Abstract
BackgroundWithin the genus Culicoides (Diptera: Ceratopogonidae), the subgenus Avaritia is of particular interest as it contains a significant number of economically important vector species. Disagreements about the systematic classification of species within this subgenus have resulted in a taxonomic imbroglio.MethodsA molecular phylogeny of the subgenus Avaritia was conducted to test the existing systematic classification, which is based on phenetic assessment of morphological characters. Three nuclear ribosomal markers, internal transcribed spacer 1 and 2 (ITS1, ITS2), 5.8S, and three mitochondrial markers, cytochrome c oxidase subunit 1 and 2, and cytochrome b (cox1, cox2 and cytb), were obtained for 37 species of the subgenus Avaritia from all six biogeographical regions. Phylogenetic reconstructions using these genes independently and in combination were implemented using Bayesian inference analysis and maximum likelihood methods.ResultsPhylogenetic reconstructions gave strong support to several monophyletic groups within the subgenus Avaritia. Both C. actoni and C. pusillus formed a single clade with C. grahamii so their respective groups, the Actoni and Pusillus groups, have been merged with the Grahamii group. Some support was provided for the Boophagus and Jacobsoni groups. A group of species currently placed into the Orientalis group clustered in a clade with poor support. The Obsoletus group was defined as a sister clade to all other Avaritia groups. The clade including the Imicola group was well supported based on phylogenetic criteria.ConclusionsThis phylogenetic study combining five distinct molecular markers has provided meaningful insights into the systematic relationships of Culicoides (Avaritia) and highlighted future directions to continue the study of this subgenus. While the cox2 marker appeared to be useful to investigate closely related species, the 5.8S marker was highly conserved and uninformative. Further investigations including species absent from this work are needed to confirm the proposed systematic scheme. However, this systematic scheme can now serve as a foundation to investigate cryptic species affiliation within the subgenus. We advocate that future studies employ a combination of morphological and molecular analyses.
Highlights
Within the genus Culicoides (Diptera: Ceratopogonidae), the subgenus Avaritia is of particular interest as it contains a significant number of economically important vector species
This study aims to (i) test species group delimitation within subgenus Avaritia; (ii) elucidate the phylogenetic relationships among the different species groups; and (iii) propose a new systematic scheme of the subgenus Avaritia, at a worldwide level, using six genetic markers including nuclear and mitochondrial molecular targets (ITS1, ITS2, 5.8S, cox1, cox2, cytb)
With the exception of C. kanagai, the species studied which have the combination of cell r2 dark to apex and hairy eyes, including C. actoni, C. grahamii and C. pusillus, were found to be phylogenetically clustered in the Grahamii group
Summary
Within the genus Culicoides (Diptera: Ceratopogonidae), the subgenus Avaritia is of particular interest as it contains a significant number of economically important vector species. The subgeneric classification of the genus has traditionally relied on morphological characters such as variations in wing patterns and male genitalia [2]. The current subgeneric classification consists of 31 subgenera containing 63% of extant species, 38 unplaced groups of species made of 24% of extant species and a further 13% of extant species that have not been placed into any of these groups [1, 2]. Attempts to subdivide this large genus into subgenera have been partially successful. Khalaf [6] subsequently attempted a classification based on features of male genitalia and female spermathecae but these two classification schemes are divergent in their grouping delimitation and species composition
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