Abstract:

The arctic-alpine tundra of western North America harbors a diverse flora, with many rare and endemic taxa. In my lab, we are asking why, when, and where arctic-alpine plants diversified. To address this question, we have taken a comparative molecular approach, employing phylogenetic and population genetic analyses of multiple genetic loci for a taxonomically diverse suite of angiosperms. The topographical and environmental heterogeneity of the region has provided a landscape for geographically structured plant populations. On this stage, the glacial cycles of the Quaternary have played out repeated rounds of population expansion, fragmentation, and isolation, which in turn have promoted genetic divergence and speciation, with the opportunity for local adaptation. Our studies have revealed colonization events, isolation in and among refugia, recent episodes of diversification, cryptic species, and environmental differences across refugia with the potential for adaptation. Thus, the upshot is that for arctic-alpine plants the Quaternary has promoted speciation. These findings have important implications for the conservation of arctic-alpine plants and the capacity of species to respond to climate change.

About the Speaker:

My research interests are focused on understanding the biogeographic history and evolution of tundra ecosystems. The overarching goal of my research is to determine how climatic variability of the Quaternary (~ the last 2.6 million years) has impacted and may further affect the distribution and diversity of the Arctic and alpine flora and fauna. During the Quaternary, the climate oscillated between glacial and interglacial periods, forcing populations to track suitable habitat across the shifting landscape and/or adapt to the environmental changes. To evaluate the consequences of the Quaternary on tundra communities, my students and I are: 1) testing biogeographic hypotheses and speciation models through coalescent-based analyses of multi-locus sequence data from various species of plants and animals across the region; 2) performing comparative paleogenomic analyses among modern populations and ancient DNA (aDNA) preserved in permafrost middens to estimate genetic responses of species to climate change; and 3) informing ecological niche models with genetic data to predict potential impacts of future warming on tundra plant distributions. Through these investigations into the history of multiple species of plants and their associated herbivores, a general understanding of the process of speciation and extinction in the tundra is emerging. These comparative analyses are akin to investigating myriad natural climate change experiments linked to the region's geology, hydrology, and ecology and are critical for understanding the paleoecological history of the Arctic and alpine ecosystems, informing conservation priorities for rare and native plants, and estimating the past and future consequences of climate change on the distribution of biological diversity.