Molecular phylogeography of the Woodland Ringlet (Erebia medusa [Denis and Schiffermüller] 1775) in Europe

Phylogeography is a recent field of biological research that links phylogenetics to biogeography through deciphering the imprint that evolutionary history has left on the genetic structure of extant populations. During the cold phases of the successive ice ages, which drastically shaped species’ distributions since the Pliocene, populations of numerous species were isolated in refugia where many of them evolved into different genetic lineages. My dissertation deals with the phylogeography of the Woodland Ringlet (Erebia medusa [Denis and Schiffermüller] 1775) in Central and Eastern Europe. This Palaearctic butterfly species is currently distributed from central France and south eastern Belgium over large parts of Central Europe and southern Siberia to the Pacific. It is absent from those parts of Europe with mediterranean, oceanic and boreal climates. It was supposed to be a Siberian faunal element with a rather homogeneous population structure in Central Europe due to its postglacial expansion out of a single eastern refugium. An already existing evolutionary scenario for the Woodland Ringlet in Central and Eastern Europe is based on nuclear data (allozymes). To know if this is corroborated by organelle evolutionary history, I sequenced two mitochondrial markers (part of the cytochrome oxydase subunit one and the control region) for populations sampled over the same area. Phylogeography largely relies on the construction of networks of uniparentally inherited haplotypes that are compared to geographic haplotype distribution thanks to recent developed methods such as nested clade phylogeographic analysis (NCPA). Several ring-shaped ambiguities (loops) emerged from both haplotype networks in E. medusa. They can be attributed to recombination and homoplasy. Such loops usually avert the straightforward extraction of the phylogeographic signal contained in a gene tree. I developed several new approaches to extract phylogeographic information in the presence of loops, considering either homoplasy or recombination. This allowed me to deduce a consistent evolutionary history for the species from the mitochondrial data and also adds plausibility for the occurrence of recombination in E. medusa mitochondria. Despite the fact that the control region is assumed to have a lack of resolving power in other species, I found a considerable genetic variation of this marker in E. medusa which makes it a useful tool for phylogeographic studies. In combination with the allozyme data, the mitochondrial genome supports the following phylogeographic scenario for E. medusa in Europe: (i) a first vicariance, due to the onset of the Würm glaciation, led to the formation of several major lineages, and is mirrored in the NCPA by restricted gene flow, (ii) later on further vicariances led to the formation of two sub-lineages in the Western lineage and two sub-lineages in the Eastern lineage during the Last Glacial Maximum or Older Dryas; additionally the NCPA supports a restriction of gene flow with isolation by distance, (iii) finally, vicariance resulted in two secondary sub-lineages in the area of Germany and, maybe, to two other secondary sub-lineages in the Czech Republic. The last postglacial warming was accompanied by strong range expansions in most of the genetic lineages. The scenario expected for a presumably Siberian faunal element such as E. medusa is a continuous loss of genetic diversity during postglacial westward expansion. Hence, the pattern found in this thesis contradicts a typical Siberian origin of E. medusa. In contrast, it corroboratess the importance of multiple extra-Mediterranean refugia for European fauna as it was recently assumed for other continental species.

Comparative phylogeography of two co-distributed arctic-alpine freshwater insect species in Europe

The distribution pattern of European arctic-alpine disjunct species is of growing interest among biogeographers due to the arising variety of inferred demographic histories. In this thesis I used the co-distributed mayfly Ameletus inopinatus and the stonefly Arcynopteryx compacta as model species to investigate the European Pleistocene and Holocene history of stream-inhabiting arctic-alpine aquatic insects. I used last glacial maximum (LGM) species distribution models (SDM) to derive hypotheses on the glacial survival during the LGM and the recolonization of Fennoscandia: 1) both species potentially survived glacial cycles in periglacial, extra Mediterranean refugia, and 2) postglacial recolonization of Fennoscandia originated from these refugia. I tested these hypotheses using mitochondrial sequence (mtCOI) and species specific microsatellite data. Additionally, I used future SDM to predict the impact of climate change induced range shifts and habitat loss on the overall genetic diversity of the endangered mayfly A. inopinatus.rnI observed old lineages, deep splits, and almost complete lineage sorting of mtCOI sequences between mountain ranges. These results support the hypothesis that both species persisted in multiple periglacial extra-Mediterranean refugia in Central Europe during the LGM. However, the recolonization of Fennoscandia was very different between the two study species. For the mayfly A. inopinatus I found strong differentiation between the Fennoscandian and all other populations in sequence and microsatellite data, indicating that Fennoscandia was recolonized from an extra European refugium. High mtCOI genetic structure within Fennoscandia supports a recolonization of multiple lineages from independent refugia. However, this structure was not apparent in the microsatellite data, consistent with secondary contact without sexual incompability. In contrast, the stonefly A. compacta exhibited low genetic structure and shared mtCOI haplotypes among Fennoscandia and the Black Forest, suggesting a shared Pleistocene refugium in the periglacial tundrabelt. Again, there is incongruence with the microsatellite data, which could be explained with ancestral polymorphism or female-biased dispersal. Future SDM projects major regional habitat loss for the mayfly A. inopinatus, particularly in Central European mountain ranges. By relating these range shifts to my population genetic results, I identified conservation units primarily in Eastern Europe, that if preserved would maintain high levels of the present-day genetic diversity of A. inopinatus and continue to provide long-term suitable habitat under future climate warming scenarios.rnIn this thesis I show that despite similar present day distributions the underlying demographic histories of the study species are vastly different, which might be due to differing dispersal capabilities and niche plasticity. I present genetic, climatic, and ecological data that can be used to prioritize conservation efforts for cold-adapted freshwater insects in light of future climate change. Overall, this thesis provides a next step in filling the knowledge gap regarding molecular studies of the arctic-alpine invertebrate fauna. However, there is continued need to explore the phenomenon of arctic-alpine disjunctions to help understand the processes of range expansion, regression, and lineage diversification in Europe’s high latitude and high altitude biota.