Date of Award:
Master of Science (MS)
Most flowering plants, including many cultivated food crops, will only produce well-developed fruits and seeds if pollen is transferred from one flower to another with the help of an animal pollinator. Honey bees are the most well-known and ubiquitous but are poor pollinators of some commercially important crops, or are in poor supply during crop bloom. In such cases, farmers will employ other managed pollinators such as bumble bees or solitary bees like mason and leafcutting bees. The blue orchard bee is North America's most agriculturally important native mason bee as effective pollinators of spring-blooming fruit crops. Differences in developmental biology between geographically distinct populations, in ways that impact their management, have recently been identified. Populations from northern Utah, where the bee was originally domesticated, have been the most well-studied and employed as pollinators. Much about how other populations differ in their development, reproduction, and nesting behavior is largely unknown. In the studies reported here, I compared development and post-emergence performance of blue orchard bees sourced from Utah with bees sourced from other western locations. In Chapter I, I compared in-orchard performance by California- and Utah-sourced bees in both states. Bees performed similarly in Utah orchards, but twice as many Utah-sourced females were observed in California orchards than were California-sourced. In Chapter II, I reared Utah- and Washington-sourced bees under constant and natural thermal regimens to compare effects on development and emergence. I found that development differed when these bee populations were reared at the same constant temperatures, and that both populations suffered from exposure to maximum temperatures in their respective orchard-growing regions. In Chapter III, I flew California- and Utah-sourced bees in screened field cages to examine the effects on development, emergence, and post-emergence performance. Bees from UT were twice as likely to establish nests than bees from CA, but nesting time and reproductive output of nesting females was similar. No disruption in male-female emergence timing was found in offspring of mixed population crosses. This research highlights novel differences in geographically distinct blue orchard bee populations and supports previous research that proposed a genetic basis for regional characteristics.
Scalici, Morgan B., "Geographic Variation in Blue Orchard Bee (Osmia lignaria) Development and Performance as a Managed Pollinator in the Western United States" (2023). All Graduate Theses and Dissertations, Fall 2023 to Present. 22.
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