Casearia austroafricana A.E.van Wyk, R.G.C.Boon & Retief, 2018

Van Wyk, Abraham E., Boon, Richard G. C. & Retief, Elizabeth, 2018, A new species of Casearia (Samydoideae, Salicaceae) from South Africa, Phytotaxa 383 (3), pp. 273-282 : 275-280

Casearia austroafricana A.E.van Wyk, R.G.C.Boon & Retief , sp. nov. ( Figs. 1 & 2 )

Casearia austroafricana resembles C. gladiiformis , but is easily distinguished from this species by, amongst others, growing under temperate or subtropical conditions, always in or near forest (vs. tropical, and in either open woodland, thicket or forest), with the trees becoming taller (> 20 m vs. <10 m), in having young twigs usually markedly zigzag (vs. straight or weakly zigzag), leaves of mature growth with blade relatively thin (firmly chartaceous vs. coriaceous), margin glandular-serrate (vs. entire), ovary glabrous (vs. hirsute, at least towards the apex), and fewer seeds per capsule (3 or 4 vs. ca. 10).

Type: — SOUTH AFRICA. KwaZulu-Natal: Ndwedwe District, Itafamana Mission, on TMS [Table Mountain sandstone] cliffs, 2500 ft [850 m], 2930DB, 16 July 1966, E.J. Moll 3290 (holotype PRE!, isotype NU!).

“ Casearia sp. nov. ” in Coates Palgrave (2002: 768); Boon (2010: 368).

Illustrations: Killick (1976: Fig. 30, 1 & a); Boon (2010: 369, bottom three photographs).

Tree, often more than 20 m, occasionally up to about 30 m high. Trunk single, rarely multistemmed, up to 0.6 m diameter at breast height; bark pale brown, flaking in old specimens, lenticels prominent; slash cream with vague yellow streaks, pale purple just below last-formed periderm. Branchlets more or less drooping, sometimes superficially resembling large pinnately compound leaves; twigs often conspicuously zigzag, especially in young plants, green in older plants, but often silvery white in young plants, becoming pale brown with age, lenticellate, puberulous, soon becoming glabrous. Leaves alternate, distichous; blade shiny mid to dark green above, somewhat duller and slightly paler green below, glabrous, with randomly scattered pellucid dots and lines, oblong, lanceolate, oblong-lanceolate, ovate or narrowly elliptic, (35–)80–135(–150) × (15–)30–50(–65) mm, firmly chartaceous, midrib pale green, raised on both surfaces, but more so below, in dried material often narrowly channelled above, principal lateral veins in (5–)8– 10(–12) pairs, apex acute or acuminate, often elongated into a drip-tip, base cuneate, usually slightly oblique, margin glandular serrate or glandular serrate-crenate, apical glands (colleters) ca. 0.5 mm long, early deciduous, serrations especially prominent in saplings; petiole (3–)5–8(–10) mm long, shallowly channelled above; stipules early caducous, narrowly triangular, ca. 2 × 0.5 mm, pubescent. Inflorescence axillary, sessile, glomerate, up to 13-flowered, produced from a cushion-like structure formed by scale-like bracteoles. Flowers faintly scented, ca. 4 mm in diameter; pedicels up to 3 mm long, puberulent. Sepals concave, pale green, 5(or 6), suborbicular, puberulent or glabrescent on the back, persistent, apex with translucent margin, margins slightly lacerate, becoming pale brown in fruit. Petals 0. Staminal tube united for about 0.3–0.5 mm and then dividing into fertile stamens and staminodes. Stamens (6–)7 or 8(–10); filaments ca. 1.5 mm long, puberulous; anthers broadly elliptic, becoming ovate after dehiscence, ca. 0.5 mm long, glabrous, pollen whitish; staminodes as many as and alternating with the stamens, as long as or slightly shorter than the filaments, flattened, oblong with apices weakly 3-pointed, greenish yellow, with white hairs towards apices. Ovary superior, 1-locular, ovoid, ca. 1.75 × 1 mm, glabrous; style ca. 0.5 mm long, persistent in fruit; stigma capitate. Fruit an ovoid to ellipsoid capsule, slightly 3-angular, ca. 15 × 10 mm, smooth, somewhat fleshy, chrome yellow when ripe, dehisces into 3 longitudinal valves. Seeds 3 or 4 per capsule, ovoid, ca. 4 × 3 mm, testa pale beige, smooth, enclosed in a soft, membranous, fimbriate, salmon-orange aril.

Phenology: —Flowering has been observed in trees of about 8 m or more in height. Flowers were recorded mainly from January to May. Fruits ripen mostly from June to October.

Etymology: —The specific epithet is the Latin for “ South Africa ”, chosen because the new species is the only member of Casearia endemic to the country.

Distribution and habitat: —Occurs from Nkandla and Qudeni Forests in northern KwaZulu-Natal, southwards through the KwaZulu-Natal midlands and Pondoland to the Manubi Forest near Mazeppa Bay in the Eastern Cape ( Fig. 3 ). Mainly associated with temperate Afromontane (Mist) Forest and subtropical Scarp Forest. Of the former type it seems to prefer Mist Belt Mixed Podocarpus Forest ( Edwards 1967) of the KwaZulu-Natal midlands, and of the latter type Pondoland Scarp Forest ( Mucina et al. 2018). Note that the claim by Mucina et al. (2018: Table 6.9) that C. austroafricana (their “ Casearia sp. nov. ”) is endemic to Pondoland Scarp Forest, is incorrect. The species has a much wider distribution and is an endemic of the Maputaland-Pondoland Region/Hotspot ( Van Wyk & Smith 2001; Steenkamp et al. 2004). It is, however, absent from more tropical northern coastal forest types in KwaZulu-Natal and from woodland. Typically a constituent of climax forest, but occasionally found on forest margins or on riverbanks in forested river gorges. The species has been recorded on a variety of soils mainly derived from granite, sandstone, shale or dolerite.

Ecological associates: —Although a subcanopy or canopy tree up to about 30 m in some forest types, the ecology and associates of the species are poorly known.Mature trees are host to epiphytes such as the ferns Pleopeltis macrocarpa (Bory ex Willdenow 1810: 147) Kaulfuss (1820: 41) and P. polypodioides ( Linnaeus 1753: 1068) E.G.Andrews & Windham in Windham (1993: 46) subsp. ecklonii ( Kunze 1836: 249) Roux (2009: 163) , the orchids Polystachya ottoniana Reichenbach (1855: 249) and Mystacidium venosum Harv. ex Rolfe (1912: 79) , and many moss and lichen species. The aril-covered seeds are popular with fruit-eating birds, especially Cape White-eyes ( Zosterops capensis virens Sundevall 1850: 101 ). As to potential pollinators, only blow flies ( Diptera : Calliphoridae ) were seen visiting the flowers.

In a comprehensive catalogue of known Lepidoptera host-plants in southern Africa, Kroon (1999) listed no larval associations with members of Casearia . One of us (RGCB) has now recorded a greenish yellow caterpillar with brownish black markings feeding on Casearia austroafricana in the KwaZulu-Natal National Botanical Garden ( Fig. 4A ). This larva is that of a moth belonging to the family Geometridae , subfamily Larentiinae .Although its identity can only be certain if reared to adult, it is most likely Chloroclystis muscosa tumefacta Prout (1917: 57) , a polyphagous larentiine ( Staude et al. 2016: S79; H.S. Staude, pers. comm.). In what may well be a case of host specificity, another caterpillar was found on C. austroafricana by lepidopterologist H.S. Staude (pers. comm.). This particular larva rolls up the leaf and feeds within the shelter ( Fig. 4B & C ). It was subsequently reared to adult (rearing number 16HSS38) and turned out to be an as yet undescribed moth of the tribe Archipini (Tortricidae) .

Conservation: — Casearia austroafricana is relatively widespread and not uncommon. There are several subpopulations and many of the larger forest patches with which it is associated enjoy some form of protection. As there are no severe threats to this species, the population is not suspected to be declining and it is categorised as “Least Concern” according to the IUCN Red List Category and Criteria ( IUCN 2012).

Common names: —Existing names include swordleaf, southern swordleaf, suidelike bosswaardblaar (Afrikaans), smozob (Zulu?; from Henkel s.n.) and qokama (Xhosa; from Acocks 12820).

Notes: — Casearia austroafricana belongs to section Casearia , the only one of the six proposed sections in the genus represented outside of the New World ( Sleumer 1980). With the recognition of Casearia austroafricana , the distribution of C. gladiiformis in South Africa is confined to that part of KwaZulu-Natal to the east of the Lebombo Mountains and to the north of Richard’s Bay. Known as Maputaland, this rather featureless low lying coastal plain is at the southern end of the tropics in Africa and many plant and animal species reach the southernmost limit of their range here ( Van Wyk & Smith 2001). Hence the distribution pattern displayed by C. gladiiformis is typically that of a tropical species. Casearia austroafricana , on the other hand, favours subtropical to temperate conditions and has not yet been recorded from Maputaland. The two species can therefore be distinguished on climatic preference and geographical distribution alone.

The maximum elevation Casearia gladiiformis occurs at locally is about 60 m a.s.l. It grows in swamp forest, coastal forest, sand forest, thicket and woodland and is usually a large shrub or small tree less than 8 m tall. The leaves are very glossy above, leathery, entire and the midrib on the upper surface is often yellowish and up to 2 mm wide. Occasionally specimens may have leaves with a few serrations (notably on sucker shoots), but these are rather indistinct. Casearia austroafricana , on the other hand, usually grows at much higher elevations (up to ca. 1600 m a.s.l.) and is a forest tree, usually with a single bole and when mature is more than 20 m tall. It has relatively thin leaves with conspicuously serrate-crenate margins and the midrib above is quite narrow (ca. 0.3 mm) and often narrowly channelled in dried material. Twigs, especially in young growth, are also more pronouncedly zigzag than those of C. gladiiformis . Both species, however, are similar in having leaf blades with randomly scattered pellucid dots (secretory cavities) and lines (secretory ducts).

In floral and fruit features these two species are very similar, but the ovaries in C. austroafricana are glabrous (vs. hairy, at least towards the apex), and the capsules usually contain fewer seeds (less than five, vs. about ten). Flowering times, however, are quite different. Casearia austroafricana has its peak flowering period from January to May (late summer and autumn) and fruits in spring, whereas C. gladiiformis flowers mainly from late September to beginning of October (early spring) and fruits in summer.

Casearia battiscombei ( Wild 1960: 295, Tab. 52A) resembles C. austroafricana in also being a tall (up to 40 m) forest tree, but in southern Africa it is rare and confined to the highlands of eastern Zimbabwe and bordering western Mozambique (otherwise known from Malawi, Tanzania, Kenya and Uganda). We have contrasted C. austoafricana mainly with C. gladiiformis , the species under which it hitherto has consistently been treated. It may, however, have a closer affinity with C. battiscombei , but the latter is comparatively poorly known and descriptive information in the literature is rather scant. Casearia austroafricana differs from C. battiscombei in having leaves with fewer principal lateral veins (8–10 vs. 14–20 pairs), distinctly and regularly serrate-crenate margins (vs. entire or rarely shallowly and irregularly crenulate), glabrous anthers (vs. minutely pubescent) and smaller seeds (4 × 3 mm vs. 6 × 4.5 mm). Coates Palgrave (2002) described the aril of C. battiscombei as “pale whitish”, which is quite different from the salmon-orange state in C. austroafricana , or the shades of orange (becoming reddish when exposed to air), which are the prevailing colours in other members of the genus, but this statement is in need of confirmation as it may well be a mistake.

Additional collections (paratypes): — SOUTH AFRICA. KwaZulu-Natal: Qudeni Forest , 5000 ft [1524 m], (2830DB), 8 October 1941, Bayer 831 (NU!, PRE!) ; Nkandla , (2831CA), 4 April 1986, Jordaan 766 (NH!, PRE!) ; Nkandla District, Bhoyiza Village, Nkandla Forest Reserve , ca. 1 km from NE boundary of reserve, (2831CA), 16 May 2001, Ngwenya 2245 ( NH!) ; Nkandla District, lower Nkandla Forest , (2831CA), 18 June 1956, Edwards 1446 ( PRE!) ; Nkandla District, Nkandla Forest , (2831CA), 29 May 1959, Schutz 959 ( PRE!) ; Zululand, Nkandhla [Nkandla], (2831CA), 27 March 1903, Wood 8987 (NH!, PRE!) ; Eshowe , opposite town hall, (2831CD), 16 July 1937, Gerstner 2057 ( PRE!) ; Eshowe, Dlinza Forest , (2831CD), 2 August 1949, Lawn 986 ( NH!) ; Forest near Entumeni Road, 6 miles from Eshowe , (2831CD), February 1950, Lawn 1621 ( NH!) ; Nkandla, north-west side of Ngoye Forest , (2831DC), 26 February 1970, Moll 4953 (NH!, PRE!) ; Nkandla, Ngoye Forest , c. 1000 ft [c. 305 m], (2831DD), 4 June 1972, Moll & Muller 5673A ( NH!) ; Karkloof , 5000 ft [1524 m], (2930AC), June 1940, Bayer 821 (NU!, PRE!) ; Howick, The Start , 3000 ft [914 m], (2930AD), 20 November 1967, Cooper 3 (NH!, PRE!) ; Lions River District, farm The Start , (2930AD), 01 October 1966, Moll 3366 ( PRE!) ; Lions River District, farm The Start , (2930AD), 22 February 1967, Moll 3537 ( PRE!) ; New Hanover District, Blinkwater , (2930BC), 1916, Sim 20415 ( PRE!) ; Pietermaritzburg, Botanic Gardens , (2930CB), 17 August 1946, Bayer 1421 ( NU!) ; Pietermaritzburg, Kettlefontein Mountain Rise , 200 yards above level crossing, (2930CB), 29 September 1956, Butcher s.n. ( NH!) ; Pietermaritzburg, Botanical Gardens , (2930CB), 6August 1918, Henkel PRE 47832& 47842 ( PRE!) ; Pietermaritzburg, Zwakop [Swartkop] Valley ,(2930CB), September 1919, Henkel PRE 47843 ( PRE!) ; Pietermaritzburg, Botanical Gardens , (2930CB), August 1940, Luckhoff s.n. NH 32946 ( PRE!) ; Pietermaritzburg, Town Hill , c. 3000 ft [c. 914 m], (2930CB), 18 February 1962, Moll 548 ( NU!) ; Sweetwaters , 2500 ft [762 m], (2930CB), 1916, Sim 19354 ( NU!) ; Baynesfield , farm of R. Moody, (2930CD), 15 September 1987, Nichols 972 ( NH!) ; Camperdown, Nagle Dam , in partially cleared forest below west krantz, 2800 ft [853 m], (2930DA), 22 June 1957, Wells 1495A ( NU!) ; Gillits, Long Shadows , (2930DD), 14 June 1973, Moll 5726 ( PRE!) ; Long Shadows, downriver of Acutts Drive, Krantzkloof Nature Reserve , (2930DD), 8 January 2005, Styles 2167 ( NH!) ; Ngele , forest patch, 1244 m, (3029DA), 20 February 2012, Grieve 74 ( PCE!) ; Kokstad, Weza State Forest, Lorna Doone , along Hoopoe Trail , (3029DA), 3 October 1983, Nicholas 1577 ( NH!) ; Mt. Ingeli [Ngeli], (3029DA), 2 January 1969, Nicholson 760 ( PRE!) ; Weza, Mt. Ngele, Bangeni Forest , (3029DA), 23 November 1994, Van Wyk 12523 ( PRU!) ; Umzinto District, Vernon Crookes Nature Reserve , streamside in forest near the main gate, 420 m, (3030BC), 20 November 1984, Balkwill & Cadman 2177 (NU!, PRE!) ; Mtwalume River, farm Mgai , in kloof, (3030BC), 23 June 1972, Nicholson 1249 ( PRE!) ; Port Shepstone, river valley just south of Success , 1700 ft [518 m], (3030CB), 19 July 1967, Moll 3591 (NH!, NU!, PRE!, UDW!) ; Port Shepstone, Umtamvuna Nature Reserve, Smedmore Forest , under north krans, (3030CC), 24 November 1984, Abbott 2224 ( PCE!, PRU!) ; Port Shepstone, Burntwood, Paddock , (3030CC), 4 September 1965, Strey 5995 (NH!, PRE!) ; Umtamvuna Nature Reserve, Smedmore Forest , (3030CC), 4 September 1994, Van Wyk BSA 2579 ( PRU!) ; South Coast, Umzumbe, Bonnievale Farm , (3030DA), 16 June 1977, Nicholson 1778 ( PRE!) ; Umtamvuna Nature Reserve , SE of Rooielsbos, (3130AA), 28 January 1984, Abbott 1688 ( PCE!, PRU!) ; Umtamvuna River , forest fringe, (3130AA), 16 February 1972, Nicholson 1173 ( PRE!) . Eastern Cape: Transkei, Kwaka [Icwaka] River , 300 m, (3030CC) Abbott 2915 (NH!, PCE!, PRU!) ; Hlolweni River , S of Umtamvuna Nature Reserve, (3030CC), 20 April 1989, Abbott 4352 ( PRU!) ; Port St. Johns, Egossa Forest , (3129BC), 22 August 1969, Strey 8870 (NH!, NU!, PRE!, UDW!) ; Port St. Johns, Caguba , (3129CB), 16 August 2002, Schuhardt DS 03695 ( PRE!) ; Transkei, Qokama Forest, 9 miles from Ngqeleni on road to coast, (3129CC), 28 July 1946, Acocks 1338 ( PRE!) ; Ngqeleni District, Qokama , (3129CC), 28 July 1946, Acocks 12820 ( PRE!) ; Port St. Johns , (3129DA), May 1929, Kotze PRF 7302 ( PRE!) ; Port St. Johns, Siqora Forest , (3129DA), September 1921, Miller D 42 ( PRE!) ; Port St. Johns (3129DA), Miller FD 7302 ( PRE!) ; Port St. Johns District, Sigovu Forest , (3129DA), September 1921, Miller 1476 FD 3637 ( PRE!) ; Port St. Johns, Mount Sullivan, Nxolweni Forest , below Devil’s Bite , near Umtweni , (3129DA), 13 April 1990, Van Wyk 10140 ( PRU!) ; Transkei, Mzamba, iNgwanyama [Engonyama] River , Tributary to the Mzamba River , (3130AA), 29 August 1994, Arkell 229 ( PRU!) ; Mzamba, Hlolweni / Icwaka Rivers junction, 260 m, (3130AA), 19 November 1994, Abbott 6554 ( PCE!, PRU!) ; Transkei, Mzamba, Hlolweni River at junction with Icwaka , (3130AA), 15 December 1994, Abbott 6629 ( PRU!) ; Transkei, Elliotdale District, Mpame Forest , (3228BB), September 1924, Miller D 278 ( PRE!) ; Kentani District, Manubi Forest , (3228BC), 16 September 1954, Marais 481 ( PRE!) ; Manubi , in moist forest, (3228BC), 15 October 1988, Van Daalen 420 ( PRE!) ; Transkei, Mazeppa Bay, Manubi Forest , (3228BC), 30 July 1988, Van Wyk 8285 ( PRU!) ; Elliotdale District, The Haven , 1 mile SW of Ntlonyana, (3228DB), 13 May 1967, Gordon Grey 1441 ( NU!)

Figures

FIGURE 1. Casearia austroafricana. A. Fruiting branchlet placed horizontally; to view original hanging orientation, turn plate 90º clockwise. B. Flowers. C. Ripe and dehisced fruit. Photographs: R.G.C. Boon.

FIGURE 2. Casearia austroafricana. A. Flowering branchlet. B. Flower. C. Flower; one sepal and half the staminal tube removed. D. Part of staminal tube opened out. E. Fruit. F. Dehisced fruit; seeds all shed. G. Seeds, both from same capsule and each covered by an aril. Scale bar = 10 mm (A, E & F), or 1 mm (B–D & G). A–D from Luckhoff s.n., sub NH 32946, E & G from Miller 5824 and F from Miller 652. Artist: Daleen Roodt.

FIGURE 3. Topographical map showing the known distribution (black dots) of Casearia austroafricana based on herbarium collections in NH, NU, PCE, PRE, PRU and UDW. The insert shows a map of southern Africa with names of countries; the grey rectangle indicates the area depicted by the topographical map.

FIGURE 4. Lepidoptera that use Casearia austroafricana as host-plant. A. Larva of a moth belonging to the family Geometridae, subfamily Larentiinae; probably Chloroclystis muscosa tumefacta. B & C. Larva (B) and adult (C) of an as yet undescribed moth of the tribe Archipini (Tortricidae). Rearing number of B & C: Staude 16HSS38. Photographs: R.G.C. Boon (A) and H.S. Staude (B & C).