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 nearly 130 years of the African genus Pseudohydrosme , formerly considered endemic to Gabon. Sister to Anchomanes, Pseudohydrosme is distinct from Anchomanes because of its 2–3-locular ovary (not unilocular), peduncle concealed by cataphylls at anthesis and far shorter than the spathe (not exposed, far exceeding the spathe), stipitate fruits and viviparous (vegetatively apomictic) roots (not sessile, roots non-viviparous). 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, is maintained in Sect. Pseudohydrosme together with Pseudohydrosme ebo sp.nov . of the Ebo Forest, Littoral, 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 paper. All three species of Pseudohydrosme 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. One of the species may occur in a formally protected areas and is also cultivated widely but infrequently in Europe and the USA for its spectacular inflorescences.