Phylogenetic relationships of Atocion and Viscaria (Sileneae, Caryophyllaceae) inferred from chloroplast, nuclear ribosomal, and low-copy gene DNA sequences

Atocion and Viscaria are two of seven small genera recognised in the tribe Sileneae on the basis of molecular phylogenies. The aim of the present study is to infer phylogenetic relationships among their subordinate taxa, using chloroplast (rps16 intron,psbE-petG spacer region) and nuclear (ITS and the RNA polymerase gene family) DNA sequences. Relative dating was used to discriminate among intralineage and interlineage processes that cause incongruence among different gene-tree topologies. Atocion asterias is demonstrated to belong to Viscaria, which contains three species: V vulgaris (incl. V atropurpurea), V alpina, and V asterias. Infraspecific differentiation of V alpina is not supported by the sequence data. The traditional sectional delimitation of Atocion taxa within Silene is not supported phylogenetically, and Silene tatarinowii as well as S. hoefftiana do not belong to Atocion, as classified previously. Atocion contains six species: A. armeria, A. compactum, A. lerchenfeldianum, A. reuterianum, A. rupestre, and A. scythicinum (not included in our study). With this circumscription, Atocion and Viscaria, respectively, form monophyletic groups in the cpDNA, ITS, RPD2a and RPD2b trees, but not in the RPA2 tree, where such relationships were possibly distorted by ancient hybridisation. Hybridisation with subsequent chloroplast capture is likely to have taken place in the evolutionary history of A. compactum. Three novel nomenclatural combinations are made: Atocion reuterianum, A. scythicinum and Viscaria asterias.