Letters to Nature

Nature 397, 151-154 (14 January 1999) | doi:10.1038/16451; Received 6 May 1998; Accepted 20 October 1998

Experimental variation in polyandry affects parasite loads and fitness in a bumble-bee

Boris Baer1 & Paul Schmid-Hempel1

  1. ETH Zürich, Experimental Ecology, ETH-Zentrum NW, CH-8092 Zürich, Switzerland

Correspondence to: Paul Schmid-Hempel1 Correspondence and requests for materials should be addressed to P.S.-H. (e-mail: Email: psh@eco.umnw.ethz.ch).

In many species of animals, females typically mate with more than one male (polyandry). Some social insects carry this behaviour to extremes1. For example, honeybee queens mate with ten to twenty (or even more) males on their nuptial flights2. The reasons for this behaviour remain unknown, given the obvious costs of time, energy and exposure to predation. Several potential benefits of polyandry have been proposed1,3,3,4, but none are well supported yet. Here we test the hypothesis that genetic diversity among a female's offspring may offer some protection from parasitism5, 6, 7. We artificially inseminated queens of a bumble-bee (Bombus terrestris L.) with sperm of either low or high genetic diversity. The resulting colonies were exposed to parasitism under field conditions. High-diversity colonies had fewer parasites and showed greater reproductive success, on average, than did low-diversity colonies. We suggest that female mating frequency may be influenced in part by parasites.