Evolution and ecology of plant sexual systems

在历史进程中反复发生的进化转变是生物学家与生俱来的兴趣。其中一个转变涉及生物体繁殖方式的根本性改变，仅在开花植物中就发生了至少100次：雌雄同体的进化。在这一过渡期间，个体不再能够同时作为雌性和雄性父母(即两性人)生育，而是仅作为其后代的母亲或父亲(即雌雄异体)。为什么个人应该放弃他们的性别角色之一，成为专业的女性或男性？回到达尔文的生物学家已经考虑过这个问题，但有两个关键问题仍然不清楚--这些问题可以通过结合现代分子遗传学和实验操作开始解决，这是本文提出的研究的特点。首先，生态条件在进化到雌雄异株的转变过程中的重要性得到了广泛的认识，但人们对此知之甚少。我将利用本地植物宽叶慈姑的实验和遗传分析，首次就环境条件对雌雄异株进化的关键步骤--雄性进化--的影响进行实证研究。本种具有雌雄异株和两性的种群是不寻常的，使它成为理想的实验系统。其次，有证据表明，雌雄异株血统包含的物种比两性血统少，但其产生的过程在很大程度上是未知的。在性别系统经历了迅速多样化的谱系中，关于组合性别和单独性别对多样性模式的影响，我们可以了解到很多。加那利群岛辐射的Echium似乎就是这样一个谱系，四分之一的物种具有二态繁殖系统。利用Echium的遗传学和田野研究，我将研究形成组合性别和分离性别进化的历史和当代过程。这里提出的方法的组合将提供(A)对雌雄异株的进化的新见解，以及(B)为学生提供高通量分子遗传学以及高级实验设计和统计方面的培训--这些技能在一系列生物学职业中备受欢迎。

Evolutionary transitions that occur repeatedly over the course of history are of inherent interest to biologists. One such transition involves a fundamental change in the way organisms reproduce and has occurred at least 100 times in the flowering plants alone: the evolution of separate sexes from hermaphroditism. During this transition, individuals cease being able to reproduce as both female and male parents (i.e., hermaphrodites) and instead act solely as mothers or fathers to their offspring (i.e., dioecy). Why should individuals give up one of their sex roles to become specialist females or males? Biologists going back to Darwin have thought about this question, but two key issues remain unclear - issues that can begin to be resolved using the combination of modern molecular genetics and experimental manipulations that characterizes the research proposed here. First, the importance of ecological conditions in evolutionary transitions to dioecy is widely recognized but poorly understood. I will provide the first empirical investigation of the effects of environmental conditions on a key step in the evolution of dioecy - the evolution of males - using experiments and genetic analysis of the native plant Sagittaria latifolia. This species is unusual in having both dioecious and hermaphroditic populations, making it an ideal experimental system. Second, there is evidence that dioecious lineages contain fewer species than hermaphrodite lineages, but the processes responsible are largely unknown. Much can be learned about the effect of combined vs. separate sexes on patterns of diversity using lineages that have undergone rapid diversification in their sexual systems. The Canary Islands radiation of Echium appears to be such a lineage, with one quarter of species having dimorphic breeding systems. Using genetic and field studies of Echium, I will investigate the historical and contemporary processes that shape the evolution of combined vs. separate sexes. The combination of approaches proposed here will provide (a) novel insights into the evolution of dioecy, and (b) training for students in high-throughput molecular genetics, and advanced experimental design and statistics - highly sought skills across a range of biological careers.