Guadua leonardoana Afonso, L. G. Clark & P. L. Viana 2023, sp. nov.
Creators: name: Afonso, Edgar Augusto Lobato
name: Clark, Lynn G.
name: Mansano, Vidal De Freitas
name: Filgueira, Joana Patrícia Pantoja Serrão
name: Viana, Pedro Lage
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Liliopsida
Poales
Poaceae
Guadua
Guadua leonardoana

description: Guadua leonardoana Afonso, L.G. Clark & P.L. Viana, sp. nov.
(Figs. 1, 2)
Type:— BRAZIL. Pará: Parauapebas, FLONA de Carajás, Serra dos Carajás, próximo ao N7, 6°09’10.4”S, 50°10’43.3”W, 625 m, 16 November 2019 (st), E. A. L. Afonso 433 (holotype MG!, isotypes BHCB!, INPA!, ISC!, NY!, RB!, US!).
Diagnosis: — Guadua leonardoana is most similar to G. chaparensis Londoño & Zurita (2008: 31) (see table 1). However, it differs mainly by the culm wall thickness 4.1–7.1 mm vs. 10–15 mm in G. chaparensis; supranodal ridge not prominent vs. supranodal ridge prominent; culm leaf blade / sheath length ratio 1/2.3–1/3.4 vs. 1/4–1/5; and pseudopetiole 1.1–1.6 mm long. vs. 2–4 mm long., respectively.
Description: —Woody, loosely caespitose, thorny bamboo. Rhizomes sympodial, pachymorph, long-necked. Culms light green to dark green, slightly decumbent to erect at the base, arching at the upper 1/3, 2–5 culms per m², 0.5–1 m apart from each other, 15–20 m tall, 5–10 cm diam.; internodes 30–70 cm long, cylindrical to sulcate above the bud, smooth, glabrescent or sericeous to floccose, with whitish trichomes 0.2–0.3 mm long; hollow, wall thickness 4.1–7.1 mm, lumen 4.1–8.2 diam.; nodal line horizontal, not prominent, supranodal ridge horizontal, a band of pale beige, velutinous trichomes extending 1.2–1.5 cm above and 0.8–1.2 cm below the nodal line, forming spaced patches below the nodal line, trichomes 1.2–1.7 mm long. Bud solitary, 1.4–1.6 × 0.9–1.1 mm, oval, elevated on a promontory, with velutinous and glabrescent cataphylls, densely fringed towards the apex. Branch complement consisting of a single branch, patent, thorny, usually unbranched at the lower nodes, the middle and upper nodes with a dominant central branch, sometimes with branchlets or thorns arising from basal nodes, and then rebranching up to three times. Branching usually extra-vaginal at the basal nodes, intravaginal at the median and apical nodes, the lowermost branches growing horizontally, 90° in relation to the culm, generally unbranched, aphyllous and with many thorns, the middle and apical branches growing at an angle of 30°–45° in relation to the culm, branching many times forming branches of smaller diameter towards the apex of the culm, densely foliated and usually with few or no thorns, the lowermost branch ca. 2–4 m long; the branches 0.7–1.9 cm diam., solid, smooth, glabrous. Culm leaves late deciduous or persistent on the culm; sheaths 21.5–42.8 × 28–38.5 cm, rounded abaxially, rigid, glabrous on both surfaces, sometimes pubescent near the base of the abaxial surface, margins entire, smooth, confluent at the junction with the blade; auricles, oral setae and fimbriae absent; outer ligule absent; inner ligule 0.7–1.0 mm, ciliate, stramineous, slightly curved towards the leaf base, straight or curved towards the apex, extending to the leaf margin; blades 9.1–12.5 × 13–14.5 cm, 1/2.3–1/3.4 as long as the sheath, persistent, triangular, rigid, coriaceous, erect, brown, the base usually truncate, sometimes slightly rounded, symmetric or rarely asymmetric, abaxially glabrous, adaxially hirsute, entirely covered by brown trichomes, these 2–2.5 mm long, appressed towards the apex, tessellate venation absent, apex acute, margins entire, smooth, glabrous. Foliage leaves 3–9 per complement; sheaths 3.3–6.5 cm long, rounded abaxially, stramineous to light-brown, vascular bundles conspicuous on the adaxial surface, inconspicuous on the abaxial surface, abaxially pubescent to hirsute, adaxially glabrous, margins scabrous, with trichomes ca. 0.1 mm long; auricles usually present, 0.8–1.3 mm long, brown, margins fimbriate, fimbriae 4.9–8.9 mm long; oral setae absent; outer ligule 0.4–1.7 mm long, entire, glabrous on both surfaces, stramineous; inner ligule 0.2–0.4 mm long, entire, glabrous on both surfaces, stramineous, margins with unicellular trichomes, 0.1–0.2 mm long; pseudo-petiole 1.1–1.6 × 1–2 mm, abaxially glabrous, adaxially glabrous or with hyaline trichomes, ca. 0.1 mm long, yellowish to stramineous; blades 5.9–23.4 × 0.6–3.2 cm, linear to linear-lanceolate, light-green, glabrous on both surfaces, rarely with hyaline trichomes, 0.1–0.5 mm long, concentrated at the base of the adaxial surface, base acute to slightly rounded, apex acute, 15–19-nerved, margins scabrous, with hyaline trichomes ca. 0.1 mm long. Synflorescences and fruits not seen.
Distribution and habitat: —The new species is only known from two populations in the Serra Norte, part of the Serra dos Carajás, southeastern Pará state, Brazil (Fig. 4). It was found in dense ombrophilous forests at elevations between 550–631 m, forming large stands along a water drainage on the slopes of the canga plateaus, which are characterized by iron-rich soils (Viana et al. 2016).
Etymology: —The specific epithet honors Leonardo V. C. Silva, known as “Léo do Mel”, discoverer of the type population and the first to collect samples of this species. Leonardo contributed to an important collection of specimens from the Serra dos Carajás deposited in the BHCB herbarium, which was crucial for the development of the Flora of the cangas of the Serra dos Carajás project (Viana et al. 2016, Mota et al. 2018).
Comments: — Guadua leonardoana is morphologically similar to G. chaparensis and the other species included in the “ Guadua weberbaueri group”, informally proposed by Londoño & Zurita (2008), formed by: G. incana Londoño (2008: 26), G. tagoara (Nees 1829: 532) Kunth (1833: 434), G. sarcocarpa Londoño & Peterson (1991: 631), G. weberbaueri Pilg. (1905: 152). This species grows in very humid, lowland forests and they have in common the presence of water inside of the hollow internodes. This internal water phenomenon seems to be associated with very high relative humidity and a high water-table, and it may occur after strong changes of temperature that break tissues allowing water to leak into and accumulate in the lumen (Londoño & Zurita 2008). In addition, the presence of water inside the internodes can often lead to the deposition of peculiar laminar and dark structures on the inner wall (Fig. 2–D). A comparative table for distinguishing the Amazonian species of the G. weberbaueri group is presented in Table 1.
Although reproductive characters are unknown for Guadua leonardoana, a set of vegetative features are informative for its recognition within the G. weberbaueri group. Culm walls are thinner (Fig. 1–A) than in all other species of this group (4.1–7.1 mm vs. 10–15 mm in the others), and a supranodal ridge is not prominent (Fig. 1–A, 2–B) in the nodal region of culms (vs. prominent or slightly prominent). The culm leaves are also distinctive in the new species: blades are longer than in other species of G. weberbaueri group (9.1–12.5 cm long vs. up to 11 cm long), especially their relative length to the sheath (Fig. 1–B) (blade / sheath length ratio 1/2.3–1/3.4 vs. 1/4–1/6.6). Considering the foliage leaves, the pseudopetioles in G. leonardoana are the shortest within the group (Fig. 1–H) (1.1–1.6 mm long vs. 2–10 mm long).
In the field, the new species can be recognized by the young culms covered by whitish trichomes (Fig. 2–B), which are deciduous and restricted to the nodal region in old culms. The rhizomes with long necks (Fig. 2–E) and, consequently, the long distance between the culms (0.5–1 m) give an open aspect to the clumps (Fig. 2–F), which is usually not observed in other species of the G. weberbaueri group.
Additional material examined (paratypes):— BRAZIL. Pará: Parauapebas, N 7, Floresta, 6°09’09”S, 50°10’42”W, 631 m, 24 June 2012 (st), L. V. C. Silva et al. 1314 (BHCB, MG); ibidem, 15 October 2015 (st), S. S. Pereira et al. 8 (BHCB, MG, RB); ibidem, 27 May 2017 (st), E. A. L. Afonso et al. 200 (HUEFS, MG, RB); ibidem, trilha depois do N9, na margem do córrego d’água, 6°11’34”S, 50°07’42”W, 505 m, 14 May 2022 (st), R. G. Barbosa - Silva et al. 1720 (MG).
description: Published as part of Afonso, Edgar Augusto Lobato, Clark, Lynn G., Mansano, Vidal De Freitas, Filgueira, Joana Patrícia Pantoja Serrão & Viana, Pedro Lage, 2023, A new species of Guadua (Poaceae: Bambusoideae: Guaduinae) from Pará state in Amazonian Brazil, pp. 208-218 in Phytotaxa 597 (3) on pages 209-212, DOI: 10.11646/phytotaxa.597.3.2, http://zenodo.org/record/7958552