When Morphology and Biogeography Approximate Nuclear ITS but Conflict with Plastid Phylogeny: Phylogeography of the Lotus dorycnium Species Complex (Leguminosae)

s.l. is a complex of taxa traditionally regarded as members of . It has a wide Mediterranean range, extending in the north to Central and Eastern Europe, and in the east to the Crimea, the Caucasus, and the Western Caspian region. Molecular phylogenetic data support placement of the complex in the genus . The present study investigated the phylogeny, phylogeography and morphological variability of the complex across its distribution range to reveal the main trends in genetic and morphological differentiation in this group. The results of the morphological analyses demonstrated some degree of differentiation, with ssp. , ssp. , and ssp. more or less well defined, whereas ssp. , ssp. , and ssp. can be hardly distinguished from each other using morphology. Analyses of the complex based on nrITS revealed a tendency towards a geographic differentiation into Western, Eastern, and Turkish groups. Phylogenetic and phylogeographic analyses of the same set of specimens using concatenated plastid markers L-F, 16, and A- H demonstrated a low resolution between the complex and , as well as among the taxa within the complex, which can be interpreted as evidence of an incomplete lineage sorting or hybridization. The evolutionary processes responsible for incongruence in phylogenetic signals between plastid and nuclear sequences of the morphologically well-defined species and were most likely localized in the Eastern Mediterranean. A possibility of rare gene exchange between the complex and the group of is revealed for the first time.