Eriosema triforme Burgt

IUCN Red List of Threatened Species https://www.iucnredlist.org/species/15368367/176946500

Conservation

CR - critically endangered

van der Burgt, X.M., Haba, P.K., Haba, P.M. et al. 2012. Kew Bulletin 67: 263. https://doi.org/10.1007/s12225-012-9357-5

Morphology General Habit

Pyrophytic herb, rootstock perennial, stems annual; annually exhibiting 3 phases: a dormant phase with only the underground rootstock remaining; a flowering/fruiting phase with erect, unbranched stems with axillary inflorescences and/or infrutescences and young leaves, total height 6 – 16 cm; and a sterile phase with mature leaves on scrambling, sparsely branched stems to 60 cm long

Morphology Roots

Rootstock vertical, fibrous to woody, subterranean; abundant red juice in bark; to c- 20 cm long, to 2.5 cm thick near the apex, tapering towards the base; apex rounded, with 1 – 2 (– 6) fibrous to woody pegs, subterranean, 1 – 3 cm long and 0.2 – 0.5 cm thick, 1 – 3 stems sprouting from the apex

Morphology Stem

Stems longitudinally ridged, gland-dotted, densely hirsute, hairs retrorse, whitish, 0.5 – 1 mm long; internodes 1.5 – 4 (–6.5) cm; stem base with up to 3 leafless nodes with a scale-leaf to 6 × 4 mm, and sometimes 2 small linear stipules

Morphology Leaves Stipules

Stipules in pairs, free, caducous, venation parallel; densely hairy outside and on edge, hairs to 1 mm; glabrous inside; stipules on lower, fertile nodes ovate 6 – 10 × 2 – 3 mm; on upper, infertile nodes linear 4 – 7 × 1 mm

Morphology Leaves Stipel

Stipels absent

Morphology Leaves

Leaflets ovate to orbicular, ovate leaflets 3 – 7.5 × 1.8 – 3.4 cm; orbicular leaflets 2.6 – 6.5 × 2.3 – 5.0 cm, leaflet blade length/width ratio 1.1 – 2.3; base obtuse, rounded or subcordate, apex acute; slightly 3-veined at base, 6 – 9 pairs of secondary veins, veins raised on lower surface; leaflets slightly lighter green beneath, gland-dotted both sides, with transparent yellow resin drops; moderately hirsute both sides, hairs erect, upper part curved, 0.5 – 1 mm long, whitish, on and in between venation; young leaves densely hairy on both sides Leaves unifoliolate, petiole 4 – 8 mm, densely hirsute, upper part pulvinate

Morphology Reproductive morphology Inflorescences

Inflorescences axillary racemes, erect, 1 – 3 (– 5) per stem; 1 (– 2) per node; usually inserted in the lowest 1, 2 or 3 leaf nodes; sometimes also in the leafless node below the lowest leaf, or in the 4th leaf node; inserted at (0 –) 1.5 – 9 (– 13) cm above ground level; total length 2.3 – 8.3 (– 10.3) cm, fertile part 0.3 – 1.4 (– 1.8) cm long; 3 – 10 flowers; axis longitudinally ridged, gland-dotted, densely hirsute, hairs antrorse and retrorse, whitish, 0.5 – 1 mm long

Morphology Reproductive morphology Inflorescences Bracts

Bracts caducous, inserted at the base of the pedicel, lanceolate, 5 × 1 mm, moderately hairy outside and on edge, glabrous inside; bracteoles absent

Morphology Reproductive morphology Flowers

Flowers yellow

Morphology Reproductive morphology Flowers Calyx

Calyx reddish brown, gland-dotted outside, with transparent yellow resin drops, moderately hirsute outside, hairs whitish, 0.5 – 1 mm long, glabrous inside, calyx tube 1.5 – 2 mm long, lobes 5, equal in size and shape, narrowly triangular, 4 – 5 × 1.3 mm

Morphology Reproductive morphology Flowers Corolla

Corolla: standard petal obovate, 14 × 8 mm, including claw 2 mm; outside light yellow with reddish veins, moderately hirsute and gland-dotted, hairs whitish, to 0.7 mm; inside yellow with reddish veins, glabrous; wing petals yellow, glabrous, 12 × 2.5 mm, including claw 2 mm, blade with slight pocket; keel petals light yellow, apex reddish, partly united near the apex, 13 × 3.5 mm, including claw 3 mm

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens diadelphous, 9 + 1, filaments 13 – 14 mm, glabrous, anthers c- 0.5 mm long. Pistil 15 mm, ovary 3 mm, with 2 ovules, densely hairy with whitish hairs to 3 mm; style 12 mm, upper part glabrous; stigma punctiform

Morphology Reproductive morphology Fruits

Fruits elliptic, green to brown, 10 – 12 × 7 – 8 mm, densely hairy with erect whitish hairs 3 mm long, 1 – 2 seeded

Morphology Reproductive morphology Seeds

Seeds smooth, somewhat glossy, light brown with irregular dark spots, 5 × 3 × 1.5 mm, aril light yellow

Distribution

West Africa, Guinea, Simandou Range, Pic de Fon (Map 1).

Ecology

Submontane grassland on well-drained rocky soil, 1,250 – 1,600 m. In this habitat type and altitudinal range, 32 species of Poaceae, 12 species of Cyperaceae and many other species of herbs have been recorded.

Conservation

A number of expeditions were organised to nearby mountain ranges in Guinea, in order to find additional localities for Eriosema triformum and other rare plant species, and to find suitable localities for transplanting these species. Some localities were visited two or three times, during different times of the year. Submontane grassland habitat at altitudes above 1,000 m was found in 19 localities, but Eriosema triformum was never found (Map 2). However, in some of these 19 localities there are extensive areas with habitat suitable for E. triformum that could not be searched through completely; the species may occur there. In 14 of these 19 localities, one or more of the other four pyrophyticsubmontaneEriosema spp. found in the study area were recorded: E. chrysadenium Taub., E. monticola Taub., E. parviflorum E. Mey. subsp. collinum Hepper and E. shirense Baker. f.; indicating that the habitat would be suitable for E. triformum. One of these localities is situated in Liberia, and was not visited but taken from J. G. Adam 21032: E. parviflorum subsp. collinum. In the ZiamaMts no submontane grassland was found; the area is mostly under forest cover, with a few rock outcrops.  riosematriformum appears to be endemic to a 16 km long and maximum 2 km wide section of the Simandou Range, both north and south of Pic de Fon. The species tends to grow in groups of c. 10 – 100 plants; each group occupying an area of c. 50 – 500 m2. The species’ habitat quality and quantity is at risk of negative changes in the future, as a result of planned mining activities in a part of this section of the Simandou Range. The possible future population reduction could be >50 % if the mining activities are carried out as planned. However, three sites within the 16 km section are outside the current mine plan. The extent of occurrence as defined by IUCN (2001) is <100 km2, but since three sites are not threatened, E. triformum is here assessed as Endangered A3c; B2ab(i,iii) (IUCN 2001). Rio Tinto, the mining company that is planning the mining activities, has already greatly assisted with measures to protect Eriosema triformum and other rare plant species in the area, and is dedicated to continue doing so. Future conservation work on E. triformum will consist of further searching for the species on nearby mountain ranges, transplanting threatened populations by seed, propagating the species in the on-site nursery, and storing its seeds in a seed bank in Guinea and in the Millennium Seed Bank of the Royal Botanic Gardens, Kew.

Phenology

Flowering starts during the dry season after fire has passed through the grassland. Flowering was recorded at the end of March 2008, and at the end of January to mid-February 2010. In a dry season without fire, the plants would probably start to grow after the start of the rains, in March or April. Fruiting begins quickly after the start of flowering; flowering and fruiting together are completed in a few weeks. The sterile phase begins after fruiting and has been recorded from early July to early December. The dormant phase begins after the start of the dry season.

Note

Many pyrophytic species of Eriosema flower before the first leaves appear, or at the same time as the first leaves; but in most species a sterile, leafy phase was not recorded. Many species of Eriosema keep on flowering and fruiting as the plants grow larger. The sterile phase is known to exist, or was predicted to exist, for only a few species of Eriosema . Tisserant (1930) observed a sterile, leafy growth phase, during which the plants may grow to over 1 m high, for E. pauciflorumKlotzsch, E. praecox R. E. Fr. (now a synonym of E. rhodesicum R. E. Fr.), E. sacleuxiiTisser. and E. sparsiflorum Baker f. A sterile phase was predicted by Jacques-Félix (1971) for E. raynaliorum. Jacques-Félix (1971: 143) also mentions that in E. mirabile R. E. Fr. (now also a synonym of E. rhodesicum) the lowest nodes of the stems have inflorescences but are leafless; after flowering these stems continue to grow and produce leaves but no flowers. Since sterile plants are seldom collected and sterile collections are difficult to identify to species, the sterile, leafy phase may occur in more species of Eriosema .