Free Access
Volume 38, Number 6, November-December 2007
Page(s) 518 - 524
Published online 19 October 2007
Apidologie 38 (2007) 518-524
DOI: 10.1051/apido:2007032

Aggregations of male Bombus muscorum (Hymenoptera: Apidae) at mature nests. Incestuous brothers or amorous suitors?

Ben Darvill, Gillian C. Lye and Dave Goulson

School of Biological and Environmental Sciences, University of Stirling, Stirling, FK9 4LA, UK

(Received 6 April 2006 - Accepted 20 June 2007 - Published online 19 October 2007)

Abstract - Aggregations of male bumblebees are occasionally observed at the nest entrances of conspecifics. It has always been assumed that they originate from nearby nests and are hoping to mate with emerging gynes. However, it is possible that they are males from within the nest that have not yet dispersed, or are hoping to mate with their sisters. Inbreeding in Hymenoptera with single locus complimentary sex determination (sl-CSD) is costly and should be avoided. Nevertheless, other taxa with sl-CSD have been found to inbreed in this way. We use microsatellites to compare aggregating males with workers from within a Bombus muscorum nest. All males have genotypes inconsistent with origination from within the nest. Estimates of $F_{\rm IS}$ are near zero, indicating low rates of non-random mating. Clearly male bumblebees can detect mature nests, and congregate in the hope of mating with virgin queens. These data suggest that mechanisms may exist to avoid brother-sister matings at the nest, and perhaps beyond.

Key words: Bombus / mating / inbreeding avoidance / Hymenoptera / microsatellites

© INRA, DIB-AGIB, EDP Sciences 2007