The genetics of parallel evolution : a case study using thermal and non-thermal ecotypes of Mimulus Guttatus from Yellowstone National Park

Hendrick, Margaret

Understanding the genetic mechanisms of adaptation has long been a goal of evolutionary biologists. Historically, development of an overarching theory of adaptation has proved prolonged and controversial (Orr 2005). While adaptation was first described as the slow accumulation of many small-effect mutations (Fisher’s “infinitesimal model”, 1930), we now know that adaptation can also occur in ecological time via the fixation of relatively few alleles of large effect (Gillespie 1984). Recent quantitative trait loci (QTL) and microbial evolution studies have further revealed that alleles fixed during adaptive events arise from both novel mutations and standing genetic variation, presenting a variety of genetic architectures across traits and organisms (Orr 2005; Barrett and Schluter 2007; Nadeau and Jiggins 2010). However, the predictability of genetic change across adaptive events and the patterns observed during adaptive transitions across species remain poorly understood. Specifically, in populations that undergo similar adaptive transitions, do we see a parallel genetic basis underlying observed, parallel phenotypes, or, are there many alternative genetic routes to the same phenotypic end? -- First Paragraph, Introduction.