Pleroma joelsilvae F. S. Mey. & Brotto 2022, sp. nov.
Creators: name: Meyer, Fabrício Schmitz
name: Brotto, Marcelo Leandro
name: Goldenberg, Renato
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Myrtales
Melastomataceae
Pleroma
Pleroma joelsilvae

description: Pleroma joelsilvae F.S.Mey. & Brotto sp. nov. (Figures 1–2).
Type:― BRAZIL. Paraná, Castro, PCH Rio Iapó – Fazenda Marumbi, 24°44’14” S, 50°07’12” W, alt. 980 meters, 14 February 2016, J. M. Silva, I. Bayeri & G. Noguchi 9219 (holotype: UPCB!; isotypes: FUEL!, HCF!, MBM!, RB!).
Diagnosis: — Pleroma joelsilvae differs from P. oleifolium by the elliptical to ovate leaves (vs. lanceolate to ovate-lanceolate leaves in P. oleifolium), these slightly discolor (vs. strongly discolorous), with shorter, 2.6–6.9 mm long petioles (vs. 4.2–20 mm long). It also differs from P. oleifolium by the dendritic trichomes that cover young branches, petioles, and inflorescence branches (vs. stellate trichomes), larger petals, 17.6–20.9 × 11.4–14.4 mm (vs. 8–13.3 × 5–7.5 mm), and shorter antesepalous pedoconnective appendages, 0.9–1.2 mm long (vs. 1.5–3 mm long).
Description: —Erect shrubs 0.8–2.7 m tall, with sympodial growth, poorly to strongly branched. Younger and older branches quadrangular, moderately hirsutulous to setulose, trichomes 0.5–2 mm long, dendritic, with inconspicuous arms, eglandular, erect, the base linear to slightly broadened, not immersed, not forked; the older branches basally decorticating, brownish; nodes slender. Leaves opposite; chartaceous, petioles 2.6–6.9 mm long; blades 6.3–9.2 × 2–4.1 cm, chartaceous, slightly discolorous, elliptical to ovate, base obtuse to slightly cordate, apex acute, margins slightly crenulate, 7 acrodromous veins, basal, but the first and second lateral pairs confluent near the leaf base, domatia absent and reticulation conspicuous on the abaxial surface; adaxial surface flat, brown to dark green in dry specimens, dark green in fresh material, moderately strigose, trichomes 0.3–1.1 mm long, dendritic, with inconspicuous arms, eglandular, appressed, the base linear, immersed, not forked to rarely forked, followed by a sequence of white dots, abaxial surface flat, light brown in dry specimens, pale-green to yellowish-green in fresh material, moderately sericeous to setose on the surface, primary and secondary veins, trichomes 0.7–2.7 mm long, dendritic, with inconspicuous arms, eglandular, appressed or curved, the base linear to slightly broadened, not immersed, not forked. Thyrsoids 11–24 × 5.5–11.5 cm, terminal, 30–100 flowers, axis quadrangular, with the same indumentum as the branches, reddish to greenish; bracts in pairs, the color similar to the leaves, late deciduous, leafy, petioles 1–2 mm long, blade 2.9–3.8 × 0.8–1 cm, elliptic, indumentum the same as the leaves; bracteoles in pairs, cream to reddish cream, early deciduous, 5.1–17.4 × 3.3–7.6 mm, ovate to oblanceolate, apex acute, not covering the apex of the flower bud, margins entire, ciliate, adaxial surface glabrous, abaxial surface moderately strigose or moderately sericeous, with indumentum arranged along the entire abaxial surface, trichomes 0.5–2.9 mm long, dendritic, with inconspicuous arms, eglandular, appressed, the base slightly broadened, not immersed, not forked. Flowers 5(–6)-merous, pedicels 2.4–3.3 mm long; hypanthium, 5.9–7.8 × 3.2–4.3 mm, obovate, not costate, green to reddish-green epidermis (adaxial surface), moderately to densely sericeous, trichomes 0.8–2.2 mm long, dendritic, with inconspicuous arms, eglandular, appressed, the base linear to slightly broadened, not immersed, not forked; sepals early deciduous, 3.5–4.8 × 2–2.6 mm, triangular, green to reddish-green epidermis (in both surfaces), margins ciliolate, apex acute, adaxial surface glabrous, abaxial surface with the same indumentum as the hypanthium, trichomes arranged along the entire abaxial surface; petals 17.6–20.9 × 11.4– 14.4 mm, obovate, apex rounded to slightly cuspidate, purple (during anthesis) or purple with a red base (in senescent flowers), glabrous in both surfaces, margin cilate, moderately pubescent, trichomes 0.1–0.4 mm long, dendritic, with inconspicuous arms, eglandular, or glandular and mixed with eglandular trichomes, erect, the base linear, not immersed, not forked; stamens 10(–12), strongly dimorphic, the antesepalous with the filaments purple (during anthesis) to lilac (in senescent flowers), 10.9–11.7 mm long, sparsely setulose on the lower half, trichomes 0.2–1 mm long, unbranched, glandular, curved, the base linear to slightly broadened, not immersed, not forked, pedoconnective purple, 3.1–3.6 mm prolonged below the thecae, glabrous, ventral appendages biauriculate, purple, ascendent, apex acute, 0.9–1.2 mm long, glabrous, thecae purple, white apex, 10.5–11 × 0.8–1 mm, falcate, the antepetalous with filaments purple (during anthesis) to lilac (in senescent flowers), 8.5–9 mm long, sparsely setulose on lower half or lower two thirds, trichomes 0.2–1 mm long, unbranched, glandular, curved, the base linear to slightly broadened, not immersed, not forked, pedoconnective white to slightly pink, 0.7–1 mm prolonged below the thecae, glabrous, ventral appendages biauriculate, white to slightly pink, ascendent, apex acute, 0.9–1.1 mm long, glabrous, thecae white, 8.7–9.1 × ca. 0.8 mm, falcate; ovary 5.7–6 × 3–3.2 mm, 5(–6)-locular, apex densely sericeous to densely setose, trichomes 0.3–2.2 mm long, unbranched, glandular and mixed with eglandular trichomes, erect, the base slightly broadened, not immersed, not forked; style purple (during anthesis) to lilac (in senescent flowers), 19–21.1 mm long, apex curved, glabrous, stigma truncate. Capsular fruits 8.3–9 × 4.6–5.1 mm, sepals early deciduous, epicarp undivided when mature, ecostate. Seeds 0.1–0.3 × ca. 0.2 mm, cochleate, with a tuberculate testa.
Paratypes: — BRAZIL. Paraná, Municipality of Carambeí, Catanduva de Fora, Mineração Carambeí, 2 March 2013, M. E. Engels s.n. (UPCB0049003!); ibidem, 30 March 2014, M. E. Engels 2380 (UPCB!). Municipality of Castro, APP da PCH Castro, várzea ou campo hidromórfico na orla da barragem, 7 February 2022, F. S. Meyer & M. L. Brotto 2725 (BHCB!, EFC!, FLOR!, FURB!, HCF!, MBM!, RB!, SPSF!, UPCB!); ibidem, F. S. Meyer & M. L. Brotto 2727 (MBM!, RB! UPCB!); ibidem, F. S. Meyer & M. L. Brotto 2728 (UPCB!, RB!).
Distribuition and habitat:— Pleroma joelsilvae occurs only in the state of Paraná, in natural grasslands either on dry areas (“Estepe Gramíneo-lenhosa”) or periodically flooded areas (“Formação Pioneira com Influência Fluvial”) associated with Araucaria Forest (“Floresta Ombrófila Mista”, according to the classification of IBGE 2012; see Figure 3).
Phenology:—Flowering and fruiting between January to February.
Conservation status:—According to IUCN’s criterion D, P. joelsilvae should be considered as Critically Endangered (IUCN 2022). The species is current known by a very small population, with restricted distribution. Its Extent of Occurrence (EO) is 11.9 km 2 and its Area of Occupancy (AO) is about 8,0 km 2. One of the two localities where these plants have been collected by 2013/14, at Carambeí, has been recently devastated by mining activities; we went back to the same place, but were unable to find individuals/populations. Therefore, P. joelsilvae is currently known only from a small population in the municipality of Castro, on the banks of the Iapó River, along which several small hydroelectric power plants have been implemented in the last few decades, with a devastating impact on riverbeds and floodplains. Natural grasslands in this region are also being largely converted to agricultural use, which in turn may be a consequence of changes in Brazilian law that deals with the protection of native vegetation and riparian environments; the new law 12.651/2012 (BRASIL, 2012) reduced the protection of vegetation along riverbanks, when compared to the previous one (4.771/1965; BRASIL, 1965). In conclusion, the natural grasslands and floodplains along the Iapó river basin are expected to be strongly reduced in the coming years and, in consequence, the habitat of P. joelsilvae.
Etymology:—The epithet “ joelsilvae ” is a tribute to Joel Morais da Silva, for his extensive work as a plant collector and as part of the staff of the “Museu Botânico Municipal de Curitiba”, accompanying the collection team headed by Dr. Gerdt Guenther Hatschbach from 1979–2018. Joel, known as “Bagre”, also assisted several botanists from around the world, and is notorious for his fieldwork skills and a keen eye for finding plants in general. Now retired, he is still actively collecting plants: his samples are rich and well prepared. Due to its important contribution to the regional botanical collections, as well as collecting the holotype (and the isotypes), and helping us to find in vivo specimens of the new species, we dedicate this new species to him.
Note:— Pleroma joelsilvae can be easily recognized among the species occurring in southern Brazil by the (1) branched trichomes covering branches, leaves, inflorescence axes, bracteoles, and hypanthium (see Figures 2 B-1, 2B-2, and 2G-1), and (2) stamens with auriculate pedoconnective appendages (see Figures 1I, 2 I-1, 2J-1). This set of morphological features is shared with P. oleifolium, as well as the pairs of ovate to elliptical and concave bracteoles, and the relatively small flowers (4–4.5.cm diam. in P. joelsilvae, and 3.2–3.5 cm in P. oleifolium), with purple to lilac petals and styles, antepetalous anthers with white thecae, and antesepalous anthers with purple thecae, but white on their apex. Pleroma joelsilvae differs from P. oleifolium by the characters pointed in the diagnosis, and by the leaves with 7 veins (vs. 5 veins; see Figure 4), and larger, 5.1–17.4 × 3.3–7.6 mm bracteoles (vs. 4–10 × 2–5 mm; Figure 5). Both species may be sympatric.
Another sympatric species that also resembles P. joelsilvae is Pleroma ursinum (Chamisso 1835: 443) Triana (1872: 43). Both are shrubs with inflorescences with reddish axes, ovate to oblanceolate bracts and bracteoles, white anthers (only in antepetalous stamens in P. joelsilvae; see Figures 1G–I), and purple to lilac petals and styles. Pleroma joelsilvae differs from P. ursinum by the obtuse to slightly cordate leaf base (vs. leaves strongly cordate in P. ursinum; see Figure 4), covered with dendritic trichomes on both surfaces (vs. covered with unbranched trichomes on both surfaces; Figure 4 C-3, 4C-4), in addition to stamens with auriculate appendages (Figure 5 D-2; vs. bilobed appendages; Figure 5 F-1).
Stamens with auriculate pedoconnective appendages are uncommon in Pleroma; this character is also found in some species classically treated in Tibouchina s.l. section Purpurella (Naudin 1850: 301) Cogniaux (1885: 411), or in the genus Itatiaia Ule (1908: 234; currently a synonym of Pleroma). These species group has Pleroma cinereum (Cogniaux 1885: 416) Guimarães & Michelangeli (2019: 976), Pleroma cleistoflorum (Ule 1908: 235) Guimarães et al. (in Oliveira et al. 2014: 225), Pleroma hospitum (De Candole 1828: 129) Triana (1872: 42), and Pleroma minutiflorum (Cogniaux 1885: 415) Guimarães & Michelangeli (2019: 985). All the aforementioned species are easily distinguished from P. joelsilvae by the pendulous flowers (vs. erect in P. joelsilvae), with white petals (vs. purple), and anthers with a truncate apex (vs. attenuate). Among the species mentioned above, only P. hospitum occurs in southern Brazil.
Only one species of Pleroma other than P. joelsilvae found in southern Brazil has dendritic trichomes covering the hypanthium: Pleroma candolleanum (De Candolle 1828: 129) Triana (1872: 44). It is not native to Paraná (see Meyer et al. 2010a), and its cultivated plants are easily distinguished from P. joelsilvae by its arboreal habit (vs. shrubby in P. joelsilvae), leaves with 3 suprabasal veins (vs. 7 basal veins, the first and second pairs confluent at the base) and stamens with the pedoconnective and appendages covered with glandular trichomes (vs. glabrous).
description: Published as part of Meyer, Fabrício Schmitz, Brotto, Marcelo Leandro & Goldenberg, Renato, 2022, Pleroma joelsilvae (Melastomataceae): a new and endemic species from Paraná, Brazil, pp. 257-268 in Phytotaxa 554 (3) on pages 258-265, DOI: 10.11646/phytotaxa.554.3.4, http://zenodo.org/record/6831544