Ochna holstii Engl. (Engler 1894: 69)

Shah, Toral, Mashimba, Fandey H., Suleiman, Haji. O., Mbailwa, Yahya S., Savolainen, Vincent, Larridon, Isabel & Darbyshire, Iain, 2023, A taxonomic revision of the ecologically important Ochna holstii (Ochnaceae) complex using molecular and morphological data, Plant Ecology and Evolution 156 (2), pp. 174-200 : 174

1. Ochna holstii Engl. (Engler 1894: 69)

Figs 2C-D , 4A-B , 6

Diporidium holstii (Engl.) Tiegh. ( Tieghem 1902: 356) - Type: same as for Ochna holstii .

Biramella holstii (Engl.) Tiegh. ( Tieghem 1903: 97) - Type: same as for Ochna holstii .

Ochna prunifolia Engl. ( Engler 1895: 273; Gilg 1903: 236; Brenan and Greenway 1949: 384) - Type: TANZANIA • Rombo Mku; 1894; Volkens 1960; lectotype (designated here): E! [E00200459]; syntype: B† • KENYA • Kitui; Hildebrandt 2825; syntype: B† • TANZANIA • Mkulia; Volkens s.n.; syntype: B†.

Diporidium prunifolium (Engl.) Tiegh. ( Tieghem 1902: 356) - Type: same as for Ochna prunifolia .

Ochna longipes Baker ( Baker 1897: 247; Brenan 1953: 234; White 1962: 251) - Type: MALAWI • Mt Malosa near Zomba; 1896: Whyte 429; holotype: K! [K000431165].

Ochna shirensis Baker ( Baker 1897: 247) - Type: MALAWI • Mt Zomba & Mt Malosa; 1896: Whyte 430; holotype: K! [K000431163].

Ochna acutifolia Engl. ( Engler 1900: 433) - Type: TANZANIA • West Usambaras; Buchwald 350; lectotype (designated here): K! [K000431145]; isolectotype: BM; syntype: B† • TANZANIA • Uluguru, near Nghweme; Stuhlmann 8852; syntype: B†.

Diporidium acutifolium (Engl.) Tiegh. ( Tieghem 1902: 356) - Type: same as for Ochna acutifolia .

Ochna densicoma Engl. & Gilg ( Gilg 1903: 241; Brenan and Greenway 1949: 382) - Type: TANZANIA • East Usambaras, Nderema; 1901; Scheffler 169; holotype: B†; lectotype (designated here): EA! [EA000002025]; isolectotypes: BM [BM000798536], BR [BR0000006266356], E! [E00200461], K! [K000431144].

Ochnella densicoma (Engl. & Gilg) Tiegh. ( Tieghem 1903: 40) - Type: same as for Ochna densicoma .

Ochna chirindica Baker f. ( Rendle et al. 1911: 37) - Type: ZIMBABWE • Melsetter District, Chirinda Forest; 1905; Swynnerton 106; holotype: K! [K000431166]; isotype BM [BM000798543].

Ochna keniensis Sleumer ( Sleumer 1934: 69; Dale and Greenway 1961: 338; Beentje 1994: 121) - Type: KENYA • Mt Rupingazi River; 1922; Fries & Fries 2031; holotype: UPS [fide Verdcourt 2005]; isotype: S [S-G-4319].

Type.

TANZANIA • West Usambaras , Mbalu; 1893; Holst 2601; holotype: B†; lectotype (designated here): K! [K000431146]; isolectotypes: BR [BR0000006265694], HBG [HBG509293] .

Description.

Small to large tree 4-27 m tall, usually over 10 m tall, rarely with shrubby forms 1.5-3 m tall. Bark grey-brown. Stems dark grey, sometimes peeling, with white lenticels, these sometimes sparse; young stems dark brown, with white lenticels, glabrous. Stipules brown, linear, sometimes persistent to deciduous, 2-15 mm long. Leaves green, often drying brown or rarely blue-black, chartaceous, glabrous, lanceolate to oblanceolate, 4-12(-16.5) cm long, 1-5(-5.5) cm wide; leaf base attenuate-cuneate (rarely rounded), leaf apex attenuate, margins serrate; lateral veins 20-28, appearing at right angles to midrib, tertiary vernation reticulate; petiole 0.5-3.5 mm long; buds brown, large, up to 7.5(-9) mm long. Flowers in racemes with 6-16 flowers; rachis 0.5-2 cm long, glabrous; pedicels 1.5-4 cm long, articulated at or near the base, or up to 3(-10) mm above the base, glabrous throughout. Sepals green to brown in flower, oblong to elliptic, 8-10 mm long, 4-6 mm wide in flower, turning red in fruit, then 11-14 mm long, 4-8(-10) mm wide. Petals yellow, often pale, obovate, 8.5-10.5 mm long, 3.5-4 mm wide. Anthers dehiscing by longitudinal slits, 1.5-2 mm long; filaments 2-3.5 mm long. Carpels 5; styles united to apex, 4-7 mm long Drupelets black, ellipsoid, 8-13 mm long, 4-6 cm wide, attached at the base.

Distribution.

Widespread in montane regions of eastern Africa: South Sudan, Ethiopia, Democratic Republic of the Congo (DRC), Uganda, Kenya, Tanzania, Burundi, Rwanda, Mozambique, Malawi, Zambia, Zimbabwe, South Africa (Fig. 6 ).

Habitat.

Usually found in upland and montane (Afromontane) moist forests as a medium- to large-sized tree; occasionally recorded in more open habitats including montane grassland and amongst rocky boulders. Altitude: 1000-4600 m.

Phenology.

Most flowering and fruiting specimens are collected from October to March. This corresponds to the shorter rainfall season in East Africa (October to December) and the longer rainfall season in southern Africa (November to March).

Preliminary IUCN conservation assessment.

Ochna holstii is a medium- to large-sized tree (rarely in shrubby form), widespread across montane forests in East and Southern Africa. The estimated extent of occurrence (EOO) is 3,888.294 km2, and the area of occupancy (AOO) is 548 km2. Forest loss due to agricultural expansion and wood harvesting, particularly at its lower altitudinal limit, may have an impact on some subpopulations. Although the species falls within the range of values for the vulnerable category due to its AOO for criteria B2, the species is known from substantially more than 10 threat-defined locations, it is assessed as Least Concern (LC).

Additional material examined.

SOUTH SUDAN - Equatoria Province • Mt Lotuke, Didina Mts; 6500 ft; 20 Apr. 1939; fl.; Myers 10959; K [K001383230] • Imatong Mountains, Bushbuck Hill; 2300 m; 21 Feb. 1982; fl.; Friis & Vollesen 982; K [K001383227].

ETHIOPIA - Oromia • Mogada ; 5°30'N, 38°20'E; 1700 m; Jun. 1976; fr.; Haile 696; K [K001271514] .

KENYA • Baringo • Eldama Ravine and Mau ; 7500 ft; May 1900; fr.; Whyte 1898; K . - Narok • Nguruman Range, Lebetero Hills ; Jan 1961; fr.; van Someren EA 12286; K [K001082543] . - Kericho • Londiani District, Tinderet Forest Reserve, between Camp 4 and Tinderet Triangulation Point ; 0°05 ’00” S, 35°21 ’30” E; 2300 m; 1 Jul. 1949; fr.; Maas Geesteranus 5311; K [K001082539] . - Samburu • Lorogi forest ; 1°04'N, 36°52'E; 2170 m; 26 Mar. 1967; fr.; Gillett 18095; EA, K [K001082519] • Elgon; 7500 ft; 23 Apr. 1968; fr.; Hamilton 809; K [K001082523] . - Meru • Mount Kenya Forest Reserve between Naro-Moro and Nyeri; 21 Feb. 1973; fr.; Lawton 1751; K [K001082534] .

UGANDA - Eastern • N.E. Mt Elgon; 6500 ft; May 1933; fr.; Dale 3121; K [K001082516; K001082517] • Imatong Mountains; 7800 ft; Apr. 1938; fr.; Eggeling E3539; K [K001082514]. - Northern • Dodoth, Kidepo National Park; 1800 m; 16 May 1972; fr.; Synnott 984; EA, K [K001082512].

TANZANIA - Korogwe District • Shume, Korogwe, in the Shume valley bottom, about 0.5 miles from the Forest House ; 7 Jan. 1947; fr.; Hughes 16; EA, K [K001082587] . - Lushoto District East Usambaras, Derema ; 3200 ft; 29 Dec. 1932; fl.; Greenway 3308; EA, K[K001082578] • W. Usambaras; 6200 ft; 16 Jan. 1952; fr.; Parry 105; EA, K [K001082589] • Near Lushoto water supply; 20 Feb. 1962; fl.; Mgaza 452; EA, K [K001082591] . - Njombe District • Ruhuji Waterfalls ; 9°14 ’12.48” S, 34°45 ’44.46” E; 1823 m; 26 Jan. 2020; fr.; Shah TS 98; K [K001271562] .

DEMOCRATIC REPUBLIC OF THE CONGO - South Kivu • Kalehe, Mikouzi, vallée de la Tshinganda; 1950 m; 10 Dec. 1957; fr.; Pierlot 1731; K [K001391607]. - Haut Katanga • Plateau des Kundelungu ; 1960 m; 28 Nov. 1968; fr.; Malaisse 6122; K [K001391606] .

MALAWI - Thyolo District • Cholo Mt ; 1400 m; 20 Sep. 1946; fl.; Brass 17668; BM, K [K001387307] . - Chitipa District • Lundazi, upper slopes of Kangampande Mt, Nyika Plateau ; 7000 ft; 8 May 1952; White 2793; K [K001271529] • Mulanje Mt forest ; 8 Oct. 1957; fl.; Chapman 454; BM, K [K001387304] • Nyika Plateau, Luselo Evergreen Forest patch; Salubeni 356; K [K001387298] . - Mulanje District • Mt Mulanje, close to the site of the old Boma hut; 1840 m; 3 Nov. 1986; Chapman & Chapman 8186; E [E01123512], K [K001387295] .

MOZAMBIQUE - Zambezia Province • Chiperone Mountain; 29 Nov. 2006; Patel & Bayliss HP 7183; K [K000545146] • Namuli Mountain, Naconha Plateau; 15°22 ’40” S, 37°01 ’09.2” E; 1977 m; 21 Nov. 2007; fr.; Timberlake et al. 5267; K [K000613996] • Namuli Mountain , Muretha Plateau-Mukocha forest ; 15°23 ’57.4” S, 37°02 ’29.9” E; 1730 m; 28 May 2007; Timberlake et al. 5054; K [K000613434] .

ZIMBABWE - Mutare District • Umtali; 8 Nov. 1948; fl.; Chase 1256; BM, K [K001387323]. - Chipinge District • Chirinda Forest; 4 Jan. 1948; fr.; Chase 433; BM, K [K001387316] • Old Bikita, on edge of forest plateau; 4300 ft; 16 Dec. 1953; fr.; Wild 4407; K [K001387315] • Gwasha, on the first range; 4500 ft; 22 Sep. 1960; fr.; Rutherford-Smith 168; K [K001387335]. - Chimanimani District • Chimanimani Mountain, Martin Forest Reserve; 17 Nov. 1967; fl.; Mavi 678; K [K001387313]. - Mberengwa District • Bukwa Mt, main ridge; 1700 m; 30 Oct. 1973; fl.; Pope et al. 1126; K [K001387336].

SOUTH AFRICA - KwaZulu-Natal • Ingeli Forest Reserve ; 18 Dec. 1915; fr.; Chilvers 1946; K [K001271523] . - Mpumalanga • Barberton ; 22 Jan. 1957; Story 5993; K [K001271517] . - Limpopo • Mariepskop ; 3 Dec. 1959; fr.; Schiff 4754; K [K001271518] . - Eastern Cape • Engcobo Forest ; 18 Jan. 1996; fr.; Flanagan 2696; K [K001271522] .

Bibliography.

Engler (1895: 273); Gilg (1903: 234, 241); Brenan and Greenway (1949: 382); Eggeling and Dale (1952: 279); Dale and Greenway (1961: 337); Robson (1963: 240); Bamps and Farron (1967: 8); du Toit and Obermeyer (1976: 5); Blundell (1987: 62); Beentje (1994: 121); Vollesen (1995: 66); Verdcourt (2005: 2).

Notes.

Morphological work on this species has proved challenging. Like taxonomists in the past ( Robson 1963; Verdcourt 2005), we note significant variation in habit, leaf size and arrangement of leaves along the branches, and inflorescence structure. This widespread species is generally recognizable by being a medium- to large-sized tree, occurring in upland moist forest with leaves variable in size (4-12 cm long and 1-5 cm wide) with a distinct attenuate leaf apex, and 6-16 flowers with long pedicles arranged in a distinct raceme. Difficulty arises with specimens that are sterile, shrubbier in habit, and/or with smaller leaves occurring in more open and drier habitats. These individuals may be confused with O. stolzii and O. oxyphylla ; however, they differ by the latter two species generally having smaller leaves (1-4.5 cm long, 0.5-2 cm wide and 2-8 cm long, 1-4 cm wide respectively) without prominent attenuate leaf apices, and fewer flowers per inflorescence, often solitary but sometimes up to six flowers.

Figures

Figure 2. Species of Ochna, habit and leaf margin. A. Ochna stolzii (from Richards 22529). B. Ochna oxyphylla (from Carmichael 354). C - D. Ochna holstii (C from Maas Geesteranus 4971, D from Pierlot 1731). Drawn by Andrew Brown.

Figure 4. Dissection of rehydrated drupelets shows that there are no distinguishing morphological characters in the embryo of any of the mentioned taxa, particularly separating Ochna holstii I and II. A. Ochna holstii II. B. Ochna holstii I. C. Ochna stolzii. D. Ochna oxyphylla.

Figure 6. Distribution map of Ochna holstii from georeferenced herbarium specimens in Africa.