Molecular Phylogenetic Analysis of the Simulium jenningsi Species-Group (Diptera: Simuliidae)

A molecular phylogenetic investigation was undertaken to identify species within the morphologically homogeneous Simulium jenningsi species group, a pestiferous group of 22 species of black flies restricted to the Nearctic region. Several species in this group have well documented medical and veterinary importance, most notably S. luggeri and S. jenningsi. Unfortunately, females are monomorphic, a conundrum given their pest status. The objective of this study was to examine the utility of molecular data in species identification, with obvious application to identification of pest females. Towards this end, we sequenced approximately 2 kilobases of sequence data from the mitochondrial (Cox I + proximal one-half of Cox II) and nuclear (big zinc finger 2) genomes from positively identified exemplars (pupae, some larvae) and analyzed them phylogenetically using parsimony and Bayesian criteria. Combined analyses were not conducted due to extreme incongruence between the data sets. Mitochondrial and nuclear data sets sufficient for ready identification of approximately one-third and one-half, respectively, of the known species. Both genes recovered S. aranti, S. luggeri, S. ozarkense, S. penobscotense, and portions of the S. fibrinflatum complex (S. fibrinflatum, S. underhilli, S. notiale, and S. snowi). Species positively identified by analyses of independent data sets include S. taxodium and S. chlorum with the mitochondrial data and S. haysi, S. krebsorum, S. dixiense, S. definitum, S. remissum, S. infenestrum, S. podostemi, and S. jenningsi with big zinc finger 2. Future studies to better resolve species identities in this group should focus on additional nuclearly encoded markers or perhaps amplified fragment length polymorphism (AFLP) approaches. However, we suspect that introgression, lineage sorting, and differential sorting of ancestral polymorphisms occurred in various lineages within this group and may make complete phylogenetic reconstruction of all species lineages impossible.