A central goal of ecological and evolutionary biology is to understand processes that contribute to adaptive divergence of populations. We are using a QTL (quantitative trait locus) mapping approach to investigate the genetic architecture underlying differences in phenotypes associated with divergent life-histories in two populations of Mimulus guttatus. One population consists of large-flowered, thick-stemmed succulent perennials which inhabit the barren sand dunes along the temperate Oregon coast. The other population contains diminutive, small-flowered, tiny annual plants which inhabit an alpine environment in the Cascade Mountains that experiences heavy snowfall in the winter followed by short, dry summers. These two populations display extreme differences within a single wildflower species with respect to morphology, life-history, and ecology. We measured morphological traits on annual, perennial, and 540 F2 hybrids in a common garden experiment-illustrating that the differences in traits have a heritable basis. We also performed reciprocal transplant experiments which demonstrate that each of the populations is locally adapted to its native habitat. We are currently constructing a linkage map using AFLP, microsatellite, and gene-based markers on 540 F2 plants in order to map QTLs responsible for the phenotypic differences between these populations. We are also constructing recombinant inbred lines (RILs) in order to investigate the genetic basis for adaptive differences between these two populations of M. guttatus in their native environments.

Key words: adaptation, life-history evolution, Mimulus guttatus, QTL mapping