Phylogeny of the genus Lotus (Leguminosae, Loteae): evidence from nrITS sequences and morphology

Abstract

Lotus (120–130 species) is the largest genus of the tribe Loteae. The taxonomy of Lotus is complicated, and a comprehensive taxonomic revision of the genus is needed. We have conducted phylogenetic analyses of Lotus based on nrITS data alone and combined with data on 46 morphological characters. Eighty-one ingroup nrITS accessions representing 71 Lotus species are studied; among them 47 accessions representing 40 species are new. Representatives of all other genera of the tribe Loteae are included in the outgroup (for three genera, nrITS sequences are published for the first time). Forty-two of 71 ingroup species were not included in previous morphological phylogenetic studies. The most important conclusions of the present study are (1) addition of morphological data to the nrITS matrix produces a better resolved phylogeny of Lotus; (2) previous findings that Dorycnium and Tetragonolobus cannot be separated from Lotus at the generic level are well supported; (3) Lotus creticus should be placed in section Pedrosia rather than in section Lotea; (4) a broad treatment of section Ononidium is unnatural and the section should possibly not be recognized at all; (5) section Heinekenia is paraphyletic; (6) section Lotus should include Lotus conimbricensis; then the section is monophyletic; (7) a basic chromosome number of x = 6 is an important synapomorphy for the expanded section Lotus; (8) the segregation of Lotus schimperi and allies into section Chamaelotus is well supported; (9) there is an apparent functional correlation between stylodium and keel evolution in Lotus.