Molecular phylogeny of the North AmericanSimulium malyschevi-group species (Diptera: Simuliidae)

We investigated species limits and phylogenetic relationships among chromosomally distinct North American members of the Simulium malyschevi species-group. Maximum parsimony and Bayesian analyses were conducted based on 12S, COII, cyt b and ITS-1 gene sequences. In terms of species limits, monophyly was highly supported for each chromosomally and morphologically distinct taxon analysed (S. decimatum, S. defoliarti, S. malyschevi, and S. murmanum). In contrast, support for monophyly of morphologically homogeneous S. arcticum complex members was significant only in one case (S. saxosum) and not the other (S. negativum). Considering the overall topology, three principal conclusions were drawn: (i) the status of S. subvariegatum as a member of the S. malyschevi species-group remains uncertain. This species either was excluded from the malyschevi-group or formed a sister group with S. malyschevi at the base of the tree; (ii) although S. murmanum and S. decimatum branch after S. malyschevi, the position of the two species relative to each other remains unresolved; and (iii) the structurally homogeneous S. arcticum species complex was not monophyletic due to the inclusion of S. defoliarti. Further investigation may warrant changes to current malyschevi-group classification. Molecular datasets alone may be insufficient for resolving relationships among particular lineages of black flies.