Phylogenetic relationships of Limonium (Plumbaginaceae) inferred from multiple chloroplast and nuclear loci

Limonium (Plumbaginaceae) is a nearly cosmopolitan halophytic genus with ca. 350 species, a large number of which occurs in the Mediterranean region. We have generated a sequence dataset of several plastid (trnK intron including the matK gene, petD intron with the petB-petD spacer, trnL intron with the trnL-trnF spacer) and one nuclear region (nrITS), spanning the major lineages within the genus (102 accessions representing 76 species of Limonium) and related genera. Bayesian inference, maximum likelihood and maximum parsimony analyses converge on a Limonium clade that includes the genera Afrolimon, Eremolimon and Linczevskia. Plastid and nuclear trees congruently depict a number of major clades, most of them with a characteristic vegetative morphology and growing in specific habitats. Although the position of Afrolimon is incongruently resolved as the sister of a subclade comprising Limonium vulgare and relatives in the plastid trees versus being the sister to a Limonium sogdianum-L. bellidifolium-L. aureum clade in the nrITS tree, both genomic compartments show that Afrolimon is deeply nested in Limonium. Eremolimon is resolved as a close relative of L. sogdianum and L. ferganense based on plastid and nuclear genomic compartments. Our phylogenetic analysis resulted in an improved picture of internal relationships. Apart from the monophyletic subgenera Limonium subg. Limonium and L. subg. Pteroclados, nine well-supported clades of L. subg. Limonium are evident, several of which are predominantly constituted by species of a certain geographic range. A subclade of Irano-Turanian species (L. iranicum, L. suffruticosum and relatives) is shown to be unrelated to a L. axillare subclade, indicating an independent origin of the woody habit in these two lineages. Limonium sect. Iranolimon sect. nov. is described for the Irano-Turanian woody lineage. The new combination L. sect. Circinaria comb. nov., is established for taxa sometimes included in Afrolimon.