Discrimination of four Culex (Culex) species from the Neotropics based on geometric morphometrics

Abstract

Achieving correct identification of Culex species is difficult because many anatomical characters of larvae and females are polymorphic or overlap among distinct species. The overlapping is known to occur between Culex bidens, Cx. interfor, Cx. mollis and Cx. tatoi, from the subgenus Culex. The first three were incriminated in viruses’ transmission in Argentina. The purpose was to distinguish between specimens of four species using geometric morphometric procedures. From field and entomological collections, 10 type I and 10 type II landmarks on the wings of females and the dorsomentum of larvae, respectively, were defined. The free morphometric software modules by J.P. Dujardin were used. Landmark coordinates were submitted to Procrustes and TPS analyses to generate size (centroid size, CS) and shape (partial warps, PW) variables. Size analysis was performed by nonparametric comparisons of CS measurements based on permutations, and shape, by submission of PW to discriminant analysis. Re-identification and identification of external specimens were also realized. Wing and Dm shapes gave similar results. The individuals arranged into three groups coinciding with Cx. bidens + Cx. interfor, Cx. mollis and Cx. tatoi. The latter two had a very different wing and Dm shapes. The accurate re-identification was greater than or equal to 77 % in all cases, and the identification of external specimens was achieved for all the species and both structures. Larval characters are more informative than female features. Geometric morphometrics, as a complementary tool, will facilitate identification in junction with others, such as DNA sequence analysis.