Facteurs affectant le succès reproducteur des bourdons en milieu naturel

Authors: Pelletier, Luc
Advisor: McNeil, Jeremy Nichol
Abstract: Factors that limit the reproductive success of bumblebee field colonies are poorly known. I explored the effect of the queen’s body size, food availability, and some parasites on reproductive success by following the development of more than 200 field colonies of eight species of bumblebees (Bombus impatiens, B. fervidus, B. perplexus, B. terricola, B. bimaculatus, B. ternarius, B. rufocinctus et B. vagans vagans). Larger queens were more likely to reproduce, and, for queens that did so, there was a positive relationship between their body size and the number of sexuals produced. The higher success of larger queens is, at least in part, attributable to the production of larger colonies and, in some species, to the ability to prevent usurpations by Psithyrus (a parasitic subgenus of bumblebees). The higher success of larger queens was not related to the date of nest establishment or to usurpations by other Bombus queens. A field experiment in which I added food to half of the colonies over the entire season showed that food availability was also an important factor. Colonies with increased food supplies reached larger sizes (in number of workers) and had a higher reproductive success than controls, by 51% and 86% respectively. In particular, food supplementation increased the number of males produced and the probability of producing gynes (young queens). However, despite some clear advantages of having larger food supplies such as the build-up of larger worker populations, food supplementation did not appear to help colonies defend themselves against macroparasites because experimental and control colonies experienced similar levels of parasitism by Psithyrus, Fannia canicularis, Brachicoma devia, and Vitula edmandsae. By recording the foraging activity rate in some of these colonies, I showed that food supplementation reduced the foraging activity rate per worker by 25% relative to control colonies. Workers from colonies with abundant food supplies thus appear to forage less on a daily basis to reduce foraging risks and costs. If workers benefit from an increased longevity by reducing their activity, this would provide an additional mechanism to explain the increased reproductive success of colonies with increased food supplies.
Document Type: Thèse de doctorat
Issue Date: 2003
Open Access Date: 11 April 2018
Permalink: http://hdl.handle.net/20.500.11794/17812
Grantor: Université Laval
Collection:Thèses et mémoires

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