Cyanogenesis and the Genetics of Local Adaptation in White Clover (Trifolium repens L.)
Geographically widespread species experience varied selection across their ranges, and adaptation to local environments plays a critical role in their ability to persist. Understanding the genetic basis of local adaptation is a longstanding goal in evolutionary biology and provides practical informa...
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| Format: | Text |
| Language: | English |
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Washington University Open Scholarship
2019
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| Online Access: | https://openscholarship.wustl.edu/art_sci_etds/1964 https://openscholarship.wustl.edu/cgi/viewcontent.cgi?article=2998&context=art_sci_etds |
| Summary: | Geographically widespread species experience varied selection across their ranges, and adaptation to local environments plays a critical role in their ability to persist. Understanding the genetic basis of local adaptation is a longstanding goal in evolutionary biology and provides practical information for agriculture and conservation. However, the genetic architecture of local adaptation has been characterized in relatively few plant species, primarily those with short lifespans and high rates of self-fertilization. Moreover, for plants, chemical defenses are known to play an important role in adaptation, but the extent to which they contribute to local adaptation is less understood. This dissertation provides a genome-wide, multi-environment assessessment of the importance of a well-studied chemical defense polymorphism for local adaptation, relative to other genetic factors, and addresses fundamental questions in evolutionary biology about the genetic architecture of local adaptation in an outcrossing plant. White clover (Trifolium repens L.) is a perennial, obligately outcrossing legume and an important forage crop. Naturalized populations occur across a wide range of climates, from subtropical to near arctic. White clover populations display adaptation related to a chemical defense polymorphism, cyanogenesis—the production of hydrogen cyanide upon tissue damage. Adaptive cyanogenesis clines have repeatedly evolved across the species range, such that higher proportions of cyanogenic plants are found in warmer climates. However, the relative adaptive importance of the cyanogenesis polymorphism for local adaptation, compared to other genetic factors, is unknown. Chapter 1 in this dissertation provides evidence of local climatic adaptation in white clover by documenting correlations between fitness traits and home-site climate variation for 15 widespread populations grown in a central North American common garden experiment. Chapter 2 demonstrates that divergent life history strategies associated with early ... |
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