Systematics of Libinhania, a new endemic genus of Gnaphalieae (Asteraceae) from the Socotra archipelago (Yemen), inferred from plastid, low-copy nuclear and nuclear ribosomal DNA loci

Abstract

The Socotra archipelago offthe Horn of Africa shelters morphologically diverse endemic species of Asteraceae tribe Gnaphalieae, eight species placed in Helichrysum and five newly discovered. We reconstructed their phylogenetic relationships, analysing nuclear ribosomal DNA (nrDNA) internal transcribed spacer and external transcribed spacer, three plastid DNA and two low-copy nuclear DNA loci with Bayesian inference and maximum parsimony. The plastid DNA and nrDNA trees resolve the endemic helichrysoids as a monophyletic group and agree in that they are not members of Helichrysum or even part of the Helichrysum-Anaphalis-Pseudognaphalium clade, but disagree as to their sister group. In the nrDNA tree, they are nested in the Filago-Leontopodium-Antennaria-Gamochaeta (FLAG) clade, whereas in the plastid DNA tree they are sister to Syncarpha mucronata. The endemic helichrysoids possess two divergent copies of each of the nDNA low-copy markers, similar to those previously found for the FLAG clade. This suggests an ancient allopolyploid origin, with the putative ancestors among the ancestors of Gnaphalium or relatives and of S. mucronata or relatives. The reconstruction of ancestral states of morphological characters suggested hypotheses on the origin and evolution of the morphological diversity of the endemic helichrysoids. We conclude a taxonomic treatment with a key to, and descriptions for, the 13 species accommodated in a new genus, Libinhania.