A phylogenetic analysis of cuckoo bumblebees (Psithyrus, Lepeletier) and bumblebees (Bombus, Latreille) inferred from sequences of the mitochondrial gene cytochrome oxidase I.

PCR amplification and direct sequencing of a 532-bp region of the mt CO-1 (cytochrome oxidase I) gene from five true bumblebee species and six cuckoo bumblebee species were performed. The sequences were then aligned to the corresponding sequence in the honey bee. Phylogenetic analyses based on parsimony and maximum likelihood indicate that the cuckoo bumblebees form a monophyletic group within the true bumblebees. The Bombus lucorum group (subgenus Bombus) falls out as the sister group to a clade comprising the cuckoo bumblebees and the remaining true bumblebees. A strong A + T bias (A + T = 75%) was recorded. Comparisons of all the sequences show a high-transversion bias (A<-->T) even among closely related species. The bias is most pronounced in third positions.