The southeastern Alps and the southerly adjacent areas are considered an important refugium for plant species during the Pleistocene glaciations; consequently they harbour many endemic taxa. One of them is Cerastium subtriflorum, which in this area occurs sympatrically with morphologically similar, but more widespread C. sylvaticum. Here, we used Amplified Fragment Length Polymorphisms (AFLP) as well as ITS and ndhJ-trnT region of plastid DNA sequences to explore phylogenetic relationships between the two species as well as their relationships to other Cerastium taxa previously deemed closely related. Our data show that both species are genetically well differentiated sister taxa, but their relationship to other taxa remains unclear; both species rather form an independent evolutionary lineage within European Cerastium. Cerastium sylvaticum exhibits low genetic differentiation among populations in the investigated area, suggesting a single Pleistocene refugium in that part of Europe. The much more pronounced genetic differentiation within C. subtriflorum is likely a result of multiple Pleistocene refugia or more recent vicariance among the three disjunct partial distribution areas. Phylogenetic sequence data suggest hybridisation between the two taxa, resulting in a discordant phylogenetic position between ITS and plastid trees of one population of C. subtriflorum. Flow cytometric and multivariate morphometric analyses show that C. subtriflorum and C. sylvaticum differ in their genome size as well as in multiple morphological traits. Most of the results of this study were published in the paper Skubic et al. (2018; doi: 10.1007/s00606-018-1535-y).
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