Host specificity revisited: New data on Myrmica host ants of the lycaenid butterfly Maculinea rebeli

Larvae of Maculinea rebeli, one of the most endangered European butterflies, are obligatory social parasites of Myrmica ants. At present, this relationship is thought to be highly specific, with Myrmica schencki being regarded as the primary host. Here we present data on six populations from Poland and Austria, including the first record of Myrmica specioides as a host, together with published data from other central European countries, which severely questions the inference that M. schencki is the exclusive host of M. rebeli. Our results indicate that Myrmica sabuleti is the most frequently used host ant in central Europe, whereas M. scabrinodis, M. sulcinodis, M. specioides and M. schencki are used as secondary hosts. Possible explanations for this highly variable host use include (1) regional differences in semiochemicals, behaviour or social structure of the potential Myrmica host species and (2) the existence of different ecological subspecies or cryptic species of M. rebeli. Finally, we emphasize the importance of identifying local host ant species prior to further conservation strategies in order to avoid failure of management programs or even damage to populations on the edge of extinction.