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

Understanding the genetic mechanisms of adaptation has long been a goal of evolutionary biologists. However, the predictability of genetic change across adaptive events and the patterns observed during adaptive transitions across species remain poorly understood. Numerous parallel evolutionary transitions within the model plant genus Mimulus (monkeyflowers) provide a wonderful comparative context for investigating the predictability of the underlying mechanisms. Because multiple traits, with inherent differences in the underlying molecular pathways and potentially different vulnerabilities to negative pleiotropy, are often involved in parallel adaptation to harsh edaphic conditions, the diversity in Mimulus provides an opportunity to compare genetic architecture among traits as well as among transitions. Here, I use the yellow monkeyflower (Mimulus guttatus) to investigate the genetic basis of edaphic adaptive divergence along a thermal soil gradient in Yellowstone National Park (YNP). Thermal and non-thermal M. guttatus are differentiated for annuality/perenniality, flowering time, mating system, and two more putatively adaptive traits; trichome production and pigment patterning. I employ a targeted comparative quantitative trait loci (QTL) analysis to ask whether the genetics underlying the transitions I observe in YNP are the same or different compared to parallel phenotypic transitions previously characterized within the M. guttatus species complex. I found a parallel genetic basis for some traits and a disparate basis for others. The evolution of annuality (and associated traits) in thermal M. guttatus is accomplished through novel genetic mechanisms as compared to parallel phenotypic transitions in Mimulus. While the genetic architecture of early flowering, reproductive output, and allocation to vegetative growth is not highly conserved, a striking number of target regions implicated in other transitions are involved in this system. I found reduced complexity in the architecture underlying early trichome production. Finally, the genetic architecture involved in anthocyanin production in YNP is highly conserved and predictable based on previous work in Mimulus and other flowering plants. My research elucidates the genetic basis of thermal/non-thermal divergence of M. guttatus in YNP. It also provides an important comparative context for evolutionary trajectories within the M. guttatus species complex and amongst other parallel, adaptive evolutionary transitions.

Name thesis:degree_name

Master of Science (MS)

Grantor dc:publisher

University of Montana

Year

2011

Author dc:creator

• Hendrick, Margaret Frisbie

• edaphic adaptation
• genetics of divergence
• parallel evolution

Repository record dc:identifier

https://scholarworks.umt.edu/etd/1015

OAI identifier oai:identifier

oai:scholarworks.umt.edu:etd-2034