Free access
Volume 40, Number 4, July-August 2009
Page(s) 429 - 440
Published online 25 March 2009
Apidologie 40 (2009) 429-440
DOI: 10.1051/apido/2009004

Nest density, genetic structure, and triploid workers in exotic Bombus terrestris populations colonized Japan

Teruyoshi Nagamitsu1 and Hiroki Yamagishi2

1  Hokkaido Research Center, Forestry and Forest Products Research Institute (FFPRI), Sapporo 062-8516, Japan
2  Laboratory of Ecology and Genetics, Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan

Received 13 September 2007 – Revised 27 August 2008 – Accepted 24 October 2008 - Published online 8 August 2009

Abstract - A commercialized pollinator introduced from Europe, Bombus terrestris, has colonized Japan. We investigated nest density and genetic structure in two sites based on worker genotypes at 12 microsatellite loci. We confirmed that five workers were triploids using multilocus genotypes and flow cytometry, indicating that queens mated with diploid males and produced triploid workers. The inbreeding coefficient of diploid workers representing individual colonies was significantly positive (F$_{\rm IS}$ = 0.048) in a site where triploids were found. Genetic diversity in the sites was as high as that in native regions in Europe, and genetic differentiation between the sites was low (F$_{\rm ST}$ = 0.006). The maximum distance between sampling locations of full-sib worker pairs indicated that the radius of a foraging range was at least 782 m. The estimates of nest density were 31 and 89 km-2 in the two sites, suggesting that the nest density in a colonized region can be higher than that in the native regions.

Key words: nest density / foraging range / genetic diversity / inbreeding coefficient / triploid female

© INRA, DIB-AGIB, EDP Sciences 2009