Rausher studies
evolutionary biology at both the
phenotypic and genetic levels, with a focus on the genetic basis of adaptation and the evolutionary diversification of
metabolic pathways. His work examines the molecular genetic basis of phenotypes as well as patterns of
natural selection acting on those phenotypes under natural conditions, particularly for ecologically relevant traits. A major theme of his research is the
coevolution of plant defenses and their natural enemies, including
herbivores and pathogens, as well as interactions with
pollinators, with particular emphasis on members of the
morning glory family. His work has produced quantitative evidence of natural
adaptation in plant populations and has tested long-standing hypotheses concerning the costs of resistance in plants, diffuse coevolution, and adaptive constraints. More recent research has explored the genetic changes underlying the evolution of floral color patterning in the genus
Clarkia, demonstrating that ancient gene duplications, rather than polyploidization, have facilitated diversification of petal pigmentation patterns. In collaboration with former graduate student Robin Hopkins, Rausher provided the first empirical example of reinforcing selection acting on a gene responsible for reproductive isolation, based on studies of flower color divergence in two species of
Phlox. Together with former graduate student David L. Des Marais, he also clarified the distinction between
neofunctionalization and escape from adaptive conflict through an investigation of gene duplication and divergence in the anthocyanin pigment pathway of the common morning glory (
Ipomoea purpurea). == Selected honors and awards ==