A linkage analysis of sex determination in Bombus terrestris (L.) (Hymenoptera: Apidae).

We constructed a linkage map of Bombus terrestris (Hymenoptera, Apidae) phase unknown. The map contains 79 markers (six microsatellite and 73 RAPD markers) in 21 linkage groups and spans over 953.1 cM. The minimal recombinational size of the B. terrestris genome was estimated to be 1073 cM. Using flow cytometry, the physical size of the haploid genome of B. terrestris was calculated to be 274 Mb. This is the second linkage map for a social insect species. Bombus terrestris has on average five times less recombinational events per kb than the honey bee Apis mellifera. Male haploidy, chromosome size, and eusociality can now be excluded as reasons for the high recombination frequency of Apis mellifera. Finally, the sex determination locus of B. terrestris was placed on the map using bulked segregant analysis.