Chusquea contrerasii Ruiz-Sanchez & L.G. Clark, 2021

Ruiz-Sanchez, Eduardo, Romero-Guzman, Rafael, Flores-Argüelles, Alejandra, Ortiz-Brunel, Juan Pablo & Clark, Lynn G., 2021, Chusquea contrerasii and C. guzmanii (Poaceae, Bambusoideae, Bambuseae, Chusqueinae), two new endemic species from Jalisco, Mexico, Phytotaxa 497 (3), pp. 285-297 : 287-288

Chusquea contrerasii Ruiz-Sanchez & L.G. Clark , sp. nov., Figs. 1 A–G , 2 A-E

TYPE:— MÉXICO. Jalisco: Puerto Vallarta, Ojo de Agua, aproximadamente 7 km al SE de Vallejo, arroyo Las Chalas , 20°30’48.42 N, 105°11’15.98” W, 840 m, 11 December 2013 (fl), A. Flores-Argüelles y A.R. Romero-Guzmán 919 (holotype IBUG! , isotype MEXU! ).

Chusquea contrerasii differs from C. nelsonii by having fewer branches per node (9–13 vs. 15–30), a shorter glume III (3.1–3.8 vs. 3.8–5 mm), a shorter glume IV (3.4–4.4 vs. 3.8–6 mm), and glumes III and IV scabrous vs. pubescent.

Rhizomes pachymorph. Culms 2–2.7 m tall, 0.5–0.9 cm in basal diameter, erect at the base, scandent toward the apex. Internodes (6–) 10–15 (–15.5) cm long, terete, strigose, with short hirsute hairs, green, solid. Culm leaves (6.5–) 8.5–10 cm long, glabrous, green when young, becoming straw-colored when old, deciduous after branch development; sheaths (5.5–) 7–9 cm long, rectangular with rounded shoulders, 4–10 times as long as the blade, the margins entire on both sides; blades 10–11 mm long, broadly triangular, erect and deciduous, wine-red when young, apex acuminate, margins finely scabrous, glabrous; girdle asymmetrically developed, prominent only near the bud complement, 3–5 mm wide, developing a patella; inner ligule 0.4–1.2 mm long, irregular, glabrous. Nodes at mid-culm with 10–14 buds, composed of one larger triangular central bud subtended by 9–13 smaller triangular, closely adjacent subsidiary buds arranged in a single constellate row, the base of the buds arising above the nodal line; lower nodes developing roots that encircle the node; nodal line dipping markedly below the bud/branch complement; supranodal ridge present, prominent. Branching infravaginal; the culm leaf sheaths deciduous, 9–13 branches per node, diverging from the main culm at 45 o, (7–) 11–13 (–18) cm long, 0.8–1 mm in diameter, the larger main branch 1.5–3 mm in diameter, 44–76 cm long, always rebranching. Foliage leaves 3–4 per complement; sheaths glabrous, the summit with sparsely hirsute hyaline hairs; outer ligule 0.2–0.4 mm long, glabrous; inner ligule 0.6–1.2 mm long, truncate; pseudopetioles 1–2 mm long, adaxially and abaxially glabrous; blades 3–7 cm long, 4–9 mm wide, ratio L:W = 6.6–10, lanceolate, adaxially glabrous, abaxially pubescent, green, not tessellate, the base rounded-attenuate, the margins entire, the apex mucronate. Synflorescences 2.5–4.5 cm long, paniculate, narrow, congested, exerted from the subtending sheath, rachis pilose; branches 2–4 mm long, appressed, terete, pilose; pedicels 0.5–1 mm long, pilose. Spikelets 6.6–7.5 mm long, laterally compressed. Glumes I and II ovate, margin entire, glabrous, enervate; glume I 0.5–1.3 mm long, 1/12–1/6 the spikelet length; glume II 0.9–1.5 mm long, 1/7–1/5 the spikelet length, apex muticous. Glumes III and IV scabrous, awned, margin entire, 3-nerved; glume III including the awn 3.1–3.8 mm long, ca. 1/2 the spikelet length, the awn 0.7–0.9 mm; glume IV including the awn 3.4–4.4 mm long, 1/2–2/3 the spikelet length, the awn 0.8–1 mm. Lemmas 6.4–7.3 mm long, 7–nerved, green becoming purplish, pubescent, acuminate. Paleas 6.4–7.3 mm long, 2–nerved, glabrous, bimucronate. Lodicules 3, membranaceous but slightly thickened at the base, vascularized, brown, apex ciliate, ca. 1.3 mm long. Ovary glabrous; style one, soon bifid. Stamens and stigmas not seen. Fruit not seen.

Habitat and distribution:— Chusquea contrerasii grows in ravines of montane cloud forest and pine-oak forest at 840–1630 m elevation in the Sierra Madre del Sur Jalisciense-Tuito district (Sierra El Cuale and Sierra de San Sebastián) ( Fig. 3 ). This species grows together with Magnolia vallartensis Vázquez & Muñiz-Castro (2012: 124) , Podocarpus matudae Lundell (1937: 212) , and Miconia vallartensis Zabalgoitia et al. (2020: 2) . It is only known from two populations, one in the Sierra El Cuale and another in the Sierra de San Sebastián in western Mexico ( Fig. 3 ). This zone hosts other microendemics such as Bessera tuitensis Delgadillo (1992: 131) , Manfreda santana-michelii Castro-Castro et al. (2018: 497) , Quercus cualensis González (2003: 49) , Q. tuitensis González (2003b: 42) , and Salvia cualensis González-Gallegos (2012: 50) .

Comparison:— Chusquea contrerasii is similar to C. nelsonii and C. guzmanii in plant size, appearance, and foliage leaf blade size. However, C. contrerasii has fewer branches per node (9–13) than C. nelsonii (15–30) and C. guzmanii (13–30) and scabrous glumes III and IV, pubescent in C. nelsonii , and glabrous in C. guzmanii ( Table 1 ).

Etymology:—The specific epithet honors Sergio Honorio Contreras Rodríguez, professor at the University of Guadalajara who teaches agrostology and conducts research on grasses in Jalisco.

Phenology:—The type specimen is the only known flowering record for this species, so we cannot infer the length of the flowering cycle.

Conservation assessment:— Chusquea contrerasii is currently known from two localities separated by 38 airline kilometers ( Fig. 3 ). The species is abundant only at the Sierra El Cuale locality and we found only two individuals at the Sierra de San Sebastián locality. However, its survival could be at risk, since it is only known from very restricted ravines.According to our results of EOO (0 km 2) and AOO (8 km 2) analyses, this species fits the criteria B2ab(ii,iii,iv,v), and should be considered as Critically Endangered (CR) ( IUCN 2019).

The Jalisciense-Tuito district is characterized by a steep mountainous complex, with tropical subperennial and subdeciduous forests in the lowlands, montane cloud forest at mid-elevations and oak and pine forest at middle and high elevations ( Vázquez-García et al. 2012, Pérez de la Rosa & Gernandt 2017, Zabalgoitia et al. 2020). In recent years, some endemic species have been described from this district, such as Magnolia vallartensis , Hyptis cualensis González-Gallegos & Castro-Castro (2014: 154) , Pinus vallartensis Pérez de la Rosa & Gernandt (2017: 234) , Manfreda santana-michelii , Hechtia ibugana Flores-Argüelles et al. (2019: 106) , and Miconia vallartensis . The recognition of Chusquea contrerasii increases the endemism found in this region ( Santiago-Alvarado et al. 2016).

Additional specimens examined:— MEXICO. Jalisco, San Sebastián del Oeste, Carretera Mascota-Puerto Vallarta , km 28.5, 20°42’25” N, 104°52’57” W, 1611 m, 28 July 2020, J.P. Brunel et al. 849 ( IBUG, MEXU, ZEA ) ; carretera Mascota-Puerto Vallarta , en cañada, 20°42’25” N, 104°52’57” W, 1627 m, 1 November 2020, J.P. Brunel & E. Ruiz-Sanchez 1028 ( IBUG, MEXU, ZEA ) .

Figures

FIGURE 1. Chusquea contrerasii. A. Apical culm fragment, showing flowering branches. B. Synflorescence. C. Lower glumes (I, II). D. Upper glumes (III, IV). E. Lemma dorsal view. F. Palea lateral view. G. Lodicules. Based on A. Flores-Argüelles & A.R. Romero-Guzmán 919. Drawn by Daniel Barba.

FIGURE 2. Chusquea contrerasii. A. Bud complement showing buds and lateral root appendages. B. Branch complement showing infravaginal branching and branches. C.Apical culm fragment, showing branches and foliage leaves. D. Mid culm, showing branches and foliage leaves. E. Synflorescences and spikelets. Photos by Eduardo Ruiz-Sanchez (A-D) and Alejandra Flores-Argüelles (E).

FIGURE 3. Geographical distribution map of Chusquea contrerasii, G. guzmanii and C. nelsonii.

Tables

TABLE 1. Comparison of morphological characters among Chusquea contrerasii, C. guzmanii, and C. nelsonii.

Character Number of branches per node	C. contrerasii 9–13	C. guzmanii 13–30
Foliage leaf blade length (cm)	3–9	5.2–8.5	(6.4–) 7.3–9 (–11)
Foliage leaf blade width (mm)	4–9	4–5	5–10
Foliage leaf blade ratio L:W	6.6–10	13–20	9–15
Foliage leaf blade indument	abaxially pubescent	abaxially glabrous	abaxially pubescent
Spikelet length (mm)	6.6–7.5	4.5–4.8	6.9–7.8
Glume I (mm)	0.5–1.3	0.8–1.5	0.6–0.8
Glume II (mm)	0.9–1.5	1.3–1.7	0.8–1.3
Glume III (mm)	3.5–3.8	1.6–2.2	3.8–5
Apex	awned	mucronate	awned
Indument	scabrous	glabrous	pubescent
Glume IV (mm)	3.4–4.4	2–2.6	3.8–6
Apex	awned	mucronate	awned
Indument	scabrous	glabrous	pubescent
Proportion vs. the spikelet length	1/2–2/3	ca. 1/2	1/2–2/3
Lemma (mm)	6.4–7.3	3.8–4.3	6.4–7.1
Indument	pubescent	pubescent	scabrous
Apex	acuminate	mucronate	awned
Palea (mm)	6.4–7.3	4.3–4.6	6–7