Chusquea yungasensis L.G. Clark & A.C. Mota

Mota, Aline Costa, Pérez, Iván Jiménez, Oliveira, Reyjane Patrícia De & Clark, Lynn G., 2014, Chusquea yungasensis (Bambusoideae, Poaceae): a new species of woody bamboo from South America and the first record of subgenus Rettbergia in Bolivia, Phytotaxa 161 (3), pp. 211-218 : 212-215

Chusquea yungasensis L.G. Clark & A.C. Mota , sp. nov. Figs. 1–3 .

Chusquea yungasensis differs from other species of Chusquea subg. Rettbergia by its racemose synflorescences.

Type: — BOLIVIA. La Paz: provincia Nor Yungas, Parque Nacional Cotapata, sendero Sillutinkara , 16º14’24.5” S, 67º53’13.8” W, 2228 m, 14 Apr 2013 (fl), I. Jiménez 5848 (holotype LPB !, isotypes BOLV! , HSB! , USZ! ).

Culms 0.6–1.2 cm in diameter, 2.5–4 m long, scandent. Internodes 26.7–43 cm long, terete, glabrous. Culm leaves 38.5–55.5 cm long, persistent, longer than the internode, juncture of sheath and blade abaxially obscure; sheaths 33.5–44.5 cm long, adaxially glabrous, lustrous and sometimes hirsute distally, abaxially retrorsely scabrous, one side ciliate along its entire length; blades 5–11.1 cm long, narrowly triangular, erect, persistent, adaxially pubescent, abaxially glabrous or sparsely scabrous, margins glabrous; girdles 2–3 mm long, glabrous, dark brown, thickened at the juncture with the sheath; inner ligules 0.8–2.0 cm long, asymmetric, lacerate. Nodes at mid-culm with one dome-shaped central bud subtended by 7–10 smaller subsidiary buds in constellate arrangement; nodal line horizontal but dipping markedly below the bud/branch complement; supranodal ridge swollen, prominent to inconspicuous. Branching infravaginal; central branch developing horizontally at first, usually becoming geniculate, nearly as robust as the main culm; leafy subsidiary branches (3–5)7–11 per node, 30–50 cm long, ca. 1.5 mm in diameter, geniculate, rebranching at the nodes of fertile branches, the girdles at the lower nodes usually dark brown, glabrous. Foliage leaves 4–6 per complement; sheaths striate, keeled toward the apex, glabrous, strawcolored, the margins glabrous, sheath summit extension 0.5 mm; blades (6.5–) 9.5–14.5 cm long, (1.3–1.6) 1.9–2.4 cm wide, L:W = 6.9–7.5, oblong-lanceolate to lanceolate, glabrous, adaxially not tessellate, green, abaxially not tessellate, basal tuft of hairs absent, lighter green, the midrib slightly excentric, abaxially slightly raised and visible for nearly the full length, adaxially barely distinguishable, the base symmetrical to slightly asymmetrical, attenuate, the apex tapering, acuminate, the margins finely serrulate, pseudopetiole 4–5 mm long, glabrous, often dark brown; outer ligule 0.2–0.3(–0.5) mm long, unlobed, erect, extending as a rim along the junction of the sheath summit extension and the inner ligule often for the full length, glabrous; inner ligule 1–1.5 mm long, rounded, abaxially puberulent, ciliate. Synflorescences 2.5–3 cm long, 1–2.5 cm wide, racemose, partially to wholly exserted, usually subtended by a spatheate bract with the sheaths 2.5–4 cm long, expanded, the blades 2–2.5 cm long, green, and arching over the synflorescence; main axis more or less flattened, crooked, pubescent; branches 0.3–0.4 cm long at the base, angular, pubescent, ascending, usually subtended by a small bract 0.2–0.4 mm long; peduncles 1–2 mm long, angular, pubescent, often subtended by a minute bract. Spikelets 9–11 mm long, slightly laterally compressed; glumes I and II awned, keeled, abaxially scabrous to hispid on midrib and awn; glume I 3–4 mm long, 0.45–0.6 times the length of the lemma, 3-nerved; glume II 4.5–6 mm long, 0.45–0.6 times the length of the lemma, 3-nerved; glumes III and IV mucronate, abaxially scabrous; glume III 5–5.5 mm long, 0.55 times the length of the lemma, 5-nerved; glume IV 7 mm long, 0.7–0.77 times the length of the lemma, 5-nerved; lemma 9–10 mm long, acute, abaxially scabrous, margins ciliate on the upper 1/2, 7-nerved, the margins free at the apex, palea 9–10 mm long, usually overtopping the lemma, acute, 6-nerved, margins connate at the apex, sulcate only at the apex, the sulcus scabrous-hispid. Ovary 2.0 mm long, glabrous. Lodicules 3, villous; anterior pair 2.5 mm long, posterior one 2 mm long. Stamens 3; anthers 6 mm long. Fruit unknown.

Etymology: —The specific epithet refers to the Yungas ecoregion of Bolivia, where this new species occurs.

Comments: —Based on vegetative characters, Chusquea yungasensis is morphologically similar to C. bambusoides . The two species share similar culm diameters, culm leaves with the same type of indument, an equivalent number of subsidiary branches, and overlapping shape and size of the foliage leaf blades. They can be separated by the shape of the foliage leaf blade base, which is attenuate with pseudopetioles 4–5 mm long in C. yungasensis versus rounded-attenuate with pseudopetioles 2–3 mm long in C. bambusoides . The racemose synflorescence distinguishes this new species from C. bambusoides and the other species known in subg. Rettbergia , which all have paniculate synflorescences. These species can be also separated based on spikelet characters. Chusquea yungasensis has slightly laterally compressed spikelets and mucronate glumes III and IV, whereas C. bambusoides is characterized by laterally compressed spikelets and obtuse glumes III and IV ( Table 1 ).

Geographic Distribution and Ecology: — Chusquea yungasensis is known from two populations in La Paz, Bolivia, one in Sud Yungas province (Huancané) and the other in Nor Yungas province (Cotapata National Park), and is found from 2200 to 2400 m in elevation. These areas are part of the Yungas ecoregion, which represents a transitional zone between the Andes and the Amazon basin, in vegetation named ‘Upper Montane Cloud Forest’ (UMCF) ( Gerold et al. 2008). In this zone the annual rainfall at 2600 m is 3,970 mm, the average annual temperature is 12.8ºC, and the soils are all acidic ( Gerold et al. 2008). The Yungas ecoregion occupies only 4% of the Bolivian territory, but nevertheless contains high diversity (e.g., orchids and ferns), which is extremely threatened by extinction due to deforestation ( Vásquez et al. 2003, Soria-Auza & Kessler 2007, Gerold et al. 2008).

In Cotapata National Park, C. yungasensis occurs in less disturbed forests and in forest gaps with early or medium successional vegetation, and is frequent where it occurs. The vegetation in this zone lacks settlements (from 2100 m to tree line) and consequently there is little anthropic disturbance. The population of C. yungasensis generally grows with species of scandent bamboos of the genera Chusquea , Arthrostylidium Ruprecht (1839: 27) and Aulonemia Goudot (1846: 75) , or it grows as isolated plants. Scabrous culm leaves and young internodes with three geniculate subsidiary branches at the tips of the culms facilitate climbing on adjacent vegetation. The canopy is about 15–20 m height, and is composed mainly of Hieronyma alchorneoides Allemão (1848: 1) , Morus insignis Bureau (1873: 247) , Ficus Linnaeus (1753: 1059) spp. , Inga Miller (1754) spp. , and Virola Aublet (1775: 904) spp. , with a 45% cover of epiphytes ( Paniagua et al. 2003, Gerold et al. 2008).

Conservation Status: — Chusquea yungasensis is considered critically endangered CRB2ab(iii) based on the existence of only two populations with an area of occupancy <10 km 2 and the continuing decline projected in quality of habitat ( IUCN 2013).

Additional Specimens Examined: — BOLIVIA. La Paz: Provincia Sud Yungas, Huancané, 7 km hacia el sur , 2400 m, 3 September 1981 (fl), Beck 4722 ( K, LPB, M, US) ; Provincia Nor Yungas, Parque Nacional Cotapata, sendero Sillutinkara , 16º14’18.1” S, 67º53’18.4” W, 2203 m, 18 September 2012, Jiménez 5694 ( BOLV, LPB, USZ) .

Figures

FIGURE 1. Chusquea yungasensis. A. Culm leaf. B. Central bud and subsidiary branches. C. Branching and foliage leaves. D. Detail of the foliage leaf sheath, pseudopetiole and abaxial base of the foliage leaf blade. E. Fertile branch. F. Detail of the synflorescence. G. Spikelet. (A, E–G: Jiménez 5848; B–D: Jiménez 5694.) (Illustration by Lucas Marinho)

FIGURE 2. Upper Montane Cloud Forest, Cotapata National Park, sendero Sillutinkara, La Paz. A. Overview of the habitat of Chusquea yungasensis. B. Node at mid-culm with one dome-shaped central bud subtended by smaller subsidiary. C. Central bud and subsidiary branches. D. Geniculate subsidiary branches. E. Habit, branching and foliage leaves. F. Synflorescence. (Photos I. Jiménez).

FIGURE 3. Geographic distribution of Chusquea yungasensis.