A single origin of leaflessness in Afro‐Malagasy angraecoids (Orchidaceae, Angraecinae)

Abstract

Microcoelia and the monospecific Taeniorrhiza and Chauliodon are notable among Afrotropical angraecoid orchids for being leafless. However, the affinity among these genera was not addressed in previous molecular phylogenetic studies, thus precluding the understanding of how many times has leaflessness evolved in angraecoids. The discovery of an additional species ascribable to Taeniorrhiza in Gabon, and a revision of all material referrable to this genus in herbarium collections, created the possibility to investigate the phylogenetic position of Taeniorrhiza relative to Microcoelia and Chauliodon. Based on phylogenetic inference using ITS-1 and two plastid regions (matK/trnK, trnL-trnF), and including 20 of the 34 species of Microcoelia recognised prior to our study, we here demonstrate that Taeniorrhiza and Chauliodon are deeply imbedded in Microcoelia, and are thus treated here as synonyms of the last. Accordingly, we describe the novelty from Gabon as a new species of Microcoelia: Microcoelia nguemae sp. nov. The new species is illustrated with colour photographs, and also with line drawings. Its preliminarily IUCN conservation status is provided. The novelty is notable for the dorsiventrally asymmetric distribution of pneumathodes along its roots and for bearing the longest lip spur in this Afro-Malagasy epiphytic genus. The new phylogenetic framework suggests a single origin of leaflessness in Afrotropical angrecoids and reveals the informative value of the rostellum to reconstruct relationships within Microcoelia. This serves as the basis of a newly proposed sectional treatment for Microcoelia, recognising 37 species, one new section, a new status for the defunct genus Encheiridion and the redefinition of Microcoelia sect. Microcoelia and sect. Brachyglossa.

Keetia gordoniisp. nov. (Rubiaceae - Vanguerieae) a new species of threatened forest liana from the littoral forest of Gabon

“…New plant species to science such as Keetia gordonii continue to be published steadily from Gabon. Recently published new species range from trees and shrubs (Barberá et al 2023; Couvreur et al 2022; Dagallier et al 2023; Lachenaud & Bidault 2022; Quintanar et al 2023) to epiphytic herbs (Farminhão et al 2023), epiphytic parasitic shrubs (Lachenaud 2023) to lianas (Jongkind & Lachenaud 2022).…”