A new saxicolous species of Acisanthera (Melastomataceae: Marcetieae) from Chapada dos Guimarães National Park, Mato Grosso, Brazil

Abstract

Acisanthera saxatilis is described, illustrated, and compared with putative relatives. The first specimen of this new species was collected 119 years ago by Oskar Andersson Gustaf Malme during his "second expedition Regnelliana". Acisanthera saxatilis is a little collected species apparently endemic to rocky sandstone formations in Chapada dos Guimarães, Mato Grosso state, Brazil. It differs from similar species by its perennial habit, lignotubers, isomorphic to slightly subisomorphic androecium, stamens positioned in a circle around the style during anthesis, antesepalous stamens with short connectives, small inconspicuous staminal appendages, and purple anthers. Photos of living specimens, a distribution map, scanning electron photographs of seeds and leaves, a preliminary conservation status assessment, as well as comments on vascular plant endemism at the Chapada dos Guimarães are provided.

A Phylogenetic Analysis of Marcetia (Melastomataceae, Marcetieae) and Three New Sprawling Species from Bahia, Brazil

“…In this study, we also confirm the placement of M. acerosa as the first diverging lineage in the genus (see Rocha et Generic Placement of Acisanthera saxatilis-The recovery of A. saxatilis within Acisanthera sensu stricto validates the generic placement of this species that was based on morphology in the protologue (Pacifico and Almeda 2022a). This evaluation was necessary because this species presents several characters atypical in that genus, i.e.…”

“…This evaluation was necessary because this species presents several characters atypical in that genus, i.e. a perennial habit associated with xylopodia, prostrate branches, isomorphic to subisomorphic stamens positioned in a circle around the gynoecium during anthesis, and all anthers purple (Pacifico and Almeda 2022a).…”

“…To this end, we generated a phylogenetic hypothesis for Marcetia to reconstruct habit and petal color evolution in the genus. We also provide notes on the intergeneric relationships and phylogeny of Marcetia , and evaluate the generic placement of Acisanthera saxatilis Almeda & R.B.Pacifico, a recently described species that is endemic to the Chapada dos Guimarães, Mato Grosso, Brazil (Pacifico and Almeda 2022a).…”