacti for this project has led to collaborations across three institutions and training of minority undergraduates in modern genetic techniques.