Chusquea guzmanii 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 : 288-294

Chusquea guzmanii Ruiz-Sanchez & L.G. Clark , sp. nov., Figs. 4 A,B , 5 A-F, 6 A-H

TYPE:— MÉXICO. Jalisco, Autlán, 5 km al W de Chiquihuitán por la brecha Autlán-Villa Purificación , 19 o 45’15” N, 104 o 27’9” W, 1231 m, 3 October 2020 (fl), E. Ruiz-Sanchez, J.P. Brunel & E. Gándara 670 (holotype IBUG!, isotypes MEXU!, ZEA!) .

Chusquea guzmanii differs from Chusquea nelsonii in having a longer glume I (0.8–1.5 vs. 0.6–0.8 mm), a smaller, glabrous glume III (1.6–2.2 vs. 3.8–5 mm) with the apex mucronate vs. pubescent and aristate, a smaller, glabrous glume IV (2–2.6 vs. 3.8–6 mm), with the apex mucronate vs. pubescent and aristate, a smaller lemma (3.8–4.3 vs 6.4–7.1 mm), a smaller palea (4.3–4.6 vs. 6–7 mm), and a shorter spikelet (4.5–4.8 vs. 6.9–7.8 mm).

Rhizomes pachymorph, short-necked. Culms 1.5–2 m tall, 0.5–1 cm in basal diameter, erect at the base, scandent toward the apex. Internodes 13.7–22.5 cm long, terete, glabrous, green, solid becoming fistulose with age in some. Culm leaves 13.5–18.7 cm long, glabrous, green when young, becoming straw-colored when old, persistent but some deciduous; sheaths 10–15.7 cm long, rectangular with rounded shoulders, 2.8–3.1 times as long as the blade, the margins entire on both sides; blades 3.5–5 cm long, narrow rectangular, reflexed and deciduous, apex acuminate, margins entire, glabrous; girdle visible, 1–2 mm wide, developing a patella, inner ligule ca. 1 mm long, glabrous, truncate, irregular. Nodes at mid-culm with 14–31 buds, composed of one larger triangular central bud subtended by 13–30 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; 13–30 branches per node, diverging from the main culm at 45–70 o, 8–22 cm long, 0.5–1 mm in diameter, the larger main branch 2–4 mm in diameter, up to 50 cm long, always rebranching. Foliage leaves 3–5 per complement; sheaths glabrous, the summit glabrous; outer ligule 0.1 mm long glabrous; inner ligule ca. 1 mm long truncate; pseudopetioles 1–2 mm long, adaxially and abaxially glabrous; blades 5.2–8.5 cm long, 4–5 mm wide, ratio L:W = 13–20, linear, abaxially and adaxially glabrous, green, not tessellate, the base attenuate, the margins scabrid, the apex acuminate. Synflorescences 4.5–8 cm long, paniculate, narrow, congested, exserted from the subtending sheath, rachis pilose; branches 5–15 mm long, appressed, terete, pilose; pedicels 0.5–1 mm long, pilose. Spikelets 4.5–4.8 mm long, laterally compressed. Glumes I and II ovate, margin entire, glabrous, hyaline; glume I 0.8–1.5 mm long, 1/6–1/3 the spikelet length, enervate; glume II 1.3–1.7 mm long, 1/3 the spikelet length, l-nerved. Glumes III and IV glabrous, hyaline, margin entire, 1-nerved, apex mucronate; glume III 1.6–2.2 mm long, 1/3–1/2 the spikelet length; glume IV 2–2.6 mm long, ca. 1/2 the spikelet length. Lemmas 3.8–4.3 mm long, 7–nerved, green becoming purplish, pubescent, mucronate. Paleas 4.3–4.6 mm long, 2–nerved, scabrous, bimucronate. Lodicules 3, membranaceous, hyaline, apex ciliate, ca. 0.7 mm long. Ovary glabrous; style one, soon bifid. Stamens ca. 2.8 mm long. Fruit a basic caryopsis, ca. 2.5 mm long, immature.

Habitat and distribution:— Chusquea guzmanii grows in ravines in montane cloud forest and tropical dry forest at 1280–1560 m elevation, in the northeastern portion of the Sierra Madre del Sur, Jalisciense-Manantlán district ( Fig. 3 ).

Comparison:— Chusquea guzmanii is similar to C. nelsonii and C. contrerasii in plant size, appearance and foliage leaf blade size. However, C. guzmanii has a mucronate glume III (1.6–2.2 mm) shorter than in C. nelsonii (3.8–5 mm, aristate) and C. contrerasii (3.5–3.8 mm, aristate), a mucronate glume IV (2–2.6 mm) shorter than in C. nelsonii (3.8–6 mm, aristate) and C. contrerasii (3.4–4.4 mm, aristate), a shorter lemma (3.8–4.3 mm) than C. nelsonii (6.4–7.1 mm) and C. contrerasii (6.4–7.3 mm), and shorter spikelets (4.5–4.8 mm) than C. nelsonii (6.9–7.8 mm) and C. contrerasii (6.6–7.5 mm) ( Table 1 ).

Etymology:—The specific epithet honors Rafael Guzmán Mejía, a Mexican grass taxonomist and retired professor at the University of Guadalajara who has made enormous contributions to our knowledge of Mexican grasses, describing new species and collecting thousands of grass specimens including bamboos.

Phenology:—This is the first known flowering record for this species. The cultivated plant started flowering in July 2019 and continued flowering for several months. In October 2020, we revisited the type locality and found that all the plants were flowering. This is the only known flowering event and therefore the flowering cycle is unknown.

Conservation assessment:— Chusquea guzmanii is currently known from three localities where the species is scarce, and thus its survival could be at risk. According to our results of EOO (0 km 2) and AOO (8 km 2) analyses, this species fits the criteria B2ab(ii,iii,iv), and should be considered as Critically Endangered (CR) ( IUCN 2019). With more than 2900 plant species, the Reserva de la Biosfera de Manantlán hosts between 35 to 40% of the vascular flora of Jalisco ( Vázquez et al. 1995). This national reserve area belongs to the Jalisciense-Manantlán district (Santiago-Alvarado et al. 2016). In recent years some plant species have been described for this district, such as Ixchelia kochii Cuevas (2019: 146) , Sloanea cuautitlanensis Cuevas & Mendoza (2018: 1) , Opuntia setocarpa Arreola-Nava et al. (2017: 793) , and Solanum edmundoi Cuevas & Núñez (2015: 294) . One of the most emblematic species growing in this district is Zea diploperennis Iltis et al. (1979: 168) . This species was extremely important for the creation of the Reserva de la Biosfera de Manantlán. The description here of Chusquea guzmanii increases the endemism in this district.

Additional specimens examined:— MEXICO. Jalisco: Autlán, 5 km al W de Chiquihuitán por la brecha Autlán-Villa Purificación, 19 o 45’5.8” N, 104 o 27’26.8” W, 1268 m, 3 June 1998, F. J. Santana-Michel 9126 ( ZEA) ; 5 km al W de Chiquihuitán por la brecha Autlán-Villa Purificación , 19 o 45’15” N, 104 o 27’9” W, 1231 m, 15 July 2019 (veg), E. Ruiz-Sanchez et al. 627 ( IBUG) ; Cultivated at the IBUG botanical garden , 24 June 2020 (fl), E. Ruiz-Sanchez et al. 650 ( IBUG) ; Villa Purificación, Villas de Cacoma , 19 o 50’11.6” N, 104 o 31’48.7” W, 1560 m., 13 July 2013, R. Cuevas, L. Guzmán y J.G. Morales 11164 ( IBUG, ZEA) .

Figures

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

FIGURE 4. Chusquea guzmanii. A. Mid-culm fragment showing branches and foliage leaves. B. Synflorescence and spikelets. Based on Ruiz-Sanchez et al. 627 (A) and Ruiz-Sanchez et al. 670 (B). Drawn by Juvenal Aragón Parada.

FIGURE 5. Chusquea guzmanii. A. Branch complement showing infravaginal branching development. B. Mid-culm of new shoot, showing culm sheath and culm leaf blade reflexed. C. Branch complement showing foliage leaf blades. D. Foliage leaf ligular area adaxial view. E. Spikelet, showing glumes, lemma, palea, stamens. F. Spikelet lateral view. Based on Ruiz-Sanchez et al. 627 (A-D) and Ruiz- Sanchez et al. 670 (E, F). Drawn by Juvenal Aragón Parada.