The phylogeographic structure of Arabis alpina in the Alps shows consistent patterns across different types of molecular markers and geographic scales

Glaciation during the Pleistocene confined alpine species to refugial areas. These range contractions had major impacts on the spatial genetic structure of alpine species. Consequently, one should take into account the often complex phylogeographic structure of species when performing genomic research, e.g. on signatures of local adaptation. Understanding the phylogeography of the widespread arctic and alpine Arabis alpina is particularly important, as this species is developing into a model species for ecological genetics. The first objective of this study was to assess the genetic variation of A. alpina across the Alps and to compare the spatial genetic patterns resulting from two different types of molecular markers, namely nuclear microsatellites and amplified fragment length polymorphisms (AFLPs). A second objective was to infer the distribution of genetic variation at the regional scale to understand the genetic structure of populations in the area of a previously suggested contact zone between genetic clusters that presumably recolonised their current range from different glacial refugia. We characterized the phylogeographic structure of 372 individuals from 127 populations across the entire Alpine range, complemented by 364 individuals from 22 populations in the western Swiss Alps. Nuclear microsatellite and AFLP markers described consistent population clustering, coherent with previous phylogeographic analyses. Furthermore, regional population structure in the western Alps of Switzerland highlighted a contact zone of genetic clusters associated with different presumed refugia. Again, this finding was in accordance with recolonisation routes formerly inferred for other plant taxa of the western Swiss Alps. Our results highlight the coincidence of large-scale patterns of genetic structure among alternative types of molecular markers and set a valuable basis for further studies on ecological genomics in A. alpina .