Abstract
Tandem repeats (TRs) are highly dynamic regions of the genome. Mutations occurred at these loci represent a significant source of genetic variation. Bumblebees are important pollinating insects occupying a wide range of habitats. However, to date, molecular mechanisms underlying the adaptation of bumblebees to such a diverse array of habitats are largely unknown. In the present study, we investigate how TRs contribute to genetic variation, thus potentially facilitating adaptation in bumblebees. We identified 26,595 TRs in the buff-tailed bumblebee (Bombus terrestris) genome, 66.7% of which reside in genic regions. We also compared TRs found in B. terrestris with those present in the whole genome sequence of a congener, B. impatiens. We found a total of 1,137 TRs were variable in length between the two sequenced bumblebee species, and further analysis reveals that 101 of them are located within coding regions. Variable-length TRs in coding regions were confirmed by PCR. Functional classification of bumblebee genes where coding sequences include variable-length TRs suggests that a majority of those genes are related to transcriptional regulation. Our results show that TRs contribute to coding sequence variation in bumblebees and TRs may facilitate the adaptation of bumblebees through diversifying proteins involved in controlling gene expression.