Beneath a hairy problem: Phylogeny, morphology, and biogeography circumscribe the new Miconia supersection Discolores (Melastomataceae: Miconieae)

Abstract

Miconia is among the largest plant genera in the Neotropics and a taxonomically complex lineage. Indeed, molecular phylogenetic data shows that none of its traditionally accepted sections are monophyletic, preventing taxonomic advances within the genus. Miconia is the largest plant genus in the Brazilian Atlantic Forest, including three main lineages, the Leandra s.s. clade (ca. 215 spp.), the Miconia sect. Chaenanthera (24 spp.), and the Miconia discolor clade (estimated 77 spp.). Out of these lineages, the Miconia discolor clade is the only currently lacking phylogenetic data, complicating its taxonomy. In this study, we reconstruct the phylogeny of the Miconia discolor clade, using three plastid (atpF-H, psbK-I, and psaI-accD) and two nuclear (ETS and ITS) markers. We sampled 60 out of the 77 species of the group, representing 78% of its diversity. Taxa were selected considering their distribution, morphology, and previous phylogenetic knowledge. We used the newly reconstructed phylogeny to better understand phylogenetic relationships among Atlantic Forest species and morphologically similar taxa, and to propose a new infrageneric classification for the Miconia discolor clade: the Miconia supersection Discolores. We further studied the evolution of seven morphological characters using a Maximum Likelihood approach, and estimated the ancestral range distribution of various lineages in order to understand the biogeographic history of this clade. We found that dichasial inflorescences represent the ancestral condition within Miconia, subsequently giving rise to scorpioid and glomerulate inflorescences in the studied group. We describe Miconia supersect. Discolores, originated in the Amazon region, which is recognized by a dense layer of branched tricomes covering young branches and non-dichasial inflorescences, including three main lineages: (i) Miconia sect. Albicantes, characterized by persistent bracts and arachnoid indument on the abaxial surface of leaves, mainly distributed in the Amazon basin; (ii) Miconia sect. Discolores, characterized by caducous calyx lobes and glomerulate inflorescences, centered in the Atlantic Forest; and (iii) Miconia sect. Multispicatae, characterized by leaves not completely covered with indument, and capitate stigma, mainly distributed in the Atlantic Forest. All three sections and the supersection originated in the Neogene, between the Late Miocene and the Early Pliocene.

Keywords: Amazon; Atlantic Forest; Inflorescence; Miconia discolor; Systematics; Taxonomy.