Variation in the shape of the wings and taxonomy of Eurasian populations of the Calopteryx splendens complex (Odonata: Calopterygidae)

We used geometric morphometrics to determine variation in the morphology of the forewings of individuals in 20 populations of Calopteryx splendens s. l. in Eurasia and related these to the circum-specific taxonomy of this taxon. We found differences in shape, with the largest and smallest centroid size of the wings in adjacent northern (orientalis) and western (intermedia) populations in Iran, respectively, so isolation and relationship are not necessarily determined by distance, but often associated with the stream basin inhabited. The variation in wing shape, however, was much greater. with Populations at the eastern edge of the range (Tajikistan, Kyrgyzstan and East Kazakhstan) uniquely different. Oddly, no taxonomic name is associated with them, although they may be among the oldest representatives of the splendens complex. The European and Asian populations are in two separate clades. One of these includes insects with no to a medium-sized wing spot, which does not reach the tip of the wing (waterstoni-group), while the other includes insects with very broad wing spots, or, when short, it extends to the very tip of the wings and most females are androchrome (ancilla or intermedia group). Turkmenistan and northern Iranian population form a separate line inside this clade, which we equate with Calopteryx orientalis. South Albanian and Greek populations are in a separate branch corresponding to ssp. balcanica; two populations from Ireland and Italy form a branch that has no equivalent in traditional taxonomy, while Calopteryx xanthostoma was not identified by its wing shape. Understanding this multitude of phenotypes and the enormous amount of variation within certain populations but not in others becomes easy if one assumes there were two probable late Pleistocene waves of migration, the first of insects lacking spots that migrated east and westwards from the South Black Sea basin, the second, perhaps from the west Caspian, composed of heavily spotted insects with androchromic females. The hybridization between these two waves resulted in the current plethora of colour forms and accounts for why similar phenotypes may turn up independently in widely distant locations