The Genetic Basis of Adaptive Differentiation in Two Species of Mimulus

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0075660BradshawThe genetic mechanism of plant adaptation to increasing elevation, from sea level to 10,000 feet in the Sierra Nevada mountains, will be studied using a combination of laboratory and field experiments. Mimulus cardinalis, a plant species adapted to long, hot summers at low elevation, has been crossed with Mimulus lewisii, a closely-related species adapted to the short, cool growing season found in high-elevation alpine meadows. More than 50 years of research has shown that the offspring of crosses between these two species differ in their ability to survive and grow at low, middle, and high elevations. This study will use DNA-based genetic maps of the Mimulus chromosomes to identify the number of genes controlling survival, growth, and reproduction at three historically important field stations (Stanford, Mather, and Timberline) in central California.The gene pools of many closely related species are kept separate by the geographic isolation resulting from adaptation to different environments. Adaptation is believed to be the principal means by which biological diversity is created and maintained. The pace of adaptive evolution depends upon the number of genes that govern adaptive traits such as tolerance of extreme temperatures or number of flowers produced during the growing season. With modern methods of molecular biology and genome mapping, it is possible for the first time to estimate the number of genes required for organisms to adapt to different natural environments.