Date of Award:

5-1-2007

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Life Sciences: Biology

Committee Chair(s)

Edward W. Evans

Committee

Edward W. Evans

Committee

James H. Cane

Committee

Eugene W. Schupp

Abstract

Federal land managers desire a consistent and cost-effective source of Hedysarum boreale Nutt. seed for rangeland restoration in the Great Basin and adjacent ecosystems. The breeding biology of H. boreale was assessed via hand pollination experiments at 2 sites in Cache County, Utah, USA in 2003. H. boreale was found to be self-compatible, but did not produce fruit and seeds in the absence of bee visitors. Xenogamy (out-crossing) treatments resulted in increased seed viability and decreased predispersal reproductive attrition. H. boreale was found to be homogamous during 2004 experiments designed to determine the timing and duration of stigma receptivity. H. boreale stigmas became receptive during the mature bud stage prior to flower opening (anthesis) and remained receptive for several days. H. boreale proved to be very rewarding in terms of floral resources; flowers contained abundant pollen grains and nectar of comparatively high sugar concentration. The bee faunas of several natural populations of H. boreale in Utah and Wyoming, USA were systematically surveyed in 2004 and 2005. Each population was surveyed once per summer, sometimes in both years. Populations were surveyed at or just after peak bloom and during the early afternoon hours. An assortment of bee species in the families Apidae and Megachilidae were collected at H. boreale flowers. Osmia species proved to be an important component of H. boreale pollinator faunas. Three solitary, cavity-nesting candidate Osmia species were chosen and evaluated for their potential use as managed H. boreale pollinators: O. bruneri Cockerell, O. lignaria Say, and O. sanrafaelae Parker. Candidate pollinator species were chosen according to several criteria including range, phenology, floral preferences, life history, pollination efficacy, and body size. The pollination efficacies of candidate Osmia species, other native bee species found to be abundant at H. boreale, and honeybees were compared via behavioral observations, foraging tempo, frequency of stigmatic contact, and pollen grains deposited per single flower visit. Females of O. bruneri and O. sanrafaelae were able to reproduce with H. boreale as their only pollen and nectar source. Nesting data from these species were combined with estimates of floral resource production by H. boreale to calculate stocking densities. In general, nesting by O. lignaria females was limited, suggesting that this species may not be the best option for managed pollination of H. boreale in most agricultural settings. O. bruneri and O. sanrafaelae proved to be effective H. boreale pollinators in terms of frequency of stigmatic contact and pollen grains deposited per single flower visit, and could be used for commercial production of H. boreale seed.

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