Molecular phylogenetic evidence for a wide circumscription of a characteristic Irano-Turanian element: Acantholimon (Plumbaginaceae: Limonioideae)

Abstract

Acantholimon is an important component of the subalpine steppe flora in the Irano-Turanian region and the second largest genus of Plumbaginaceae with c. 200 cushion-forming subshrubby species. Because the genus has been poorly represented in previous phylogenetic studies, questions regarding its monophyly, phylogenetic relationships and infrageneric classification have not been addressed in a solid evolutionary framework. We used sequences from the nuclear ribosomal internal transcribed spacers and the plastid trnY (GUA) -trnT (GGU) intergenic spacer for 197 accessions of Acantholimon and nine putatively closely related Asian genera in Limonioideae. Contrary to previous results, Bayesian, maximum likelihood and maximum parsimony analyses show that Acantholimon is not monophyletic unless its limits are extended to include species currently placed in eight of these Asian genera. As circumscribed, the new Acantholimon s.l. is sister to Goniolimon and includes the following genera: Bamiania, Bukiniczia, Chaetolimon, Cephalorhizum, Dictyolimon, Gladiolimon, Popoviolimon and Vassilczenkoa. Our phylogenetic analyses also challenge the existing classification at the generic and infrageneric levels. A maximum likelihood reconstruction of ancestral states for morphological characters illustrates the possible scenarios by which the cushion architecture combined with linear acuminate leaves, also present in other steppic Irano-Turanian elements, were acquired in this group of Plumbaginaceae. Our study shows the importance of extensive taxon sampling for phylogenetic reconstruction of species-rich lineages.ADDITIONAL KEYWORDS: Irano-Turanian region -ITS -molecular phylogenetic analysis -morphological character evolution -plastid trnY-T.

An expanded molecular phylogeny of Plumbaginaceae, with emphasis on Limonium (sea lavenders): Taxonomic implications and biogeographic considerations

“…In tribe Limonieae, our topology corroborates previous phylogenies (e.g., Lledó, Crespo, et al, ; Moharrek et al, ) in supporting the sister relationships of Armeria with Psylliostachys , Ceratolimon with Limoniastrum , and Goniolimon with a clade comprising Acantholimon and related genera (Figure ). Using nine species of Armeria and two species of Psylliostachys, we confirmed the reciprocal monophyly of these two sister genera (see also Lledó, Crespo, et al, ; Moharrek et al, ; Moharrek et al, ).…”

“…In tribe Limonieae, our topology corroborates previous phylogenies (e.g., Lledó, Crespo, et al, ; Moharrek et al, ) in supporting the sister relationships of Armeria with Psylliostachys , Ceratolimon with Limoniastrum , and Goniolimon with a clade comprising Acantholimon and related genera (Figure ). Using nine species of Armeria and two species of Psylliostachys, we confirmed the reciprocal monophyly of these two sister genera (see also Lledó, Crespo, et al, ; Moharrek et al, ; Moharrek et al, ). Armeria and Psylliostachys share a unique morphological characteristic of the calyx (i.e., the rib‐like tissue of the calyx limb is not present along the calyx tube as it fuses at the limb base; Lledó et al, ), but the former comprises perennial herbs with a primarily Western Mediterranean distribution, while the latter consists of annual herbs with an Irano‐Turanian distribution.…”

“…The Irano‐Turanian genera Acantholimon , Vassilczenkoa , Cephalorhizum, Popoviolimon, Dictyolimon, and Bukiniczia form a well‐supported clade sister to the Goniolimon clade (clade II; Figure ), confirming previous findings (Moharrek et al, ). The lack of monophyly for Acantholimon and the presence of two separate clades comprising Acantholimon species were presented by Moharrek et al (), who sampled 121 Acantholimon species and two molecular markers ( trnY‐trnT spacer and ITS region), and are in agreement with our results.…”

“…Several new, small genera have been segregated primarily from the two most species‐rich genera ( Limonium and Acantholimon ). Here, we sampled 19 out of 25 genera for Limonioideae (Table ), expanding on previous molecular phylogenetic analyses (e.g., Lledó, Crespo, et al, ; Malekmohammadi et al, ; Moharrek et al, ) and further clarifying intergeneric boundaries and relationships in the subfamily. In our phylogeny (Figure ), Aegialitis (Aegialitideae) is sister to Limonieae, confirming the taxonomic subdivision of Limonioideae and previous phylogenetic results (Lledó et al, ; Lledó, Crespo, et al, ).…”

“…, Vassilczenkoa Lincz.). However, the circumscription and relationships of these Central Asian genera are still debated (Moharrek, Kazempour‐Osaloo, Assadi, & Feliner, ), further highlighting the need for detailed phylogenetic and taxonomic studies in Plumbaginaceae.…”