Document Type

Dissertation

Degree

Doctor of Philosophy

Major

Biology

Date of Defense

5-11-2012

Graduate Advisor

Zuleyma Tang-Martinez, PhD

Co-Advisor

Hunt, James

Committee

Parker, Patricia

Cameron, Sydney

Abstract

This study investigates how photoperiod affects internal characteristics of colonies of the temperate bumble bee Bombus impatiens particularly; development, reproduction, and social behavior. To answer this question I used an experimental approach using commercially obtained colonies of B. impatiens kept under controlled environmental conditions, and using the exposure to photoperiod as the only variable. Eight different photoperiod treatments were evaluated over the social phase of the colony’s life cycle. Colonies exposed to photoperiods that simulate the species natural temperate photoperiod exhibited larger growth rates, higher, oviposition rates, and higher brood survival than colonies exposed to constant photoperiods. Similarly, colonies exposed to a simulated seasonal photoperiod produce new queens and males only after the largest day of the experiment and the subsequent decrease of the day length, which corresponds to fall conditions in the wild. In contrast, colonies exposed to constant photoperiods showed no synchronization for the timing of production of new males and queens producing them at any time point during the social phase of the colonies’ life cycle. Colonies maintain a relatively stable proportion of functional tasks for all photoperiod treatments. However, there are significant changes in individual behaviors as an effect of photoperiod, colony age and workers body size classes. Finally, I evaluated colonies’ circadian rhythms under different photoperiod treatments. I found that colonies show circadian activity patterns that resemble individual circadian clocks. Under constant darkness colonies maintain an internal circadian pattern of activities close to 24h, thus showing evidence for an endogenous clock. Similarly, circadian rhythms can be entrained by photoperiod, and finally, colonies under constant light conditions show weak circadian rhythms of rest and activity. By integrating demography, social behavior and reproduction I am able to show how colonies of B. impatiens respond to environmental changes. This research therefore provides insights on the behavioral mechanisms of social regulation in relation to environmental information in B. impatiens.

Included in

Biology Commons

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