Chaetogastra riograndensis F. S. Mey. 2016, sp. nov.
Creators: name: Meyer, Fabrício Schmitz
name: Goldenberg, Renato
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Myrtales
Melastomataceae
Chaetogastra
Chaetogastra riograndensis

description: Chaetogastra riograndensis F.S.Mey. sp. nov. (Figures 10–12).   
 Type: — BRAZIL. Rio Grande do Sul: São Francisco de Paula, Parque Estadual do Rio Tainhas, 20 April 2014, F.S. Meyer, D.P. Volet & M. Monge 1996 (holotype: UPCB!, Isotype: MBM!, ICN!).   
 Diagnosis: — Chaetogastra riograndensis differs from Tibouchina saxicola F.S. Meyer et al. (2009: 144) by the leaves with 5 veins and crenulate margins, and by the ovate or elliptic bracteoles vs. 3-veined leaves with serrate (in the distal medial portion) margin, and oblanceolate bracteoles in T. saxicola.   
Subshrub with sympodial growth, 20–80 cm tall. Branches moderately hirsute to setulose, trichomes 0.3–2 mm long, both glandular and not glandular, erect or curved, the base rounded, slightly enlarged, not immersed, not forked. Petiole 1.1–4.5 mm long, moderately to densely hirsute to setulose, trichomes 0.7–2.3 mm long, both glandular and not glandular, erect, the base rounded, slightly enlarged, not immersed, not forked; blade 1.2–4.5 × 0.4–1.2 cm, membranaceous, lanceolate or elliptic-lanceolate, surface flat or conduplicate, patent in dry specimens, apex acute, base acute, margins crenulate, short-ciliate, trichomes 0.7–1.8 mm long, not glandular, appressed, the base linear and not enlarged, immersed, not forked, followed by a sequence of white dots, adaxial surface glabrous or moderate to sparsely strigose, trichomes distribute on the whole surface or restricted to the central-basal portion, 1–2.6 mm long, both glandular and not glandular, appressed, the base linear and not enlarged, immersed, not forked, followed by a sequence of white dots, abaxial surface with the veins moderately setulose, trichomes 0.3–1.8 mm long, both glandular and not glandular, curved, the base rounded and slightly enlarged, not immersed, not forked; veins 5, first and second lateral pairs confluent. Thyrsoid elongate, cymes axillary and terminal, flowers lax; internode of the inflorescence base 4–6.1 cm long; bracteoles 0.8–1.4 × 0.3–0.8 mm, ovate or elliptic, glabrous on both surfaces, margins short-ciliate, trichomes 0.2–0.5 mm long, not glandular, curved, the base rounded, slightly enlarged, not immersed, not forked. Flowers 4–merous; hypanthium 2.6–4.6 × 2–3.6 mm, oblong, little constricted in its apical portion, green-vinous, striate (with longitudinal ribs), moderate to sparsely setulose, trichomes 0.3–1.2 mm long, glandular, curved, the base rounded and slightly enlarged, not immersed, not forked; sepals 2.1–4.3 × 1.6–1.8 mm, narrowly triangular to oblong but with a wide base, apex acuminate, abaxial surface glabrous or with the indumentum similar to the hypanthium, but concentrated on its central portion, adaxial surface glabrous, margins short-ciliate, trichomes 0.4–0.9 mm long, not glandular, curved, the base rounded, slightly enlarged, not immersed, not forked; petals 21.5–22.6 × 12–14.3 mm purple, obovate, apex obtuse or apiculate, margins short-ciliate, trichomes 0.1–0.4 mm long, both glandular and not glandular, erect, the base rounded, not enlarged, not immersed, not forked; stamens 8, antepetalous with filaments 3.9–5.1 mm long, pedoconnective 0.4–0.7 mm long, anthers 3–4.5 mm long, yellow, anther pore ca. 0.2 mm wide, antesepalous with filaments 5.8–6.8 mm long, pedoconnective 2.3–2.9 mm long, anthers 4.3–6.8 mm long, yellow, anther pore 0.2–0.3 mm wide, both anthers with attenuate apex, apical-ventral pore and pedoconnective appendages with apex obtuse; ovary 2.7–4.3 × 2.3–2.7 mm, apex sparse or moderatly pubescent with trichomes 0.1–0.6 mm long, both glandular and not glandular, erect, the base rounded and not enlarged, not immersed, not forked; style 8.1–9.3 mm long, apex curved, glabrous. Capsule 9.8–10.8 × 3.8–5 mm, striate (with longitudinal ribs).  
 Paratypes:— BRAZIL. Rio Grande do Sul: Cambará do Sul, 4 February 1985, N. Silveira et al. 1830 (HAS!). São Francisco de Paula, Parque Estadual do Rio Tainhas, 20 April 2014, F.S. Meyer et al. 1997 (UEC!); ibidem, F.S. Meyer et al. 1998 (UEC!); ibidem, F.S. Meyer et al. 2002 (NY!, UEC!); ibidem, F.S. Meyer et al. 2003 (UEC!, UPCB!); ibidem, F.S. Meyer et al. 2004 (UEC!); ibidem, F.S. Meyer et al. 2006 (UEC!); ibidem, 20 April 2014, F.S. Meyer et al. 2008 (UEC!); ibidem, 20 April 2014, F.S. Meyer et al. 2009 (UEC!); ibidem, 20 April 2014, F.S. Meyer et al. 2016 (UPCB!); ibidem, 20 April 2014, F.S. Meyer et al. 2017 (UEC!, UPCB!). Cambará do Sul, Parque Nacional de Aparados da Serra, 21 April 2014, F.S. Meyer et al. 2021 (ICN!, MBM!, NY!, UEC!, UPCB!). Jaquirana, Cachoeira dos Venâncios, 22 February 2004, V.F. Kinupp 2904 (ICN!).   
 Distribuition and habitat:— Chaetogastra riograndensis occur only in the state of Rio Grande do Sul (Figure 1D), in Grasslands, generally restricted to wet places along river banks (Figure 10D). Although with a restricted range, the populations of this species are large, with several individuals.   
 Phenology:—Flowering and fruiting between February to April.   
 Conservation status:—This species can be considered Critically Endangered according to IUCN’s category A4 (2012). The Area of Occupancy is around 2.450 km 2, and the Extent of Occurence 10.0149 km 2. Some populations are in unprotected areas, where the original vegetation has been replaced with Pinus spp., agriculture and pastures. Even the populations located inside the “Parque Estadual do Rio Tainhas” (29°5’35.32”S- 50°21’51.31”W) are threatened by the plantations of Pinus spp. in adjacent areas.   
 Etymology:—The epithet is refers to the state of Rio Grande do Sul, to which this species is endemic.   
 Affinities: — Chaetogastra riograndensis is similar to T. saxicola due to the sympodial growth, lanceolate leaves and antesepalous stamens with long pedoconnectives, 2–3.2 mm long in T. saxicola, and 2.3–2.9 mm long in C. riograndensis. Chaetogastra riograndensis differs from T. saxicola by the differences pointed in the diagnosis. It is also similar to Tibouchina nitida (Graham 1831: 186) Cogniaux (1885: 404) due to the narrow leaf blade, tetramerous flowers and antesepalous stamens with long pedoconnectives, 2–2.3 mm in T. nitida. Chaetogastra riograndensis differs by the color of the leaves in dry specimens, green in C. riograndensis and brown in T. nitida. Tibouchina nitida have leaves that are always glabrous (adaxial surface), while in C. riograndensis they can be glabrous or moderate to sparsely strigose, with trichomes distributed on the whole surface or restricted to its central-basal portion. In Chaetogastra riograndensis, the abaxial surface of the bracteoles is glabrous, while in T. nitida they are sparsely setulose.
description: Published as part of Meyer, Fabrício Schmitz & Goldenberg, Renato, 2016, Four new species of Chaetogastra (Melastomeae, Melastomataceae) from Southern Brazil, pp. 239-258 in Phytotaxa 282 (4) on pages 253-257, DOI: 10.11646/phytotaxa.282.4.1, http://zenodo.org/record/13645394