Date of Award:

5-1-1984

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Biology

Committee Chair(s)

M. E. Barkworth

Committee

M. E. Barkworth

Committee

Anne Anderson

Committee

Ivan Palmblad

Abstract

Morphological, ecological, flavonoid, and cytological studies were conducted to determine the origin of Xylorhiza glabriuscula var. linearifolia. These data strongly suggest that X. glabriuscula var. linearifolia (2n = 12, 24) has a hybrid origin, the putative parental taxa being X. glabriuscula var. glabriuscula (2n = 12) and X. tortifolia var. imberbis (2n = 12). Variety linearifolia is intermediate to the latter taxa morphologically and ecologically. In addition, it has a partially additive profile of the flavonoids found in the parental taxa. All the major types of flavonoids found in the parental taxa are represented in variety linearifolia, but it has some flavonoids with different glycosidic substitutions than from those of its parental taxa. This is similar to the situation found in other hybrid derived taxa. Variety linearifolia has some populations which are differentiated morphologically, ecologically, and cytologically. These populations probably represent different stabilized segregates of hybridization that were selected for by the respective edaphic conditions in which they occur. Most populations are tetraploid and are probably segmental allopolyploids. Interestingly, one population is diploid. Stabilized diploid, hybrid derived taxa are rarely reported in the literature. It is proposed that variety linearifolia be raised to specific rank because it has differentiated from variety glabriuscula morphologically, ecologically, geographically, chemically, and genetically.

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