RESEARCH ARTICLE Fragmentation genetics of the grassland butterfly Polyommatus coridon: Stable genetic diversity or extinction debt? Jan Christian Habel • Sabrina V. Bru ¨ ckmann • Jochen Krauss • Julia Schwarzer • Alfons Weig • Martin Husemann • Ingolf Steffan-Dewenter Received: 28 July 2014 / Accepted: 6 November 2014 Ó Springer Science+Business Media Dordrecht 2014 Abstract Habitat fragmentation can have severe effects on the intraspecific variability of populations and thus plays a pivotal role in species conservation. Especially taxa with specific habitat demands and low dispersal behaviour suffer from habitat fragmentation. One such taxon, the Chalk-hill Blue butterfly, Polyommatus coridon, nowadays mostly occurs in small and isolated, calcareous grasslands across Central Europe. Here we investigate the population genetic structure of 15 local populations of this butterfly species over major parts of the Fra ¨nkische Schweiz (south-east Germany). Based on seven polymorphic microsatellites we estimate genetic diversity and differentiation. We use the data to test for potential effects of different habitat sizes, habitat connectivity, and population density. We found high genetic diversity but no significant genetic differentiation among the 15 local populations (F ST = 0.0087, P [ 0.05). Genetic diversity was not correlated with habitat size, hab- itat connectivity, or census population size. But, we found a marginally positive correlation between increasing habitat connectivity and population density (r 2 = 0.31, P \ 0.05). Compared to other butterfly species, our data resemble a generalist species with well connected populations rather than a specialist taxon existing in a highly fragmented landscape. The high genetic diversity and the lack of dif- ferentiation might either be the result of relatively large and stable local populations and ongoing gene flow, or is the genetic legacy of formerly large and interconnected popu- lations during periods of extensive agriculture. Keywords Census population size  Genetic diversity  Genetic differentiation  Habitat fragmentation  Habitat connectivity  Habitat size Electronic supplementary material The online version of this article (doi:10.1007/s10592-014-0679-8) contains supplementary material, which is available to authorized users. J. C. Habel Terrestrial Ecology Research Group, Department of Ecology and Ecosystem Management, Technische Universita ¨t Mu ¨nchen, 85354 Freising-Weihenstephan, Germany S. V. Bru ¨ckmann (&) Population Ecology Group, Department of Animal Ecology I, University of Bayreuth, 95447 Bayreuth, Germany e-mail: Sabrina.Brueckmann@uni-bayreuth.de J. Krauss  I. Steffan-Dewenter Department of Animal Ecology and Tropical Biology, University of Wu ¨rzburg, Biocenter, 97074 Wu ¨rzburg, Germany J. Schwarzer EAWAG Centre of Ecology, Evolution and Biogeochemistry, Swiss Federal Institute for Aquatic Science and Technology, Fish Ecology and Evolution, 6047 Kastanienbaum, Switzerland J. Schwarzer Zoologisches Forschungsmuseum Alexander Koenig, 53113 Bonn, Germany A. Weig DNA Analytics and Ecoinformatics, University of Bayreuth, 95440 Bayreuth, Germany M. Husemann General Zoology, Institute of Biology, University of Halle (Saale), 06120 Halle, Germany 123 Conserv Genet DOI 10.1007/s10592-014-0679-8