The thorny subject of insular endemic taxonomy: morphometrics reveal no evidence of speciation between Coenonympha corinna and Coenonympha elbana butterflies (Lepidoptera: Nymphalidae)

Abstract

Species demarcation between mainland and island endemic populations is often subjective according to the biological concept of species. However, the recognition of the specific status of island endemics is decisive for biogeography and conservation studies. In this paper we applied rigorous morphometric analyses instead of subjective visual evaluation to solve the long debated question whether the endemic butterfly from Tuscany Coenonympha elbana should be considered as a separated entity from the endemic C. corinna from Sardinia and Corsica. We carried out traditional and geometric morphometric analyses of wing pattern and male genitalia comparing the populations from Corsica, Sardinia, Tuscan Archipelago and Tuscany. We found that Sardo-Corsican C. corinna and Tuscan C. elbana can be distinguished only on the basis of the dimension of ventral wing ocelli. However, this characteristic shows a clinal pattern from Sardinia to Tuscany. Moreover, there is not any clear diversification in the shape of male genitalia between the two entities and each islet population can not be unambiguously attributed to one of the two taxa. In conclusion, we found no decisive evidence for a specific diversification between these two entities and the Coenonympha corinna/elbana complex, occurring both in Sardinia-Corsica and in the Italian mainland, should not be strictly considered as an endemic insular taxa.