OPUS: MCS: Evolutionary processes underlying transitions in sexual systems, pollination mode and ploidy

许多为人类提供大量营养的作物都是靠风授粉的。在开花植物中，风传粉是从昆虫传粉反复进化而来的，但其潜在的机制尚不清楚。从动物传粉到风媒传粉以及从雌雄同体到雌雄异株传粉的转变代表了开花植物的主要进化转变。了解风媒传粉进化的早期进展是在一个植物属中取得的，其中风媒传粉的多个起源来自昆虫传粉的祖先，伴随着性别分离和基因组复制，也称为多倍体。海芋属多年生草本植物，在世界范围内生长着约200种温带植物，其花形态、性系统和传粉方式具有很大的多样性。尽管多倍体在植物进化过程中有着悠久的历史，并对物种多样性的增加做出了贡献，但很少有研究调查多倍体是否与传粉者或性系统的变化有关。这项研究将有助于更好地了解植物繁殖变化的过程，并具有潜在的应用于农业，在农业中，由于昆虫传粉媒介的短缺，可能需要替代传粉媒介，并且分离性别在杂交种子的生产中是有用的。摘要本研究旨在探讨多种被子植物谱系在倍性水平、性系统和传粉方式等方面反复发生进化转变的性状进化顺序和性状依赖物种多样化的系统发育模式。毛茛科（Thalictrum）是研究这些生态变化的速度和模式的理想系统，因为它们反复发生，允许多次比较。本研究解决的更广泛的问题是：1)多倍体、性系统和授粉模式对净多样化率的影响是什么？多倍体和动物授粉促进物种形成吗？雌雄异株是进化的“死胡同”吗？2)性格进化的顺序是什么？是在风媒传粉的背景下更有可能向单性花过渡，还是单性花先进化而来？这两种情况中有哪一种更有可能是多倍体吗？这项跨学科研究将利用系统发育比较分析来揭示性状依赖的物种多样化，这将为未来的进化发展实验提供信息，这些实验旨在揭示独立转向风传粉、雌雄异株和多倍体的遗传基础，并确定这些物种每次是通过相同还是不同的遗传机制进化的，即，它是平行进化还是趋同进化？该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Many crops responsible for the bulk of human nutrition are pollinated by wind. Wind pollination has evolved repeatedly from insect pollination in flowering plants, yet the underlying mechanisms are poorly understood. Shifts to wind pollination from animal pollination and to separate sexes (dioecy) from hermaphroditism represent major evolutionary transitions in flowering plants. Early progress in understanding the evolution of wind pollination was made in a plant genus where multiple origins of wind pollination from insect-pollinated ancestors is accompanied by the separation of sexes and the duplication of genomes, also known as polyploidy. Thalictrum are herbaceous perennials with great diversity of flower morphology, sexual system, and pollination mode amongst its circa 200 temperate species growing worldwide. Although polyploidy has a long history of recognized relevance to the evolution of plants, and a demonstrated contribution to increased species diversity, few studies have examined whether polyploidy is associated with shifts in pollinators or sexual system. This study will contribute to a better understanding of the processes contributing to changes in plant reproduction, with potential applications to agriculture, where alternative pollination vectors may be needed due to shortage of insect pollinators, and separate sexes are useful in the production of hybrid seed.This study seeks to investigate the order of trait evolution and the phylogenetic patterns of trait-dependent species diversification in a diverse angiosperm lineage where evolutionary transitions in ploidy level, sexual system and pollination mode have occurred repeatedly. Thalictrum (Ranunculaceae) is an ideal system in which to study the tempo and mode of evolution of these ecological shifts, as they have occurred repeatedly, allowing for multiple comparisons. The broader questions addressed by this study are: 1) What is the effect of polyploidy, sexual system and pollination mode on net diversification rates? Do polyploidy and animal pollination promote speciation? Is dioecy an evolutionary "dead end"?; and 2) What is the order of character evolution? Is transition to unisexual flowers more likely in a wind pollinated background or did unisexual flowers evolve first? Are either of these more likely in a polyploid background? This interdisciplinary research will make use of phylogenetic comparative analyses to uncover trait-dependent species diversification that will inform future evolutionary development experiments aimed at uncovering the genetic basis underlying independent shifts to wind pollination, dioecy and polyploidy and at determining whether these evolved through same or different genetic mechanisms each time, i.e., is it a case of parallel or convergent evolution?This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.