CAREER: Polyploid speciation in the Achillea millefolium aggregate

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Nearly all animals are diploid, i.e., they have two sets of chromosomes. In contrast, many plants are polyploid and have four or more sets of chromosomes, yet the role of polyploidy in speciation remains sharply debated. Polyploid plants that cannot interbreed with diploid plants are rarely recognized as different species, in large part because it is uncertain whether diploids and polyploids are ecologically distinct. This project combines field observations and transplant experiments to investigate reproductive barriers between diploid and polyploid populations of wild yarrow, a native perennial wildflower, and rigorously test the nature of polyploid speciation. The project will use naturally-occurring polyploid lineages and new polyploid mutants that arise spontaneously within diploid populations to separate the effects of ecological divergence and ploidy-based barriers on reproductive isolation. This project has broad implications for the interpretation of global biodiversity patterns. Taxonomic recognition of polyploids, which are common at high latitudes, could double the number of flowering plant species and fundamentally alter understanding of species diversity, which is generally thought to be greatest in tropical regions. This project will involve faculty and graduate students not only in the laboratory and field research, but also in development of a public education and outreach program on urban forests and their conservation. Urban forests provide critical habitat for wildlife as well as recreational opportunities for urban and suburban citizens, yet are increasingly threatened by habitat fragmentation and invasive organisms. The project will develop urban forests as sites of formal and informal biology education and as a public resource.