The genomics of multi-trait adaptation to Yellowstone’s geothermal soil mosaic in monkeyflowers

Environmental mosaics can generate strong divergent selection on plant traits even in the face of cross- habitat gene flow, leading to microgeographic local adaptation and (perhaps) incipient speciation. Here, we use yellow monkeyflower adaptation to the fine-scaled yet physically-extreme mosaic of soil conditions in the geyser basins of Yellowstone National Park to explore fundamental questions about the genomic and molecular mechanisms of adaptation to extreme conditions. For two traits with simple genetic bases (trichome density and minimum critical photoperiod for flowering), candidate variants in predictable molecular pathways underlie dramatic phenotypic divergence over a out6 locus draws on both old (but novel relative to known life-history polymorphisms) standing variation and recent introgression to confer adaptation to extreme thermal soils, and contains several strong functional candidates. Finally, although Yellowstone thermal annuals are highly specialized to the unique niche created by winter snowmelt on hot soils, thus escaping summer’s deadly heat and drought, they have also evolved remarkable xylem drought/heat resistance. Together, these instances of extreme local adaptation provide a composite picture of how different plant traits and pathways evolve in response to novel environments.

Speaker: Lila Fishman, University of Montana