Ancistrocladus korupensis

Notes

The Thomas collection was a voucher for a 0.5-kg sample of dried stems and leaves, collected under Contract No. NO 1-CM-67923 between the Missouri Botanical Garden and the Developmental Therapeutics Program of the United States' National Cancer Institute (N.C.I.). Extracts of this sample tested for in vitro biological activity were found to inhibit the destruc- tion of cultured human lymphocytes by both HIV-1 and HIV-2 (Manfredi et al., 1991). Before it was realized that a new species was involved, the new alkaloids that inhibit HIV had been isolated and named michellamine A and B. These are apparently dimers of other naphthyl is- oquinoline alkaloids (Bringmann, 1986) previously identified from the genus (references in Leonard, 1982, 1986). At this point, the N.C.I. requested more material for further testing; samples of A. abbreviatus from Gabon, however, showed no in- hibitory activity against HIV. When the original population from which the biologically active sam- ples had been taken was relocated in Korup, it became clear that the plants belonged to a new species, apparently narrowly endemic to the Korup area. With the discovery of flowers and fruits, we have been able to complete the description of this species; the initial impetus for this task came from the plant's pharmaceutical potential. Thomas and Gereau (1993) provided detailed in-formation about the physical environment, ecology, and phytochemistry of this species. This species was initially misidentified as Ancistrocladus abbreviatus, and Bringmann et al. (1990) and Manfredi et al. (1991) reported studying A. abbreviatus, but actually studied the alkaloids of A. korupensis, which had not yet been described when they published their work (Foster & Sork, 1997). Boyd et al. (1994) and Bringmann and Pokorny (1995) also investi-gated the chemistry of this species. Foster and Sork (1997) studied in detail the population and genetic structure and alkaloid content of this species in Korup National Park in Cameroon. Label data for D. W. Thomas 9971 (MO) report flowers of A. korupensis opening at night and with a faint aromatic odor; this is the only report of floral biology for any species of the genus.

Distribution (General)

Ancistrocladus korupensis was apparently first collected near Oban in the Cross River State of southeastern Nigeria (Talbot 1726, BM); this sterile specimen was identified only as Ancistrocladus sp. The second collection, Thomas 6889 (MO, YA), was collected in 1987 in the Korup National Park, probably about 50 km from Talbot's locality; this collection, also sterile, was tentatively identified as the widespread species A. abbreviatus. Southeast Nigeria to westernmost Cameroo.

Diagnosis

Plantae omnino glabrae. Caules adulti parce ramosi; ramis principalibus elongatis, rectis subcurvatisve; ramis lateralibus extra-axillaribus, uncos gerentibus. Folia adulta sessilia, ex formis duabus constantia: folia ramorum principalium remote disposita, ex ellipticis oblonga, basi cuneata, apice rotundata, venis secundariis paucijugis; folia ramorum lateralium in rosulas apicales crebra, oblanceolata, (8-)14.5-33.1 x (2.9-)4.6-8.5 cm, basi ex anguste cuneatis ad longe cuneata, apice ex acutis rotundata, margine prope basim valde revoluta, sursum nonnihil revoluta, venis secundariis paribus 8-18 dispositis, brochi- dodromis; foliorum omnium costa infra prominente, in herbario supra parum impressa, venis secundariis utrinque prominulis, venis tertiariis tenue reticulatis. Inflorescentia ex panicula dichotoma laxa inter rosulas foliorum portata constans; pedunculo extra-axillari, (4-)5.5-9.8 cm longo; pedicellis 6.5-8.5 mm longis, sub calyce ca. 2 mm articulatis. Flores sepalis ex suborbicularibus oblongis, manifeste dimorphis, majoribus tribus ca. 5 x 4 mm, mino- ribus duobus ca. 2.5 x 3.5 mm, basi truncatis, apice rotundatis, sub anthesi ad ovarii basim breve decurrentibus; petalis suborbicularibus quam sepalis brevioribus, prope basim convexis incrassatisque; staminibus 10 in verticillos duos dispositis, filamentis validis, internis ca. 1 mm longis, externis perbrevibus, antheris ca. 1 mm longis; stylis 3, distinctis, ca. 2 mm longis, distaliter incrassatis. Fructus hebetate brunneus; sepalis tenuibus, inaequalibus, majoribus spathulatis 3.4-4.8 x 1.3-2.1 cm, minoribus ex anguste oblongis spathulatis 1.1-2.8 x 0.5-1.1 cm, alarum marginibus 5 ad basim fructus decurrentibus costas prominentes 5 formantibus; fructus corpu turbinato, receptaculo supra alas inflato tholiformique; styli basi persistente accrescente conica; pericarpio crasso sicco coriaceo; semine diametro ca. 8 mm

Habitat

The area in which Ancistrocladus korupensis is known to grow supports closed-canopy evergreen forest with areas of secondary growth following human disturbance (Gartlan et al., 1986). The area lies at 50-100 m above sea level and is flat to gently undulating with numerous small creeks in shallow valleys. There are occasional outcrops and boulders of the hard, acidic metamorphic rocks of the African basement complex. The autochthonous soils are highly acidic (pH ca. 3.9-4.5), leached, and infertile, with a high to very high sand content (60- 91%) and the clay fraction greatly depleted near the surface. The rainfall pattern is pseudo-equato- rial, with only a single wet and dry season rather than the two wet and two dry seasons found further south. Rainfall at the nearby Ndian oil palm plantation averaged 5,460 mm annually in the period 1963-1983. The single long wet season peaks in July-September; November-March is the dry sea- son, with January the driest month. There is little annual variation in mean temperatures. Letouzey (1985) classified the vegetation of the area as Atlantic-Biafran evergreen forests, rich in Caesalpiniaceae. This forest type is widespread at low elevations near the coast in Cameroon; however, the forest on low-lying sandy clay soils in which Ancistrocladus korupensis occurs has a unique and distinctive vegetation. Ancistrocladus korupensis occurs in forests of well-defined physical structure with a high degree of local endemism. Common or locally dominant trees of the upper canopy include Afzelia bipindensis Harms, Berlinia bracteosa Bentham, Didelotia africana Baillon, Erythrophloeum ivorense A. Chevalier, Julbernardia seretii (DeWildeman) Troupin, Microberlinia bisulcata A. Chevalier, Tetraberlinia bifoliolata (Harms) Hauman (Caesal- piniaceae), Lecomptedoxa klaineana (Pierre ex Engler) Dubard (Sapotaceae), and Lophira alata Banks ex Gaertner (Ochnaceae). The lower canopy is dominated by Oubanguia alata Baker f. (Scytopetalaceae), apparently common only in the Korup area; other common smaller trees include Dichostemma glaucescens Pierre, Klaineanthus gaboniae Pierre ex Prain, Mareyopsis longifolia (Pax) Pax & K. Hoffmann (Euphorbiaceae), Diogoa zenkeri (Engler) Exell & Mendonca, Strombosia pustulata Oliver (Olacaceae), Diospyros gabunensis Giirke (Ebenaceae), Hymenostegia afzelii (Oliver) Harms (Caesalpiniaceae), and Tabernaemontana brachyantha Stapf(Apocynaceae). The genus Cola Schott & Endlicher (Sterculiaceae) is well represented in the understory, which is dominated by C. semecarpophylla K. Schumann, a monocaulous tree with rosettes of very large leaves; C. caulifora Masters, C. lateritia K. Schumann, C. megalophylla Brenan & Keay, and C. rostrate K. Schumann are also common. Deinbollia unijuga D. W. Thomas (Sapindaceae) appears to be limited to the same area as A. korupensis, and additional narrow endemics to be described from Korup collections include new species of Corymborkis Thouars (Orchidaceae), Uvariopsis Engler (Annonaceae), and Vepris Commerson ex A. Jussieu (Rutaceae). The area is rich in species of lianas. Ancistrocladus guineensis occurs in the same area as the new species, while A. abbreviatus is common in nearby seasonally flooded forests. Ancistrocladus letestui occurs on nearby hills, while A. uncinatus is known only from Cross River State, Nigeria, adjacent to the Korup area. Other climbers include many species in the genus Strychnos L. (Loganiaceae) and in the families Annonaceae, Apocynaceae, Connaraceae, Fabaceae, Icacinaceae, and Menispermaceae. Moist evergreen forests at 50-360 m.

Conservation

With an EO of less than 5000 km2 and occurring primarily within the well-protected Korup National Park, Cameroon, and neighboring Oban Hills of Nigeria, this taxon is common, though endemic and potentially threatened outside of these areas: Vulnerable (Blac); Cheek (2000: 876) proposed a status of Lower Risk, but Conservation Dependent (LR/cd).

Description

Plants glabrous throughout. Saplings unbranched or very sparingly branched, to 4 m high, lacking hooked lateral branches; sapling leaves long-lived, indense terminal rosettes, 38.8-75.1 x 11.0-13.8 cm (L/W = 3.5-5.4), the secondary veins in 25- 32 pairs; saplings becoming lianas by branching from lateral bud some distance below leaf rosette, this "main branch" long and scandent, bearing hook- producing lateral branches. Adult stems climbing to 20 m, to 10.4 cm maximum diameter, sparingly branched, not normally rooting when in contact with ground, terete, with outer bark purplish brown, inner bark red and fibrous; main branches elongate, straight or somewhat curving, not twining; lateral branches extra-axillary, to ca. 50 cm long, bearing 1-several hooks in a single plane. Adult leaves sessile, of 2 kinds: leaves of main branches widely spaced, elliptic to oblong (ca. 12 x 5 cm in type), cuneate at base, rounded at apex, with as few as 7 pairs of secondary veins; leaves of lateral branches crowded in rosettes produced near apex of current year's growth and persisting up to three years, oblanceolate, (8-)14.5- 33.1 x (2.9-)4.6-8.5 cm (L/W = 2.9-4.2), narrowly cuneate to long-attenuate at base, acute to rounded at apex, the margin strongly revolute near base, somewhat revolute distally, the secondary veins in 8-18 pairs, brochidodromous, forming an intra- marginal vein 2-4 mm from margin; all leaves drying dull dark green above, yellow-green beneath, the midrib extending to apex, terminating in a gland, prominent beneath, slightly impressed above in her- barium specimens, the secondary veins prominulous on both surfaces, shortly decurrent on midrib, the tertiary veins finely reticulate, rather obscure. In- florescence a lax, dichotomously branched panicle, borne among leaf rosettes, sometimes bearing hooks; peduncle extra-axillary, (4-)5.5-9.8 cm; pedicels 6.5-8.5 mm long, articulated ca. 2 mm below calyx. Flowers with sepals suborbicular to oblong, distinctly dimorphic, the larger three ca. 5 x 4 mm, the smaller two ca. 2.5 x 3.5 mm, pale yellow-green with fine brownish veins, truncate at base, rounded at apex, shortly decurrent on base of ovary at an- thesis; petals suborbicular, shorter than sepals, pale yellow, entire, convex and thickened toward base; stamens 10 in 2 whorls, the filaments stout, those of inner stamens ca. 1 mm long, those of outer stamens very short, the anthers ca. 1 mm long with thecae separated by well-developed connective; styles 3, distinct, ca. 2 mm long, distally thickened, each terminating in a broad flattened stigma. Fruit dull brown; sepals thin, dry, brittle, unequal, the larger spathulate, 3.4-4.8 x 1.3-2.1 cm, the smaller narrowly oblong to spathulate, 1.1-2.8 x 0.5-1.1 cm, with both margins of smaller wings and one margin of one larger wing decurrent on base of fruit, forming 5 prominent ribs; fruit body turbinate, broadest at level of wings with diameter of 1.0-1.2 cm, the receptacle inflated and domelike above wings; scars of fallen petals and stamens forming a pale annulus 1-2 mm above wings; style base persistent, enlarged, conical; pericarp thick, dry, coriaceous; seed ca. 8 mm diam., with cerebriform-ruminate endosperm evident through thin testa; germination epigeal in moist litter layer, the cotyledons remaining inside fruit. Juvenile plants unbranched or sparingly branched saplings to 4 m tall, lacking hooked branchlets. Juvenile leaves numerous in terminal rosettes, long-lived, oblanceolate, 38.8-75.1 X 9.5- 13.8 cm, L/W 3.5-5.4, at apex acute to acuminate, at base attenuate, drying papyraceous to chartaceous, dull to shiny on both surfaces; pits dimorphic, similar to those of adult leaves; midrib adaxially shallowly sulcate, abaxially prominent, terminating in a tiny gland; secondary veins 23 to 35 pairs; secondary and tertiary venation adaxially and abaxially prominulous; margins plane to thinly re volute. Adult stems arising from extra-axillary buds well below apex of juvenile stem, climbing to 20 m high, main stems to 14 cm diam., not twining, sparingly branched, with bark purplish brown, smooth to roughened, bearing scattered leaves and lateral branchlets to 50 cm long, these each bearing 1 to several hooks and sometimes a terminal rosette of leaves; hooks recurved to spiraling, 9-19 mm diam. Adult leaves drying papyraceous to chartaceous, on both surfaces shiny, in life a little discolorous, green above, yellow-green below, when dry discolorous, dark green above, yellow-green below; pits dimorphic, small pits sparse to frequent on both surfaces though usually denser on adaxial surface, large pits 0.4-0.6 mm diam., circular or broadly elliptic, scattered on abaxial surface, scat-tered usually near base on adaxial surface; midrib adaxially nearly plane to shallowly sulcate, abaxially prominent, terminating in a tiny gland; secondary veins prominulous on both surfaces; tertiary veins reticulated and prominulous on both surfaces; margins narrowly to markedly revolute; stem leaves apparently long-lived, elliptic to oblong or oblan-ceolate, 12-57 X 5.0-12.8 cm, L/W 3.5-4.2, at apex acute to rounded, at base cuneate to acute; secondary veins 7 to 20 pairs; leaves at branchlet apices persisting up to 3 years, oblanceolate, (8.0-)14.5-34.2 X (2.9-)4.6-11.0 cm, L/W 2.9- 4.2, at apex acute to rounded and sometimes abruptly shortly acuminate, at base narrowly cuneate to long-attenuate; secondary veins 8 to 18 pairs, with intramarginal vein situated 2-4 mm from margin. Inflorescence lax, paniculate, lateral among leaves at apices of branchlets, occasionally bearing hooks (e.g., Gereau et al. 5532, MO), without bracteal leaves; peduncle (4.0-)5.5- 13.0 cm long, often flexuous; branched portion corymbiform, 7-16 X 12-20 cm, dichotomously branched; bracts triangular to narrowly ovate, 0.5-1.0 X 0.2-0.4 mm, at apex acute to obtuse, at base obtuse, abaxially eglandular; pedicels 6-9 mm long. Flowers pedicellate, rarely (e.g., Gereau & Thomas 5204, MO) borne singly on hook-bearing branches from sapling; sepals 5, suborbicular to elliptic-oblong, rounded and ciliolate at apex, at base rounded to truncate and shortly decurrent on ovary, pale yellow-green to greenish white with slender brown to translucent veins, abaxially apparently eglandular, adaxially with small pits, unequal, larger 3 sepals 5.0-6.0 X 3.0^.0 mm, smaller 2 sepals 2.5-3.5 X 2.0-3.5 mm; petals 5, convolute, suborbicular, pale yellow to pale rose-pink, 2.0-3.0 X 2.0-2.9 mm; stamens 10 in 2 whorls; filaments stout, dimorphic, the shorter 0.5-0.7 mm long, the longer 0.8-1.3 mm long; anthers 0.5-0.8 mm long; ovary fully inferior, 1-3 mm long; styles 3, ca. 2 mm long, stigmas ca. 0.5 mm long. Fruit turbinate; nut 10 X 10-12 mm, on sides longitudinally shallowly 5- ridged by decurrent margins of accrescent sepals; persistent sepal limbs spreading, chartaceous to papyraceous, unequal, larger 3 sepals spathulate to oblanceolate, 34-48 X 13-21 mm, smaller 2 sepals narrowly oblong to spathulate, 11-28 X 4-11 mm; pericarp drying dull brown, coriaceous; seed obconical, ca. 8 mm diam.

Habitat

The area in which Ancistrocladus korupensis is known to grow supports closed-canopy evergreen forest with areas of secondary growth following human disturbance (Gartlan et al., 1986). The area lies at 50-100 m above sea level and is flat to gently undulating with numerous small creeks in shallow valleys. There are occasional outcrops and boulders of the hard, acidic metamorphic rocks of the African basement complex. The autochthonous soils are highly acidic (pH ca. 3.9-4.5), leached, and infertile, with a high to very high sand content (60- 91%) and the clay fraction greatly depleted near the surface. The rainfall pattern is pseudo-equato- rial, with only a single wet and dry season rather than the two wet and two dry seasons found further south. Rainfall at the nearby Ndian oil palm plantation averaged 5,460 mm annually in the period 1963-1983. The single long wet season peaks in July-September; November-March is the dry sea- son, with January the driest month. There is little annual variation in mean temperatures. Letouzey (1985) classified the vegetation of the area as Atlantic-Biafran evergreen forests, rich in Caesalpiniaceae. This forest type is widespread at low elevations near the coast in Cameroon; however, the forest on low-lying sandy clay soils in which Ancistrocladus korupensis occurs has a unique and distinctive vegetation. Ancistrocladus korupensis occurs in forests of well-defined physical structure with a high degree of local endemism. Common or locally dominant trees of the upper canopy include Afzelia bipindensis Harms, Berlinia bracteosa Bentham, Didelotia africana Baillon, Erythrophloeum ivorense A. Chevalier, Julbernardia seretii (DeWildeman) Troupin, Microberlinia bisulcata A. Chevalier, Tetraberlinia bifoliolata (Harms) Hauman (Caesal- piniaceae), Lecomptedoxa klaineana (Pierre ex Engler) Dubard (Sapotaceae), and Lophira alata Banks ex Gaertner (Ochnaceae). The lower canopy is dominated by Oubanguia alata Baker f. (Scytopetalaceae), apparently common only in the Korup area; other common smaller trees include Dichostemma glaucescens Pierre, Klaineanthus gaboniae Pierre ex Prain, Mareyopsis longifolia (Pax) Pax & K. Hoffmann (Euphorbiaceae), Diogoa zenkeri (Engler) Exell & Mendonca, Strombosia pustulata Oliver (Olacaceae), Diospyros gabunensis Giirke (Ebenaceae), Hymenostegia afzelii (Oliver) Harms (Caesalpiniaceae), and Tabernaemontana brachyantha Stapf(Apocynaceae). The genus Cola Schott & Endlicher (Sterculiaceae) is well represented in the understory, which is dominated by C. semecarpophylla K. Schumann, a monocaulous tree with rosettes of very large leaves; C. caulifora Masters, C. lateritia K. Schumann, C. megalophylla Brenan & Keay, and C. rostrate K. Schumann are also common. Deinbollia unijuga D. W. Thomas (Sapindaceae) appears to be limited to the same area as A. korupensis, and additional narrow endemics to be described from Korup collections include new species of Corymborkis Thouars (Orchidaceae), Uvariopsis Engler (Annonaceae), and Vepris Commerson ex A. Jussieu (Rutaceae). The area is rich in species of lianas. Ancistrocladus guineensis occurs in the same area as the new species, while A. abbreviatus is common in nearby seasonally flooded forests. Ancistrocladus letestui occurs on nearby hills, while A. uncinatus is known only from Cross River State, Nigeria, adjacent to the Korup area. Other climbers include many species in the genus Strychnos L. (Loganiaceae) and in the families Annonaceae, Apocynaceae, Connaraceae, Fabaceae, Icacinaceae, and Menispermaceae. Moist evergreen forests at 50-360 m.

Phenology

Collected in flower in February and November, in fruit in March and December.

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