Maculinea rebeli (Hirschke) – a phantom or reality? Novel contribution to a long-standing debate over the taxonomic status of an enigmatic Lycaenidae butterfly

The main goal of our research was to carry out a comprehensive study on the obligatorily myrmecophilous Maculinea alcon (Denis & Schiffermuller) whose taxonomy has remained highly debated despite the fact that Maculinea Van Eecke species are some of the most intensively studied insects in Europe. We aimed to elucidate the relationship between the different forms exploiting different ecological environments with specific regard to ‘Hirschke's rebeli' (M. rebeli (Hirschke)) from the high altitudes of the Styrian Alps which was studied in this respect for the first time. Molecular analyses including multiple gene sequences, microsatellites and allozymes completed with Wolbachia screening, together with geometric morphometry were applied on various sets of samples. Our results showed that ‘rebeli’ from the type locality differed strongly from all other samples not only at the highly variable microsatellites, but also at standard genes and clearly represents a well-separated unit (potentially subspecies) within M. alcon. As all individuals were infected with a single Wolbachia strain, this is possibly an ancient infection with high maternal transmission rate. It also suggests that the separation of the topotypic populations was probably a relatively recent event which could have been promoted by genetic drift or specific conditions at high altitudes, and maintained by restricted gene flow. Both the genetic and the morphometric studies supported the proposition that the geographical origin of the populations has a higher effect on the structure of variation than the food plant use. Moreover, we detected more genetic lineages than could be defined by differential host plant usage.