Date of Award:

12-2020

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Committee Chair(s)

Karen Kapheim

Committee

Karen Kapheim

Committee

Joseph Rinehart

Committee

James Strange

Abstract

Bumble bees (Bombus) provide critical pollination services for wild plants and crops. They are generalist pollinators, and do not depend on one singular floral type. Native bumble bees are adapted to pollinating many native plants, such as blueberries, squash, and tomatoes. A critical component of bumble bee pollination in the greenhouse tomato industry is the domestication of commercially bred colonies. However, the domestication of Bombus is pretty early in its development, and not all aspects of the bumble bee life cycle is fully understood. This thesis addresses one of the major obstacles in domestication, which is successful mimicking of the overwintering phase of the lifecycle in captivity. Traditionally, captive Bombus queens are stored in constant low temperatures for a period of twelve weeks to mimic hibernation. However, there is a high mortality associated with this cold storage period, and we are unable to replicate wild overwintering durations in captive settings. To address the high mortality, we used three North American bumble bee species, stored queens in different cold storage regimes and assessed survivability. Here, we present results that there were other components to consider outside of thermal regimes such as initial weight, bumble bee colony age, and queen’s geographic origins. We found survivorship varied between wild queens (B. vosnesenskii and B. huntii) and commercial queens (B. impatiens). We saw with wild queens survival response was lower in a temperature cycling regime (FTR) compared to static thermal treatments (Control). However, in commercial B. impatiens, we saw the opposite outcome in survival, where survival response was higher in FTR. The variation in survival outcome may be reflective of their geographic differences. Results also suggested that high initial weight prior to cold storage determined survival and was linked to post hibernation lipids, which serves as an energy reserve. Despite the fact, lipids and weight are important to surviving captive cold storage, colony age influenced overwintering fitness. We have evidence that a queen’s initial weight prior to entering captive overwintering, survival, and colony’s age were inter-related. This study highlights that we should take a more comprehensive approach and take into account that overwintering treatments alone are not the silver bullet to addressing premature deaths in cold storage. Standardizing methods for Bombus cold storage will require careful consideration of the interplay between physiological variations, individual queen characteristics, and limitations among Bombus that emerge from seasonal colony aging.

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