Stryphnodendron holosericeum Scalon, 2022

Scalon, Viviane Renata, Paula-Souza, Juliana De, Lima, Alexandre Gibau De & Souza, Vinicius Castro, 2022, A synopsis of the genus Stryphnodendron (Fabaceae, Caesalpinioideae, mimosoid clade), Phytotaxa 544 (3), pp. 227-279 : 247-250

16. Stryphnodendron holosericeum Scalon , sp. nov. ( Fig.5 ).

— Type: BRAZIL. Minas Gerais, Formoso, Parque Nacional Grande Sertão Veredas , margem esquerda do Rio Preto , 05 November 1989, Walter et al. 510 (holotype RB 375879!, isotypes ESA! IBGE!, K!, RFA!)

Diagnosis: Stryphnodendron holosericeum resembles Stryphnodendron rotundifolium var. villosum , but differs by its fusiform petiolar nectary, usually immersed, sometimes slightly prominent, darkened, 3–4 × 0–0.5 mm (vs. verruciform with an elongated base, 2.5–3.5 × 0.5–1.5 mm), 2nd degree petiolules 0.2–0.3 mm long (vs. 0.5–1 mm), leaflets canescent, densely villous to sericeous on both surfaces (vs. subglabrous to sparsely villous at the upper surface, lower surface sparsely pubescent to villous, rarely densely villous), calyx hirsute at the upper half of the lobes or ciliate only at the apex (vs. glabrous, sparsely ciliate at the apex of the lobes), ovary glabrous (vs. white-pulverulent to whitepubescent) and prophylls late deciduous, densely yellow-tomentose and -pulverulent (vs. early deciduous, villous).

Trees 6–10 m tall, the branches lenticelate, lacking extrafloral nectaries, velutinous, glabrescent, the indumentum usually concentrated near the insertion of the leaves and the apex of the branches, yellow-velutinous at the apex. Leaves with petioles 3.5–5.5 cm long, velutinous, extrafloral nectary–1, inserted at 0.3–0.7 cm from the base of the petiole, 3–4 × 0–0.5 mm, fusiform, usually immersed at the petiole, sometimes slightly prominent, darkened; pinnae (6–)9–10, subopposite to opposite, the insertion of each pair spaced in (1–) 1.3–2.2 cm; rachis striate, velutinous; extrafloral nectaries 1–2, inserted at (1–) 3–5 mm below the distal pair of pinnae, 1–2 × 0–0.5 mm, usually fusiform with the central region cylindrical and slightly elevated, sometimes more rounded, darkened; stipels deciduous, not seen; 2nd degree petiolules 0.2–0.3 mm long, densely yellow-velutinous; leaflets (4–)6–11 pairs, the proximal and distal pairs of pinnae bearing fewer leaflets; rachillae velutinous, extrafloral nectaries 2–3(–4), inserted at 0.5–2 mm below the distal pair of leaflets, (0.5–)1 × 0.2–0.5 mm, verruciform to fusiform, darkened; stipel deciduous, not seen; leaflets usually alternate, subopoosite only at the distal pairs, blade slightly asymmetrical, moslty orbicular, sometimes ellipticorbicular or elliptic, rarely widely ovate, distal leaflets usually ovate, (6–)8–13(16) × (6–) 8–13 mm, apex usually rounded to weakly retuse, at the distal leaflets sometimes emarginate, margin subrevolute, entire and velutinous, base asymmetrical, the proximal side of the blade usually truncate, sometimes widely rounded, distal side usually rounded, the proximal side of distal pairs of leaflets usually, chartaceous, subconcolor, upper surface slightly darker, lower surface lighter, both surfaces canescent, densely villous to sericeous, unilateral tuft of trichomes on the lower surface of the leaflets present, usually prolonged up to the 4th or 5th pairs of secondary nerves, venation brochidodromous, the nerves not evident and weakly prominent on both surfaces. Inflorescences of simple thyrsi, whitish; cymulae of solitary spikes to more frequently geminate, rarely ternate, spikes 9.5–10.5 cm long; bracts deciduous, not seen; peduncle 1.5–2.2 cm long, densely ferruginous-pulverulent and velutinous, subcylindrical; rachis yellow-tomentose to yellowvelutinous, sparsely ferruginous-pulverulent, cylindrical, ca. 1.5 mm thick. Flowers monoclinous and diclinous (only staminate flowers seen), white; calyx campanulate, apiculate, hirsute at the upper half at the lobes or ciliate only at the apex, very rarely subglabrous, ca. 1 mm long; corolla 3–3.5 mm long, tubular, fused up to 1/2 of its length, glabrous, usually hirsute only at the apex of the lobes, lobes acute, erect; stamens 5–6.5 mm long, anthers ca. 0.5 mm long, lilac, nectaries stipitate, conspicuous fold present at the dorsal side of the anthers, only beyond the insertion of the filaments; ovary subsessile, glabrous, stigma porate; pistiloid sometimes present in staminate flowers; prophylls late deciduous, ca. 1 mm long, shell-shaped, densely yellow-tomentose and ferruginous-pulverulent. Fruits not seen.

Etymology: —The name of this species refers to the characteristic indumentum at the leaflets.

Remarks: — Stryphnodendron holosericeum are medium-sized trees that are frequently mistaken as S.rotundifolium var. villosum , due to the indumentum of branches and leaflets. However, S. holosericeum have a very distinct petiolar extrafloral nectary, with a fusiform shape and immersed to slightly prominent at the petiole, darker than the petiole and inserted very close to its base. Besides the new species, this type of nectary is only found in S. velutinum . Additional differences between S. holosericeum and S. rotundifolium var. villosum are listed on table 3.

Distribution and habitat: —The species is so far only known in cerrado areas of Grande Sertão Veredas National Park in Northwestern Minas Gerais state, bordering Bahia and Goiás states. Stryphnodendron holosericeum grows predominantly on sandy soils.

Conservation: —Endangered (EN B1ab(i,iii)+2ab(ii,iii)) [AOO= 16.000 km 2, EOO= 208.685 km 2]. Although there are records of Stryphnodendron holosericeum collected in protected areas as mentioned above, its distribution is very restricted and it is still a poorly known species, vulnerable to anthropogenic actions for agricultural use in the region.

Phenology: — Stryphnodendron holosericeum was collected with flowers from July to November; fruiting unknown.

Additional specimens examined (paratypes): — BRAZIL. Minas Gerais: Formoso, Parque Nacional Grande Sertão Veredas, nascente do Rio Preto , cerrado próximo à Vereda do Veado , 850 m, 15°24’20”S, 45°55’14”W, 28 November 1997, fl., D. Alvarenga et al. 1088 ( IBGE, RB) . Formoso, Parque Nacional Grande Serão Veredas, estrada de chão entre Maria Antônia e Salto ( Estrada da Faz. Mato Grande ), 15°21’10”S, 46°00’09’W, 18 October 1995, fl., R.C. Mendonça et al. 3212 ( RB, RFA) . Formoso, Faz. Matinha, ca. 750m, 08 October 1988, fl., B.A.S. Pereira 1336 ( IBGE, MO, RB, RFA). Formoso, km 28 da estrada Formoso / Buritis, Vale do Rio Ponte Grande , 15°S, 46°10’W, 15 September 1996, fl., B.A.S. Pereira & D. Alvarenga 3221 ( IBGE, K, RB, RFA). Cachoeira Grande, July 1862, fl., collector unknown s.n. (R 64038) .

Figures

FIGURE 5. Stryphnodendron holosericeum Scalon. A. Flowering branch. B. Detail of foliar rachilla with extrafloral nectaries. C. Detail of petiole with extrafloral nectary. D. Leaflet (adaxial side). E. Leaflet (abaxial side). F. Detail of inflorescence with buds and young flower. G. Flower. H. Pistil.