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| Ctenium bennae Xanthos in Xanthos, Konomou, Haba & van der Burgt, 2021. |
Summary
Ctenium bennae Xanthos is described and illustrated as the only rheophytic species in the genus. The new species is known from a single waterfall on the Benna Plateau, at the border between Forecariah and Kindia Prefectures in Guinea Conakry. Ctenium bennae is here assessed as Near Threatened according to the categories and criteria of IUCN.
Key Words: Africa, rheophyte, taxonomy
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| Ctenium bennae Xanthos. A habit; B spikelet with glumes removed; C lower glume; D upper Glume; E third lemma; F third palea; G caryopsis. From Konomou 657. Drawn by Hazel Wilks. |
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| Ctenium bennae Xanthos. A the species was only found in the waterfall seen in the distance, 5 Nov. 2019; B unmounted herbarium specimen of Konomou 657; C habitat, sandstone rocks in the rapids of a permanent stream, 2 Nov. 2019; D close up of the species growing in the rocks, 2 Nov. 2019. Photos: A, C, D Xander M. van der Burgt, B Martin Xanthos. |
Ctenium bennae Xanthos sp. nov.
Type: Guinea Conakry, border between Forécariah and Kindia Prefectures, slopes of Benna Plateau above Gombokori Village, ...
RECOGNITION. Ctenium bennae has the most reduced spikelet structure among the African species of Ctenium, with the first two florets reduced completely to awns (i.e. lemma body absent) and the fourth floret absent. Only the third floret is fully developed. Affinities occur with C. sesquiflorum but this has the first and fourth floret absent and the presence of a second rudimentary lemma. Specimens of C. newtonii var. newtonii at K have been recorded with no fourth floret but even these specimens have rudimentary first and second lemmas, and the inflorescence has 1 spike; not 3 – 7 as in C. bennae. The species is the only rheophytic representative in the genus. A comparison of C. bennae with morphologically similar species from West Africa is given in Table 1.
HABITAT. Ctenium bennae is a rheophytic species collected on rocks in the rapids of a permanent stream that flows over sandstone bedrock in gallery forest.
ETYMOLOGY. The epithet is named after the type locality of the species, Benna Plateau.
CONSERVATION STATUS. Ctenium bennae is known only from one site, the type locality, Benna Plateau. There are currently no discernible threats to this site, however a single threatening event could eliminate this species globally. The Area of Occupancy (AOO) is 4 km2, which was calculated using GeoCat (Bachman et al. 2011) using 2 × 2 km2 grid cells. Assessed against the guidelines for IUCN, this species does not quite meet the threshold for threatened taxa and is here assessed as Near Threatened (NT).
Martin Xanthos, Gbamon Konomou, Pepe M. Haba and Xander M. van der Burgt. 2021. Ctenium bennae (Poaceae; Chloridoideae), A New Rheophytic Species from Guinea-Conakry. Kew Bulletin. DOI: 10.1007/s12225-021-09989-6
