Merostachys cachimboensis Lopes-Neto & P.L.Viana, 2022

Lopes-Neto, Raimundo Balieiro & Viana, Pedro Lage, 2022, Flora of the Serra do Cachimbo (Eastern Amazon, Brazil): Bambusoideae (Poaceae), including the description of two new species, Phytotaxa 550 (2), pp. 99-129 : 112-114

Merostachys cachimboensis Lopes-Neto & P.L.Viana , sp. nov. Figs 5–6 .

Type :— BRAZIL. Pará : Altamira, BR-163, lado direito da entrada do Campo de Provas Brigadeiro Velloso, 513 m, 9°22’15.3”S, 54°51’27”W, 26 May 2021, Lopes-Neto et al. 693 (holotype MG!, isotypes IAN!, INPA!, RB!) .

Diagnosis: — Merostachys cachimboensis is morphologically similar to Merostachys delicatula R.S.Andrade et al. in Andrade et al. (2020: 72), but differs by the absence of an infranodal band of trichomes on the culms (vs. sericeous trichomes, 0.2–1.5 mm wide), branch complement with 20–55 branches (vs. 72–449 branches), foliage leaf blades narrower (L:W ratio 12.6–21.6 Vs. 4–9.5), strongly reflexed (vs. horizontal), with 2–3 prominent and scabrous lateral nerves on one side of the adaxial surface, when 3, the lateral ones more prominent than the middle one (vs. 1 lateral nerve on each side scabrous, not prominent).

Rhizomes pachymorph, short-necks, 0.6–1.2 cm long. Culms 6–9 m tall, 0.2–0.3 cm in diameter, initially erect then clambering on surrounding vegetation, basal internodes 15.3–15.9 cm long, middle internodes 15.2–20 cm long, pithy in center, glabrous to scabrous toward the apex, with short yellow trichomes (in siccus), infranodal bands of trichomes absent; primary buds subequal, prophyll unitary, ca. 1.83 x 1.84 mm, covered by short white trichomes (in siccus), margins densely pilose; nodes dark brown, glabrescent, horizontal, supranodal ridge inconspicuous. Branch complement with 20–55 subequal branches, 10–11 cm long, 0.3–0.5 mm in diameter, internodes 4–5 cm long, glabrous, secondary branches absent. Culm leaves caducous, but the blade falling first; sheath 10–12 cm long, longer than the blade, stramineous (in siccus), adaxially glabrous, abaxially scabrous, margins scabridulous; auricles absent; fimbriae ca. 2–4 mm long, straight at the base and sinuous toward the apex, stramineous (in siccus); inner ligules ca. 0.1 mm long, membranous, shortly ciliate at the apex; blades 3.8–6.5 × 0.2–0.3 cm, linear-lanceolate, stramineous (in siccus), glabrous on both surfaces, margins scabridulous, apex acuminate. Foliage leaves 8–10 per complement; sheaths 1.4–1.6 × 0.2–0.3 cm, glabrous, overlapping and underlapping margins densely ciliate; auricles absent; fimbriae 4–5 mm long, straight at the base and sinuous toward the apex, yellow-white; inner ligules 0.2–0.3 mm, membranous, symmetrical, truncate; outer ligules ca. 1 mm, membranous, shortly ciliate at the apex, symmetrical, with an inconspicuous rim at the center, glabrous; pseudopetioles ca. 1 mm long, flat, densely pilose; blades 3.7–4.7 × 0.3–0.4 cm, L:W 12.6–21.6, strongly reflexed, linear-lanceolate, glabrous on both surfaces, sometimes scabrous at the base of the abaxial surface, adaxially with 2–3 lateral nerves on one side prominent and scabrous, when 3, the lateral ones more prominent than the middle one, 27-29-nerved, green, midnerve slightly excentric, base rounded, slightly asymmetrical, margins scabrous, apex attenuate. Synflorescences not seen.

Additional specimens examined (paratypes): — BRAZIL. Mato Grosso: Ponto 23. F. sc zb. (projeto RADAMBRASIL), 288 m, 10°19’48.73”S, 54°47’06.55”W (coordenada do município de Peixoto de Azevedo ), 12 November 1976, Nascimento 472 ( MG) . Pará: Altamira, Reserva Biológica Nascentes da Serra do Cachimbo , BR-163, Acesso pela Fazenda Carrefour , trilha de mata ciliar do rio São Bento , 510 m, 9°12’58.2”S, 54°51’22.8”W, 29 September 2019, Lopes-Neto et al. 528 ( MG) .

Distribution and habitat: —This species is known from three locations in the Serra do Cachimbo. In Pará state, it was found in anthropogenic area and Open ombrofilous forest, in humid soil near streams.

Conservation status: — Merostachys cachimboensis is known from three populations registered in the Serra do Cachimbo, along the BR-163 highway. The extent of occurrence (EOO) is 212.172 km 2 and the area of occupancy (AOO) is 12.000 km 2. According to the IUCN Red List Categories and Criteria (2019), the new species fits in the Endangered (EN) category, based on the EOO, AOO, number of locations and area extent and/or quality of habitat [EN B1ab(iii) + B2ab(iii)].

Etymology: —The epithet refers the type-locality, in the Serra do Cachimbo.

Comments: — Merostachys cachimboensis is similar to M. delicatula , an Atlantic Forest species only known from its type-locality in Serra da Pedra Lascada, Bahia (Northeast Brazil). Along with M. leptophylla Sendulsky (1997: 295) (registered in Bahia, Espírito Santo and Minas Gerais states), they represent the species with the smallest culm diameter of the genus (between 0.1 and 1.5 cm), sharing also the narrow foliage blades (<0.8 cm), a character also found in M. argentea Sendulsky (1997: 287) and M. bifurcata Sendulsky (1997: 290) , both Atlantic Forest species ( Sendulsky 1997).

Merostachys cachimboensis resembles M. delicatula by the habit initially erect then arching and clambering surrounding the vegetation, culms <0.5 cm in diameter, glabrous to scabrous toward the apex, foliage leaf sheath glabrous, fimbriae yellow-white, straight to sinuous at the apex, blades linear-lanceolate to lanceolate, base rounded and apex attenuate. However, M. cachimboensis differs by the absence of an infranodal band of trichomes, branch complement with 20–55 branches, foliage leaf blades with the L:W ratio = 12.6–21.6, strongly reflexed and adaxially with 2–3 prominent and scabrous lateral nerves on one side, when 3, the lateral ones more prominent than the middle one ( Table 2 ).

Figures

FIGURE 5. Illustration of Merostachys cachimboensis: A. Rhizomes. B. Bud frontal view. C. Bud lateral view. D. Terminal culm with culm leaves. E. Culm leaf sheath, abaxial view. F. Culm leaf fimbriae. G. Culm leaf blade. H. Internode with branch complement and foliage leaf complement. I. Foliage leaf fimbriae. J. Foliage leaf blade detail of the adaxial surface with prominent nerves. Drawn by R.B.Lopes-Neto, based on the holotype [Lopes-Neto et al. 693 (MG)].

FIGURE 6. Field photographs of Merostachys cachimboense: A–B. Habit. C. Detail of the foliage leaf complements. D. Branch complement. E. Terminal culm with culm leaves. F–G. Detail of the culm leaves. H. Detaching culm leaf sheaths. I. Foliage leaf fimbriae. J. Detail of the prominent nerves of the foliage leaves. Photos: P.L.Viana.