The genetics of extreme microgeographic adaptation: an integrated approach identifies a major locus underlying leaf trichome divergence in Yellowstone Mimulus guttatus

Microgeographic adaptation provides a particularly interesting context for understanding the genetic basis of phenotypic divergence, and may also present unique empirical challenges. In particular, plant adaptation to extreme soil mosaics may generate barriers to gene flow or shifts in mating system that confound simple genomic scans for adaptive loci. Here, we combine three approaches - QTL mapping of candidate intervals in controlled crosses, population resequencing (PoolSeq), and analyses of wild recombinant individuals - to investigate one trait associated with Mimulus guttatus (yellow monkeyflower) adaptation to geothermal soils in Yellowstone National Park. We mapped a major QTL causing dense leaf trichomes in thermally-adapted plants to a < 50kb region of Linkage Group 14 (Tr14) previously implicated in trichome divergence between independent M. guttatus populations. A PoolSeq scan of Tr14 region revealed a cluster of six genes, co-incident with the inferred QTL peak, with hig...