A core linkage map of the bumblebee Bombus terrestris

The bumblebee Bombus terrestris is an economically important pollinator and an emerging model species in quantitative and population genetics. We generated genetic linkage maps for 3 independent mapping populations of B. terrestris. The linkage map with the highest resolution had 21 linkage groups, which adequately represents the haploid chromosome number of B. terrestris (n = 18). This map can be considered saturated, with an average marker distance of 10.3 cM and an estimated genome coverage of 81%. Using flow cytometry, we have estimated the genome size of this species to be 625 Mb. With an estimated total recombination genome length of 2760 cM, this results in a ratio of 226 kb/cM between the physical and genetic genome sizes. A recurring set of microsatellites and amplified fragment length polymorphism (AFLP) markers allowed the alignment of 14 linkage groups between the 3 maps. We propose to adopt this core map as a reference tool for future genetic and molecular work in B. terrestris.