Observations on the Isturgia limbaria (Fabricius, 1775) / roraria (Fabricius, 1776) complex (Lepidoptera, Geometridae, Ennominae)

Abstract

TheIsturgia limbaria(Fabricius, 1775)/roraria(Fabricius, 1776) complex is analyzed, taking into consideration the external morphology of the adults (coloration and pattern of upperside and underside of wings), the morphology of the female genitalia (signum and lamella postvaginalis), of the tympanal organs and of the preimaginal stages, as well as molecular data. Based on the molecular data and morphology of signum and tympanic organs, the populations of this complex can be divided into two groups, one more western (with the taxalimbarias. str. anddelimbaria), distributed east to north-western Italy and part of Germany, and one more eastern (with the taxarorarias. str.,rablensisandanzascaria), distributed west to northern and eastern Piedmont (Italy) and north-eastern and south-eastern Germany. However, there are no consistent differences between the two groups in the diagnostic characters used until now to identify the two taxa (pattern of the wing upperside and underside). Although there is a considerable genetic distance between these two groups, the correlation between molecular differences and morphological characters (size of the signum and presence ̶ or absence ̶ of a roundish lobe in the bullae tympani) is not completely constant and the two groups of populations are not completely separated from each other: some populations of the northern Apennines (taxondelimbaria) cannot be clearly attributed to one or the other group. In the absence of constant morphological characters associated with the molecular differences and in the presence of Italian populations with intermediate characters, we suggest that the different taxa of this complex be considered as subspecies of the same species, as already proposed by Povolný and Moucha (1957, 1959). However, the data available do not allow definitive clarification of the taxonomic problem and further research is necessary.