Taxonomic revision of the threatened African genus Pseudohydrosme Engl. (Araceae), with P. ebo, a new, critically endangered species from Ebo, Cameroon

Abstract

This is the first revision in more than 100 years of the African genus Pseudohydrosme, formerly considered endemic to Gabon. Closely related to Anchomanes, Pseudohydrosme is distinct from Anchomanes because of its 2-3-locular ovary (vs. unilocular), peduncle concealed by cataphylls at anthesis and far shorter than the spathe (vs. exposed, far exceeding the spathe), stipitate fruits and viviparous (asexually reproductive) roots (vs. sessile, roots non-viviparous), lack of laticifers (vs. laticifers present) and differences in spadix: spathe proportions and presentation. However, it is possible that a well sampled molecular phylogenetic analysis might show that one of these genera is nested inside the other. In this case the synonymisation of Pseudohydrosme will be required. Three species, one new to science, are recognised, in two sections. Although doubt has previously been cast on the value of recognising Pseudohydrosme buettneri, of Gabon, it is here accepted and maintained as a distinct species in the monotypic section, Zyganthera. However, it is considered to be probably globally extinct. Pseudohydrosme gabunensis, type species of the genus, also Gabonese but probably extending to Congo, is maintained in Sect. Pseudohydrosme together with Pseudohydrosme ebo sp.nov. of the Ebo Forest, Littoral Region, Cameroon, the first addition to the genus since the nineteenth century, and which extends the range of the genus 450 km north from Gabon, into the Cross-Sanaga biogeographic area. The discovery of Pseudohydrosme ebo resulted from a series of surveys for conservation management in Cameroon, and triggered this article. All three species are morphologically characterised, their habitat and biogeography discussed, and their extinction risks are respectively assessed as Critically Endangered (Possibly Extinct), Endangered and Critically Endangered using the IUCN standard. Clearance of forest habitat for logging, followed by agriculture or urbanisation are major threats. Pseudohydrosme gabunensis may occur in a formally protected area and is also cultivated widely but infrequently in Europe, Australia and the USA for its spectacular inflorescences.

Kupeantha yabassi(Coffeeae- Rubiaceae), a new Critically Endangered shrub species of the Ebo Forest area, Littoral Region, Cameroon

“…Numerous new species have been published from Ebo in recent years. Examples of other species that, like Kupeantha yabassi, appear to be strictly endemic to the Ebo area on current evidence are: Ardisia ebo Cheek (Cheek & Xanthos, 2012), Crateranthus cameroonensis Cheek & Prance (Prance & Jongkind, 2015), Gilbertiodendron ebo Burgt & Mackinder (van der Burgt et al 2015), Inversodicraea ebo Cheek (Cheek et al 2017), Kupeantha ebo M.Alvarez & Cheek (Cheek et al 2018a), Palisota ebo Cheek (Cheek et al 2018b) and Pseudohydrosme ebo Cheek (Cheek et al 2021).…”

Pseudohydrosme bognerisp. nov. (Araceae), a spectacular Critically Endangered (Possibly Extinct) species from Gabon, long confused withAnchomanes nigritianus

“…The new species described below as Pseudohydrosme bogneri was mainly described from herbarium specimens (gross morphological structures) and spirit preserved material (details of the spadix). The terms and format of the description follow the conventions of Mayo et al (1997) and Cheek et al (2021). Georeferences for specimens lacking latitude and longitude were obtained using Google Earth (https://www.google.com/intl/en_uk/earth/versions/ ).…”

“…However, in the course of a research project revising the genus Anchomanes, a comparison of the dimensions and proportions of the inflorescence of Bogner's Gabonese material with that of the only material known of Anchomanes nigritianus, the type from Oban, Nigeria (Talbot 1247, BM), shows morphological differences so numerous and disjunct that they cannot be accommodated in the same species (see Table 1 below). Moreover, re-examination of Bogner's material shows it to have the key features of Pseudohydrosme, a genus of three species closely related to Anchomanes but centred in Gabon, and which was recently revised (Cheek et al 2021). In this paper we describe morphologically the taxon represented by Bogner's material for the first time, and we test the hypothesis that it is a fourth, hitherto undescribed species of Pseudohydrosme.…”

“…Anchomanes are 1locular, and Pseudohydrosme 2( -3)-locular. However, in a recent taxonomic revision of Pseudohydrosme, five additional characters separating the genera are given (Cheek et al 2021, Table 2, see discussion below). In one of these, peduncle length, the new species described here fits Anchomanes, not Pseudohydrosme.…”

“…In contrast in all four species of Pseudohydrosme, the ovary is globose or globose-ovoid, and not polygonal. The style is always symmetrical, distinct, stout, cylindric and bears a thickened, 2 -3-lobed stigma, and the stigmatic lobes are reflexed (Mayo et al 1997 Cheek et al (2021).…”