Natural selection on floral traits: variation in agents and targets

花性状的自然选择：媒介和目标的变化

• 批准号: RGPIN-2014-05399
• 负责人: Worley, Anne
• 金额: $ 1.97万
• 依托单位: University of Manitoba
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=588391
• 关键词: Natural; selection; floral; traits; variation

Flowers determine mating opportunities in animal-pollinated plants because pollinators transport male gametes (pollen) between flowers and plants. Pollinators form an essential “ecosystem service” in natural and agricultural ecosystems by ensuring fruit and seed production. As a result, natural selection by pollinators contributes to the tremendous diversity in wild flowers and inflorescences. Our understanding of floral evolution is still limited in several areas. These include: (1) selection through siring success, even though male parents contribute half the genes to each generation; (2) how selection affects floral traits when floral visitors are diverse; and (3) how often reproduction is limited by pollen receipt versus the availability of water, nutrients or other resources. My proposed research addresses these gaps. Polemonium brandegeei is a perennial herb pollinated by hummingbirds and hawkmoths, and visited by pollen consuming flies (pollen thieves). Our work to date indicates that the two pollinators exert contrasting natural selection on sex-organ position and flower width, suggesting that flower shape may be a compromise between the phenotype that is best under each pollinator. My lab will first conduct controlled experiments measuring how selection by each pollinator is modified by differences in flower number, a trait that varies widely in natural populations. Second, we will determine how pollen consumers affect siring potential of different flower shapes, and whether they limit the pollen available for seed set. Third, we will initiate long-term studies to quantify selection in natural populations. We will include estimates of siring success (paternity) based on genetic fingerprints. Supplementation of natural pollen receipt will distinguish selection by pollinators from selection caused by other factors such as nutrient limitation or drought. Lady’s slipper orchids (Cypripedium) trap insect visitors in their flowers rather than producing floral rewards to retain pollinators. I hypothesize that the small flowers and narrow pollination routes of endangered C. candidum contribute to low fruit set in northern populations because few insects are both small and strong enough to escape past the sex organs. Higher fruit set in widespread C. parviflorum and hybrids may reflect larger flowers and wider pollination routes. These differences in fruit set may affect gene transfer between species. First, I propose to extend our surveys of flower size, fruit set, and habitat quality across C. candidum’s range, compare pollinator communities in selected populations, and use genetic fingerprints to assess the direction of gene flow between species. Second, my lab will examine the direct effect of pollination route size on pollen movement; we will use plants from a C. parviflorum population, where flowers are comparable in size to either typical flowers of C. candidum (small) or C. parviflorum (larger) flowers, but do not differ in other traits such as flower colour or scent. These studies will advance my long-term goals of understanding how diverse floral visitors affect selection on floral design and display, and how floral phenotypes affect reproduction and mating patterns when flowers do not reward pollinators. They will also contribute to general evolutionary questions regarding the importance of variation in selection for the maintenance of genetic variation, evolution of specialized vs. generalized phenotypes, and gender conflict in selection. Findings will increase our understanding of evolution and ecological genetics, and will inform conservation biologists about strategies for preserving endangered species, and members of the public interested in evolution and natural history.

花决定了动物授粉植物的交配机会，因为授粉者在花和植物之间运输雄性配子（花粉）。授粉者通过确保水果和种子的生产，在自然和农业生态系统中形成了一种重要的“生态系统服务”。 因此，传粉者的自然选择促成了野花和花序的巨大多样性。我们对植物进化的理解仍然局限于几个领域。其中包括：（1）通过父系成功的选择，即使雄性父母为每一代贡献了一半的基因;（2）当花访客多样化时，选择如何影响花的性状;（3）繁殖受到花粉接收与水，营养或其他资源的可用性的限制。我的研究旨在填补这些空白。 布氏花葵是一种多年生草本植物，由蜂鸟和天蛾授粉，并被花粉消费苍蝇（花粉小偷）访问。我们的工作迄今表明，这两个传粉者施加对比自然选择的性器官的位置和花的宽度，这表明花的形状可能是一个折衷的表型，是最好的下每个传粉者。我的实验室将首先进行受控实验，测量每种传粉者的选择是如何被花朵数量的差异所改变的，花朵数量是一个在自然种群中变化很大的特征。其次，我们将确定花粉消费者如何影响不同花形的交配潜力，以及它们是否限制了可用于结实的花粉。第三，我们将启动长期研究，以量化自然种群中的选择。我们将包括基于遗传指纹的父系成功（父权）的估计。自然花粉接收的补充将区分传粉者的选择与其他因素如营养限制或干旱引起的选择。 女士的拖鞋兰花（Cypripedium）陷阱昆虫游客在他们的花，而不是产生花的奖励，以留住授粉者。我推测，小花和狭窄的授粉路线濒危C。Candidum导致北方种群的坐果率低，因为很少有昆虫既小又强壮到足以逃脱性器官。广泛分布的C. parviflorum和杂种可能反映了更大的花朵和更广泛的授粉路线。坐果的这些差异可能会影响物种之间的基因转移。首先，我建议扩大我们的调查，花的大小，坐果，和栖息地的质量在C。candidum的范围，比较选定的种群中的传粉者群落，并使用遗传指纹来评估物种之间的基因流动方向。其次，我的实验室将研究授粉路线大小对花粉移动的直接影响; parviflorum种群，其中花的大小与C. candidum（small）或C. parviflorum（较大）的花，但在其他性状，如花的颜色或气味没有区别。 这些研究将推进我的长期目标，了解不同的花卉游客如何影响花卉设计和展示的选择，以及花卉表型如何影响繁殖和交配模式时，花朵不奖励传粉者。他们还将有助于一般的进化问题，关于选择中的变异对维持遗传变异的重要性，特化与广义表型的进化，以及选择中的性别冲突。研究结果将增加我们对进化和生态遗传学的理解，并将告知保护生物学家保护濒危物种的策略，以及对进化和自然历史感兴趣的公众成员。