Agarista revolutissima A. A. Sampaio & R. P. Oliveira 2023, sp. nov.
Creators: name: Sampaio, Ariadne A.
name: Romão, Gerson O.
name: Dorea, Marcos C.
name: Oliveira, Reyjane P.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Ericales
Ericaceae
Agarista
Agarista revolutissima

description: Agarista revolutissima A.A. Sampaio & R.P. Oliveira, sp. nov.
Type:— BRAZIL. Bahia: Morro do Chapéu, Morrão, 11º55’49’’S, 41º15’66’’W, 06 November 2008, E. Melo et al. 6002 (holotype HUEFS! Barcode HUEFS000049756; isotype HUEFS! Barcode HUEFS000042289) (Figs. 1–5)
Diagnosis: Agarista revolutissima differs from other Agarista species in having longer and strongly revolute leaves; glabrous branches, petioles, inflorescence, pedicels and corollas, ciliate calyx, bracts and bracteoles; fruit subglobose and subapical placentation.
Tree ca. 4 m; branches glabrous. Leaves coriaceous, elliptic, 4–6.2(–8) × 2–2.4 cm (length × width) with rounded to irregular base and mucronate acute apex, entire margin, revolute to strongly revolute, adaxial and abaxial surfaces glabrous, inconspicuous foveolate glands on the abaxial surface along the main vein, petiole 1.5–1.8 cm long, glabrous, reddish (in vivo). Inflorescences racemose, axillary, 6–7 cm long, glabrous, pedicel glabrous, 8–9 mm long, 1 lanceolate ciliate bract at the base of the pedicel ca. 1.3 mm long, 2 lanceolate, ciliate, bracteoles subopposite on the median portion of the pedicel. Flowe r calyx glabrous, lobes triangular, ciliate, apex acuminate, ca. 1.6 × 1.5 mm; corolla glabrous, cylindrical, lobes triangular, apex rounded, ca. 9 mm long, white to reddish; filaments pubescent, 5–5.5 mm long, anthers ca. 1.2 mm long; ovary pubescent at base. Fruit capsular, subglobose, ca. 5.5 × 7 mm, placentation subapical.
Etymology: The epithet comes from the word revolutus, which means turned backwards, combined with the suffix issima = a superlative that denotes superior quality to the adjective (Rizzini 1955), expressing the leaf characteristics that differentiates this species from others in the genus.
Taxonomic comments: The individuals here described as Agarista revolutissima have been formerly confused with A. revoluta, mainly due to similar vegetative characters, including coriaceous leaves as well as entire and revolute margins. However, other vegetative characters can be used to differentiate them (Tab. 1), as leaf size and indumentum type, since A. revolutissima displays larger leaves (4–6.2(–8) × 2–2.4 cm), glabrous on both surfaces, while A. revoluta has smaller leaves (1.3–4.5 × 0.5–2.2 cm), pubescent on both surfaces.
Regarding reproductive organs (Tab. 1), Agarista revolutissima has glabrous corolla and pedicel (Fig. 2 F, I), ciliated calyx and bracteoles (Fig. 2 G, I), pubescent filaments (Fig. 2 J), trichomes present only at the base of the ovary (Fig. 2 G), subapical placentation and subglobose fruit (Fig. 2 H); while in A. revoluta, corolla and pedicel (Fig. 2 A, D) as well as calyx and bracteoles are pubescent (Fig. 2 B, D), the filaments are densely pubescent to tomentose (Fig. 2 E), the ovary is completely pubescent or densely pubescent (Fig. 2 B), the placentation is apical and the fruit ovoid (Fig. 2 C).
Leaf anatomy: In paradermal section, Agarista revolutissima has tall and juxtaposed epidermal cells with periclinal division (Fig. 3 A–B); hypostomatic leaves with anomocytic stomata and subsidiary cells, not differentiated from the others, and located in the intercostal region of the leaf blade (Fig. 3 C–D). In cross section, leaves have a thick cuticle, uni-stratified epidermis with cells on the adaxial surface more elongated than the abaxial ones; dorsiventral mesophyll with two to three layers of palisade parenchyma and 4(–5) layers of lacunar parenchyma with a braciform shape, with fibrous tissue associated with secondary vascular bundles with hypodermis present (Fig. 4 B; E); unifacial midrib vascular bundle surrounded by fibrous tissue (Fig. 4 A; D). These anatomical features were observed in other members of this genus (Judd et al. 1984), as well as in species of Agarista occurring in Bahia, which will be described in detail soon (Sampaio et al. in preparation).
However, we observed several differences in the leaf anatomy between Agarista revolutissima and A. revoluta, which are highlighted in the Table 1. Agarista revolutissima presents more elongated or rectangular epidermal cells and three layers of palisade parenchyma (Fig. 4 D–E); the midrib vascular bundles are slightly concave on the adaxial surface and present a wide collar with two layers of collenchyma (Fig. 4 D); abaxial surface is convex, presenting asymmetry and approximately seven strata of collenchyma, the secondary bundles present two layers of hypodermis, the margins are flexed with one stratum of collenchyma and large cells described by Morretes (1988) as achlorophyllous cells (Fig. 4 D–F); unicellular trichomes are absent on both surfaces (Fig. 4 D–F).
In Agarista revoluta, the epidermal cells are square, with two layers of palisade parenchyma (Fig. 4 A–B); the midrib vascular bundles are concave on the adaxial surface, and a narrow collar with two layers of collenchyma is found below the epidermis (Fig. 4 A). The abaxial surface is convex and has four layers of angular collenchyma (Fig. 4 A); the secondary bundles present one layer of hypodermis (Fig. 4 B), and the margins slightly flexed with two layers of collenchyma (Fig. 4 C); unicellular trichomes associated with the adaxial and abaxial midrib vascular bundles and on the abaxial surface are present (Fig. 4 A–C).
Habitat and distribution: Agarista revolutissima occurs in Morro do Chapéu municipality, in the northern end of the Chapada Diamantina and limited by semiarid depressions (Lobão & Vale 2009). Due to the influence of its tabular relief, the region presents four climates, being the tropical altitude climate the commonnest (Barbosa 1995). The local vegetation is composed of forests, caatinga, cerrado and campo rupestre (Lobão et al. 2011) and presents great floristic diversity (Staudt & Roque 2020; Junqueira & Simão-Bianchini 2006). According to the speciesLink platform (specieslink.net), two species of Agarista occur in Morro do Chapéu, both in campo rupestre: Agarista oleifolia Chamisso (1833: 504) George Don (1834: 838) on a rocky outcrop near the Ferro Doido waterfall and the new species, A. revolutissima, occurring near a sandy field and rock outcrop (Fig. 3). Contrasting to this, A. revoluta is known to occur in the restinga, being widely distributed in coastal Brazil, along the Atlantic forest, in the states of Bahia, Espirito Santo, Rio de Janeiro and Sergipe (Judd 1984, 1995, Romão et al. 2020).
Conservation status: The calculated Area of Occupancy (AOO) was 2 km ² and the Extent of Occurrence (EOO) was 13.679 km ². According to these values, the new species fits the IUCN Red List criteria B1ab+B2ab(i,ii,iv), being assessed as Critically Endangered (CR) (IUCN 2019). The economy of Morro do Chapéu municipality has been based on subsistence farming and mining, which are still the main causes of deforestation in the region (Rocha & Pedreira 2012), however, with the arrival of new technologies, grape-vines are increasingly being planted on the sandy plateau.
In 1998 the Bahian Government created the conservation unit Parque Estadual Morro do Chapéu, with the purpose of protecting archeological sites with records of cave paintings and geological formations (Rocha & Pedreira 2012). The region has two other conservation units, the Cachoeira do Ferro Doido Natural Monument and the Gruta dos Brejıes/Veredas do Romão Gramacho APA. Currently, the Public Ministry of Bahia has been structuring and managing the conservation units, aiming to prevent activities that generate environmental impacts from being carried out in any of these three areas (Pinheiro 2022). However, none of the known populations of A. revolutissima appear to occur within these preservation areas, being found mostly near roads and antennas where anthropic disturbance is frequent. Thus, we conclude that the CR level of threat given to A. revolutissima truly reflects its fragile situation and its risk of survival in that region.
Additional Materials (paratypes): BRAZIL. Bahia, municipality of Morro do Chapéu, Estrada para Utinga, ca. 5km, 18 July 2001 (fr), G.O. Romão et al. 771 (MBM! UEC!); Estrada para Utinga, ca. 5km, 18 July 2001 (fr), G.O Romão et al. 770 (MBM!, UEC!, SPF!); Estrada para Utinga, ca. 5km de Morro do Chapéu, 18 July 2001 (fr), V.C. Souza et al. 26368 (ESA!, MBM!, UEC!); Piemonte da Diamantina, 11º59’13’’S, 41º20’80’’W, 13 March 1996 (fr), A.A. Conceição et al. 2354 (UEC!, HUEFS!, ALCB!); Morro da Antena, 19 July 2001 (fr), V.C. Souza et al. 26440 (ESA!, MBM!, UEC!).
description: Published as part of Sampaio, Ariadne A., Romão, Gerson O., Dorea, Marcos C. & Oliveira, Reyjane P., 2023, Revealing a new species of Agarista (Ericaceae) endemic to the Chapada Diamantina, Brazil, segregated from A. revoluta by multiple evidence, pp. 81-90 in Phytotaxa 583 (1) on pages 82-89, DOI: 10.11646/phytotaxa.583.1.8, http://zenodo.org/record/7609187