Merostachys ximenae D.F. Parma, R. Vinícius-Silva & A.P. Santos-Gonçalves, 2016

Parma, Daniele F., Pianissola, Evandro M., Vinícius-Silva, Ronaldo, Clark, Lynn G. & Santos-Gonçalves, Ana Paula, 2016, Two new species of Merostachys (Poaceae: Bambusoideae) from the Brazilian Atlantic forest, Phytotaxa 267 (3), pp. 219-227 : 223-226

Merostachys ximenae D.F. Parma, R. Vinícius-Silva & A.P. Santos-Gonçalves , sp. nov. ( Fig. 2 )

This species can be distinguished from all the other species of the genus by a combination of these characters: culm leaf sheaths lanate abaxially, internodes covered with lanate trichomes, which occur in higher density on both the supranodal and the infranodal bands (bands 2–13 mm wide), culm and branches with thickened ring-like nodes, and paired (two fertile or one fertile and the other rudimentary), sometimes solitary, spikelets.

Type:— BRAZIL. Minas Gerais: Viçosa, Fazenda Bom Sucesso, Mata do Sr. Nico, 20º47’40.02”S, 42º50’38.24”W, 750 m, 12 September 2014 (fl.), D. F. Parma & Celso Antônio 44 (holotype VIC, isotypes ISC, MO, RB, SP).

Plants with culms initially erect then clambering on vegetation. Culms 2–15 m tall; internodes 30.5–86 cm long, 0.5–3 cm in diam., hollow, cylindrical, yellowish-green, covered by lanate trichomes which occur in higher density on the supranodal and infranodal bands, bands 2–13 mm wide; walls 1–2.4 mm thick, ratio of wall thickness: culm diam. 0.12–0.28, very thin to thin, lumen 1.3–2 cm in diam., large, not filled by a pith; nodes prominent, thickened, ring-like, dark brown to black, without a fringe of trichomes at the nodal line. Culm leaves 19.5–45 cm long; sheaths 13.2–32.6 × 2.4–12.5 cm, glabrous on the adaxial surface, shiny, lanate on the abaxial surface, apex scabrous, sparsely hirsute, margins apically fimbriate; auricles absent; fimbriae 3.6–14 mm long, not fused, straight at the base and sinuous at the apex, yellowish to reddish, sometimes yellowish at the base and becoming brown toward the apex; inner ligule 0.5–3.4 mm long, membranous, apex ciliate; blades 6.3–12.3 × 0.56–1.3 cm, glabrous on the adaxial surface, glabrous and glaucous on the abaxial surface, margins scabrous toward the apex, apex acute. Branch complement with 10–87 branches, the branches 50–171.5 cm long, 2.7–4.8 mm in diam., lower nodes not rebranching; nodes prominent, thickened, ring-like, brownish to black, with an infranodal band of lanate trichomes ca. 1.5 mm long. Foliage leaves 8–27 per branch; sheaths 3.4–11 cm × 2.4–13.2 mm, hirsute to lanate, sometimes glabrous, overlapping margin ciliate; auricles absent; outer ligule 0.2–0.6 mm long, apex ciliate; inner ligule 0.2–1.6 mm long, membranous, pubescent, apex ciliate; fimbriae 1–9.3 mm long, not fused, straight to sinuous, yellowish to reddish, sometimes yellowish at the base and becoming reddish toward the apex; pseudopetiole 3–8.5 mm long, greenish to brownish, glabrous, straight to twisted; blades 14.5–27 × 3–6 cm, L: W = 3.2–6.6, lanceolate to oval-lanceolate, with 2–4 scabrous marginal ribs toward the apex on the adaxial surface, the opposite marginal region with minute antrorse strigose trichomes toward the apex, glabrous elsewhere, with a band of minute antrorse strigose trichomes between the marginal stripe and the rest of the blade along the upper 2 / 3 of the marginal stripe on the abaxial surface; marginal region opposite to the stripe hispid, glabrous elsewhere, the base asymmetric, the apex acuminate, margins scabrous. Inflorescences ca. 7 cm long, racemose, pectinate, with ca. 26 spikelets per raceme; rachis velutinous; pedicels 0.5–1 mm long, velutinous. Spikelets 11–12.5 × 1.5 mm, 1-flowered, paired, sometimes solitary, pairs composed of two fertile spikelets or one fertile and one rudimentary spikelet; glumes 2, unequal, puberulous on the abaxial surface, midribs minutely scabrous; lower glume 2–2.5 × 1–1.5 mm, ca. 1 / 5 of the spikelet length, 1-nerved, margins ciliate; upper glume 4–4.5 × 2.5–3 mm, ca. 2 / 5 of the spikelet length, mucronate, 8–9-nerved, dark-spotted on the adaxial surface, margins ciliate toward the apex; lemma 8–10 × 4–5 mm, 10–13-nerved, dark-spotted on the adaxial and puberulous on the abaxial surfaces, margins apically ciliate, one margin ciliate from the base towards the apex; palea 9.5–11 × 3–5 mm, 8-nerved, dark-spotted on the adaxial and puberulous on the abaxial surfaces, margins apically ciliate, midribs forming a keel; keel ciliate towards the apex; rachilla extension ca. 9–10.5 mm long, with a rudimentary floret at the apex; lodicules 3, 2.5–3.5 mm long, membranous; androecium degraded; gynoecium with an elongate ovary, style bifid, stigmas 2, plumose. Caryopsis not seen.

Comments:— Merostachys ximenae resembles M. annulifera Sendulsky (1997: 286) because of the prominent, thickened ring-like nodes of the culms and branches, and by the lanceolate to oval-lanceolate foliage leaf blades. However, M. ximenae differs by having lanate internodes, culm leaves lanate abaxially, and a branch complement with 10–87 branches 50–171.5 cm long; M. annulifera has scabrous internodes, culm leaf sheaths glabrous to scabrous on the abaxial surface and a branch complement with 5–25 branches 30–35 cm long ( Table 2).

Distribution and habitat:— Merostachys ximenae is known only from the state of Minas Gerais, Brazil. It is known from five populations (Parque Estadual do Rio Doce, Parque Estadual da Serra do Brigadeiro, Conceição do Ibitipoca, Estação Experimental de Treinamento e Educação Ambiental Mata do Paraíso and Fazenda Bom Sucesso), at 250–750 m elevation, along the borders of the vegetation locally known as Floresta Atlântica Estacional Semidecidual Montana ( Veloso et al. 1991).

Conservation:— We applied the IUCN criteria (2015) and propose an IUCN red list category of least concern (LC) because of the wide distribution of the taxon in the state, especially within conservation units.

Etymology:— The specific epithet honors the Colombian researcher Lic. Ximena Londoño, who has greatly contributed to knowledge of Neotropical bamboos.

Additional specimens examined:— BRAZIL: Minas Gerais: Lima Duarte, Estrada para Conceição do Ibitipoca, próximo à Cachoeira das Andorinhas, 16 April 1992, veg., R.C. Oliveira, M.C.M. Garcia & L.P. Oliveira 87 (CESJ); Marliéria, Parque Estadual do Rio Doce, Estrada da Ponte-Queimada, 24 August 1999, veg., Santos-Gonçalves et al. 196 (VIC); ibidem, 22 September 1999, veg., Santos-Gonçalves et al. 204 (VIC); Viçosa, Fazenda Bom Sucesso, Mata do Sr. Nico, 27 August 2014, veg., D.F. Parma & R.V. Silva 39 (VIC); ibidem, 12 September 2014, veg., D.F. Parma & Celso Antônio 43 (VIC); Viçosa, EPTEA— Mata do Paraíso, trilha da Pesquisa, 15 March 2015, veg., R.V. Silva & D.F. Parma 57 (VIC); Araponga, Parque Estadual da Serra do Brigadeiro, Trilha do Jequitibá, 26 June 2015, veg., A.P. Silva & D.F. Parma 238 (VIC).

Figures

FIGURE 2. Merostachys ximenae. A–D (Parma & Celso Antônio 44) A. Culm leaf. B. Branch complement with foliage leaves. C. Infranodal band of lanate trichomes. D. Floriferous branch. E–M (Santos-Gonçalves et al. 196) E. Branch leaf and fimbriae. F. Section of inflorescence. G. Spikelet. H. Lower glume. I. Upper glume. J. Lemma. K. Palea and rachilla extension. L. Lodicules. M. Gynoecium. (Illustration by Reinaldo Pinto).