Phyllanthus megastylus Marques-Torres & M. J. Silva 2023, sp. nov.
Creators: name: Torres, Alícia Marques
name: Silva, Marcos José Da
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Malpighiales
Phyllanthaceae
Phyllanthus
Phyllanthus megastylus

description: Phyllanthus megastylus Marques-Torres & M.J. Silva, sp. nov. (Figures 1, 2)
Type:— BRAZIL. Espírito Santo, Santa Teresa, S „o Sebasti„o, Várzea Alegre, 1,4 km de Santa Barbara na estrada para Colatina, Fazenda Sr. Djalma Novelli, 19º50’48”S, 40º43’10”W, 30 January 2002, fl., fr., J. R. Pirani, A. C. Marcato, M. Groppo Jr., P. Fiaschi, & V. Demuner 4924 (holotype SPF!; isotype SP!).
Diagnosis:— Phyllanthus megastylus differs from P. itamarajuensis by its densely papillose branches, narrowoblong leaves with 12–14 pairs of secondary veins, pink pistillate flowers, disk with undulate margin and punctiform stigmas.
Description:—Erect subshrubs, 40–50 cm tall, monoecious, branching phyllantoid. Main stem brownish, densely papillose with scars left by deciduous phyllantoid branching, these measuring 5–12 cm long, are cylindrical, pinatiform, brownish, densely papillose, and distributed along the main stem or its ramifications. Cataphylls 0.5–1 mm long, triangular or ovate, apex acute, margin entire, scarious, membranaceous, surface smooth, glabrous, persistent. Stipules 1–1.5 mm long, triangular or oval, apex acute, margin entire, membranaceous, surface smooth, glabrous, persistent. Petiole 0.5–0.8 mm long, cylindrical, slender, smooth, glabrous; leaf blade 10–14 × 5–7 mm, alternate distichous, oblong, base asymmetrical-rounded, apex obtuse, sometimes slightly rounded, face abaxial and adaxial glabrous, discretely papillose, membranaceous, discolor, margin entire, with 12–14 pairs of secondary veins, brochidodromous. Staminate cymules with two flowers, one in maturity and the other in bud, concentrated mainly in the basal portion of the branches and solitary pistillate flower, concentrated mainly in the terminal portion. Staminate bracts 1.5–2 mm long, linear, apex acute, margin discreetly serrate, membranaceous, surface smooth. Staminate flowers: pedicel 4–6 mm long, whitish, smooth; sepals 5, 1.2–1.5 × 0.5–1 mm, uniseriate, obovate, apex rounded, whitish, with greenish central vein, membranaceous, margin entire; 5-segmented glandular disk, segments obtriangular, surface verruculose, margin entire, alternating sepals; stamens 3, 1.2–1.8 mm long, free, anthers with horizontal dehiscence. Pistillate bracts 1.5–2 mm long, linear, apex acute, margin entire, membranaceous, surface smooth. Pistillate flowers: pedicel 12–19 mm long, pinkish, smooth; sepals 5, 2.2–3 × 1–1.5 mm, uniseriate, widely obovate, apex obtuse, pinkish, vein conspicuous, membranaceous, margin entire; disk patelliform, margin undulate; ovary ca. 1 × 1 mm, globose, greenish or pinkish, smooth, glabrous; styles 3, 2.4–2.7 mm long, free, bifid, discreetly papillose, erect, stigmas punctiform. Capsules immature, ca. 2 × 2 mm globose, smooth, glabrous. Seeds immature ca. 1mm long, trigonous.
Paratypes:— BRAZIL. Espírito Santo: Santa Teresa, S „o Sebasti„o, Várzea Alegre, Fazenda do Djalma Novelli, encosta com riacho encachoeirado, 19º50’44”S, 40º42’58”W, 11 September 2021, fl., A. M. Torres & R. S. Ribeiro 235 (UFG); Ibid., 11 September 2021, fl., A. M. Torres & R. S. Ribeiro 236 (UFG); Ibid., 11 September 2021, fl., A. M. Torres & R. S. Ribeiro 237 (UFG); Ibid., S „o Sebasti„o, (Propriedade Djalma Novelli), 26 September 2000, fl., V. Demuner & E. Bausen 1397 (MBML).
Distribution and habitat:— Phyllanthus megastylus is restricted to the municipality of Santa Teresa, in the state of Espírito Santo, southeastern Brazil (Fig. 3), where it grows in the Atlantic Forest, on the edge of a slope in a highly disturbed forest patch, next to a stream in overgrown environments.
Etymology:—The specific epithet “ megastylus ” refers to the long styles of the new species, a feature rarely reported for species of Phyllanthus sect. Phyllanthus subsect. Phyllanthus.
Phenology:—Collected with flowers in January and September and with fruits in September.
Preliminary conservation status:— Species with an estimated Area of Occupancy of 8 km 2, and therefore must be classified as Critically Endangered (CR). However, the new species is only known from four collections from the same locality, and it grows in a type of vegetation common in the state of Espírito Santo, which means that it can be collected in other places in the state. Therefore, the species should be categorized as Data Deficient (DD).
Stem and Leaf Anatomy:— Phyllanthus megastylus and P. itamarajuensis have uniseriate epidermis on both leaf surfaces, with common cells rounded, rectangular, or ovate, cells with straight periclinal and anticlinal walls straight or slightly sinuous, covered by a thin cuticle (Fig. 4A, G). The leaves are hypostomatic, with stomata occurring at the same level as the common epidermal cells with tiny substomatal chambers (Fig. 4 B, H). In cross-section, the epidermal cells of the abaxial and adaxial surface have different sizes, some of the in a papillose aspect (Fig. 4 A, G). In these species, the mesophyll is dorsiventral (Fig. 4 A, G). The palisade parenchyma is constituted by a single layer of cells obovoid or conic loosely arranged containing phenolic compounds (Fig. 4 A, G). In P. megastylus the spongy parenchyma is formed by two layers of cells with rounded to rectangular shapes with large intercellular spaces (Fig. 4 A), while in P. itamarajuensis three layers of cells with the same shapes are found (Fig. 4 G). In this region, druses were observed in P. megastylus (Fig. 4 A). The edge was rounded in P. megastylus (Fig. 4 B) and obtuse in P. itamarajuensis (Fig. 4 I), being the cell walls thickened in the first species than in the second. The midrib in both species, has contour biconvex, epidermis uniseriate with quadrangular, rectangular, and rounded common cells covered by a thin cuticle (Fig. 4 C, J). In P. megastylus, the adaxial surface of the midrib is formed by two or three layers of typically parenchymal cells (Fig. 4 C), while P. itamarajuensis has a layer of palisade parenchyma and 3 layers of ground parenchyma (Fig. 4 J). On the abaxial surface, P. megastylus presents two layers of ground parenchyma (Fig. 4 C), and in P. itamarajuensis (Fig. 4 J) three layers are observed. The vascular bundles of both species are collateral (Fig. 4 D, K). However, only P. megastylus present one to three layers of fibers adjacent to the vascular tissues (Fig. 4 D), whereas in P. itamarajuensis the vascular tissues are surrounding only by parenchyma cells being those associated to the vascular cells tinier (Fig. 4 K). Both species have petioles with circular outline, uniseriate epidermis with rounded or transversely elliptic cells and a thick cuticle (Fig. 4 E, L). In both species, the cortex consists of three or four layers of parenchyma with rounded or quadrangular cells (Fig. 4 E, L). The vascular bundles is collateral in an open arch in both species (Fig. 4 F, M), however the vascular bundles are surrounded by fibers only in P. megastylus (Fig. 4 F).
Both species have stems with circular outline and only primary structure (Fig. 5 A, E). The epidermis is uniseriate and composed by rounded common cells, rectangular, quadrangular, ovoid and transversely elliptic, with walls uniformly delgate and cuticle thin (Fig. 5 B, F). Larger epidermal cells of varying sizes were observed only in P. megastylus (Fig. 5 B). The cortex of the studied species consists of three or four layers of ground parenchyma composed by rounded or rectangular cells with straight or slightly sinuous walls of different sizes (Fig. 5 B, F). In perivascular position was observed two layers of gelatinous fibers on both species, while the xylematic fibers are gelatinous and libriform (Fig. 5 C, G). In P. megastylus cells containing druses are observed in the cortical parenchyma (Fig. 5 B). In both species the collateral vascular bundles are arranged in a ring shape (Fig. 5 C, G). The outermost vessels of the phloem are arranged together with the parenchyma cells and fibers (Fig. 5 C, G). The pith of P. megastylus is composed of cells with thick walls that store large grains of starch (Fig. 5 D) while in P. itamarajuensis the pith is composed of cells with non-thickened walls (Fig. 5 H).
description: Published as part of Torres, Alícia Marques & Silva, Marcos José Da, 2023, Anatomical and macromorphological data support a new species of Phyllanthus (Phyllanthaceae) from Southeastern Brazil, pp. 185-196 in Phytotaxa 601 (2) on pages 186-192, DOI: 10.11646/phytotaxa.601.2.5, http://zenodo.org/record/8129641