Hydnophytum minirubrum Jebb & C.R.Huxley, 2019

38. Hydnophytum minirubrum Jebb & C.R.Huxley View in CoL , sp. nov. —

Fig. 41 View Fig

Tuber sphaericum usque ellipsoideum,contextu rubello-purpurea;superficies sparsis tuberculis et radicibus obtecta. Aperturae numerosae, grandes, labrosae, ad 2 cm in diametro. Caules numerosi, libere ramosi; internodia fertilia contorta. Lamina ovata usque subrotunda, 1.2 per 0.6 ad 2 per 1.5 cm, apice acuto, basi rotundata usque sensim attenuata. Petiolus minus quam 2 mm. Inflorescentia binata, sessilis. Bracteae ad 0.4 cm, papyraceae, triangulares; nonnulli ex pilis bractealibus ad 0.3 cm. Calyx 3.5 mm; margo 4 vel 5 dentato acuminatis, ad 2 mm longis, interdum fimbriatis instructus. Corollae tubus albus,ad 7.5 mm,pilis in fauce dimidio superiore conspersus, vel glaber. Lobi rubello-purpurei, ad 2.5 mm. Antherae exsertae ex fauce, 1.5 mm. Pyrenae hemisphericae, 3.5 per 2 mm.

— Typus: Jebb 289 (holo LAE; GoogleMaps iso A, GoogleMaps BRI, CANB, GoogleMaps K, GoogleMaps L), Papua New Guinea, Southern Highlands Province,S6°07'E143°57', SE of Mt Giluwe , above Onin ,‘ Beechwoods No.2’logging track , 24 Apr. 1983 GoogleMaps .

Etymology. There are two taxa in Papua New Guinea with red tuber tissue and red-tipped corollas, of the two this has the smaller leaves.

Tuber regularly spherical to ellipsoid, to 30 by 18 cm. Surface covered by numerous scattered tubercles to 0.15 cm, and roots. Entrance holes numerous; 0.2–1.2 cm across internally, overall to 2 cm; rimmed, the rims to 0.4 cm across. Cavity walls silvery or dull reddish brown. Tuber tissue reddish purple. Stems numerous, to 70 by 0.8 cm, freely branching, elliptic in section towards node, cylindrical elsewhere; upcurved to ascending. Internodes 2–4 by 0.3–0.8 cm when sterile, shorter, 0.15–1.5 cm and contorted when fertile. Leaves clustered, more or less erect, recurved. Lamina ovate to subround; 1.2 by 0.6 to 2 by 1.5 cm; apex acute; base rounded to tapered; glossy green above, yellowish green below; venation obscure. Petiole <0.2 cm, rounded, yellow-green; stipules 0.1–0.2 cm, triangular, acute, with a small central process, papery and caducous. Inflorescence paired sessile. Bracts to 0.4 cm, papery, triangular, some bract hairs to 0.3 cm. Flowers [4]?not heterostylous. Calyx 3.5 mm; margin with 4 or 5 acuminate, sometimes fringed appendages to 2 mm long. Corolla white, lobes reddish purple, tube to 7.5 mm, with short scattered hairs in upper half, or glabrous, lobes 2.5–3 mm. Anthers to 1.5 mm, exserted from mouth of corolla tube. Pollen 3 or 4 colporate, 86 (80–100) μm, brochi irregular 1–5 μm; vesicles absent. Stigma 2- or 3-lobed, exserted. Fruit globose to 4 mm, orange-red. Pyrenes hemispherical, 3.5 by 2 mm.

Ecology & Habitat — Mid- to high-level epiphyte in Nothofagus forest, 2 400–2 800 m. Tuber not inhabited by ants, occupied by spiders, myriopods or other arthropods.

Distribution — Papua New Guinea (Western Highlands and Southern Highlands Province).

Conservation status — Endangered (EN) under criteria B1ab (iii)+2ab(iii). The three known localities lie within 40 km of one another in the montane forests of Mt Giluwe and Mt Hagen. Other information: AOO 43 km 2 (using an auto-value cell width of 4 km), EOO 247 km 2.

Additional specimens examined. Jebb 301 (CANB, K, L, LAE ), Western Highlands Province: S5°47' E143°59', Tomba Pass, on road from Wabag to Hagen; Huxley & Turton in UPNG 5919A (A, BRI, K, L, UPNG), Southern Highlands: S5°57' E143°51', foothills of Mt Giluwe, on Mendi-Hagen Road; Jebb 267 ( LAE ), Jebb 268 ( LAE ), Jebb 283 (L, LAE ), Jebb 288 (FHO),S6°07' E143°57', SE of Mt Giluwe, above Onin, ‘Beechwoods No. 2’ logging track.

Note — This species is very similar to H. magnirubrum [37] with which it occurs co-extensively. Each has a reddish purple fleshed tuber, contorted and contracted nodes, small leaves and a reddish purple tipped flower. The two species are sympatric throughout their range. The two species can be distinguished by a combination of characters: the leaves of H. minirubrum are smaller, the apex in particular being more acute, the venation of the leaves is less apparent; the tubers of H. minirubrum are more regular in outline, with a roughened surface covered by numerous small tubercles; the entrance holes of this species are also striking for their large regular rims, reaching up to 2 cm across, in H. magnirubrum the rimmed entrance holes are smaller, and the surface is mostly smooth while the larger entrance holes are distinctly funnel-shaped; lastly H. magnirubrum may have up to 3 pyrenes in each fruit.