Monotes hypoleucus var. loandensis (Exell) Meerts, 2017

Meerts, Pierre, Rougelot, Quentin & Sosef, Marc, 2017, Revision of the genus Monotes (Dipterocarpaceae) in D. R. Congo, with implications for Angola and its distinction from Marquesia, Phytotaxa 308 (2), pp. 151-205 : 189

9e. Monotes hypoleucus var. loandensis (Exell) Meerts , comb. et stat. nov.

Basionym: Monotes loandensis Exell (1932: 220) ; Bancroft (1937: 137; 1939a: 353); Catarino et al. (2013: 270); Duvigneaud (1949: 50); Figueiredo & Smith (2008: 67); Lebrun & Stork (1991: 144).

Type: — ANGOLA. Malange , Quirima, 23 January 1931, Gossweiler 9492 (holo-: BM! [barcode BM000603380]; iso-: COI!, K! [barcode K000240344], LISC! [barcode LISC019576]) .

= Monotes loandensis var. griseotomentosus Duvigneaud (1949: 51 & Pl. 12 e–h). Type :—D.R CONGO. Kwango, 42 km SW Kenge, forêt claire à Uapaca , 9 May 1948, Duvigneaud 856M (holo-: BRLU! [barcode BRLU0000090022319]; iso-: BRLU! (6 sheets)), syn. nov.

Diagnosis:— Differs from the type variety in the following traits: leaf blade smaller, more or less spathulate, lower surface of leaf with secondary nerves glabrous, reddish chestnut, basal gland narrowly elliptic.

Branchlets quickly glabrous, grey. Leaf: petiole 7–13 mm long, ca. 2 mm in diameter, blade obovate-spathulate to elliptic, 5–8 × 2–4 cm, generally at least 2.5 times longer than wide, base cuneate, apex rounded to emarginate, with 8–13 pairs of nerves; basal gland shiny, narrowly elliptic, 2–5 times longer than wide; upper surface of leaf generally reticulate, often granular (yellow sessile glands), generally glabrous, occasionally with minuscule hairs, glabrescent; lower surface discolorous, whitish to ash-greyish, with cottony indumentum covering areoles; secondary nerves and costa prominent, almost glabrous, red to chestnut coloured, contrasting with the grey-whitish indumentum; tertiary nerves generally forming a striking scalariform pattern. Flowers unknown. Fruit 8–10 mm, globose with an apicule, wings large, 3–5 × 1–2 cm.

Illustrations: — Figs. 3P , 4O .

Distribution in D.R. Congo: — Kwango; Upper Katanga.

Distribution elsewhere: — Angola; known only from a few collections.

Habitat and ecology: —Mixed dry semi-evergreen forests (“Mabwati”); wooded savannahs.

Other representative specimens examined:—D.R. CONGO. Kasaï (Kwango): 42 km SW Kenge, forêt claire à Uapaca , 9 May 1948, Duvigneaud 856M. Upper Katanga: Kambove-Kamoia, 1957, Duvigneaud 3352–3353 (BRLU!)).

Discussion:— We have maintained this taxon after much hesitation. All the supposed diagnostic traits can actually be found in var. caloneurus and in var. angolensis and their combination in some specimens is probably fortuitous. In agreement with this hypothesis, the single collection from Katanga perfectly matches the type in leaf size and shape, but departs from it in having a pubescent upper surface of the leaf. Catarino et al. (2013) indicate that “...the species is known from three collections and three different localities. Two of these locations were surveyed several times after the species description, but no further collections are known”. This, in our opinion, is another indication that this taxon represents individual variation of little taxonomic value. Intermediates with var. angolensis occur, e.g. Duvigneaud & Timperman 2402 (BRLU!), Desenfans 5919 (BRLU!), Plancke 121/1584 (BRLU!).

Figures

FIGURE 3 A–H. Details of lower surface of the leaf.A. Monotes adenophyllus var. adenophyllus (Duvigneaud 5112). B. M. adenophyllus var.homblei (Duvigneaud 4601). C. M.africanus (Duvigneaud 2006). D.M.autennei (Duvigneaud 5260). E.M.dasyanthus var.dasyanthus (Duvigneaud & Timperman 2341). F. M.dasyanthus var. heterotrichus (Duvigneaud 1141). G. M. dasyanthus var. mutetetwa (Duvigneaud 950). H. M. doryphorus (Duvigneaud 5267).

FIGURE 4 A–H. Details of upper surface of the leaf.A. Monotes adenophyllus var.adenophyllus (Duvigneaud 5044). B. M.adenophyllus var.homblei (Duvigneaud 4570). C. M.africanus(Duvigneaud 2006). D. M.autennei(Plancke 111/1532). E.M.dasyanthus var.dasyanthus (Duvigneaud & Timperman 2341). F. M. dasyanthus var. heterotrichus (Duvigneaud 4493). G. M. dasyanthus var.mutetetwa (Duvigneaud 950). H. M. doryphorus (Duvigneaud 5267).