In most of the populations analysed we detect a high genetic variability, which might reflect a former wide distribution for this species - or at least interconnected populations within each mountain area. In general, isolated population remnants show reduced genetic diversity as a result of genetic erosion (Lesica and Allendorf 1995), as shown for other butterflies like Parnassius apollo (Habel et al. 2009), Parnassius smintheus (Keyghobadi et al. 2005), Speyeria idalia (Keyghobadi et al. 2006), Proclossiana eunomia (Neve et al. in press), and the ground beetle Carabus auronitens (Drees et al. 2008). Obviously, the present mountainous retreats of Central Europe left sufficient space for intact metapopulations of Lycaena helle to maintain this high genetic diversity to the present day. The phenomenon of high genetic diversity despite long-term isolation was also shown for other relict organisms, which maintained their genetic variability through intact population networks within isolated areas (cf. Baali-Cherif and Besnard 2005). As the detected private alleles do not appear in further populations over the entire European distribution area (Habel et al. unpublished data), their evolution should have taken place in most cases after the species colonised these mountain areas during the post-glacial warming.
The strong genetic differentiation among mountain areas coincides with the orographic structure of the study species and with the optimal areas (potential suitable habitats surpassing a Maxent value of 0.75) of the CEM. Less suitable regions (potential suitable habitats with a Maxent value of at least 0.50) enclose these hotspots. Most of the classified mountain areas are not linked with neighbouring areas by habitats of potential suitability (not even areas with a Maxent value of at least 0.50). As many studies reveal the importance of habitat size to maintain genetic information, we analysed all genetic diversities in respect to area size of suitable habitats obtained from the Ecological Niche Model and could not find any correlations.
Even within each mountain area, we detected a strong genetic differentiation among neighbouring populations. Detected private alleles are often restricted to a single population of a mountain group, which underpins restricted or absent geneflow among populations of Lycaena helle within mountain massifs. Within the Ardennes-Eifel, we detected a significant correlation between the level of genetic differentiation among populations and the geographical distance between them, which suggests a restricted geneflow among populations between these two adjoining areas, clustering into two genetic groups with only a few outliers (Finger et al. 2009). For the Jura massif the statistic analysis revealed a significant split into a Southern and Northern group and is in accordance with two morphologically characterised subspecies (Meyer 1982). These two morphological and genetic character sets give results which allow us to conclude that the two groups of populations inhabiting the Jura massif represent two distinct Evolutionarily Significant Units (ESU) sensu Moritz (1994). However, these deep structures are probably not the result of recent habitat isolation but of historic species separation into distinct refugia, as described for the snail Trochulus vil-losus in the same area (Depraz et al. 2008).
The CEM suggests strongly fragmented potential suitable areas for Lycaena helle, corresponding with the higher elevations of our study area. The obtained pattern coincides with the recent genetic and distribution situation of this species (Drews and Pretscher 2003). The CEM projection onto a future climate change scenario suggests a severe decline of most potential suitable habitats over Western
Central Europe, restrictions to higher elevations of the Jura and Alps and an increase in the habitat fragmentation of the remaining areas. Similar changes in distribution patterns have been suggested for birds occurring in the same climatic zone as Lycaena helle, such as Hazel Grouse (Bonasa bonasia) or the Pygmy owl (Glaucidium passerinum) (Huntley et al. 2007).
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