Phylogeographic patterns of<i>Deschampsia cespitosa</i>(Poaceae) in Europe inferred from genomic data

Abstract The highly variable tufted hairgrass Deschampsia cespitosa is a tussock-forming plant especially of cool and humid environments. Although common widespread, its phylogeographic structure the significance polyploidy for evolution are poorly understood. Here we used phylogenomic approach to study genetic this species in Europe how polyploid cytotypes/subspecies related diploids. Using genomic data (RADseq whole plastid sequencing) found divergent Iberian group, including Spanish subsp. (diploid tetraploid) Macaronesian island endemic diploid argentea. Moreover, substantial divergence pseudoviviparous tetraploids (Deschampsia subspp. neoalpina rhenana) from seminiferous (except littoralis) all diploids remaining European samples. (D. tetraploid D. littoralis probably represent periglacial relict lineages unknown origin regarding auto- and/or allo-polyploidy, whereas other variants always nested cespitosa, suggesting multiple autopolyploid origins. An analysis after excluding Group revealed five groups with overlapping geographical patterns. However, recovered structure, overall low diffuse point recolonization various refugial areas secondary contact. Effective wind dispersal pollen seeds an open early post-glacial tundra landscape and, finally, increasing human impact on grass since Neolithic, may have enhanced admixture resulted complex patterns detected today.