Chusquea kochii Ruiz-Sanchez, Mejía-Saulés & L.G. Clark, 2022

Ruiz-Sanchez, Eduardo, Mejia-Saulés, Ma. Teresa & Clark, Lynn G., 2022, A new species of Chusquea sect. Serpentes (Poaceae: Bambusoideae: Bambuseae: Chusqueinae) endemic to Oaxaca, Mexico, Phytotaxa 542 (2), pp. 199-206 : 200-204

Chusquea kochii Ruiz-Sanchez, Mejía-Saulés & L.G. Clark sp. nov., Figs. 1–4

TYPE:— MEXICO. Oaxaca, San Miguel Suchixtepec, 5 km al S. de Suchixtepec (55 km al sur de Miahuatlán) sobre la terracería a Pochutla , 2220 m, 21 November 1978, Koch & Fryxell 78399 (holotype CHAPA!, isotypes ISC!, MEXU, US!).

Chusquea kochii differs from C. glauca in having green culms, a ring of cilia at the base of culm leaves absent, culm leaf blades reflexed, subsidiary buds 7–12 per node, and foliage leaf blades 9.5–13.5 × 1–1.9 cm.

Rhizomes pachymorph. Culms 2–4 m tall, 0.4–0.8 cm in basal diameter, vining and scandent. Internodes 8.4–24.5 cm long, 12–25 per culm, terete, glabrous, green when young, becoming yellow with age, not maculate. Culm leaves 5.8–12 cm long, abaxially hispid at the base, becoming glabrous, mostly persistent but some deciduous; sheaths 5–10.5 cm long, rectangular with rounded shoulders, 4–8 times as long as the blade, the margins ciliate on both sides, cilia becoming deciduous; inner ligule ca. 0.5 mm long, glabrous; blades 0.8–1.5 cm long, narrowly triangular, reflexed, deciduous, apex apiculate, margins entire, glabrous; girdle asymmetrically developed, prominent only near the bud complement, 3–5 mm wide. Nodes at mid culm with 7–12 buds, composed of one larger circular central bud subtended by 7–12 smaller, subequal, triangular, closely adjacent subsidiary buds arranged in a single row, the base of the buds arising above the nodal line, nodal line dipping markedly below the bud, supranodal ridge present and prominent, developing into a patella, without a ring of cilia at the base. Branching infravaginal, the sheaths persistent but becoming deciduous with age, 7–12 subsidiary branches per node, diverging from the main culm at 60–135 o, 16–32 cm long, 1–1.5 mm in diameter, sometimes rebranching, the larger central branch ca. 3 mm in diameter, up to 70 cm long, always rebranching. Foliage leaves 7–11(12) per complement; sheaths glabrous, the summit and margins ciliate; leaf blades 9.5–13.5 cm long, 1–1.9 cm wide, ratio L: W = 7.2–8.8, abaxially pubescent and adaxially glabrous, not tessellate, the base rounded-attenuate, the apex long subulate, the margins finely scabrous; pseudopetioles 1.5–2 mm long, adaxially glabrous, abaxially pubescent; inner ligule 0.5–1 mm long, truncate; outer ligule on one side to 0.1–0.2 mm long, glabrous. Synflorescences not seen.

Etymology:—The specific epithet honors Dr. Stephen Douglas Koch Olt (16 December 1940 – 14 January 2017). He was a distinguished plant systematist and taxonomist, specializing in grasses, and professor of the Postgrado en Botánica, Colegio de Postgraduados, Campus Montecillo, Texcoco, Estado de México. Dr. Koch made enormous contributions to our knowledge of Mexican grasses, describing new species and collecting thousands of grass specimens including bamboos. He founded the Herbarium-Hortorio (CHAPA) and served as its curator until his death.

Phenology:—Synflorescences and flowers of this species are unknown. A living plant was under cultivation in the National Bamboo Collection at the Francisco Javier Clavijero Botanic Garden in Xalapa, Veracruz, Mexico, until 2016 when it died before flowering.

Habitat and distribution:— Chusquea kochii is known so far from pine and cloud forests in Oaxaca state, at ca. 2200 m elevation, in the Sierra Madre del Sur ( Fig. 4 ). The Sierra Madre del Sur province is divided into two subprovinces and five districts ( Santiago-Alvarado et al. 2016). Chuquea kochii is distributed in the eastern subprovince and Oaxacana district ( Fig. 4 ), where another species endemic to Mexico occurs, C. nedjadquithii et al. (2014b: 25). The latter was also recorded from the state of Guerrero during field work carried out in 2020. Field work in nearby locations is needed to better understand the distribution of C. kochii .

Notes:—The description of Chusquea kochii increases the total number of species of Chusquea to 196, and the number of species of C. sect. Serpentes in Mexico to two ( Ruiz-Sanchez et al. 2021b). It also increases the number of native Mexican woody bamboo species to 58, of which 41 (70.6%) are endemic, 25 (43.1%) are Chusquea , and 18 (72%) are Chusquea endemic to Mexico ( Ruiz-Sanchez et al. 2021a,b,c,d). Although the reflexed culm leaf blade is unique to C. kochii within sect. Serpentes , it fits well in this section based on other diagnostic features, especially the relatively small number of subsidiary buds per node in a single constellate row, and the relatively wide foliage leaf blades ( Attigala et al. 2017, McMurchie et al. in press).

Morphologically, Chusquea kochii is most similar to C. glauca . The main differences between C. kochii and C. glauca are the following: C. kochii has green culms vs. green with purple maculae in C. glauca ; a ring of cilia at the base of culm leaves is absent in C. kochii and present in C. glauca ; culm leaf blades are reflexed in C. kochii and erect in C. glauca ; subsidiary buds are 7–12 per node in C. kochii vs. 2–3 in C. glauca ; foliage leaf blade length is 9.5–13.5 cm in C. kochii vs. 14.4–19 cm in C. glauca , and blade width is 1–1.9 cm in C. kochii vs. 2.1–4 cm in C. glauca ( Clark 1989, Ruiz-Sanchez et al. 2015; Table 1 ).

The geographic distribution of Chusquea glauca extens from the eastern Trans-Mexican Volcanic Belt to the southern Sierra Madre Oriental, whereas C. kochii is located in the Sierra Madre del Sur, more than 200 km from the closest C. glauca population ( Fig. 4 ). In 2021 C. contrerasii Ruiz-Sanchez & Clark in Ruiz-Sanchez et al. (2021b: 287) and C. guzmanii Ruiz-Sanchez & Clark in Ruiz-Sanchez et al. (2021b: 288) were described from the northern part of Sierra Madre del Sur ( Ruiz-Sanchez et al. 2021b). These novelties, along with the description of C. kochii , make this biogeographic area the richest in woody bamboos in all Mexico with 22 species.

Additional specimens examined (paratypes):— Oaxaca, San Miguel Suchixtepec, road to Pochutla to Miahuatlan , 5 km S of San Miguel Suchixtepec , Rio Molino , 16°5’N, 96°29’W, 2200 m, 21 January 1993, Clark et al. 1150 ( ISC, MEXU, XAL, ZEA); ibidem, Km 153 a 5 km aprox. de San Miguel Suchixtepec rumbo a Puerto Angel, 16°4’39” N, 96°28’44.5” W, 2207 m, 1 June 2013, Ruiz-Sanchez & Cervantes 444 ( XAL) .

Figures

FIGURE 1. Chusquea kochii. A. Mid-culm segment showing a culm leaf sheath with a reflexed culm leaf blade. B. Branch complement showing foliage leaf blades. C. Detail of leaf blade margin, abaxial view, showing pubescent indument and scabrous margin. D. Foliage leaf ligule area and pseudopetiole. Based on Clark et al. 1150 (XAL). Drawn by Rosa Pérez Luna.

FIGURE 2. Chusquea kochii. A. Mid-culm segment showing multiple branches and foliage leaves. B. Infravaginal branching. C. Detail of basal bract showing ciliate margin. D. Node with bud complement, showing circular central bud and triangular subsidiary smaller buds. Based on Clark et al. 1150 (MEXU, XAL). Drawn by Rosa Pérez Luna.

FIGURE 3. Chusquea kochii. A. Culm leaf showing reflexed blade. B. Node with bud complement, showing circular central bud and triangular subsidiary smaller buds. C. Branch complement showing infravaginal branch pattern. D. Developing branch showing a main central branch. E. Panoramic view showing branch complements and foliage leaves. F. Foliage leaf complement. Photos by Eduardo Ruiz- Sanchez.

FIGURE 4. Geographic distribution map of Chusquea kochii and C. glauca.