Uvariodendron dzomboense Dagallier, W.R.Q. Luke & Couvreur, 2021

Dagallier, Leo-Paul M. J., Mbago, Frank M., Luke, W. R. Quentin & Couvreur, Thomas L. P., 2021, Three new species of Uvariodendron (Annonaceae) from coastal East Africa in Kenya and Tanzania, PhytoKeys 174, pp. 107-126 : 107

Uvariodendron dzomboense Dagallier, W.R.Q. Luke & Couvreur sp. nov. Fig. 3

Type.

Kenya - Coast • S. A. Robertson et al. Mrima Dzombo Expedition 207 (holotype: K, isotypes: EA, MO, WAG), Kaya Dzombo Hill; 4°25'48"S, 39°12'36"E; alt. 300 m; 07 Feb. 1989 .

Diagnosis.

This species differs from other Uvariodendron species by its 50-75 carpels that are densely pubescent and its leaves smaller than 150 mm in length and narrowly elliptic to elliptic. It differs from U. kirkii by its smaller leaves (132 mm maximum versus 210 mm maximum) and higher number of carpels (50-75 versus 7-20) (Table 1 ).

Description.

Tree 4-7 m tall, d.b.h. unknown, young branches sparsely pubescent to glabrous, old branches glabrous. Leaf bud ‘eragrostiform’, composed of 5, distichous, longitudinally folded, velutinous scales. Leaves distichous, simple, entire, pinnately veined. Petiole 3-4 mm long, 1-1.5 mm in diameter, slightly pubescent to glabrous. Lamina 65-132 mm long, 20-45 mm wide, length:width ratio 2.9-3.6, narrowly elliptic to elliptic, coriaceous, apex attenuate, base acute to slightly decurrent, above glabrous, below glabrous when young and old; midrib sunken above, raised below, above glabrous when young and old, below slightly pubescent to glabrous when young, glabrous when old; secondary veins 12-13 pairs, weak brochidodromous; tertiary veins reticulate. Inflorescence borne on trunk or old branches, 1-flowered. Flowering pedicel 8-30 mm long, 2-2.5 mm in diameter, densely pubescent. Flowers actinomorphic, hermaphroditic, buds spherical 4-4.5 mm in diameter, sparsely pubescent. Bracts 6 at base of the pedicel in flower bud, 1 on mature flower in the lower half of the pedicel, 5-6 mm long, 5-8 mm wide, pubescent to shortly pubescent outside, glabrous inside. Sepals 3, 5- 7 mm long, 4.5-7 mm wide, fused at base, pubescent to shortly pubescent outside, glabrous inside. Outer petals 3, ca. 16 mm long, ca. 9 mm wide, shortly velutinous outside, glabrous inside, color unknown. Inner petals 3, ca. 18 mm long, 8 mm wide, shortly velutinous outside, glabrous inside, color unknown. Stamens more than 700, 2 mm long, 0.5 mm wide, anthers linear, connective truncate. Carpels 50-75, ca. 2 mm long, ca. 1-1.5 mm wide, densely pubescent. Stigma not seen. Fruiting pedicel ca. 14 mm long, ca. 4 mm in diameter, pubescent. Monocarps (unripe?) ca. 35, ca. 15 mm long, ca. 10 mm wide, length:width ratio ca. 1.5, ovoid, sessile, densely pubescent, golden brown. Seeds (unripe?) ca. 5 per monocarp, uniseriate, ca. 4.5 mm long, ca. 1 mm wide, glabrous.

Distribution.

Endemic to Kenya, only known from Dzombo Hill (Kaya Dzombo) (Fig. 2 ).

Habitat.

Moist semi-deciduous forest on igneous intrusion.

Conservation status.

This species is known from five collections from a single location. Literature found on the Dzombo Hill forest reports a surface of 2.95 km 2 ( Critical Ecosystem Partnership Fund 2005). We calculated a surface of 5.31 km 2 for the forested part of the hill (see Material and Methods for details). EOO and AOO are thus estimated at less than 5.40 km 2. The Kaya Dzombo forest is gazetted as a sacred forest under the National Museums protection as a National Monument. However, the forest suffers from local logging for timber, poles and firewood, and has been impacted by fire on several occasions ( W. R. Q. Luke, personal observations). Following IUCN criterion B ( IUCN 2012), Uvariodendron dzomboense is therefore assigned a preliminary status of Endangered EN B 1ab(iii)+2ab(iii).

Etymology.

The specific epithet comes from the Dzombo Hill where the species is endemic.

Paratypes.

Kenya - Coast • W. R. Q. Luke 1654 ( EA ( EA000008806 ), K); Kwale District, Dzombo Forest Reserve ; 4°25'48"S, 39°12'36"E; alt. 270 m; 06 Jan. 1989 . • W. R. Q. Luke et al. 2884 ( EA, K); Kwale District, Dzombo Forest Reserve ; 4°25'48"S, 39°12'36"E; alt. 270 m; 04 Oct. 1991 . • W. R. Q. Luke et al. 3370 ( EA); Kwale District, Dzombo Forest Reserve ; 4°25'48"S, 39°12'36"E; alt. 270 m; 12 Nov. 1992 . • W. R. Q. Luke & M. Pakia 7443 ( K, EA ( EA000008810 )); Kwale District, Dzombo ; 4°25'48"S, 39°12'36"E; alt. 270 m; 28 Jun. 2001 .

Discussion.

This species is known as " Uvariodendron sp. nov. 1 of CFS " in the annotated checklist of the coastal forests of Kenya ( Ngumbau et al. 2020).

The only fruit known from this species (Robertson S. A. et al. MDE 207) presents ca. 35 ovoid monocarps. These are densely pubescent and have small seeds compared to other Uvariodendron species (4.5 mm long vs. 8-20 mm long). However, it is unclear whether this observed fruit is ripe or not. Further collections could bring more information. This species also presents an ‘eragrostiform’ leaf-bud (see discussion of Uvariodendron schmidtii below).

During a field trip in Tanzania in November 2019, we explored the forest of Kilulu hill (TANZANIA- Tanga, 4°46'22"S, 39°07'30"E, see Fig. 2 ). Kilulu hill is ca. 40 kilometers as the crow flies south from Dzombo hill were U. dzomboense occurs. We expected to find U. dzomboense there but our quest on every slope of the hill was unsuccessful. This indicates that the dispersal distance of U. dzomboense might be very short .

Figures

Figure 2. Map of the distribution of the three new Uvariodendron species. Protected areas are represented in grey shades (see Material and Methods for details). The red cross indicates Kilulu hill, where Uvariodendron dzomboense was expected to occur but was not found.

Figure 3. Uvariodendron dzomboense A young branch with leaves B petiole and young branch detail C, D young fruit: C apical view D from the side E-G old flower: E entire on trunk F from top with details of ovaries G close-up. ip inner petal, mo monocarp, ov ovary, se sepal, sts stamen scars. Photos by L. - P. M. J. Dagallier from the specimens W. R. Q. Luke 1654 (F, G), W. R. Q. Luke 7443 (B) and S. A. Robertson MDE 207 (A, C, D, F). Scale bars: 10 mm unless stated.