Neighbor-joining tree of the 26 Thai species of the Simulium asakoae species group based on COI gene sequences (586 positions). The numbers at the nodes mean the bootstrap confidence values after 500 replicates. The bootstrap values above 50% are shown. The scale bar indicates the distance in substitutions per nucleotide. The symbols in front of the species names are each the collection number (corresponding to those in the text), developmental stages (F, female; M, male; L, larva), and sample number (if two or more samples were examined) in this order.