Calycosiphonia albertina Ntore & Robbr., 2024

Ntore, Salvator, Nkengurutse, Jacques, Backer, Sander De, Sonké, Bonaventure, Block, Petra De, Janssens, Steven B., Verstraete, Brecht & Robbrecht, Elmar, 2024, Calycosiphonia or Kupeantha (Coffeeae, Rubiaceae)? A morphological and molecular study of a new species from the Albertine Rift, European Journal of Taxonomy 935, pp. 1-28 : 19-22

Calycosiphonia albertina Ntore & Robbr. sp. nov.

urn:lsid:ipni.org:names:77340650-1

Figs 1–3 , 4A–B

Diagnosis

A member of the tribe Coffeeae because of its axillary inflorescences, paired at the nodes, its contorted corolla aestivation, and its ovules impressed in fleshy placentas attached to the middle of the septum. In that tribe belonging to the Argocoffeopsis-Calycosiphonia clade for its plano-convex seeds (mostly two per fruit) with rudimentary seed coat. Peculiar in the reddish brown suberisation of the bark and the plagiotropous branches with numerous nodes having reduced to scaly leaves besides nodes with normal leaves. Belonging to Calycosiphonia as indicated by nuclear DNA data, and readily distinguished from C. macrochlamys and C. spathicalyx by the non-septate anthers with narrow connective that are reminiscent of Kupeantha .

Etymology

The epithet ʻ albertina ʼ refers to the Albertine Rift in which the species is found.

Type material

BURUNDI • Rugazi, Ruce, P.N. de la Kibira ; 03°12′06.2″ S, 29°31′43.8″ E; 2004 m a.s.l.; 19 Jul. 2022; Ntore et al. 14; holotype: BR [ BR0000026554747V ]; isotypes: BJA, BR [ BR0000027462416V ], MO, P, K, YA .

Other material examined

BURUNDI • Bubanza, Rugazi, Ruce , Musezero , Parc national de la Kibira ; 03°11′39.5″ S, 29°32′12.8″ E; 2205 m a.s.l.; 2 Oct. 2019; Nkengurutse 6; BJA, BR [ BR0000025464368V ] • Bubanza, Rugazi, Ruce , Musezero , Parc national de la Kibira ; 03°11′45″ S, 29°31′53″ E; 2070 m a.s.l.; 2 Oct. 2019; Nkengurutse 8; BJA, BR [ BR0000025464382V ] • Rugazi, Ruce , P.N. de la Kibira ; 03°12′04.8″ S, 29°31′42.3″ E; 2001 m a.s.l.; 8 Jun. 2022; Nkengurutse 130; BJA, BR [ BR0000027462409V ] • Rugazi, Ruce , P.N. de la Kibira ; 03°12′04.8″ S, 29°31′42.3″ E; 2001 m a.s.l.; 8 Jun. 2022; Nkengurutse 131; BJA, BR [ BR0000027462430V ] • Rugazi, Ruce , P.N. de la Kibira ; 03°12′04.6″ S, 29°31′41.36″ E; 2000 m a.s.l.; 8 Jun. 2022; Nkengurutse 132; BJA, BR [ BR0000027462508V ] • Rugazi, Ruce , P.N. de la Kibira ; 03°12′05″ S, 29°31′42.3″ E; 2005 m a.s.l.; 8 Jun. 2022; Nkengurutse 133; BJA, BR [ BR0000027462423V ] • Rugazi, Ruce , P.N. de la Kibira ; 03°12′05.2″ S, 29°31′42.5″ E; 2004 m a.s.l.; 8 Jun. 2022; Nkengurutse 134; BJA, BR [ BR0000027462324V ] • Rugazi, Ruce , P.N. de la Kibira ; 03°12′06.1″ S, 29°31′43.6″ E; 2009 m a.s.l.; 8 Jun. 2022; Nkengurutse 135; BJA, BR [ BR0000027462331V ] • Rugazi, Ruce , P.N. de la Kibira ; 03°12′06.7″ S, 29°31′43.4″ E; 2011 m a.s.l.; 8 Jun. 2022; Nkengurutse 136; BJA, BR [ BR0000027450451V ] • Rugazi, Ruce , P.N. de la Kibira ; 03°12′06.5″ S, 29°31′43.7″ E; 1997 m a.s.l.; 8 Jun. 2022; Nkengurutse 137; BJA, BR [ BR0000027462317V ] • Rugazi, Ruce , P.N. de la Kibira ; 03°12′06.6″ S, 29°31′44″ E; 1997 m a.s.l.; 8 Jun. 2022; Nkengurutse 138; BJA, BR [ BR0000027462300V ] • Rugazi, Ruce , P.N. de la Kibira ; 03°12′06.3″ S, 29°31′44.4″ E; 1990 m a.s.l.; 8 Jun. 2022; Nkengurutse 139; BJA, BR [ BR0000027450413V ] • Parc national de la Kibira , à env. 8 km de Teza , versant ouest, le long d’un sentier menant vers Bubanza (non loin de la lisière); 03°12′06″ S, 29°31′45″ E; 2008 m a.s.l.; 19 Jul. 2014; Ntore 700; BR [ BR0000013563493 , BR0000013563615 ], LG • Parc national de la Kibira , à env. 8 km de Teza , versant ouest, le long d’un sentier menant vers Bubanza (non loin de la lisière); 03°12′06″ S, 29°31′45″ E; 2008 m a.s.l.; 19 Jul. 2014; Ntore 701; BR [ BR0000013563653 ], LG, MO, P • Parc national de la Kibira , 8 km ouest de Teza , versant ouest, le long du sentier menant vers Bubanza (non loin de la lisière); 03°12′06″ S, 29°31′45″ E; 2008 m a.s.l.; 19 Jul. 2014; Ntore 702; BJA, BR [ BR0000013563479 ] • Parc national de la Kibira , à env. 8 km de Teza , versant ouest, le long du sentier menant vers Bubanza (non loin de la lisière); 03°12′06″ S, 29°31′45″ E; 2008 m a.s.l.; 19 Jul. 2014; Ntore 703; BJA, BR [ BR0000013563486 ] • Parc national de la Kibira , à env. 8 km de Teza , versant ouest, le long du sentier menant vers Bubanza (non loin de la lisière); 03°12′06″ S, 29°31′45″ E; 2008 m a.s.l.; 19 Jul. 2014; Ntore 704; BJA, BR [ BR0000013563462 , BR0000013563622 ] • Ruce, Parc national de la Kibira ; 03°12′06″ S, 29°31′45″ E; 2004 m a.s.l.; 4 Jul. 2023; Ntore & Bukuru 1212; BJA, BR [ BR0000026650685V , BR0000026650692V ] • Ruce, Parc national de la Kibira ; 03°12′06″ S, 29°31′45″ E; 2004 m a.s.l.; 4 Jul. 2023; Ntore & Bukuru 1213; BJA, BR [ BR0000026650722V , BR0000026650739V ] • Ruce, Parc national de la Kibira ; 03°12′06″ S, 29°31′45″ E; 2004 m a.s.l.; 4 Jul. 2023; Ntore & Bukuru 1214; BJA, BR [ BR0000026650708V , BR0000026650715V ] • Rugazi, Ruce , P.N. de la Kibira ; 03°12′06″ S, 29°31′45″ E; 2008 m a.s.l.; 19 Jul. 2022; Ntore et al. 8; BJA, BR [ BR0000027450475V ], K, P • Rugazi, Ruce , P.N. de la Kibira ; 03°12′06″ S, 29°31′45″ E; 2008 m a.s.l.; 19 Jul. 2022; Ntore et al. 9; BJA, BR [ BR0000027467633V ], S • Rugazi, Ruce , P.N. de la Kibira ; 03°12′06.4″ S, 29°31′45″ E; 2008 m a.s.l.; 19 Jul. 2022; Ntore et al. 11; BJA, BR [ BR0000027467688V ], MO, P • Rugazi, Ruce , P.N. de la Kibira ; 03°12′06.4″ S, 29°31′45″ E; 2008 m a.s.l.; 19 Jul. 2022; Ntore et al. 12; BJA, BR [ BR0000027467756V ], L • Rugazi, Ruce , P.N. de la Kibira ; 03°12′06.2″ S, 29°31′43.8″ E; 2004 m a.s.l.; 19 Jul. 2022; Ntore et al. 13; BJA, BR [ BR0000027468609V , BR0000027468784V ], BRLU, G • Rugazi, Ruce , P.N. de la Kibira ; 03°12′06.2″ S, 29°31′43.8″ E; 2004 m a.s.l.; 19 Jul. 2022; Ntore et al. 15; BJA, BR [ BR0000027468791V , BR0000026554761V ], C, E, EA, YA • Rugazi, Ruce , P.N. de la Kibira ; 03°12′06.2″ S, 29°31′43.8″ E; 2004 m a.s.l.; 19 Jul. 2022; Ntore et al. 16; BJA, BR [ BR0000026554365V ] • [ Bururi Forest Nature Reserve ], forest gallery of the Sikuvyaye W of the road Mutambara – Bururi; [03°58′07.2″ S, 29°36′00.8″ E]; [1828 m]; 19 Sep. 1974; Rammeloo 4672; BR [ BR0000008651358 ], GENT .

RWANDA • Préfecture de Cyangungu, Commune de Busozo , Forêt de Busoro , sous-bois de forêt à Cleistanthus polystachyus , Diospyros gabunensis au sommet de la montagne; 02°34′5.0448″ S, 29°14′27.402″ E; 1740 m a.s.l.; 2 Jul. 1999; Ewango 2087; BR [ BR0000009717664 ], GIS, M, MO • Préfecture de Cyangungu, Commune de Busozo , Bweyeye , Forêt de Uruvirevire , sous-bois de la forêt à Chrysophyllum rwandense ; 02°34′26.7384″ S, 29°12′ 43.7256″ E; 1740 m a.s.l.; 9 Jul. 1999; Ewango 2108; BR [ BR0000009698956 ], GIS, M, MO, WAG.

Description

Shrub 1.5–4 m tall, with the habit of Coffea , often drying blackish in herbarium; branches first glossy and vivid green, soon becoming reddish brown, corky (colours as seen in vivo; brown when dried); bark of older stems greyish brown, fissured; vegetative parts glabrous, except for the domatia; plagiotropous stems with microphyllous nodes in between nodes with normal leaves; internodes below microphyllous nodes shortened to almost reduced. Leaves with petioles 5–9 mm long; blades elliptic to obovate, 9–16 × 4–6 cm, with cuneate base and an apical acumen 10–15 mm long; (4–)6–7 pairs of lateral nerves; sparsely hairy domatia, with the hairs perpendicular to the main or lateral nerve; leaves of microphyllous nodes often with rounded base, (20–)40–90% smaller than normal leaves or even reduced to minute scales. Stipules sheathing, triangular, ca 1 mm long, bearing a central awn 1–2 mm long, inside hairy, rapidly deteriorating and becoming corky. Inflorescences 1-florous, often appearing 2–3-florous (2 or 3 coaxillar 1-florous inflorescences); peduncle 0–2 mm long; bracts and bracteoles fused into 2–4 calyculi per flower, with 2 triangular stipular parts and 2 foliar appendages, the foliar appendices leafy on the upper calyculus, scale-like on the lower ones; inside of the calyculi covered with curled hairs and bearing colleters at the base. Flowers 5–6-merous, sessile; calyx shortly tubular, ca 1 mm long, truncate at margin; corolla white, glabrous inside and outside, with a tube 5 mm long, shorter than the lobes of 6–7 × 3 mm; style ca 6 mm long, topped by 2 massive stigmatic arms of almost the same length; ovary 2-locular, with in each cell a peltate placenta bearing 1 embedded ovule; stamens inframedifixed, with filaments 1 mm long and inserted at the throat; anthers ca 5 mm long, exserted, blunt at apex; thecae without transverse septa; connective as wide as the thecae. Fruits fleshy, ellipsoidal, ca 15 × 12 × 12 mm, vivid red, glabrous, 2-locular, crowned by the nectary disc surrounded by the slightly accrescent calyx. Seeds hemi-ellipsoidal, ca 12 × 10 × 10 mm, one in each locule, without placental outgrowth around the seeds, flat at the adaxial side (less so in case of abortion of the ovule in the second locule) and convex at the abaxial side; seed coat rudimentary; embryo straight, with short cotyledons and long inferior radicle.

Distribution

The species has been collected in western Burundi and southwestern Rwanda ( Fig. 5 ). Photographs of the species were taken in September 2021 in Kahuzi-Biega National Park, Mulolo 2 (or Idunga) village, South Kivu province in eastern Democratic Republic of the Congo (approximate coordinates: 02°21′37″ S, 28°21′52″ E) (Supp. file 7).

Habitat and ecology

The species grows in the understorey of wet ombrophilous montane or gallery forest, at an elevation of 1740–2205 m (the occurrence in DR Congo is at ± 1438 m). The label of the specimen Ewango 2108 mentions that the plant occurs in the understorey of Chrysophyllum rwandense Troupin forest, while the specimen Ewango 2087 occurs in the understorey of a forest with Cleistanthus polystachyus Hook.f. ex Planch. and Diospyros gabunensis Gürke. The specimens Nkengurutse 6, 8 occur in the understorey of ombrophilous forest of Xymalos monospora (Harv.) Baill. , while the specimens Ntore & Bukuru 1212, 1213, 1214 are found in a forest dominated by Syzygium guineense subsp. parvifolium (Engl.) F.White.

Phenology

Most specimens were collected in June and July and have both flowers and fruits. This is also the case for a single alcohol collection (Bukuru 01, BR) made in April 2023. Two specimens were collected in September: Rammeloo 4672 has fruits and mentions white flowers on the label; Dumbo s.n. (photograph) has fruits. The two specimens collected in October (Nkengurutse 6, 8) bear fruits. The labels of Ntore & Bukuru 1212, 1213, 1214 mention that the species flowers year-round.

Vernacular names

In Kirundi, the species is known as ikawa, ikawakawa, ikawa y’ishamba, or umukawakawa, which means coffee, wild coffee, or similar to coffee.

Preliminary IUCN conservation assessment

The extent of occurrence (EOO) is estimated at 8313 km 2, which falls within the range of the Vulnerable category under subcriterion B1. The area of occupancy (AOO) is estimated at 28 km 2, which falls within the range of the Endangered category under subcriterion B2. The species occurs at four locations that all lie inside nominally protected areas: the Kibira National Park and the Bururi Forest Nature Reserve in Burundi, the Nyungwe National Park in Rwanda, and the Kahuzi-Biega National Park in Democratic Republic of the Congo. In the single location in Kibira National Park, we observed a large subpopulation and no obvious threats were noticed. The single location in Bururi Forest Nature Reserve is within a wellprotected area and no threats to the subpopulation could be perceived. The single location in Nyungwe National Park occurs in a well-managed park and therefore no threats to the subpopulation were observed. The single location in the Kahuzi-Biega National Park (Mulolo 2) in DR Congo is nominally within a protected area but the forest is heavily used by the local people and this could pose a threat to the species ( Aveling 2010; UNESCO 2021). However, apart from the decline in quality habitat in this area, the species seems generally safe. It is conserved ex situ at the University of Burundi. In summary, Calycosiphonia albertina sp. nov. is preliminary assessed as Endangered B2ab(iii).

Figures

Fig. 1. Calycosiphonia albertina Ntore & Robbr. sp. nov. A. Habitat. B. Habit. C. Reddish brown bark of older branches. D. Microphyllous node. E. Flowering node. F. Fruiting node, lateral view of red fruits. G. Fruiting node, apical view of red fruits. Photographs by Salvator Ntore from the subpopulation in Kibira forest, Burundi.

Fig. 2. Calycosiphonia albertina Ntore & Robbr. sp. nov. A. Root system of a young individual.B. Greyish brown bark of an older stem. C. Anisophyllous node. D. Reduced leaves on the main axis. Photographs by Salvator Ntore from the subpopulation in Kibira forest, Burundi.

Fig. 3. Calycosiphonia albertina Ntore & Robbr. sp. nov. A. Plagiotropous branch with flowers, flower buds, and young fruits. B. Underside of a leaf with two sparse tuft domatia. C. Node with stipule and a 1-florous inflorescence (the dashed line shows the position of the removed second inflorescence. D. Base of flower showing calyculi enfolding each other and the ovary; the calyx is visible. E. Ovary and calyx (uppermost detail) and three calyculi separated from each other.F. Longitudinally opened upper calyculus from E, showing inside covered with fine curled hairs and some colleters at the base. G. Longitudinal section of ovary and calyx.H. Style and stigma. I. Adaxial view of placenta. J. Abaxial view of placenta. K. Side and frontal views of stamen. L. Transverse section of an anther. M. Fruit and seed. N. Transverse and longitudinal section of seed, showing the position of the embryo. O. Embryo. A from Nkengurutse 136; B–L from Ntore et al. 16; M–O from Ntore et al. 15. Scale bars: A = 5 cm; B–C, K = 2 mm; D–F, H, M–O = 3 mm; G, I–J, L = 1 mm. Drawn by Elmar Robbrecht.

Fig. 4. Scanning electron micrographs of pollen grains. A–B. Calycosiphonia albertina Ntore & Robbr. sp. nov. (from Nkengurutse 130). C–D. Kupeantha spathulata (A.P.Davis & Sonké) Cheek (from Sonké 4117). E–F. Argocoffeopsis rupestris subsp. rupestris (Hiern) Robbr. (from Essou 1472). A, C, E = equatorial views; B, D, F = mesocolpia. Scale bars = 1 μm.

Fig. 5. Distribution of Calycosiphonia albertina Ntore & Robbr. sp. nov. in western Burundi, southern Rwanda, and eastern DR Congo.