New large threatened populations of <Emphasis Type="Italic">Phengaris nausithous</Emphasis> discovered in the SW of Europe

The near threatened Phengaris nausithous is distributed in two large mountainous areas in the northern part of the Iberian Peninsula, living in small dispersed populations. During July and August of 2012–2015 we systematically searched for the species in the southeastern part of the Cordillera Cantábrica. We found 38 new populations grouped into seven metapopulations. Two of the latter are the largest known, representing 34 % of the species’ occurrence range in Spain. The discovery of these new metapopulations does not improve the conservation status of P. nausithous in the SW of Europe because a land consolidation project currently underway and an established peat extraction plant could lead to the imminent extinction of the largest metapopulations. However, there is still time to reverse the present course of change. Knowledge of these recently discovered populations allows the establishment of management measures to protect them over the long term.