MtDNA COI barcodes reveal cryptic diversity in the Baetis vernus group (Ephemeroptera, Baetidae)

Partial mitochondrial COI sequences (barcoding fragment) were explored for the understanding of the species boundaries of Baetis vernus group taxa (Ephemeroptera, Baetidae) in northern Europe. We sampled all species of this group occurring in Finland, but focused on taxa for which morphological and taxonomical confusion have been most apparent. The sequence matrix comprised 627 nucleotides for 96 specimens, and was analysed using parsimony. Results provided strong evidence that Baetis macani Kimmins and B. vernus Curtis comprise morphologically cryptic but molecularly distinct taxa, as intraspecific uncorrected divergences within haplogroups ranged between 0.3% and 1.4% and interspecific divergences were from 13.1% to 16.5%. These interesting findings prompt for further taxonomic studies of B. vernus taxa using more extensive specimen sampling from the known distributional areas in the Palaearctic/Holarctic region for better understanding of haplotype distributions. We stress the importance of integration of morphological and molecular data, and the necessity to employ additional nuclear DNA sequence data.