Pseudohydrosme bogneri sp. nov. (Araceae), a spectacular Critically Endangered (Possibly Extinct) species from Gabon, long confused with Anchomanes nigritianus

Abstract

A Gabonese taxon cultivated for decades in the botanic gardens of Europe as Anchomanes nigritianus is shown to be a new species to science, and on current evidence, is best placed as the fourth species of the Gabonese-centred, poorly known genus Pseudohydrosme. Data on the morphological separation between Anchomanes and Pseudohydrosme are reviewed. Although phylogenomic studies may show in future that the two genera need to be merged, for the moment their separation is reinforced on morphological grounds. Anchomanes lacks the spathe tube, ovoid-globose, 2 – 4 locular pistil and thick, lobed stigma on a symmetric, stout style that we show to characterise the redelimited Pseudohydrosme. (Anchomanes has oblong, polygonal, 1-locular pistils, stigmas asymmetric, sessile, thin and disc-like or on asymmetrical conical styles and are pointed or brush-like). In addition, Pseudohydrosme (where known) has stipitate (versus sessile) fruits and on current evidence lacks the lacticifers recorded from Anchomanes. We test the hypothesis that the taxon is a new species to science, naming it as Pseudohydrosme bogneri, and conclude that it is Critically Endangered (Possibly Extinct) using the IUCN 2012 standard. Pseudohydrosme bogneri appears to be the tenth documented probable global extinction of a plant species that has occurred among the narrowly endemic plant species of the Libreville area, Gabon.