Graduate Thesis Or Dissertation
 

The gene-ecology of Crepis nana Richardson and Crepis elegans Hooker in Arctic and Alpine North America

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  • A gene-ecological transplant study was made on populations of the Crepis nana and C. elegans complex from the Arctic and Alpine of North America. Transplants were collected from the Brooks Range, Eagle Summit, and Alaska Range in Alaska, the Rocky Mountains in Alberta, the Olympic Mountains in Washington, the Wallowa Mountains in Oregon, and the Sierra Nevada Mountains of California. Chromosome numbers were found to be uniformly 2N=14 throughout the entire range of both species. The morphological variability present in Crepis nana is shown to be ecotypical and correlated with habitat type. Crepis nana ssp. typica Babcock is here divided into a taprooted river gravel ecotype, with inflated fistulous caudex, and a creeping rhizomatous talus ecotype, with narrowly inflated fistulous caudex, C. nana ssp. clivicola Legge. The subspecific concept of the creeping rhizomatous C. nana ssp. ramosa Babcock which lacks a fistulous caudex is enlarged. The pattern of major and minor ribs on achenes and the number of major ribs at the point of attachment to the receptacle are shown to be excellent ecotypic markers. All ecotypes were found to be naturally self-pollinating. Cross-pollinations between ecotypes revealed at low frequency a splitting of the fruit coats. This splitting was taken as a measure of hybrid vigor and heterosis and hence genetic compatibility. The suggestion is made that this may be morphological evidence for mitochondrial heterosis. Comparative growth chamber experiments on transplants from the field were used to show by statistical methods the degree of phenotypic plasticity and the genetically controlled differences in the achenes of both Crepis elegans and the ecotypes of Crepis nana. Discriminant functions were generated from achene characteristics using the program *BMDO5M on the CDC 3300 and shown to be statistically significant. The possible evolutionary history of both species is presented with special reference to the Bering Sea Land Bridge, the Alaskan refugium, central Asia and Siberia.
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