Date of Award:

5-1-1996

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Committee Chair(s)

Paul G. Wolf

Committee

Paul G. Wolf

Committee

Vincent J. Tepedino

Committee

Eugene W. Schupp

Abstract

I examined the reproductive biology and population genetics of the narrow endemic, Mirabilis macfarlanei (Nyctaginaceae) Constance and Rollins, from the Snake and Salmon Rivers in Idaho and Oregon. The results of this study provide further evidence for the proposed effects of rarity on plant reproductive systems and population genetics. Breeding system results indicated that M. macfarlanei is self-compatible, but requires a pollen vector for fertilization. Seed set was not pollen limited, but may be resource limited during others. The major floral visitors were long-tongued bees such as Anthophora spp. and Bombus spp., unlike other species of Mirabilis, which are moth-pollinated. Observations of pollinators and a pollen deposition study indicated that visitation occurred during light hours and was lacking during the night. The greatest number of flowers opened in the late afternoon (1500-1900) (40%); however, 25% opened during the day (0700-1500). More flowers opened during the day and remained open longer than other Mirabilis species, possibly to ensure pollination due to the lack of night pollinators. Floral morphometrics varied significantly among populations, and may relate to variation in floral visitors among sites. Using enzyme electrophoresis, I determined that M. macfarlanei had lower genetic diversity than other plant species with similar life history traits. In multi-locus clonal maps there is evidence that genets were generally not large (average of 4.8 ramets per genet), but had a phalanx growth pattern that may promote selfing. Direct estimates of outcrossing were t = 0.56, indicative of both selfing and outcrossing occurring in plants. The measure of genetic differentiation (FST was high, 0.47, suggesting low gene flow among the 15 populations studied. Small population size, isolation, and clonal growth may have resulted in genetic drift and inbreeding, causing low genetic diversity.

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