Evolutionary Genomics of Plant Adaptation and Speciation

自从达尔文的名著《物种起源》出版以来，新物种是如何出现的一直是生物学的中心焦点。然而，推动物种形成的进化过程的重要性仍然存在争议。在这个项目中，我将进行一系列实验，以向日葵属野生向日葵为模型系统，检验关于植物界物种形成的几个非正统假说。首先，我将测试性选择是否是植物物种形成的重要因素。虽然性选择在动物身上很重要，但它在植物物种形成中的作用尚不清楚。其次，我将确定反对杂交种的自然选择是否会推动跨物种交配障碍的进化。这个假说被称为强化物种形成，最早是由19世纪的英国博物学家阿尔弗雷德·罗素·华莱士提出的。然而，对强化的经验支持是有限的，可能是因为人们关注的是昂贵的可见特征，如花色或开花时间。我将研究强化通常涉及隐蔽的配偶选择机制的可能性，涉及花粉-花柱相互作用。最后，我将尝试解开物种形成研究中最古老的谜团之一，那就是大规模的染色体重排是如何建立的。大规模的重组极大地降低了最初出现这些变化的个体的生育能力。因此，根据进化论，重排应该从种群中消除。取而代之的是，它们经常成为老牌企业。对这个谜题的一个可能的解释是一种被称为雌性减数分裂驱动的现象，在这种现象中，重排偏向了减数分裂的结果(有性繁殖的关键步骤)，从而使重排的染色体更有可能最终进入下一代。我将测试向日葵的重排是否表现出减数分裂驱动。这些项目将提供对性别选择和强化在推动植物物种形成中的重要性的初步估计，并可能潜在地解开关于染色体进化的一个突出谜团。对加拿大的好处包括培训高素质的基因组学和生物信息学人员，潜在地发现有农业价值的基因，以及开发有助于将这些基因导入栽培的向日葵种质的遗传图谱。**

How new species arise has been a central focus of biology since the publication of Darwin's famous book, “On the Origin of Species.” However, the importance of the evolutionary processes that drive speciation remain controversial. In this project, I will conduct a series of experiments to test several unorthodox hypotheses about the formation of species in the plant kingdom, using wild sunflowers of the genus Helianthus as a model system. First, I will test whether sexual selection, which refers to competition for reproduction, is an important contributor to plant speciation. While sexual selection is known to be important in animals, its role in plant speciation is unknown. Second, I will determine whether natural selection against hybrids drives the evolution of barriers to cross-species mating. This hypothesis, known as speciation by reinforcement, was first put forward by the 19th century British naturalist Alfred Russel Wallace. However, empirical support for reinforcement is limited, perhaps because of a focus on costly visible traits such as flower color or flowering time. I will examine the possibility that reinforcement commonly involves cryptic mate choice mechanisms involving pollen-stylar interactions. Lastly, I will attempt to solve one of the oldest mysteries in speciation studies, which is how large-scale chromosomal rearrangements are established. Large rearrangements greatly reduce the fertility of the individual in which they first arise. Thus, according to evolutionary theory, the rearrangements should be eliminated from populations. Instead, they frequently become established. A possible explanation for this puzzle is a phenomenon called female meiotic drive, in which the rearrangement biases the outcome of meiosis (a key step in sexual reproduction) to make it more likely that the chromosome with the rearrangement ends up in the next generation. I will test whether rearrangements in Helianthus sunflowers exhibit meiotic drive. These projects will provide a first estimate of the importance of sexual selection and reinforcement in driving plant speciation, and may potentially solve an outstanding mystery about chromosomal evolution. Benefits to Canada include the training of highly qualified personnel in genomics and bioinformatics, the potential discovery of agriculturally valuable genes, and the development of genetic maps that will facilitate the introgression of such genes into cultivated sunflower germplasm. **