Andropogon saxicola A. Zanin, P. L. Viana, Welker & Filg. 2019, sp. nov.
Creators: name: Zannin, Ana
name: Viana, Pedro Lage
name: Dorneles Welker, Cassiano A.
name: Filgueiras, Tarciso S.
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Liliopsida
Poales
Poaceae
Andropogon
Andropogon saxicola

description: Andropogon saxicola A. Zanin, P.L. Viana, Welker & Filg., sp. nov.
TYPE:— BRAZIL. Minas Gerais: São Gonçalo do Rio Preto, Rio Preto State Park, on the ascent to Dois Irmãos peak, 18°12’31”S, 43°18’38”W, 1733 m, 12 April 2012, P.L. Viana, N.F. O. Mota, R.M. Salas & S. Sobrado 5864 (holotype BHCB!, isotypes FLOR!, HUFU!, MG!, RB!, SP!). (Figs. 1, 2).
Diagnosis: —It differs from the other species of Andropogon by its sessile and pedicellate spikelets 8–12 mm long, densely covered with whitish trichomes, upper glume of sessile spikelets awned, the awn (2–) 5–7.5 mm long, upper lemma of sessile spikelets pilose on the back, awned, the awn 14–20 mm long.
Description: —Plants perennial, caespitose, without rhizomes, 145–160 cm tall; culms glabrous, nodes 7–12, glabrous. Leaf sheaths shorter or longer than the internodes, glabrous; leaf blades 15–35 × 0.5–0.8 cm, linear-lanceolate, glabrous or scabrous on the base of adaxial surface and margins when young, base truncate, apex acuminate; collar glabrous or glabrescent; ligule 0.7–2 mm long, membranous-ciliate. Synflorescences composed of terminal and axillary synflorescence units, these units consisting of 2 flowering branches, conjugate or subconjugate, similar or almost so in length, exserted from the spatheole. Pedicels and rachis internodes linear, subequal, 5–8 mm long, with trichomes on both margins, sometimes one margin glabrous, the trichomes shorter than the sessile spikelet. Sessile spikelets 8–12 mm long, bisexual, awned, with a typical constriction at the base, callus pilose; lower glume 7–11 × 1.5–2.2 mm, flat, not grooved, subcoriaceous, lanceolate, 5–7-nerved, 3–5 nerves between the keels, pilose along the entire surface, the trichomes whitish and up to 3 mm long, muticous or with a short awn 0.5–1.5 mm long; upper glume 7–11 × 1.5–2.2 mm, chartaceous, lanceolate, pilose along the entire surface, the trichomes similar to those of lower glume but usually less densely arranged, awned, the awn (2–) 5–7.5 mm long; lower anthecium sterile; lower lemma 7–10 × 1.8–2 mm, hyaline or hyaline-vinaceous, 3-nerved, ciliate on the upper half; lower palea absent; upper anthecium bisexual; upper lemma 4.5–7.2 × 0.5–2 mm, hyaline or hyaline-vinaceous, 3-nerved, ciliate, pilose on the back, bifid on the upper 1/3 portion or bidentate, awned, the awn 14–20 mm long, sometimes atrophied, then 2–6 mm long, column short-pilose, longer than the subula, the subula scabrous; upper palea 1–1.2 × 0.2 mm, hyaline, veinless, glabrous or ciliate at the apex; lodicules 2, 0.8–1 mm long, truncate, glabrous; stamens 3, anthers 3–4 mm long, yellow to light brown or vinaceous; caryopsis 3.2–4 × 1–1.2 mm. Pedicellate spikelets 8–12 mm long, staminate, similar to the sessile spikelets in length and indumentum, muticous or with a short awn, with a typical constriction at the base (more conspicuous than in the sessile spikelets), callus glabrous or glabrescent; lower glume 8–12 × 2–2.1 mm, chartaceous, lanceolate, 10-nerved, pilose along the entire surface, the trichomes whitish and up to 3 mm long, muticous or with a short awn, the awn 0.8–1 mm long; upper glume 8–10.5 × 1.5–2.1 mm, chartaceous, lanceolate, pilose along the entire surface, the trichomes similar to those of lower glume, muticous or with a short awn, the awn ca. 1 mm long; lower anthecium sterile; lower lemma 7–9.5 × 2 mm, hyaline or hyaline-vinaceous, 3-nerved, ciliate on the upper half; lower palea absent; upper anthecium staminate; upper lemma 7–8.5 × 1–1.2 mm, hyaline or hyaline-vinaceous, 3-nerved, ciliate on the upper half, muticous; upper palea 1 × 1 mm, hyaline, veinless, glabrous or ciliate at the apex; lodicules 2, 0.8–1 mm long, truncate, glabrous; stamens 3, anthers 2.5–3 mm long, yellow to light brown or vinaceous.
Etymology: —The epithet alludes to the fact that the plants of this new species were found growing on rocks.
Phenology: —Flowering specimens were collected in April and November.
Distribution, habitat, and conservation status: — Andropogon saxicola is only known from the campo rupestre vegetation of the Espinhaço Range, in Minas Gerais state, Brazil. The new species was collected in two localities: Serra do Caraça and Dois Irmãos peak in Diamantina Plateau (Fig. 3), encompassed by the Santuário do Caraça Private Reserve of Natural Heritage (RPPN Caraça) and Rio Preto State Park protected areas, respectively. In both localities, the species was found growing associated with quartzite rocky outcrops at elevations ranging from 1300 m (Serra do Caraça) to 1800 m (Dois Irmãos peak).
The calculated value of area of occupancy (AOO = 8 km 2) suggests the conservation status of Endangered (EN) for the new species, according to the IUCN criteria [B2ab(iii)].
Campo rupestre vegetation in eastern Brazil was recently classified as an old climatically-buffered infertile landscape (OCBIL) (Silveira et al. 2016) and is remarkable for a high level of plant diversity and endemism (Giulietti et al. 1997). At least 30 species of Poaceae are considered endemic to the campo rupestre of the Espinhaço Range (Viana & Filgueiras 2008), three of which belong to the genus Andropogon [A. campestris Trinius (1832: 277), A. durifolius Renvoize (1984: 181), and the new species A. saxicola]. Increasing threats to this ecosystem, such as repeated anthropogenic fires, opencast mining, uncontrolled urbanization, and eucalyptus plantations, are compromising ecosystem services and plant diversity of campo rupestre (Silveira et al. 2016).
Additional material examined (paratype): — BRAZIL. Minas Gerais: Catas Altas, Santuário do Caraça, Serra do Caraça, near Cascatinha, 20°06’21”S, 43°28’27”W, 1300 m, 15 November 2013, C. Silva, C. Snak, M. Monge & P.L. Viana 1024 (HUEFS).
Taxonomic notes: —The linear pedicels and rachis internodes, and the flat, not grooved, subcoriaceous lower glume of sessile spikelets, with nerves between the keels, place the new species in Andropogon sect. Andropogon established by Stapf (1919) and accepted by Clayton & Renvoize (1986). This section includes species distributed in the tropics and in the Mediterranean region (Clayton & Renvoize 1982, 1986).
Most of the species of Andropogon that occur in Brazil belong to Andropogon sect. Leptopogon Stapf (1919: 211), which is distinguished from A. sect. Andropogon mainly by the membranous lower glume of sessile spikelets, without nerves between the keels (Clayton & Renvoize 1986). A few other Brazilian species belong to Andropogon sect. Notosolen Stapf (1919: 211) or Andropogon sect. Piestium Stapf (1919: 211) because they present clavate to oboval rachis internodes and pedicels, as well as a longitudinal groove and nerves between the keels in the lower glume of sessile spikelets (in A. sect. Notosolen), or lower glume deeply concave, with or without nerves close to the keels (in A. sect. Piestium).
In Brazil, Andropogon carinatus Nees (1829: 330) and A. ingratus Hackel (1901: 151) resemble superficially the new species because they present pedicels and rachis internodes usually linear and the lower glume of sessile spikelets not grooved, generally with nerves between the keels (Zanin & Longhi-Wagner 2011). In Andropogon campestris and A. durifolius, nerves between the keels also occur, but the shape of rachis internodes and pedicels is distinct (subclavate). In these species, a longitudinal groove on the lower glume of sessile spikelets is sometimes present (Zanin & Longhi-Wagner 2011).
Andropogon saxicola is recognized by its spikelets (both the sessile and the pedicellate) densely covered with long whitish trichomes, a feature that is useful for distinguishing the new species from the above-mentioned taxa (see Table 1). In those putatively related species, the spikelets are usually only scabrous on the nerves at the apical portion of the glumes, or sometimes scaberulous along the entire surface (Zanin & Longhi-Wagner 2011). In A. saxicola, the upper glume of sessile spikelets is awned, the awn (2–) 5–7.5 mm long, while in the other species it is muticous. Moreover, the sessile and pedicellate spikelets in the new species are longer (8–12 mm vs. 1–7.3 mm long). Other comparative characters between A. saxicola and these species are presented in Table 1.
description: Published as part of Zannin, Ana, Viana, Pedro Lage, Dorneles Welker, Cassiano A. & Filgueiras, Tarciso S., 2019, Andropogon saxicola (Poaceae: Andropogoneae), a new species from Brazil, pp. 83-90 in Phytotaxa 397 (1) on pages 84-88, DOI: 10.11646/phytotaxa.397.1.8, http://zenodo.org/record/13717838