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Date of Award
Master of Science (M.S.)
First Committee Member
Alice S. Hunter
Second Committee Member
Steven C. Anderson
The taxa of the Allium obtusum complex were examined morphologically, chromosomally, and with the use of the scanning electron microscope, Additional field studies included ultraviolet photography, caging experiments, and collection of insect visitors.
Based on the cumulative information gathered during this investigation, of the 7 taxa previously proposed in this complex, 4 are considered to be valid: A. cratericola, A. obtusum, A. tribracteatum, and A. yosemitense, A new variety of A. obtusum, var, robustum is described.
The base chromosome number among all members of the complex is seven, All species are diploid (2n=14), except for one population of A. cratericola which was found to be tetraploid (2n=28).
Scanning electron microscope studies demonstrated the usefulness of outer bulb coat reticulation as a taxonomic character in differentiating between the species of the complex.
Preliminary data collected during field investigations suggest that the strong absorption of ultraviolet radiation by all members of the complex relative to their reflecting soils may act as a visual cue to insects whose visual spectrum includes UV, Furthermore, in mature flowers the sexual parts of the inflorescence were found to be reflective under UV, perhaps acting as a guide to foraging insects.
Caging experiments revealed that all members of the complex are capable of seed set in the absence of insect visitors. It was found, however, that the relative number of seeds produced was significantly higher among control populations.
From the cumulative evidence obtained from these various approaches, supported by morphological resemblances, it can be concluded that the Allium obtusum complex represents a distinct and homogeneous assemblage of interrelated species and varieties.
Mortola, William R.. (1983). A comparative study of the Allium obtusum comples : a thesis .... University of the Pacific, Thesis. https://scholarlycommons.pacific.edu/uop_etds/2096