Abstract
The Arabidopsis arenosa complex is closely related to the model plant Arabidopsis thaliana. Species and subspecies in the complex are mainly biennial, predominantly outcrossing, herbaceous, and with a distribution range covering most parts of latitudes and the eastern reaches of Europe. In this study we present the first comprehensive evolutionary history of the A. arenosa species complex, covering its natural range, by using chromosome counts, nuclear AFLP data, and a maternally inherited marker from the chloroplast genome [trnL intron (trnL) and trnL/F intergenic spacer (trnL/F-IGS) of tRNALeu and tRNAPhe, respectively]. We unravel the broad-scale cytogeographic and phylogeographic patterns of diploids and tetraploids. Diploid cytotypes were exclusively found on the Balkan Peninsula and in the Carpathians while tetraploid cytotypes were found throughout the remaining distribution range of the A. arenosa complex. Three centers of genetic diversity were identified: the Balkan Peninsula, the Carpathians, and the unglaciated Eastern and Southeastern Alps. All three could have served as long-term refugia during Pleistocene climate oscillations. We hypothesize that the Western Carpathians were and still are the cradle of speciation within the A. arenosa complex due to the high species number and genetic diversity and the concurrence of both cytotypes there.
Highlights
Pleistocene climatic fluctuations strongly shape the evolutionary history of new species and the distribution of genetic variants at the population level within species (e.g., Arabidopsis [2] and hominins [3])
The Western Carpathian Mountains are the cradle of speciation within the A. arenosa complex
Within the A. arenosa complex two ploidal levels, diploid and tetraploid, were observed. Contact zones of these two cytotypes were localized in the northwestern part of the Balkan Peninsula and in the Western Carpathians, and, at least one independent polyploidisation event can be assumed for each of these regions
Summary
Pleistocene climatic fluctuations strongly shape the evolutionary history of new species (e.g., grasshoppers [1]) and the distribution of genetic variants at the population level within species (e.g., Arabidopsis [2] and hominins [3]). Arabidopsis arenosa is a colline, montane, and subalpine species complex with a mainly Central European distribution range including parts of the Alps and Carpathians. A few studies have been attempted to unravel the evolutionary history of the A. arenosa complex [9], [10]. Polyploidisation, mainly tetraploidisation, is frequent in several taxa of the A. arenosa complex [14], indicating repeated independent polyploidisation events. Introgression, the stable integration of genetic material from one species into another through repeated backcrossing, was observed between members of the A. arenosa and A. lyrata complexes [5], [15]
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