Phylogeography and taxonomic reassessment of Arabidopsis halleri – a montane species from Central Europe

Abstract

Evolutionary histories of plants from the mid-elevation (montane) zone of European mountain ranges have only rarely been documented, standing in contrast to those of well-researched inhabitants of (sub-)alpine and foothill zones. To fill this gap, we have reconstructed the phylogeography of Arabidopsis halleri, a species preferring coniferous woodlands and corresponding secondary habitats in the montane zone of the Alps, Carpathians, Hercynian massif and Dinaric Alps. Based on range-wide sampling and finer-scale analyses of multiple multilocus DNA markers, we have addressed phylogeographic patterns among the Carpathian populations and inferred their relationships to A. halleri from neighbouring mountain ranges. We also present a taxonomic re-evaluation of the species in Europe, based on the revealed genetic structure complemented by morphological data. Besides two distinct Alpine groups, we identified a major phylogeographic split between the Western and South-Eastern Carpathians. Interestingly, Western and South-Eastern Carpathian populations were genetically closer to populations from neighbouring mountain ranges (the Hercynian massif and the Dinaric Alps for the Western and South-Eastern Carpathians, respectively) than they were to each other, likely reflecting long-term isolation in different parts of the Carpathians or different (re)colonization pathways during the Holocene. In spite of the considerable environmentally correlated variation, the five major European genetic groups exhibited distinctive morphological characters, and we therefore propose treating them as separate subspecies: A. halleri subsp. halleri (Western Europe, Hercynian massif), A. halleri subsp. tatrica (Western Carpathians), A. halleri subsp. ovirensis (Eastern Alps), A. halleri subsp. occidentalis (Western Alps) and A. halleri subsp. dacica (Eastern and Southern Carpathians and Dinaric Alps).