Phylogenetics of the Chiliotrichum group (Compositae: Astereae): The story of the fascinating radiation in the paleate Astereae genera from southern South America

Abstract

AbstractThe Chiliotrichum group (Compositae: Astereae) is an informal taxonomic group consisting of shrubby daisies that grow mainly in the Andean and Patagonian regions of South America; it is composed of 31 species in 11 genera: Aylacophora, Cabreraea, Chiliotrichiopsis, Chiliophyllum, Chiliotrichum, Haroldia, Katinasia, Lepidophyllum, Llerasia, Nardophyllum, and Ocyroe. We analyzed phylogenetic relationships in the Chiliotrichum group using five DNA regions from two plant genomes: the plastid trnL‐trnF and rpl32‐trnL(UAG) spacers, the rpl16 intron, and the nuclear ribosomal internal and external transcribed spacers, ITS and ETS respectively. The dataset includes 21 ingroup species representing all the genera, and 10 outgroup species belonging to six genera. Maximum parsimony, maximum likelihood, and Bayesian inference analyses performed on the chloroplast and nuclear data support the monophyly of the group. The four major clades recovered on the basis of the combined nuclear evidence (ITS+ETS) are: (1) Llerasia clade, (2) Nardophyllum clade, (3) Chiliotrichum clade, and (4) a clade formed by Nardophyllum+Llerasia clades. As regards the status of the four non‐monospecific genera, Chiliotrichum (2 spp.) and Llerasia (14 spp.) were recovered as monophyletic, whereas the other two, Nardophyllum (5 spp.) and Chiliotrichiopsis (3 spp.), were not recovered as monophyletic. These two are nonetheless recognized as distinct genera because of robust morphological support despite the lack of resolution in the phylogeny based solely on sequence data. The rest of the genera composing the group are monospecific, and they are scattered among the major clades in the group. The only genus with no clear position is Haroldia. An analysis of the morphological data shows that the presence of paleae, believed to function as a defensive structure for the protection of the achenes, is well correlated with other derived head and floret traits such as the number of florets per head and the type of pappus.