Evolutionary theory predicts that high genetic
variation maintains plasticity in a species’ response to
parasite pressure. However, higher genetic diversity might
also cause easier infiltration by social parasites, because
odour diversity is high and nest-mate recognition poor.
Here we test if the obligate myrmecophile Lycaenid butterfly
Phengaris nausithous, a parasite of colonies of the
highly polygynous ant Myrmica rubra causes local adaptation
by enhancing genetic variance in parasitized versus
non parasitized ant populations M. rubra colonies from six
infested and three uninfested sites were assayed at five
microsatellite loci to quantify genetic variation. Our results
reveal isolation by distance and a significantly enhanced
intracolonial variance due to the parasite pressure.