Geometric morphometrics of the wing in the subgenus Culicoides (Diptera: Ceratopogonidae): from practical implications to evolutionary interpretations

Biting midges of the genus Culicoides Latreille have been incriminated in transmission of bluetongue. Since 1998, the disease has spread across Europe provoking the largest epidemic ever recorded with important economic loses. Some species of the subgenus Avaritia and Culicoides have been described as candidate vectors involved in these epizootics. Both subgenera contain groups of cryptic species that could differ in their vectorial capacity. For this reason, the correct identification of vector species is considered an essential issue in epidemiological programs. In the current study, the usefulness of wing form in differentiating morphologically similar species of the subgenus Culicoides by means of geometric morphometric techniques is assessed in specimens previously identified through molecular analyses based on cytochrome oxidase subunit I gene sequences. Significant differences between species were detected in the two components of form, i.e., size and shape. Although wing size was affected by temperature, wing shape showed a more stable specific variation, allowing the proper classification of a high percentage of specimens. In addition, the concordance between phylogenies inferred from molecular data and phenetic clusters suggests the existence of a phylogenetic signal in wing shape. These findings enhance the use of this complex phenotypic trait not only to infer genetic relationships among species of the subgenus Culicoides but also as a potentially powerful tool to differentiate cryptic species within the genus.