Date of Award:

5-1969

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Plant Taxonomy

Committee Chair(s)

Arthur H. Holmgren

Committee

Arthur H. Holmgren

Committee

E. J. Gardner

Committee

Richard J. Shaw

Committee

W. S. Boyle

Committee

Richard C. Anderson

Abstract

A biosystematic study of the Caltha leptosepala DC. complex was attempted using comparative data acquired from 13 experimental populations distributed throughout the Intermountain and Rocky Mountain regions (U. S. A.). Taxonomic evidence was obtained from the disciplines of anatomy, cytogenetics, embryology, biochemistry, palynology, ecology, and morphology.

Taxonomic evidence derived from the various disciplines showed that character discontinuity was lacking between plants of the same and different populations. Populations of Caltha leptosepala DC. distributed throughout the Rocky Mountains exhibited complex patterns of continuous variation in leaf shape. Although the shape of the lamina varied continuously between populations, blade length always exceeded blade width.

Populations of the Caltha leptosepala DC. complex in the Rocky Mountains appeared nearly identical, per characteristic, to populations inhabiting the Sierra Nevada and Cascade ranges. Leaf shape appeared to be the only characteristic that could be used to separate plants of these two geographical areas. Plants of Rocky Mountain populations typically possess cordate leaves or slight modifications thereof while plants of the West Coast populations have reniform-like laminae. Leaf forms intermediate to the cordate and reniform shapes were recognized in populations throughout the mountains of Western United States.

Although populations indigenous to the Sierra Nevada-Cascade ranges have not been examined experimentally, it appears certain that only one taxonomic species, Caltha leptosepala DC., can be justifiably conceived on the basis of accumulated evidence. It is suggested that all of the previous taxonomic synonyms applying to the Caltha leptosepala DC. complex in the Intermountain and Rocky Mountain regions be united under Caltha leptosepala DC. var. leptosepala. The West Coast combination of Caltha leptosepala DC. var. biflora Lawson may be valid, but its systematic relationship to the type variety needs further substantiation. Taxonomic application of the subspecies category was not recognized since a bi-level infraspecific hierarchy could not be logically ascertained.

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