Chusquea robinfosteri Refulio, Klahs & L.G. Clark, 2025

Refulio-Rodriguez, Nancy F., Klahs, Phillip C., Leandro, Thales D., Mcmurchie, Elizabeth K. & Clark, Lynn G., 2025, A new species of Chusquea subg. Swallenochloa (Poaceae: Bambusoideae) from the Peruvian upper montane forest, Phytotaxa 716 (4), pp. 231-247 : 232-239

Chusquea robinfosteri Refulio, Klahs & L.G. Clark , sp. nov. ( Figs. 1–5 ; 8A–D ; 9A–C ).

Type: ― PERU. Junín: Satipo Province / Cusco: La Convención Province. Cordillera Vilcabamba, Otishi National Park , Rio Ene slope, near summit of divide. 11°39'36" S, 73°40'02" W, 3350–3400 m, 8 June 1997, B. Boyle, M. Arakaki & H. Beltrán 4221 ( holotype: USM!; isotypes: F!, ISC!) .

Diagnosis: ―Within Chusquea section Swallenochloa , Chusquea robinfosteri is most similar to C. depauperata in having awnless falcate spikelets, foliage leaf blades with the abaxial epidermis exhibiting abundant single and branched papillae, a simple midrib, and mesophyll comprising rosette cells and lacking fusoid cavities. However, it differs by usually having both glumes I and II developed (rarely lacking glume I) and by possessing a long acuminate extension at the summit of the foliage leaf sheath.

Description: ―Rhizomes pachymorph. Culms scandent. Internodes 2.2–3.8 cm long, 2.4–3 mm in diameter, terete but slightly flattened for much of the length above the central bud, fistulose, glabrous, maroon to golden-yellow, waxy. Culm leaves 1.9–3.5 cm long, juncture of the sheath and blade abaxially horizontal, more or less visible; sheaths 1.8–3.3 cm long, 18–22 times as long as the blade, persistent and disintegrating on the culm, more or less triangular with rounded shoulders, glabrous adaxially and abaxially pubescent, with no marginal fusion, margins glabrous, sheath summit extension absent; girdle glabrous, slightly developed, 0.8–1 mm; outer ligule absent; inner ligule ca. 0.1 mm long, a faint line; blades 1–1.5 mm long, triangular, minute, erect, deciduous. Nodes with a triangular central bud and several adventitious roots; nodal line horizontal; supranodal ridge conspicuous. Branching intravaginal, at mid-culm with 3 branches per node, the central one thicker than the other two. Foliage leaves 4–7 per complement on vegetative branches, 5–7 per complement on flowering branches; sheaths pubescent, keeled, margins glabrous; sheath summit extension present on both sides, acuminate, confluent with the inner ligule, glabrous, 4–9 mm long; outer ligules erect, glabrous, ca. 0.1 mm long; inner ligules fused with sheath summit extension, 2–4 mm long; pseudopetioles 0.1–0.2 mm long, glabrous; blades 2.7–5.7 cm long, 1–2.5 mm wide, linear, stiff, erect to ascending, flat in cross-section, slightly yellow-green, adaxially pubescent and abaxially mostly glabrous, not tessellate, margins ca. 0.2 mm wide, yellow, scabrid, cartilaginous, midrib centric and abaxially barely distinguishable, attenuate at base, subulate at apex. Synflorescences 4–10 cm long, 0.4–1 cm wide, paniculate, narrow, congested and appearing spicate, not or only slightly interrupted, branches appressed; subtending bract absent; rachis angular, flattened, glabrous; basal primary branches 1.5–2.5 cm long, becoming progressively shorter towards the apex until ending in pedicels, pulvinus absent; pedicels 1–5 mm long, rounded, glabrous. Spikelets 5.8–6 mm long, 1.5–1.8 mm wide, laterally compressed, slightly falcate; glume I developed (sometimes absent), 0.4–0.8 mm long, scalelike, glabrous, nerves absent; glume II developed, 0.8–1.2 mm long, scalelike, glabrous, nerves absent; glumes III and IV subequal, ca. ½ the spikelet length, 3-nerved; glume III 2.8–3 mm long, pubescent on the base and on middle nerve, acute; glume IV 3.3–3.5 mm long, pubescent on the base and on middle nerve, mucronate; lemma 5–5.2 mm long, glabrous, acuminate, 7-nerved; palea 5.2–5.4 mm long, emarginate, glabrous, 2-nerved. Stamens 3; anthers 2.5–3 mm long, yellow. Gynoecium 1.8–2.6 mm long, styles 2, stigmas plumose. Caryopsis not seen.

Distribution and habitat: ― Chusquea robinfosteri is currently known only from a very remote and difficult to access area located on the border between Junín Department (Province Satipo) and Cusco Department (Province La Convención) which forms part of the Otishi National Park and the Cordillera Vilcabamba ( Fig. 1 ). It was found on the Rio Ene slope, near the summit of divide at 3350–3400 m elevation in mossy upper montane forest dominated by Weinmannia Linnaeus (1759: 997 , 1005, 1367), Clethra Linnaeus (1753: 396) , Symplocos Jacquin (1760: 5) , and Myrsine Linnaeus (1753: 196) . It is patchily distributed, but often locally dominant in restricted areas of pajonal (herbaceous meadows with scattered low shrubs).

Phenology: ―Flowering collections are only known from 8 June 1997. There are no observations on extent of flowering in the label data.

Recognition: — Chusquea robinfosteri is distinguished from the other small(shrubby)species in sect. Swallenochloa by the combination of its vegetative and reproductive attributes (see identification key below). Chusquea robinfosteri and C. depauperata are similar in having awnless falcate spikelets ( Figs. 5C–D , 7D ). Morphological key differences that help to differentiate these two species are the shape of the leaf sheath summit extension and the presence or absence of glumes ( Table 1). While C. robinfosteri has a long acuminate foliage leaf sheath summit extension and usually both glumes I and II developed (rarely lacks glume I) ( Figs. 3E–F , 5E ), C. depauperata has a truncate foliage leaf sheath summit extension and usually lacks both glumes I and II (rarely glume II is present) ( Fig. 7B,D ).

Etymology: ―This species is named in honor of Robin B. Foster (Field Museum, Chicago and ForestGEO) in recognition of his immense contributions to tropical botany, in particular to the poorly known areas with complex topography and limited access of the Peruvian tropical Andes and Amazon.

Figures

FIGURE 1. Type locality of Chusquea robinfosteri Refulio, Klahs & L.G. Clark in Otishi National Park, Peru.

FIGURE 2. The holotype specimen of Chusquea robinfosteri Refulio, Klahs & L.G. Clark.

FIGURE 3. Chusquea robinfosteri Refulio, Klahs & L.G. Clark. A. Pachymorph rhizome. B. Foliage leaves per complement. C–D. Branch complement. E–F. Foliage leaf sheath summit extension. G. Detail on the inner ligule fused to the foliage leaf sheath summit extension. H. Foliage leaf outer ligule and pseudopetiole. I. Abaxial foliage leaf blade. J. Adaxial foliage leaf blade. K. Foliage leaf blade apex. Scale bars: 2 cm (A,B); 3.5 mm (E–G); 2.5 mm (I–K). Photographs from the isotype, Boyle et al. 4221 (ISC).

FIGURE 4. Chusquea robinfosteri Refulio, Klahs & L.G. Clark. A. Fistulose culm. B. Culm leaf girdle. C. Supranodal ridge. D. Culm leaf sheath and blade. E. Central triangular bud. F. Adventitious root. G–H. Adventitious root buds. Scale bar: 3 mm (A–H). Photographs from the isotype, Boyle et al. 4221 (ISC).

FIGURE 5. Chusquea robinfosteri Refulio, Klahs & L.G. Clark. A–B. Synflorescence. C–D. Spikelets. E. Glume I and Glume II. F. Glume III. G. Glume IV. H. Floret. I. Lemma. J. Palea. Scale bars: 1 mm (F,G); 2 mm (H–J). Photographs from the isotype, Boyle et al. 4221 (ISC).

FIGURE 7. Chusquea depauperata Pilg. A. Fistulose culm. B. Foliage leaf outer ligule, pseudopetiole, and sheath summit extension. C. Synflorescence. D. Spikelet. E. Glume III and IV. F. Lemma. G. Palea. Scale bar: 2 mm (F,G). Photographs from Weberbauer 3709 (US- 2874618): A–C and (US-1127078): D–G.

FIGURE 8. Micromorphology of the foliage leaf blades of Chusquea robinfosteri [Boyle et al. 4221 (ISC)]: A–D and C. depauperata [Weberbauer 3709 (US)]: E–F. A,E. SEM adaxial surface. B,F. SEM abaxial surface. C. Adaxial surface after pectinase treatment for epidermal peel. D. Abaxial surface after pectinase treatment for epidermal peel. cz = costal zone; iz = intercostal zone; mi = microhair; pa = papilla; pr = prickle; sc = silica cell; st = stoma.

FIGURE 9. Cross-sections of the foliage leaf blades of Chusquea robinfosteri [Boyle et al. 4221 (ISC)]: A–C and C. depauperata [Weberbauer 3709 (US)]: D–F. A,D. General view showing midrib, first- and second-order vascular bundles associated with girders. B,E. General view showing the mesophyll comprising rosette cells and second-order vascular bundles associated with girders. C,F. Simple midrib consisting of a first-order vascular bundle with girders and surrounded by rosette cells. ab = abaxial epidermis; ad = adaxial epidermis; bc = bulliform cell; fvb = first-order vascular bundle; gi = girder; pa = branched papilla; rc = rosette cell; si = silica cell; st = stoma; svb = second-order vascular bundle.