Speciation and extinction risk in the vascular plants of Canada

在加拿大已知的5211种维管植物中，有650种处于不同程度的灭绝危险之中。确定每个物种的风险水平是一项耗时的工作，导致科学家试图设计灭绝风险的预测指标，以产生值得最直接关注的候选物种的短名单。 我们刚刚开始了解基因组是如何随着物种形成而改变的，以及它是如何影响有机体的表型的。虽然动物物种很少在它们的基因组中容忍额外的染色体(例如，大多数人类的“三体”会导致流产或发育障碍)，但植物很容易整合完整的额外染色体集。这一过程可能导致物种形成，因为拥有额外染色体组(多倍体)的个体通常不能与其二倍体(两组染色体)亲属产生可存活的后代。多倍体物种在适应不断变化的环境的能力上是否表现出差异尚不清楚。这项提案旨在揭示多倍体物种形成对加拿大境内植物物种灭绝风险的后果，有三个短期目标。 在第一个目标中，我将更好地估计加拿大重要谱系中多倍体物种形成的比率。大约有42种维管束植物是加拿大特有的，其中许多是加拿大植物区系中熟悉的成分的成员，如柳树、山楂和黄花。尽管已经建立了确定基因组大小的方法，但这些属有50%的物种具有未知的倍性。我的实验室将使用流式细胞术、物种分布模型和系统发育学来识别这些谱系的进化史上发生了多倍化的地方，然后测试这些过程如何影响它们目前的灭绝风险的假说。 在第二个目标中，我们将调查不同倍性水平的开花植物的花物候变化，使用标本库标本记录过去一个世纪的性状变化。最后，在第三个目标中，我将研究授粉如何随着倍性的变化而改变。多倍体被认为更多地是自亲和的，对传粉者的依赖较少，这些差异可能对预测种群将如何应对气候变暖或栖息地改变等生态变化至关重要。 目前，我们缺乏关于加拿大濒危物种是不成比例的多倍体还是最近起源的信息。对这些问题的回答将有助于我们理解是什么导致物种形成和灭绝率的差异，但也将导致制定有效的政策，优先保护物种。这项提案将从进化历史的角度研究加拿大特有的维管植物物种，以揭示物种形成历史、多倍化和专门化在使物种容易受到人类干扰方面的作用。

Of the 5211 known species of vascular plants in Canada, there are >650 at some level of risk of extinction. Determining the level of risk for each species is a time-consuming endeavor, leading scientists to attempt to devise predictors of extinction risk to produce short-lists of candidate species deserving the most immediate attention. We are just beginning to understand how the genome is altered with speciation and how it affects the phenotype of an organism. While animal species can rarely tolerate an extra chromosome in their genomes (e.g., most human "trisomies" result in miscarriage or developmental disorders), plants readily incorporate an entire extra chromosomal set. This process can result in speciation because the individuals with extra chromosome sets (polyploids) often cannot produce viable offspring with their diploid (two sets of chromosomes) relatives. Whether polyploid species exhibit differences in their ability to adapt to changing environments is not understood. This proposal aims to uncover the consequences of polyploid speciation to the extinction risk of plant species within Canada with three short-term objectives. In the first objective, I will produce better estimates of the rate of polyploid speciation in important Canadian lineages. There are approximately 42 vascular plant species endemic to Canada, and many are members of familiar elements of the Canadian flora, such as the willows, hawthorns, and goldenrods. Despite established methodology for determining genome size, these genera have >50% of their species with unknown ploidy. My lab will use flow cytometry, species distribution modelling, and phylogenetics to identify where polyploidization has occurred in the evolutionary history of these lineages and then test hypotheses of how these processes have affected their current extinction risk. In the second objective, we will survey the change in floral phenology amongst flowering plants with different ploidy levels using herbarium specimens to document trait change over the past century. Finally, in the third objective, I will examine how pollination is altered upon shifts in ploidy. Polyploids are thought to be more often self-compatible and less dependent on pollinators and these differences may be critical in predicting how populations will respond to ecological changes such as climatic warming or habitat modification. Currently, we lack information on whether species-at-risk in Canada are disproportionately polyploid, or of recent origin. Answers to these questions will contribute to our understanding of what drives differences in speciation and extinction rate, but will also lead to effective policy for prioritizing species for conservation effort. This proposal will examine Canada's endemic vascular plant species in terms of their evolutionary history to uncover the role of speciation history, polyploidization, and specialization in making species vulnerable to human disturbance.