Speciation and extinction risk in the vascular plants of Canada

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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.