Contrasting genetic and…

Species often respond differently to identical environmental changes. Such different responses might be the consequence of varying ecological requirements and tolerances of specialists compared to generalists. We selected two closely related burnet moth species with contrasting ecological requirements: Zygaena carniolica is restricted to semi-natural calcareous grasslands and represents a stenotopic taxon, while Zygaena viciae occurs more widespread at extensively used meadows forming larger metapopulations. To examine different responses to recent habitat fragmentation, we analysed genetic and morphologic variation between populations of these two Zygaenid species in western Germany and adjoining areas in France and Luxembourg. Our data indicate contrasting genetic and morphologic patterns for both species: the genetic differentiation among populations is lower for Z. carniolica (F ST: 0.049) compared to Z. viciae (F ST: 0.058). The genetic diversity for Z. carniolica is rather low and homogeneously distributed over all populations, while Z. viciae has more alleles, which are unevenly distributed and often restricted to single populations, as shown by GENELAND models. The level of morphologic variance among and within (e.g. asymmetry) individuals is low for Z. carniolica, but much higher for Z. viciae. We conclude that these contrasting patterns mirror opposite responses on recent habitat degradation and associated loss of interconnectivity as a result of habitat destruction and land-use intensification. The data suggest that species like Z. viciae, with (historically) higher abundances suffer even stronger under the recent habitat loss. Morphologic asymmetry and genetic differentiation in the latter species rises, while diversity declines. More specialised taxa occurring in naturally isolated habitats (indicated by Species Distribution Models) feature an originally lower level of genetic diversity, and thus the impact of habitat decline on species’ persistence is less dramatic, as shown for Z. carniolica. Hence, we conclude that past and recent occurrence pattern has to be taken into account when interpreting data in the light of conservation measures.