European Journal of Taxonomy 833: 46–59 https://doi.org/10.5852/ejt.2022.833.1883 ISSN 2118-9773 www.europeanjournaloftaxonomy.eu 2022 · Darbyshire I. et al. This work is licensed under a Creative Commons Attribution License (CC BY 4.0). Research article Cladoceras rovumense sp. nov. (Gentianales-Rubiaceae), a new species from southeast Tanzania and northeast Mozambique Iain DARBYSHIRE 1,* , John E. BURROWS 2, Quentin LUKE Clayton LANGA 4 3 & 1 Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AE, United Kingdom. Buffelskloof Herbarium, Buffelskloof Nature Reserve, P.O. Box 710, Lydenburg, Mpumalanga Province 1120, South Africa. 3 East African Herbarium, National Museums of Kenya, P.O. Box 45166, Nairobi, 00100, Kenya. 4 Instituto de Investigação Agrária de Moçambique (IIAM), P.O. Box 3658, Mavalane, Maputo, Mozambique. 2 * Corresponding author: i.darbyshire@kew.org 2 Email: botartburrows@gmail.com 3 Email: quentinluke1@gmail.com 4 Email: claytonlanga@gmail.com 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. Darbyshire I., Burrows J.E., Luke Q. & Langa C. 2022. Cladoceras rovumense sp. nov. (Gentianales-Rubiaceae), a new species from southeast Tanzania and northeast Mozambique. European Journal of Taxonomy 833: 46–59. https://doi.org/10.5852/ejt.2022.833.1883 Introduction The genus Cladoceras Bremek. (Rubiaceae Juss.) was described to accommodate the species C. subcapitatum (K.Schum. & K.Krause) Bremek., a scandent shrub from coastal Kenya and Tanzania with unusual recurved spines derived from modified branches to aid climbing (Bremekamp 1940; Bridson & Verdcourt 1988). Robbrecht & Bridson (1984) considered the taxonomic position of Cladoceras and 46 DARBYSHIRE I. et al., A new species of Caldoceras from Mozambique and Tanzania placed it with confidence within the tribe Pavetteae Dumort. of subfamily Ixoroideae Bremek. They suggested that it is closely allied to the palaeotropical genus Tarenna Gaertn., noting the particular similarity to another eastern African lianescent species, T. junodii (Schinz) Bremek. They further noted that, whilst Tarenna s. lat. is morphologically diverse with several distinct species groupings recognisable, the group of continental African species that includes T. junodii share with Cladoceras seeds that are smooth to the naked eye, with a pronounced hilar cavity and entire endosperm, and that the placentation is broadly similar between the two taxa. Cladoceras subcapitatum also possesses the same type of exotestal cells on the seeds as present in that same group of continental African species of Tarenna, in which the walls are sinuate and so the cells together resemble a jigsaw-puzzle (Robbrecht & Bridson 1984; De Block et al. 2015). Cladoceras subcapitatum has a corolla with a tube that is markedly longer than the lobes, whilst most African Tarenna have the tube shorter than or ± equal to the lobes, but Robbrecht & Bridson (1984) noted the exception of T. gossweileri S.Moore, where the tube is distinctly longer than the lobes. However, in that species, both the stamens and the stigma are exserted from the corolla tube, whereas in C. subcapitatum the stigma is included well within the corolla tube. De Block et al. (2015) also noted that the pollen of C. subcapitatum is (3–)4-colporate, whilst it is 3-colporate in continental African Tarenna, but they did not consider this to be a significant distinction at the generic rank. Robbrecht & Bridson (1984) chose to maintain Cladoceras as a separate genus from Tarenna, but that was largely based on the likelihood that Tarenna s. lat. would be segregated into several morphologically discrete genera in the future, and so they considered it premature to sink Cladoceras at that time. The anticipated segregation of Tarenna has since begun, with the reinstatement of Coptosperma Hook.f. (including Zygoon Hiern) as an accepted genus with approximately 50 species in Africa and Madagascar, separated from Tarenna on the basis of having single-seeded drupes and seeds with ruminate endosperm (De Block et al. 2001; Degreef et al. 2001). In its current circumscription, Tarenna, excluding Coptosperma, is a palaeotropical genus of ca 200 species (De Block et al. 2015). In the most recent taxonomic account of Tarenna in continental Africa, 42 accepted species were documented (Degreef 2006), with two further species added since that publication (Burrows 2009; Cheek et al. 2015). A recent phylogenetic analysis of tribe Pavetteae using rps16, trnT-F and ITS (De Block et al. 2015) revealed that Tarenna as currently circumscribed is polyphyletic and that African species of Tarenna fall within a lineage together with Pavetta L., separated from the Asian lineage to which the type species of Tarenna belongs. Further, Cladoceras subcapitatum was resolved as nested within the African Tarenna clade, sister to T. pembensis J.E.Burrows from coastal northeast Mozambique. Tarenna junodii was not included in that phylogenetic study, but given the morphological similarities between T. pembensis and T. junodii, it is considered highly likely that T. junodii will belong within the same clade. De Block et al. (2015) concluded that African species named Tarenna can no longer be included in that genus, and suggested that the name Cladoceras could be adopted for at least some of the African clade. However, the renaming of African Tarenna is complicated by the fact that monophyletic Pavetta arises from within the African taxa of Tarenna, thus rendering it paraphyletic. Hence, it is likely that more genera will need to be segregated from African Tarenna and the exact delimitation of an expanded Cladoceras remains moot. De Block et al. (2015: 79) concluded that “further molecular and morphological studies are necessary to clarify the phylogeny of Pavetteae, especially regarding African Tarenna species …”. Degreef (2006) noted a number of incompletely known species of African Tarenna, including his sp. 53 for which he had only seen two collections: S. Bidgood et al. 1357, a fruiting specimen from the Rondo Plateau of southeast Tanzania, and Q. Luke 11016, a specimen with flower buds from the Mueda Plateau of northeast Mozambique. A further collection was made in 2008 from the forests near Quiterajo in Mozambique by one of the current authors (J.E.B.: J.E. & S.M. Burrows 10748) during research for the publication Trees and Shrubs of Mozambique, but only old, wilted flowers were found at that time 47 European Journal of Taxonomy 833: 46–59 (2022) and so the species remained undescribed, and was again listed as Tarenna sp. 53 in that publication (Burrows et al. 2018). However, fresh flowering material had been collected independently by another of the current authors (Q.L.: Q. Luke 13883) on the Mueda Plateau in 2009. With four collections now available, including good flowering and fruiting material, this highly distinctive species can be described. Whilst placed within Tarenna in previous literature (Degreef 2006; Timberlake et al. 2011; Burrows et al. 2018), possible affinity to Cladoceras has also been noted on some of the herbarium specimens of this taxon. In particular, the long corolla tube is strikingly similar to that of C. subcapitatum. Here, we investigate Tarenna sp. 53 of Degreef (2006) as a taxonomic novelty. The study area The new species in question is recorded from Lindi Region in southeast Tanzania and Cabo Delgado Province in northeast coastal Mozambique. The sites fall within the proposed Rovuma Centre of Plant Endemism (CoE), which comprises coastal and lowland dry forest, thicket and woodland habitats spanning from east-central Tanzania south to Quelimane in coastal northern Mozambique (Burrows & Timberlake 2011; Darbyshire et al. 2019). The core area of this CoE is centred on the Rovuma River, which forms the boundary between Tanzania and Mozambique towards the Indian Ocean coastline. This core area is an expansion of the Lindi Local Centre of Endemism as proposed by Clarke (2001). The extension of this CoE into Mozambique has been confirmed by recent botanical surveys of the coastal dry forests and associated habitats, with a particular focus on Cabo Delgado Province (Timberlake et al. 2011; Darbyshire et al. 2020). These surveys, together with existing collections, revealed nearly fifty species new to science as well as a large number of new country records for Mozambique across a wide range of plant families (Timberlake et al. 2011; Darbyshire et al. 2020). In addition to the new species described here, we also report additional new records for Mozambique of species endemic to the Rovuma CoE. The coastal dry forests and thickets of the Rovuma CoE are particularly rich in species of Rubiaceae, many of which are range-restricted endemics (Timberlake et al. 2011; Burrows et al. 2018; Darbyshire et al. 2019, 2020). This includes the genus Tarenna, where two recently described species are of note: T. bridsoniana Degreef from Mlinguru in Lindi Region of Tanzania (Degreef 2006) and T. pembensis from coastal Cabo Delgado and Nampula Provinces of Mozambique (Burrows 2009). A wide range of other Rubiaceae genera contain localised Rovuma CoE endemics, including Empogona Hook.f., Oxyanthus DC., Pavetta, Pyrostria Comm. ex Juss. and Vangueria Juss. (Burrows et al. 2018; K. Matheka et al., in prep.). Material and methods This taxonomic study is based on morphological analyses of herbarium material, primarily using specimens held at the EA, K and BNRH herbaria, with additional study of material at LMA where available (herbarium abbreviations following Thiers, continuously updated). Field photographs of the species in question were also consulted. Measurements were made on dry material except for flowers, which were first rehydrated using Aerosol OT 5% solution, and seeds, which were extracted from a fruit following boiling in water for ca three minutes. At least one duplicate of all cited specimens has been seen by one or more of the authors. Data on distribution, habitat and ecology and phenology were taken from herbarium specimen labels and from field observations made by the authors. Specimen georeference data were imported into SimpleMappr (Shorthouse 2010) to produce a distribution map. The preliminary conservation (extinction risk) assessment of the new species is based on application of the Categories and Criteria of the IUCN Red List (IUCN 2012; IUCN Standards and Petitions Committee 2019). The online tool GeoCAT (http://geocat.kew.org/, Bachman et al. 2011) was used to calculate the area of occupancy (AOO) and extent of occurrence (EOO). 48 DARBYSHIRE I. et al., A new species of Caldoceras from Mozambique and Tanzania Table 1. The main morphological differences between Cladoceras subcapitatum (K.Schum. & K.Krause) Bremek. and C. rovumense I.Darbysh., J.E.Burrows & Q.Luke sp. nov. Character Cladoceras subcapitatum Cladoceras rovumense sp. nov. Habit Scandent shrub with some lateral branches modified to form ± recurved spines Free-standing tree or shrub, lacking modified spinose lateral branches Leaf shape and dimensions Elliptic to oblong-oblanceolate 3.5–12 × 0.9–4.8 cm Length / width ratio 1.85–4 : 1, usually >2 : 1 Obovate or obovate-elliptic 9–17.5 × 5.8–10.5 cm Length / width ratio 1.55–1.9 : 1 Leaf indumentum Glabrous Pubescent particularly on veins beneath and midrib above, becoming scabridulous at maturity Inflorescence position Borne on lateral branches with one or more pairs of leaves at least at flowering stage, sometimes caducous at fruiting Borne on leafless lateral branches Inflorescence form Subcapitate but usually with some clear branching, 9–15-flowered Dense, capitate, usually with branching suppressed, with 20+ flowers Calyx lobes Acute-triangular to -lanceolate, without toothed margin Rounded to broadly and convexly triangular, with an irregular, sometimes toothed margin Corolla tube length 25–35 mm (30–)38–42 mm Anther length 2–2.5 mm 2.6–3 mm Combined length of style + stigma 8–10 mm 17–19 mm Results On thorough examination of the available material of “Tarenna sp. 53” of Degreef (2006), we confirm that this is a previously undescribed species of Rubiaceae and that its closest ally in morphological terms is Cladoceras subcapitatum. It shares with this species in particular a similar floral morphology in which the corolla tube is much longer than the lobes and the stigma is included in the corolla tube and held well below the stamens. The fruit and seed morphology are also a close match for C. subcapitatum. However, the two species differ markedly in a number of easily observable characters including growth habit, leaf shape, size and indumentum, inflorescence form, shape of the calyx lobes and flower length (Table 1; Figs 1–2). Given the likelihood that the group of African species currently placed in Tarenna, to which C. subcapitatum is closely related, will probably be transferred to Cladoceras in the future, it is deemed most appropriate here to describe the new species from Mozambique in that latter genus, and so the name Cladoceras rovumense I.Darbysh., J.E.Burrows & Q.Luke sp. nov. is validated below. In addition, two new country records for Mozambique of globally threatened species restricted to the Rovuma CoE and previously known only from Tanzania are recorded here: Celosia patentiloba C.C.Towns. (Amaranthaceae Juss.) and Cordia fissistyla Vollesen (Boraginaceae Juss.). 49 European Journal of Taxonomy 833: 46–59 (2022) Taxonomic treatment Class Magnoliopsida Brongn. Order Gentianales Juss. ex Bercht. & J.Presl Family Rubiaceae Juss. Genus Cladoceras Bremek. Cladoceras rovumense I.Darbysh., J.E.Burrows & Q.Luke sp. nov. urn:lsid:ipni.org:names:77302733-1 Figs 1–3 Tarenna sp. 53 sensu Degreef, Opera Botanica Belgica 14: 143 (Degreef 2006); Timberlake et al., Plant Ecology and Evolution 144: 131 (Timberlake et al. 2011); Burrows et al., Trees and Shrubs Mozambique (Burrows et al. 2018); Darbyshire et al., Plant Ecology and Evolution 153: 441 (Darbyshire et al. 2020). 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 CoE in coastal southern Tanzania and northern Mozambique. Type MOZAMBIQUE • Cabo Delgado Prov., Quiterajo, Pt. 463; 11.7676° S, 40.3743° E; alt. 115 m; 24 Nov. 2009; Q. Luke 13883; holotype: K [K000787442]; isotypes: EA, LMA, MO, P. Paratypes MOZAMBIQUE • Cabo Delgado Prov., Mueda Plateau; 11°20ʹ S, 39°26ʹ E; alt. 760 m; 14 Dec. 2003; [W.R.]Q. Luke, O. Kibure & E. Nacamo 10116; EA, K, LMA, MO, UPS • Cabo Delgado Prov., Namacubi Forest (the Banana), west of Quiterajo; 11°45ʹ55ʺ S, 40°23ʹ45ʺ E; alt. 90 m; 25 Nov. 2008; J.E. & S.M. Burrows 10748; BNRH, K, LMA. TANZANIA • Lindi Region, Rondo Plateau, Rondo Forest Reserve; 10°07ʹ S, 39°13ʹ E; alt. 750 m; 6 Feb. 1991; S. Bidgood, R. Abdallah & K. Vollesen 1357; K (2 sheets), NHT. 50 DARBYSHIRE I. et al., A new species of Caldoceras from Mozambique and Tanzania Fig. 1. 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. 51 European Journal of Taxonomy 833: 46–59 (2022) Description Small, slender deciduous tree or shrub 1.5–7 m tall; young stems ± quadrangular, with papery maroonbrown bark that readily exfoliates in strips or patches, at first puberulous with ± patent hairs to 0.35 mm long but soon glabrescent. Stipules soon caducous, triangular, 3.7–7.5 mm long, with a thickened blackish-brown central portion and with paler, somewhat hyaline margins but these often infolded in dry material, glabrous externally, with long pale hairs internally. Leaves clustered towards ends of main and widely divergent lateral branches, ± immature at flowering, subsessile or on puberulent petiole to 7 mm long; blade of mature leaves obovate or obovate-elliptic, 9–17.5 × 5.8–10.5 cm (l/w ratio 1.55–1.9 : 1), base cuneate to somewhat attenuate or some leaves abruptly obtuse at base, apex shortly acuminate or (sub)attenuate, lateral veins 7–11 per side, these and the midrib prominent and often pale beneath, surfaces pubescent with hairs densest and longest on veins beneath and midrib above, conspicuous when young, becoming more sparsely hairy with maturity, the blade then scabridulous; minute pocketdomatia present in axils of lateral veins beneath but inconspicuous. Inflorescences terminating leafless lateral branches 11–28.5 cm long, flowers 20 or more, sessile, crowded in capitate corymbs with highly reduced and thickened branches; bracts subtending the main inflorescence branches maroon at least at apex, triangular with a slender apiculum, 3.2–4.5 × 3–4 mm, those subtending the flower clusters smaller, 1–2.5 mm long. Calyx tube (hypanthium) 1.9–2.7 mm long; calyx lobes pink- to maroon-tinged, rounded to broadly and convexly triangular, ± 1 mm long, with an irregular, sometimes toothed margin, glabrous or margins sparsely ciliate. Corolla white except for yellowish-green tube and central portion Fig. 2. Species of Cladoceras Bremek. in the field. A–B. Cladoceras rovumense I.Darbysh., J.E.Burrows & Q.Luke sp. nov. (photos: A. Q. Luke; B. P.A. Luke, Mozambique). C–D. Cladoceras subcapitatum (K.Schum. & K.Krause) Bremek. (photos: W.R.Q. Luke, Base Titanium nursery, Kwale County, Kenya). 52 DARBYSHIRE I. et al., A new species of Caldoceras from Mozambique and Tanzania of lobes externally, glabrous externally; tube narrowly cylindrical, (30–)38–42 × 1.5–2 mm, pilose with long wispy hairs internally mainly in distal half; lobes oblong-elliptic, 5–9 × 3.7–4.2 mm. Stamens with anthers subsessile, held at corolla mouth, 2.6–3 mm long. Ovary bilocular, placentae affixed centrally on septum; style and stigma together 17–19 mm long, glabrous, stigma ± linear, included within corolla tube. Fruit pale green, globose-obovoid, 6–8 mm in diameter, endocarp thin, glabrous, calyx persistent, usually 6–8 seeds per fruit (as few as 2 seeds per fruit reported by Degreef 2006); seeds orange-brown, 4–5 mm in diameter, hemispheric with a slightly angular lower side and a deep circular hilar excavation ca 1.5 mm in diameter, testa smooth and glossy. Distribution and habitat Restricted to the proposed Rovuma CoE, known from the Rondo Plateau of Southeast Tanzania and the Mueda Plateau and Namacubi Forest (Quiterajo) in northeast Mozambique (Fig. 3). Occurs in deciduous and semi-evergreen coastal and lowland dry forest and thicket on sandy soils, including areas of secondary woodland/thicket, at 90–760 m altitude. At Quiterajo, it was recorded from Guibourtia schliebenii (Harms) J.Léonard dominated dry forest with species of Memecylon L., Warneckea Gilg and Strynchnos L. common in the understorey (J.E. & S.M. Burrows 10748). The type specimen from the same site was found growing in close proximity to a number of rare and globally threatened species, i.e., Xylopia tenuipetala D.M.Johnson & Goyder (Q. Luke 13884), Vismianthus punctatus Mildbr. (Q. Luke 13885), Vismia pauciflora Milne-Redh. (Q. Luke 13886A) and Warneckea cordiformis R.D.Stone (Q. Luke 13887). On the Rondo Plateau, it was noted from within forest of Milicia excelsa (Welw.) C.C.Berg, Dialium L., Albizia Durazz., and Pteleopsis Engl. (= Terminalia L. according to some authorities). Fig. 3. Distribution of Cladoceras rovumense I.Darbysh., J.E.Burrows & Q.Luke sp. nov. 53 European Journal of Taxonomy 833: 46–59 (2022) Conservation status This species is known from three locations and has an extent of occurrence of 6601 km2 and a calculated area of occupancy of 16 km2. At Mueda Plateau, there has been an estimated loss of dense woodland and dry forest vegetation cover of over 96%, whilst in the Rio Messalo-Quiterajo area this figure is 71.2% (Timberlake et al. 2011). On the Rondo Plateau in Tanzania, 2755 ha of natural forest were cleared during the Rondo Forest Programme in 1952–1978 and replaced by commercial plantation of exotic tree species. Some clearance of natural forest for subsistence agriculture and for fuelwood collection is an ongoing threat at this site (Clarke 2001). However, a sizeable area of forest remains on the western slopes of the plateau, some of which has regenerated since the cessation of forestry. The gazetting of this site as a Nature Forest Reserve in 2016 may hopefully result in increased protection for the biodiversity there (Wabuyele et al. 2020). With only three locations and a continuing decline in the extent and quality of habitat at the majority of these sites, this species is provisionally assessed as Endangered – EN B2ab(iii). Additional new records for Mozambique Class Magnoliopsida Brongn. Order Caryophyllales Bercht. & J.Presl Family Amaranthaceae Juss. Genus Celosia L. Celosia patentiloba C.C.Towns. Hooker’s Icones Plantarum 38: 41, t. 3732 (Townsend 1975); Flora of Tropical East Africa: 13 (Townsend 1985). Type TANZANIA • Newala; alt. 670 m [2200 ft]; 9 Apr. 1959; W. Hay 61; holotype: K (2 sheets). Additional collection studied MOZAMBIQUE • Cabo Delgado Prov., Mueda District; 11°31.822ʹ S, 39°26.504ʹ E; alt. 947 m; 10 Sept. 2009; A. Banze 106; K, LMA. Distribution and habitat Restricted to the Rovuma CoE, known from the Maconde Plateau of Southeast Tanzania and the Mueda Plateau of northeast Mozambique. It occurs in partial or full shade in woodland including in degraded or disturbed areas, at ca 670–950 m a.s.l. elevation. Conservation status This species is currently assessed on the IUCN Red List as Critically Endangered – CR B2ab(iii) – and possibly extinct (Howard et al. 2020). Whilst the new record from the Mueda Plateau adds a second location, this species could be considered to be severely fragmented given that the two known subpopulations are over 65 km apart, whilst the dispersal potential of this species is likely to be very limited given that it is a small understorey herb. Recolonisation between these isolated subpopulations is, therefore, unlikely to occur. Further, there is very little intact wild habitats still present on both the Maconde and Mueda Plateaux which are highly degraded, with much conversion to agricultural land. At Mueda Plateau, for example, there has been an estimated loss of dense woodland and dry forest vegetation cover of over 96% (Timberlake et al. 2011). Whilst this species appears tolerant of some disturbance, it is unlikely to persist in farmlands. Furthermore, as noted by Howard et al. (2020), it is 54 DARBYSHIRE I. et al., A new species of Caldoceras from Mozambique and Tanzania possible that the Maconde subpopulation is no longer extant. Therefore, the assessment of CR B2ab(iii) is upheld here. Taxonomic notes Two collections from the Rondo Plateau in southeast Tanzania (G.P. Clarke 35; Q. Luke 12958; both K) are closely allied to this species but have markedly smaller perianth segments. These collections may represent a further species of Rovuma CoE endemic in Celosia or possibly a distinct variant of C. patentiloba. Further material is desirable to fully assess the extent of this variation. Class Magnoliopsida Brongn. Order Boraginales Bercht. & J.Presl Family Boraginaceae Juss. Genus Cordia L. Cordia fissistyla Vollesen Nordic Journal of Botany 1: 325 (Vollesen 1981). Type TANZANIA • Selous Game Reserve, 2 km NW of Kingupira; 8°28ʹ S, 38°33ʹ E; alt. 125 m; 9 May 1975; K. Vollesen in MRC 2283; holotype: C [C10000406]; isotypes EA, K [K000418662], WAG [WAG0003807]. Additional collection studied MOZAMBIQUE • Nampula Prov., Monapo; 14°59.023ʹ S, 40°31.516ʹ E; 18 Mar. 2009; E. Schmidt 4762; Herb. Ernst Schmidt. Distribution and habitat Restricted to the proposed Rovuma CoE, known from east-central Tanzania and from Monapo of northeast Mozambique. It occurs in areas of dense thicket including on termitaria, on edges of temporary water holes and edges of riverine thickets, on alkaline soils, at ca 40–125 m a.s.l. elevation. Conservation status This species is currently assessed on the IUCN Red List as Vulnerable – VU D2 – as it was previously known from a small range (Extent of Occurrence [EOO] = 366 km2) and only 2–3 locations within the Selous Game Reserve of Tanzania, and there were some plausible future threats from expansion of camps within the reserve (Beentje et al. 2020). Whilst large areas of the Selous Reserve remain intact, it was included by UNESCO (2021) as one of 52 World Heritage sites in danger, and its conservation outlook is listed as “critical” (IUCN World Heritage Outlook 2020). This is due to a number of recent and ongoing developments within the reserve, including the proposed Julius Nyerere Hydropower Project at Stiegler’s Gorge on the Rufiji River, current and potential future mineral resource exploitation and high levels of poaching of megafauna which may have an impact on the whole Selous ecosystem (IUCN World Heritage Outlook 2020). The new record from Mozambique extends the EOO of this species considerably, to ca 10 625 km2, and adds one further location. The area around Monapo and Naguema to the east is heavily populated, with extensive conversion of thicket vegetation to farmland, hence the Mozambique location is considered to be experiencing an ongoing threat. With a continuing decline in extent and quality of habitat and with fewer than five locations known, this species is provisionally reassessed as Endangered under criterion B – EN B2ab(iii). 55 European Journal of Taxonomy 833: 46–59 (2022) Taxonomic notes The single Mozambique collection is from ca 700 km to the south of the nearest previously known records in Tanzania and is in flower bud only, but it is an excellent match for smaller-leaved specimens of C. fissistyla (e.g., K. Vollesen 4493, Kingupira) and this is a very distinctive species with no close affinity (Verdcourt 1991). Please note that, other than the type specimen, we only cite the newly seen Mozambique collection in the "Additional collection studied" section here and do not cite the other Tanzanian collections we have seen. Discussion The description of Cladoceras rovumense sp. nov. doubles the size of the genus Cladoceras as it is currently circumscribed, although it is likely to expand further in the future once the African clades of Tarenna s. lat. are fully resolved. This new species also broadens the concept of Cladoceras to include free-standing shrubs and small trees with unmodified branches as well as scandent shrubs with modified climbing branches. As noted by De Block et al. (2015), whilst it is apparent that the name Tarenna should no longer be applied to continental African species, the delimitation of genera within continental African Pavetteae requires further molecular phylogenetic study. Degreef (2006) did not propose an infrageneric classification for Tarenna, but did provide notes on potential affinities between continental African species based upon a range of morphological characters. This should help guide a sampling strategy for an expanded phylogenetic study, but ultimately it may require most or all of the continental African species, together with the two species of Cladoceras now recognised, to be included in order to circumscribe discrete taxa and enable the identification of diagnostic traits. Given the close relationship between continental African Tarenna and Pavetta, as revealed by De Block et al. (2015), it would be important to also include an enlarged sample of that genus in any future phylogenetic study. To improve support for finerscale relationships, it would be favourable to use Next Generation Sequencing techniques for such a study; one option would be to use the universal Angiosperm 353 probe set for targeted sequencing of nuclear genes, as employed in a recent order-wide study of the Gentianales where relationships were resolved with strong support (Antonelli et al. 2021). However, the current authors contend that whilst it is ultimately desirable to refine generic delimitation, both in this specific case and more generally across angiosperms, this should not detract from the urgent need to describe range-restricted and potentially threatened species that are new to science, even where there are uncertainties of generic placement. In such cases, formal description of the species can provide much-needed attention and encourage conservation action where it is most urgently required. In the current study, the documentation of the new species and the new records of Rovuma CoE endemic species from Mozambique will contribute to the documentation of Important Plant Areas (IPAs) in that country (Darbyshire et al. 2019; Tropical Important Plant Areas (TIPAs) in Mozambique). Both of the known sites for Cladoceras rovumense sp. nov. in Mozambique – Quiterajo and the Mueda Plateau, the latter also being the single known extant site for Celosia patentiloba – are currently being designated as IPAs based on the criteria of Darbyshire et al. (2017). Indeed, Quiterajo qualifies as an IPA under all three of the criteria, i.e., the presence of threatened species, threatened habitats and exceptional botanical richness, and it is known to contain amongst the highest numbers of rare and threatened species in Mozambique. 56 DARBYSHIRE I. et al., A new species of Caldoceras from Mozambique and Tanzania Acknowledgements The authors wish to thank Andrew Brown for providing the illustration of the new species, and Patricia Luke for permitting us to use her photograph from the field. 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The IUCN Red List of Threatened Species 2020: e.T158188A765731. https://doi.org/10.2305/IUCN.UK.2020-2.RLTS.T158188A765731.en Manuscript received: 13 September 2021 Manuscript accepted: 18 January 2022 Published on: 29 July 2022 Topic editor: Frederik Leliaert Desk editor: Connie Baak Printed versions of all papers are also deposited in the libraries of the institutes that are members of the EJT consortium: Muséum national d’histoire naturelle, Paris, France; Meise Botanic Garden, Belgium; Royal Museum for Central Africa, Tervuren, Belgium; Royal Belgian Institute of Natural Sciences, Brussels, Belgium; Natural History Museum of Denmark, Copenhagen, Denmark; Naturalis Biodiversity Center, Leiden, the Netherlands; Museo Nacional de Ciencias Naturales-CSIC, Madrid, Spain; Real Jardín Botánico de Madrid CSIC, Spain; Leibniz Institute for the Analysis of Biodiversity Change, Bonn – Hamburg, Germany; National Museum, Prague, Czech Republic. 59