Allozyme analysis of Erebia medusa over large regions of Europe revealed a significant population differentiation (FST: 0.149 ± 0.016). A UPGMA‐analysis showed a division into four major lineages with mean inter‐group genetic distances ranging from 0.051 (±0.010) to 0.117 (±0.024). An AMOVA revealed that rather more than two‐thirds of the variance between samples was being between these lineages and less than one‐third within lineages. An eastern group included the samples from the Czech Republic, Slovakia and north‐eastern Hungary. This genetic lineage expressed significantly higher genetic diversity than the other three. A second lineage was formed by the samples from France and Germany. The two samples from western Hungary represent a third delimited lineage and the sample from northern Italy a fourth. We suppose that this genetic differentiation took place during the last ice‐age in four disjunct refugia. The genetically more diverse eastern genetic lineage might have evolved in a relatively large refugium in south‐eastern Europe. We assume that the other three lineages developed in relatively small relict areas around the Alps. It is likely for the western lineage that its ice‐age distribution showed at least one disjunction in late Würm with the consequence of further genetic differentiation. Most probably, the eastern lineage colonized postglacial Central Europe using two alternative routes: one north and one south of the Carpathians. Up to now, neither similar glacial refugia, nor comparable secondary disjunctions in late Würm, are reported for any other animal or plant species.

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Aim The effects of glacial disjunctions on intraspecific differentiations are in the focus of phylogeographical studies. Several studies investigate the consequences of post‐glacial expansions from glacial refugia on the composition within major genetic lineages. Location and methods We analysed the geographical pattern of allozyme variation of twenty loci of Polyommatus coridon (Poda, 1761) (Lepidoptera: Lycaenidae) from thirty‐six localities spread throughout large regions of its European range. A total of 1566 individuals were analysed. Results We obtained a significant genetic differentiation (FST 0.060 ± 0.007). Further analyses showed a division into two major genetic lineages with a mean genetic distance (Nei, 1978) of 0.041 (± 0.010 SD). Applying an AMOVA, more than three quarters of the variance between populations was between these lineages and less than one quarter within these lineages. Both genetic lineages showed a significant decline in the number of alleles from southern to northern populations. Furthermore, we found a contact zone of these two major genetic lineages in eastern Central Europe extending throughout north‐eastern Germany, then following the mountain regions along the Czech‐German border and passing through the eastern Alps in a north–south direction. Main conclusions We assume that this differentiation evolved during the last ice‐age as a result of isolation in the Adriato‐ and the Ponto‐Mediterranean region. The loss of genetic diversity from the south to the north within both lineages reflects the decline of diversity during the post‐glacial expansion.

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Within the past 10 years, the yellows disease ‘bois noir’ (BN) has become one of the commercially most important diseases of grapevine [Vitis vinifera L. (Vitaceae)] in Europe. Infection pressure is caused by phytoplasmas of the stolbur 16SrXII‐A group that are transmitted by a planthopper vector, Hyalesthes obsoletus Signoret (Homoptera: Auchenorrhyncha). Infestation happens as an accidental side‐effect of the feeding behaviour of the vector, as vector and pathogen proliferation is dependent on other plants. In Germany, the increase of BN is correlated with the use of a new host plant by the vector, increase in abundance of the vector on the new host plant, and dissemination of host plant‐specific pathogen strains. In this article, we investigate geographic and host‐associated range expansion of the vector. We test whether host‐plant utilization in Germany, hence the increase in BN, is related to genetic host races of the vector and, if so, whether these have evolved locally or have immigrated from southern populations that traditionally use the new host plant. The genetic population analysis demonstrates a recent expansion and circum‐alpine invasion of H. obsoletus into German and northern French wine‐growing regions, which coincides with the emergence of BN. No H. obsoletus mitochondrial DNA haplotype host‐plant affiliation was found, implying that the ability to use alternative host plants is genetically intrinsic to H. obsoletus. However, subtle yet significant random amplified polymorphic DNA (RAPD) genetic differentiation was found among host plant populations. When combined, these results suggest that a geographic range expansion of H. obsoletus only partly explains the increase of BN, and that interactions with host plants also occur. Further possible beneficial factors to H. obsoletus, such as temperature increase and phytoplasma interactions, are discussed.

Bat-swarming sites where thousands of individuals meet in late summer were recently proposed as 'hot spots' for gene flow among populations. If, due to female philopatry, nursery colonies are genetically differentiated, and if males and females of different colonies meet at swarming sites, then we would expect lower differentiation of maternally inherited genetic markers among swarming sites and higher genetic diversity within. To test these predictions, we compared genetic variance from three swarming sites to 14 nursery colonies. We analysed biparentally (five nuclear and one sex-linked microsatellite loci) and maternally (mitochondrial D-loop, 550 bp) inherited molecular markers. Three mtDNA D-loop haplolineages that were strictly separated at nursery colonies were mixed at swarming sites. As predicted by the 'extra colony-mating hypothesis', genetic variance among swarming sites (V ST ) for the D-loop drastically decreased compared to the nursery population genetic variance (V PT ) (31 and 60%, respectively), and genetic diversity increased at swarming sites. Relatedness was significant at nursery colonies but not at swarming sites, and colony relatedness of juveniles to females was positive but not so to males. This suggests a breakdown of colony borders at swarming sites. Although there is behavioural and physiological evidence for sexual interaction at swarming sites, this does not explain why mating continues throughout the winter. We therefore propose that autumn roaming bats meet at swarming sites across colonies to start mating and, in addition, to renew information about suitable hibernacula.

Pleistocene climatic oscillations strongly influenced the genetic composition of many species which are often divided into several genetic lineages. In this context, we studied the allozymes of a common and widely distributed butterfly, the common blue Polyommatus icarus, over a large part of Europe. The species had a rather high genetic diversity within populations with a strikingly high mean number of alleles per locus (2.98). In contrast, differentiation between populations was very low (FST: 0.0187). Only a marginal trend of decline in genetic diversity from the south to the north was observed. Isolation‐by‐distance existed on a European scale (r = 0.826), but not at a regional level. Regional differentiation between populations in western Germany was extremely low (FST: 0.0041). It is probable that P. icarus was widely distributed in the Mediterranean region during the last ice age and expanded into central Europe in the postglacial period without major genetic erosion. Moderate present and past gene flow in an intact metapopulation structure may have occurred on local, regional and perhaps even continental scales. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 80, 529–538.