Are Lotus creticus and Lotus cytisoides (Leguminosae) closely related species? Evidence from nuclear ribosomal ITS sequence data

Lotus creticus is a potentially important perennial legume for soil management in the Mediterranean climate. This plant is in focus of experimental research in different countries. The so-called Lotus creticus group is taxonomically problematic. Although some authors consider all members of the group as a single variable species, others segregate several species distinct from L. creticus, especially L. cytisoides. Recent morphological studies suggested that L. creticus and L. cytisoides are taxonomically distinct at specific level and not even closely related to each other. Two molecular phylogenetic studies published so far and based on one accession of L. creticus each gave conflicting results on relationships of this species. In this paper, sequences of nuclear ribosomal ITS (nrITS) are produced from multiple accessions of both L. creticus and L. cytisoides. Taxonomic identity of each accession has been tested using morphology. The new nrITS sequences are inserted in a data matrix containing a representative set of Lotus species covering all the geographical range and all major taxonomic groups of Lotus. Phylogenetic analysis of nrITS sequence data showed that L. creticus is related to L. assakensis and other species of the section Pedrosia while L. cytisoides is related to L. longisiliquosus and other species of the section Lotea. These results are important for establishing future germplasm collection, breeding and selection programs of perennial Lotus species.