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| Cladoceras rovumense I.Darbysh., J.E.Burrows & Q.Luke, in Darbyshire, Burrows, Luke & Langa, 2022. |
ABSTRACT
Following a review of the circumscription of the genus Cladoceras Bremek. (Rubiaceae) in relation to Tarenna Gaertn., the new species Cladoceras rovumense I.Darbysh., J.E.Burrows & Q.Luke sp. nov. is described from the dry forests of the Rovuma Centre of Plant Endemism (CoE) in southeast Tanzania and northeast Mozambique. This species has previously been known as Tarenna sp. 53, following the revision of African Tarenna by Jérôme Degreef. A comparison to Cladoceras subcapitatum (K.Schum. & K.Krause) Bremek., the only other member of this genus as currently circumscribed, is provided. The new species is assessed as Endangered under the criteria of the IUCN Red List. New records for Mozambique of two further Rovuma CoE endemics are recorded: Celosia patentiloba C.C.Towns. (Amaranthaceae) and Cordia fissistyla Vollesen (Boraginaceae), both of which are globally threatened.
Keywords: new record, new species, Rovuma, taxonomy, threatened
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| Cladoceras rovumense I.Darbysh., J.E.Burrows & Q.Luke sp. nov. A. Habit, fruiting shoot. B. Habit, flowering shoot. C. Stipule, external face. D. Hairs revealed beneath fallen stipule. E. Portion of flowering stem showing indumentum. F. Leaf, adaxial indumentum. G. Leaf, abaxial indumentum. H. Dissected corolla with androecium. I. Style and stigma. J. Longitudinal section of ovary. K. Mature fruit. L. Fruit, partially dissected to reveal seeds. M. Seed in two views. A, E–G, K–M from S. Bidgood et al. 1357; B, H–I from Q. Luke 13883; C–D, J from Q. Luke et al. 10116. Drawn by Andrew Brown. |
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| Species of Cladoceras Bremek. in the field. A–B. Cladoceras rovumense I.Darbysh., J.E.Burrows & Q.Luke sp. nov. C–D. Cladoceras subcapitatum (K.Schum. & K.Krause) Bremek. (photos: A. Q. Luke; B. P.A. Luke, Mozambique; C.-D. W.R.Q. Luke, Base Titanium nursery, Kwale County, Kenya). |
Cladoceras rovumense I.Darbysh., J.E.Burrows & Q.Luke sp. nov.
Diagnosis: Cladoceras rovumense sp. nov. resembles C. subcapitatum in floral and fruit morphology, but differs most markedly in (a) being a free-standing tree or shrub, lacking modified spinose lateral branches (vs a scandent shrub with some lateral branches modified to form ± recurved spines to aid climbing in C. subcapitatum); (b) the leaves being obovate or obovate-elliptic, larger, up to 17.5 × 10.5 cm, with surfaces pubescent particularly on the veins beneath and midrib above, becoming scabridulous at maturity (vs leaves elliptic to oblong-oblanceolate, smaller, up to 12 × 4.8 cm, glabrous); (c) the inflorescences being borne on leafless lateral branches (vs inflorescence-bearing branches with one or more pairs of leaves at least in flower, sometimes caducous at fruiting); (d) the inflorescence being dense, capitate and with 20+ flowers (vs less dense and usually with clear branching, 9–15-flowered); (e) the calyx lobes being rounded to broadly and convexly triangular, with an irregular, sometimes toothed margin (vs calyx lobes acute-triangular to -lanceolate); and (f) the style and stigma together measuring 17–19 mm long (vs 8–10 mm long in C. subcapitatum); see Table 1.
Etymology: The epithet denotes that this species is endemic to the proposed Rovuma Centre of Plant Endemism in coastal southern Tanzania and northern Mozambique.
Iain Darbyshire, John E. Burrows, Quentin Luke and Clayton Langa. 2022. Cladoceras rovumense sp. nov. (Gentianales-Rubiaceae), A New Species from southeast Tanzania and northeast Mozambique. European Journal of Taxonomy. 833(1), 46-59. DOI: 10.5852/ejt.2022.833.1883
