Newly discovered colour-pattern polymorphism of Bombus koreanus females (Hymenoptera: Apidae) demonstrated by DNA barcoding

Bombus (Megabombus) koreanus (Skorikov) is a long-tongued bumblebee that specialises in visiting deep flowers. To describe the distribution, colour-pattern variation and food plants of B. koreanus, we collected specimens and DNA cytochrome oxidase I (COI) barcodes were obtained. Bayesian phylogenetic analysis of barcodes for Megabombus species shows that B. koreanus is one of the more recently diverged species and the sister species to Bombus consobrinus. Our results show that specimens with previously unknown colour patterns also belong to B. koreanus. We describe nine different colour patterns for workers and three for queens, in which the hair of the thorax varies from black to orange-brown. However, there is a lack of covariation between COI and colour-pattern variation. B. koreanus has been recorded to visit 11 species of food plants showing that B. koreanus is polylectic. Our results demonstrate that COI barcoding is an effective method for studying closely related taxa and for recognising species with variable colour patterns.