Phylogenetic Placement and Phylogeography of Large-Flowered Lotus Species (Leguminosae) Formerly Classified in Dorycnium: Evidence of Pre-Pleistocene Differentiation of Western and Eastern Intraspecific Groups

The Lotus angustissumus Group (Fabaceae): Can Phylogenetic Patterns Be Accommodated by a Taxonomic Concept?

The Lotus angustissimus group represents an example of obvious contradictions between the molecular and morphological data. This group includes from six to eight mostly annual species of Lotus section Lotus, with the center of species diversity in the Mediterranean. We performed a phylogenetic analysis of the genus Lotus with an expanded representation of all known species of the L. angustissimus group using both nuclear (nrITS) and a set of plastid DNA markers and compared the results with traditional taxonomy of this group. Our results demonstrated a non-monophyletic nature of the study group. In addition, the nrITS and plastid dataset tree topologies were incongruent with each other in both Bayesian and ML analyses. We revealed very complex phylogenetic relationships among the species of the group. Important results obtained in this study are: (1) genetic and geographical differentiation in the latitudinal direction (between L. angustissimus and L. praetermissus) and in the longitudinal direction among closely related accessions identified as L. castellanus, L. lourdes-santiagoi and L. palustris; (2) close genetic links between the Anatolian endemic L. macrotrichus and L. praetermissus from Eastern Europe and Central Asia; and (3) the hybrid nature of L. subbiflorus with L. parviflorus as its presumed male parent species. These results are discussed in the context of morphology, biogeography and taxonomy.

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

Lotus dorycnium s.l. is a complex of taxa traditionally regarded as members of Dorycnium. 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 L. dorycnium complex in the genus Lotus. The present study investigated the phylogeny, phylogeography and morphological variability of the L. dorycnium 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 L. d. ssp. herbaceus, ssp. gracilis, and ssp. anatolicus more or less well defined, whereas ssp. dorycnium, ssp. germanicus, and ssp. haussknechtii can be hardly distinguished from each other using morphology. Analyses of the L. dorycnium 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 trnL-F, rps16, and psbA-trnH demonstrated a low resolution between the L. dorycnium complex and L. hirsutus, as well as among the taxa within the L. dorycnium 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 L. dorycnium and L. hirsutus were most likely localized in the Eastern Mediterranean. A possibility of rare gene exchange between the L. dorycnium complex and the group of L. graecus is revealed for the first time.