Sabicea mildbraedii Wernham (1914: 53)

Zemagho, Lise A., Liede-Schumann, Sigrid, Lachenaud, Olivier, Dessein, Steven & Sonke, Bonaventure, 2017, Taxonomic revision of Sabicea subgenus Anisophyllae (Ixoroideae, Rubiaceae) from Tropical Africa, with four new species, Phytotaxa 293 (1), pp. 448-450 : 448-450

10. Sabicea mildbraedii Wernham (1914: 53)

Pseudosabicea mildbraedii (Wernham) N. Hallé (1963: 170) .

Lectotype (designated here):— DR CONGO. Kimuenza , April 1900, J. Gillet 775 ( BR [ BR0000013663407 ]!).

Creeping, often +/- trailing herb, 20–60 (–100) cm tall; main stems decumbent, lateral stems usually ascending and arcuate, 1–3 mm thick, usually with long stiff and short woolly hairs intermingled, sometimes with short woolly hairs only. Leaves usually opposite, strongly unequal, or rarely a single leaf per node opposed to a stipule in var. glabrescens ; smaller leaves with petioles 0–0.3 cm and blades 0.4–1.4 x 0.2–1 cm; normal-sized leaves with petioles 0.3–3.2 cm long, with same indumentum as the stems; blades elliptic, (3.1–) 4.2– 14.5 x 1.8–7.5 cm, usually slightly asymmetrical at base with proximal side acute to subcordate and distal side acute to rounded inserted 0–5 mm higher, acuminate at apex, papery to coriaceous, strongly discolorous; upper side green, usually villose above, with stiff hairs 0.5–1.5 mm long, more rarely glabrous, or sometimes sparsely felted in the young stage above; lower side whitish, densely felted with woolly hairs, often also with stiff hairs below; secondary veins 9–15 on each side of midrib. Stipules usually opposite and interpetiolar (rarely solitary and opposed to the leaf in var. glabrescens ), connate at base with the reduced leaf and very shortly with the petiole of the normal leaf, erect to patent, ovate to elliptic, 6–20 x 1.5–7 mm, usually multifid (rarely a few of them entire), divided for up to half of their length into 2–7 linear to narrowly triangular segments 1–10 mm long, glabrescent to variously pubescent outside (with woolly, or stiff hairs, or both), glabrous inside except the base with long silky hairs. Inflorescences axillary on leafy stems, one per node, in the axil of the reduced leaf, sessile, densely glomerulate, 0.7–1.6 cm in diameter, many-flowered. Bracts and bracteoles short and hidden among the flowers; bracts few, free or very shortly connate at base, ovate, 3–5 x 2.5–5 mm, entire or irregularly dentate, acute at apex, pubescent outside with either short woolly or long silky hairs, villose on the margins, glabrous inside except the base with long silky hairs; bracteoles elliptic to narrowly triangular, entire to shortly dentate, 2.5–5 x 0.7–2 mm, acute at apex, with indumentum similar to the bracts. Flower buds usually nearly cylindrical, or rarely strongly enlarged at apex. Flowers 5-merous, sessile. Hypantium variously pubescent with either long stiff hairs, or a dense felt of woolly hairs, or a mixture of both. Calyx whitish outside and green inside; tube 0.5–1.5 mm long, pubescent outside with either short woolly or long stiff hairs, glabrous inside; lobes ranging from almost linear, narrowly triangular, broadly elliptic to slightly spathulate, 1–3.5 x 0.5–1.5 mm, acute to rounded at apex, densely white-felted outside and often sparsely villose as well, glabrous or sparsely villose with short appressed stiff hairs inside; one tiny

42 • Phytotaxa 293 (1) © 2017 Magnolia Press

ZEMAGHO ET AL.

colleter between each pair of calyx lobes. Corolla white; tube cylindrical or narrowly funnel-shaped, 3.5–4.5 x 1–2 mm; lobes triangular, 1.5–3 x 1–2 mm; outside of corolla tube glabrous, the lobes with a dense felt of woolly hairs often intermingled with long stiff hairs; mouth densely bearded with white moniliform hairs ca. 1 mm long; tube either villose in the whole upper half usually in long-styled flowers or villose at the apex and with a separate ring of hairs at distal third -short-styled flowers or rarely in long-styled flowers. Stamens included, subsessile, inserted between the middle and the distal 1/4 th of the tube, with their apex almost reaching the corolla mouth in long-styled flowers, exserted to sub-exserted, with filaments 0.5–1 mm long, inserted near the mouth in short-styled flowers; anthers 1–1.2 x ca. 0.3 mm. Disk cylindrical, 0.5–1 mm long, glabrous. Style glabrous, ca. 6 mm long and exserted in long-styled flowers, ca. 3 mm long, included in short styled-flowers; stigmatic lobes elliptic, 1–1.2 mm long, slightly flat. Fruits green to whitish, becoming red at maturity (at least in var. mildbraedii ), ellipsoid or ovoid, ca. 9 x 7 mm when fresh, 4.5–7 x 2.5–6 mm when dry, variously pubescent with either long stiff or short woolly hairs, sessile or with very short pedicels to 1 mm long. Seeds pale brown, polygonal, ca. 0.6 x 0.4 mm, the surface with dense parallel striations.

Discussion: —The typification of S. mildbraedii is somewhat problematic. Wernham (1914: 53) cited five collections in his original description of the species, without designating a type: Mildbraed 3664 (B†), Gillet 775 (BR), Vanderyst s.n. (BR), Butaye s.n. (BR) and Butaye 1487 (BR). The former collection was destroyed during the Second World War, but a photograph remains in BM, and a duplicate in HBG. The HBG sheet was selected as lectotype by Hallé (1964: 399). However, this specimen, which was not seen by Wernham, is in conflict with several elements of the protologue, notably “caule (...) dense et patente rufo-piloso”, “foliis (...) supra asperis demum scabrello-pubescentibus” and “calycis lobis planis lanceolatis vix 3 mm longis, apicem versus saepius purpureo-barbatis”. The HBG sheet of Mildbraed 3664 instead has appressed hairs on the stems, leaves glabrous above except for the midrib, and shorter calyces lacking purple hairs. It corresponds very well with var. glabrescens , while the original B collection (judging from the BM photograph) was much more pubescent and typical of var. mildbraedii . According to Art. 9.19 of the International Code of Nomenclature for algae, fungi, and plants (ICNafp; McNeill et al. 2012), the choice of a lectotype can be superseded if it is found to be seriously in conflict with the protologue; we therefore reject Hallé’s lectotype and choose instead the specimen Gillet 775 deposited at BR, a specimen seen by Wernham and matching very well his original description.

In general habit, Sabicea mildbraedii resembles S. medusula , S. parmentierae and S. sthenula ; it differs from these species in the smaller and entirely white corolla, and in the shape and indumentum of the calyx lobes (see Table 5). S. mildbraedii also shows a resemblance to Sabicea jacfelicis , but differs in the smaller habit, the inflorescences borne on young leafy stems, and the corolla lobes densely pubescent outside.

The variants of S. mildbraedii var. glabrescens with pseudoalternate leaves can also be mistaken for S. batesii or S. mapiana , from which they differ mostly in their shorter calyx; see Table 4 for differences between these species.

Sabicea mildbraedii is the most widespread and variable species in subg. Anisophyllae , and might actually consist of more than one species. The current taxonomic treatment is tentative and recognises three varieties: var. glabrescens , var. letestui and var. mildbraedii . We have not recognised var. dubia of Hallé (1966) which, in our opinion, is just a robust extreme of var. mildbraedii . On the other hand, his var. jacfelicis is sufficiently different from the rest to be treated as a separate species, Sabicea jacfelicis ; as a result S. mildbraedii does not occur in Cameroon.

Sabicea mildbraedii normally has two stipules and two strongly unequal leaves per node, but occasional variants with a single leaf opposed to a stipule, the reduced leaf being completely absent, have been noted in var. glabrescens (Ley & Yedi 75 and Moungazi 1536 from Gabon; Bouquet 1907 and Lejoly 86/366 from the Republic of Congo).

There is a great level of polymorphism in var. mildbraedii concerning the shape of the calyx lobes. Some specimens, e.g. Bequaert 7546, have broad and slightly spathulate calyx lobes, while at the other extreme is Champluvier 5029 with very narrow calyx lobes resembling S. medusula . Various types of intermediates occur between these two forms.

Some collections from Gabon are difficult to name varietally. Dessein et al. 1987 (BR, LBV), from the Doudou Mts, resembles var. letestui (the only one recorded in its range) but has unusually narrow calyx lobes. Bidault et al. 1485 (BRLU, MO) from the Mabounié region resembles var. glabrescens , but has long stiff hairs on the ovary and fruits; since it comes from a region where the ranges of var. glabrescens and var. letestui closely approach each

TAXONOMIC REVISION OF SABICEA SUBGENUS ANISOPHYLLAE

Phytotaxa 293 (1) © 2017 Magnolia Press • 43 other, it may well be a hybrid between them. Sonké et al. 6186 (BR, BRLU, MO) from the same area comes very close to var. mildbraedii , but since the latter is not recorded from west Gabon and the material is imperfect, more collections are needed to decide on its status.

Conservation status:— IUCN Red List Category: Least Concern [LC]. The extent of occurrence is estimated as 458,004.337 km 2 and the area of occupancy as 384 km 2. The latter value falls within the limit for Endangered under criterion B2, but is obviously underestimated, S. mildbraedii being a fairly ubiquitous forest edge species in some parts of its range (e.g. southeast Gabon). The species is known from more than 10 locations (sensu IUCN 2012), is usually common where it occurs, and benefits from some degree of forest degradation due to its preference for open habitats. It is not therefore threatened.