Phylogeny and biogeography of Astraea with new insights into the evolutionary history of Crotoneae (Euphorbiaceae)

• Published in: Molecular phylogenetics and evolution 2020-04, Vol.145, p.106738-106738, Article 106738
• Main Authors: Silva, Otávio Luis Marques, Riina, Ricarda, Cordeiro, Inês
• Format: Article
• Language: English
• Subjects: Brasiliocroton; Croton; Crotonoideae; Neotropics; Sagotia; Sandwithia
• ISSN: 1055-7903; 1095-9513
• DOI: 10.1016/j.ympev.2020.106738

[Display omitted] •Astraea is monophyletic and consists of three main clades.•Diversification in Astraea started ca. 25 Ma and intensified in middle Miocene.•There is incongruence in the phylogenetic signal between nuclear and chloroplast.•The ancestor of Crotoneae was arborescent and occupied Amazon Basin.•Reduced pistillate petals might be a synapomorphy for tribe Crotoneae. We investigated species relationships in Astraea, a primarily Neotropical genus of tribe Crotoneae centered in Brazil, using data from the nuclear ribosomal ITS, and the plastid trnL-trnF and psbA-trnH spacers. With all species of Astraea sampled, along with representatives from across Crotoneae, the evolutionary history of Astraea was interpreted in a broader framework, as well as divergence time estimates and reconstructions of ancestral areas and morphological character states for Crotoneae. Our results show that Astraea is monophyletic, consisting of three main clades, and that most of its diversification took place from the Oligocene to the Pliocene, coincident with the formation of the South American “dry diagonal”. As for Crotoneae, our data show incongruent phylogenetic positions between the nuclear and chloroplast data for most of its genera, and that the ancestor of the tribe was probably arborescent and might have occupied the Amazon Basin, most likely in moist forest, from which it spread throughout South America in the early Eocene. Ancestral state reconstruction recovered deeply lobed leaves and staminate petals bearing moniliform trichomes as putative synapomorphies for Astraea, whereas the absence or strong reduction of pistillate petals is widespread in Crotoneae and may be a synapomorphy for the tribe.