Phylogeny of the genusLotus(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.

The correct phylogenetic position of Lotus conimbricensis Brot. (Leguminosae, Loteae) based on nuclear ribosomal ITS sequences

“…Another explanation may be that considerable variation exists within species. For instance, DEGTJAREVA et al (2006) identified an ITS sequence in L. creticus, which was very different from those reported by ALLAN et al (2003), and suggested that further studies are needed to assess intraspecific variation within this species. Again, however, we think that this explanation is unlikely in most cases FARIA M. A., HARRIS D. J., VISNEVSCHI-NECRASOV T., TAVARES DE SOUSA M., NUNES E. Fig 1. Phylogram of relationships of available Lotus species estimated using a Bayesian approach.…”

“…Later studies included the same sequence from GenBank and reached the same conclusions (e.g. DEGTJAREVA et al 2006). However, it is now clear that several published sequences in GenBank are anomalous, with extremely divergent sequence types recovered by different authors from the same species.…”

“…However, this has changed considerably with the advent of phylogenetic studies based on nrITS sequences. These have clearly shown that the New World species of Lotus are not closely related to the Old World species (ALLAN and PORTER 2000), and in particular DEGTJAREVA et al (2006) revised sectional classifications proposed by KRAMINA and SOKOLOFF (2003) and SOKOLOFF (1999a, b). Some sections appeared as non-monophyletic, including the section Lotus, which was resolved as paraphyletic since Lotus conimbricensis Brot.…”

“…Furthermore, the ITS region is known to display intra-individual variation in some taxonomic groups, that can confound phylogenetic studies (HARRIS and CRANDALL, 2000). DEGTJAREVA et al (2006) combined new data with previously published sequences and noted that in the case of Lotus creticus they obtained a very different sequence and phylogenetic placement when compared to the sequence by ALLAN et al (2003ALLAN et al ( , 2004.…”

“…Historically there has been little agreement in the taxonomic literature regarding the generic limits of Lotus and its infrageneric subdivision (DEGTJAREVA et al 2006). However, this has changed considerably with the advent of phylogenetic studies based on nrITS sequences.…”