Homalium coriaceum Jongkind, 2023

Jongkind, Carel C. H., 2023, Homalium coriaceum Jongkind, sp. nov. (Salicaceae): a new and Critically Endangered tree from Liberia, Adansonia (3) 45 (15), pp. 273-277 : 274-277

Homalium coriaceum Jongkind , sp. nov.

( Figs 1 ; 2 )

Homalium littorale Sleumer ined. on Voorhoeve 266 (WAG).

Homalium coriaceum Jongkind , sp. nov. resembles H. longistylum Mast. and H. smythei Hutch. & Dalziel by its almost glabrous leaves with cuneate leaf bases. It differs from both by its smaller leaves, from H. longistylum by its branched and not simple inflorescence, and from H. smythei by its disk-glands that are densely pubescent and not glabrous.

KEY TO THE SPECIES OF HOMaliUM IN LIBERIA

1. Stamens with 2 or 3 together by each petal; leaves up to 4 cm wide; petals up to 5 mm long; in Liberia only known from river side near Greenville ........................................................................... H. angustifolium Sm.

— Stamens solitary by each petal; leaves often exceeding 4 cm wide; petals often longer than 5 mm ................ 2

2. Inflorescence axillary or sub-terminal, simple; leaf base cuneate, leaf blade glabrous or only with hairs on and near the midrib below .................................................................................................... H. longistylum Mast.

— Inflorescence branched, mostly terminal; leaf base cuneate or not, leaf blade hairy below or not ................. 3

3. Leaf base cuneate, 4-7(-9) pairs of secondary veins, leaf almost glabrous ..................................................... 4

— Leaf base obtuse to cordate/auriculate, often with more pairs of secondary veins, glabrous to clearly hairy ......... 5

4. Leaves 3.5-8 × 1.5-3.5 cm; disk-glands between stamens densely hairy .......... H. coriaceum Jongkind , sp. nov.

— Leaves 6-18 × 3-10 cm; disk-glands between stamens glabrous .......................... H. smythei Hutch. & Dalziel

5. Petals hardly accrescent, up to 4 mm long; flowers in dense compact clusters along the inflorescence axes; leaf blade densely short pilose below to glabrous ....................................... Homalium africanum (Hook.f.) Benth.

— Petals clearly accrescent and longer; flowers usually more spaced, often with two together; leaf blade glabrous or hairy below but never densely short pilose ............................................................................................... 6

6. Leaf base widely cordate to auriculate; blade (almost) glabrous and 12 - 30 cm long; secondary veins near leaf base not closer together than those far from the base ......................................................... H. le-testui Pellegr.

— Leaf base obtuse or slightly cordate; blade often smaller and often clearly hairy; secondary veins near leaf base often closer together than those far from base .............................................................................................. 7

7. Leaf blade densely tomentellous all over the lower surface ....................................... H. lastoursvillense Pellegr.

— Leaf blade with only a few hairs between the nerves on the lower surface ............ H. stipulaceum Welw. ex Mast.

TYPUS. — Liberia. Grand Bassa County, Buchanan , dans la forêt côtière près de mangrove, fl., 3.V.1973, J-G Adam 27392 (holo-, BR[BR0000015978936]; iso-, L[L.2465627], WAG[WAG0295160]) .

PARATYPES. — Liberia. Grand Bassa County, Goe Range , 6°162’N, 10°172’W, 100 m alt., ster., 10.V.2022, Jongkind 14529 (BR, P, WAG) ; Montserrado County, Monrovia, Arboretum Paynesville , fl., 29.IV.1969, Voorhoeve 266 (WAG) .

DISTRIBUTION AND ECOLOGY. — Liberia, between Monrovia and Buchanan in patches of forest in coastal savannah and in closed forest on nearby hills.

CONSERVATION STATUS. — On base of the three specimens cited here the EOO of H. coriaceum sp. nov. is 761 km 2 and the AOO is 12 km 2 (based on a cell width of 2 km), both count as “Endangered” (EN). However, the new species is found in a part of Liberia that is quickly becoming more densely populated and around the original location of the two oldest specimens there is today not much original vegetation left anymore. From “Arboretum Paynesville” (Voorhoeve 266) there is no trace left, this area is part of Monrovia now, and Buchanan is not a village anymore but a town with a large harbour area where the iron ore from Nimba County arrives by train. At the site where H. coriaceum sp. nov. is most recently seen, the Goe Range , many of the larger trees have been cut down in recent years and the ridge is part of a mining concession. From the three cited location there is today only one left and that one is threatened. The species is therefore provisionally assessed as “Critically Endangered”, CR B1ab(i, iii)+2ab(ii, iii, iv, v) using the IUCN 2012 standard.

DESCRIPTION

Medium size tree to 30 cm dbh; bark shallowly fissured, below the surface with pale orange-brown streaks; twigs glabrous. Leaves alternate, glabrous except for the hairy domatia; blade almost elliptic, 3.5-8 × 1.5-3.5 cm, coriaceous; margin crenulate; base attenuate; apex acuminate; 4-6 pairs of secondary veins, tertiary nervation conspicuously reticulate below, less so above; domatia visible at upper leaf surface as small bumps; petiole 7-12 mm long, slightly winged; stipules early caducous. Inflorescence a laxly branched panicle, up to 12 cm long, axis puberulous; dropping flowers leaving c. 1 mm long pegs on the inflorescence axis. Flowers bisexual, 6-7-merous; sepals oblong-lanceolate, c. 1 mm long; calyx cup 2 mm high, pubescent; petals spathulate, up to 8 × 3 mm, appressedpubescent on both sides; stamens solitary by each petal; filaments c. 3 mm long, with erect hairs on the lower half; anthers broadly ellipsoid, 0.25 mm, 2-celled; disk-glands between stamens velutinous; styles 6-7, c. 3 mm long, for the larger part united, pubescent; ovary semi-inferior.

NOTES

The most recent collection of the new species shows that it not only grows in the coastal savannah, where the first two specimens were found, but also in the closed forest on the hills slightly more inland. In this it differs from several other species endemic to this coastal area, like Dinklageodoxa scandens Heine & Sandwith , Englerodendron libassum Jongkind & Breteler , Eugenia liberiana Amshoff , Fegimanra acuminatissima Keay and Trichoscypha laxissima Breteler , because these are only known from the coastal savannah on old beach sand ( Jongkind & Breteler 2020).

In most African Homalium species the petals are accrescent and act like small wings for the fruits, the maximum size of these petals is often characteristic for a species. The petals usually start to expand very quickly after the flower opens and the other flower parts are persistent in fruit, this makes it hard to see what is still a flower and what is a fruit.

Figures

FIG. 1. — Homalium coriaceum Jongkind, sp. nov.; A, shoot; B, leaves, with domatia visible as small bumps; C, bark; D, flowers. A-C, Jongkind 14529; D, J-G Adam 27392. Photos C. Jongkind. Scale bar: D, 1 cm.

FIG. 2. — Homalium coriaceum Jongkind,sp.nov.;holotype BR0000015978936.Photo Botanic Garden Meise.