Can Geometric Morphometry of Pupal Gill Filaments Be Used as a Tool for Identification of the Simulium ornatum Species-Group (Simuliidae: Diptera)?

Abstract

Accurate species identification is the first step in biological research. The configuration of the pupal gill filaments (e.g., the number of filaments and their branching form) is one of the most basic source of characters used in the discrimination of species in Simuliidae taxonomy. However, the use of these characters is not always sufficient for identification, especially for the separation of cryptic species such as in the Simulium ornatum species-group. In this study, the reliability of pupal gill filaments as a morphotaxonomic character in the identification of four species of the S. ornatum species-group (Simulium ornatum Meigen, 1818; S. intermedium Roubaud, 1906; S. kiritshenkoi Rubtsov, 1940 and S. ornatum sp.) was tested by using geometric morphometric analysis. Geometric morphometry was applied for the first time to the pupal stage of the family Simuliidae. A total of 196 pupae representing the S. ornatum species-group were used. Eighteen landmarks were determined by tpsDIG 2.32 analysis to reflect the length and width measurements of filament common stems for pupae, which are thought to differ among target species. As a result of the geometric morphometric analysis made with the Tps program series Morpheus and NTSYS Programs, the pupal gill filaments were found to be insufficient for distinguishing the evaluated species in this group.