Pleroma piranii F.S.Mey. & Almeda, 2022

Meyer, Fabrício Schmitz, Pacifico, Ricardo & Almeda, Frank, 2022, A new species of Pleroma (Melastomataceae: Melastomateae) endemic to Southern Cadeia do Espinhaço, Minas Gerais, Brazil, Phytotaxa 560 (1), pp. 30-42 : 32-37

Pleroma piranii F.S.Mey. & Almeda sp. nov. ( Figures 1−2 ).

Type:― BRAZIL. Minas Gerais, Santana do Riacho [“Jaboticatubas”], Serra do Cipó , entre Km 112 e 113 na estrada para Conceição do Mato Dentro , 19º10’S, 43º30’W, elev. 1280 m, 31 May 1998, F. Almeda 7762, R. Romero, O. Robinson & D. Robinson (holotype: UEC!; isotypes: CAS!, HUFU!, UPCB!) .

Diagnosis: — Pleroma piranii differs from P. velutinum by the larger leaves, 2.5 7.1 × 1.4 4.7 cm (vs. 2.4 4.1 × 1.3 2.1 cm in P. velutinum ) that are densely sericeous on the adaxial surface (vs. moderately strigose), with 7 veins (vs. 5 veins) and the base rounded to slightly cordate (vs. the base only obtuse). It also differs by the more elongated inflorescences, 7 17.9 cm long (vs. 3.3 8.3 cm long), and completely glabrous style (vs. moderately beset with appressed white eglandular trichomes along much of their length).

Description: ―Erect shrubs to 1.5 m tall with sympodial growth, few-branched. Younger branches roundedquadrangular becoming rounded with age, densely strigose with a mixture of fine smooth ± appressed white to tan trichomes 0.5–1.5 mm long and longer mostly smooth (sometimes forked) ± appressed trichomes 0.75–2 mm long with swollen bases; the older branches brown, glabrate and decorticating; nodes initially bordered by trichomes similar to the internodes but these falling away with age. Leaves opposite, petioles 3–6 mm long; blades 2.5–7.1 × 1.4–4.7 cm, chartaceous, green (in live specimens) and brown (in dehydrated specimens), but mostly obscured by the indumentum on both surfaces, ovate, base rounded to slightly cordate, apex acute, margins entire and largely concealed by the indumentum, 7 acrodromous veins with the outermost secondary veins confluent near the leaf base on abaxial surface, domatia absent and reticulation (if present) not evident and obscured on abaxial surface by dense indumentum; adaxial surface ± flat, green to brownish in dry specimens, copiously strigose with a mixture of smooth eglandular linear-based trichomes 1–3 mm long concentrated near the impressed primary and secondary veins and smooth eglandular trichomes 2–2.5 mm long with swollen bases, abaxial surface flat with elevated primary and secondary veins, color obscured by the tan indumentum when dry, densely sericeous to strigose on the surface and elevated primary and secondary veins, trichomes 2.5–3.5 mm long, eglandular, mostly appressed, the base mostly linear (slightly swollen on the trichomes covering the elevated veins), not immersed, rarely forked, eglandular. Thyrsoids 7–18 × 4–6 cm, terminal, 20–45 flowers, axis rounded to slightly quadrangular, with the same indumentum as the upper branch internodes; bracts paired, similar to leaves in color and shape, petioles up to 2 mm long, blade 1.3–2.5 × 0.9–1.5 cm, ovate, indumentum similar to the leaves; bracteoles paired, reddish to reddish-brown, deciduous, 7–9 × 3–4 mm, elliptic-lanceolate, apex acute, enveloping flower buds but mostly not concealing bud apex, margins entire, finely ciliate, adaxial surface glabrous, abaxial surface densely sericeous, with indumentum covering the entire surface, or sparsely sericeous or glabrous at the margin, trichomes 2–3 mm long, smooth, eglandular and unforked, appressed, the base not swollen, not immersed. Flowers 5-merous, subsessile or on pedicels up to ca. 0.75 mm long; hypanthia with the epidermis green or reddish green, barely visible (obscured by dense indumentum), 6–8 × 4–5.5 mm, not costate, densely sericeous, trichomes 2–4 mm long, smooth, eglandular, appressed, the base linear, not immersed, sometimes forked; calyx lobes with the epidermis with the same color as the hypanthium, barely visible (obscured by the dense indumentum), late deciduous, 5–6 × 1.5–3 mm, oblong, margins ciliate, apex obtuse to rounded with a tuft of smooth trichomes, adaxial surface glabrous, abaxial surface with indumentum similar to the hypanthia, trichomes dense and concealing the entire abaxial surface; petals purple (at anthesis) but white at the base, 14–15 × 9–10 mm, obovate to ± obdeltoid, apex rounded-truncate, ciliate (some of the trichomes glandular); stamens 10, isometric, antesepalous with the filaments white (at anthesis), 7 mm long, sparsely glandular-pilose on its midportion, trichomes 0.25 mm long, unbranched, glandular, straight, the base linear, not immersed, not forked, pedoconnective white, ca. 1 mm prolonged below the thecae, glabrous, ventral appendages bilobed, white, ascendant, apex bluntly acute to obtuse, 0.5 mm long, glabrous, thecae purple but white distally, 8–9 × 0.25–0.50 mm, falcate, antepetalous with filaments white (at anthesis), 6.5 mm long, sparsely glandular-pilose on its middle or upper middle portion, trichomes 0.25 mm long, unbranched, glandular, straight, the base linear, not immersed, not forked, pedoconnective white, ca. 0.75 mm prolonged below the thecae, glabrous, ventral appendages bilobed, white, ascendant, apex bluntly acute to obtuse, 0.5 mm long, thecae purple but white distally, ca. 7.5 × 0.25–0.50 mm, falcate; ovary 4–4.5 × 3–3.5 mm, 5-locular, densely sericeous throughout, trichomes 1.5–3 mm long, unbranched, eglandular, appressed, the base linear, not immersed, not forked; style purple but white just below the stigma, 18–20 mm long, distally curved, glabrous, stigma truncate, white. Velatidium 5.8–6.5 × 5–7.3 mm, sepals late deciduous, pedicels 0.9–1.3 mm long. Seeds not seen.

Paratypes: — BRAZIL. Minas Gerais, unspecified municipality, s.d., A. F. M . Glaziou 19294 ( K000329046 !); ibidem, ca 15 km E . of Diamantina , 20 March 1970, H. S . Irwin et al. 27966 ( NY!, US online image); ibidem, Estrada Diamantina-Conselheiro Mata, 20.3 kms depois do asfalto, 23 September 1994, Splett & Gröger 654 ( SPF!, UB!, US online image). Municipality of Alvorada de Minas, Distrito de Itapanhoacanga , estrada para Cachoeira Campina , 24 May 2009, L . Menini Neto et al. 708 ( HUFU!, K!, RB online image, SPF!). Municipality of Datas, rodovia Datas-Serro, Km 451, 1 March 1998, J. R . Pirani et al. 4061 ( SPF!). Municipality of Diamantina, Margem de estrada para a formação, 4 May 2016, J. E. Q . Faria 5955 ( HDJF online image, HUFU!, SP!, UB!). Municipality of Itambé do Mato Dentro, Estrada para a Serra Cabeça de Boi , 8 August 1992, J. R . Stehmann & M. E . Sobral 1122 ( UEC!). Municipality of Santana de Pirapama, Faz. Inhame, Serra do Cipó , 20 March 1982, J. R . Pirani et al., CFSC 7978 ( SP!, SPF!, UEC!, US online image); Trilha de captação da Faz. Toucan Cipó, Capela de São José , 15 March 2009, D. C . Zappi et al. 2149 ( RB online image, SPF!). Municipality of Santana do Riacho, [“Jaboticatubas”], Km 139, ao longo da rodovia Lagoa Santa – Conceição do Mato Dentro – Diamantina , 8 July 1970, A. B . Joly et al., CFSC 307 ( SP!, UEC!); Serra do Cipó, Km 109 (antigo 114) da estrada a Lagoa Santa a Conceição do Mato Dentro , 6 September 1980, E . Forero et al. 7828, CFSC 8735 ( SP!, SPF!); ibidem, UCAT , 22 February 1985, M. A . Lopes & P. M . Andrade s.n. (HUFU-6293!). Municipality of Serro, Distrito de Mato Grosso, Pedra do Cruzeiro Mineração , 28 March 2001, R . Romero & J . Nakajima 6006 ( HUFU!) .

Distribution and habitat:— Pleroma piranii is apparently endemic to Serra do Cipó and the Planalto de Diamantina in Minas Gerais state, where it occurs on quartzitic campo rupestre associated with rocky outcrops exposed to full sun, at elevations between 800–1390 m ( Fig. 3 ). All known populations of P. piranii are within the Planalto de Diamantina biogeographic district of Colli-Silva et al. (2019). The distribution pattern of P. piranii is shared with several other species of Melastomataceae ( Pacifico et al. 2020b, Paranhos 2020).

Phenology:—Collected flowering and fruiting from February to September (except June).

Conservation:— Pleroma piranii should be considered Endangered (EN) according to IUCN (2022) criterion B1. The species is known from few populations, and its distribution is restricted. Its Area of Occurrence (EO) is 3,499.736 km 2 (less than 5,000 Km 2), and its Area of Occupancy (AO) is about 48,000 km 2. Pleroma piranii has been collected only 13 times between the years 1970 and 2016. One specimen was collected within the boundaries of the Serra do Cipó National Park ( Fig. 3 ), the only fully protected conservation unit within the Serra do Cipó. Five specimens were collected inside the Morro da Pedreira APA (Environmental Protection Area; Fig. 3 ), a conservation unit with few environmental restrictions. Other conservation units that can potentially protect populations of P. piranii include three Brazilian state parks (Serra do Intendente State Park, Pico do Itambé State Park, Biribiri State Park), one national park (Sempre-Vivas National Park) and one environmental protection area (Águas Vertentes APA). According to Fernandes (2016), major threats to campo rupestre endemic vegetation include biological invasions, deforestation, mining, road construction, tourism, human-caused fires, plant extraction, cattle ranching, and agriculture.

Etymology:—The epithet “ piranii ” honors our colleague Dr. José Rubens Pirani (1953–), Professor of Botany at the University of São Paulo and Curator of the SPF herbarium. Dr. Pirani is one of the major organizers of the Flora of Serra do Cipó, and an active plant collector in the region. In addition to a productive research career concentrated on the systematics of Neotropical Sapindales (especially Rutaceae and Simaroubaceae ), he has mentored numerous graduate students and has routinely provided botanical assistance to all students and colleagues who have solicited his help. Two of the paratypes of this species (Pirani et al. 4061, and Pirani et al. CFSC 7978) were collected by Pirani.

Note:— Pleroma piranii resembles the species traditionally recognized in Tibouchina Aublet (1775: 177) section Pleroma ( Don 1823: 283) Cogniaux (1885: 330) , especially the group defined by the following morphological characters: (1) the appendages and connectives of the stamens are glabrous, (2) filaments glabrous or covered with short trichomes, (3) hypanthia and leaves sericeous, (4) calyx lobes elongated, (5) branches tetragonal and devoid of wings, and (6) leaves oval, sericeous on the adaxial surface (see the key of Tibouchina section Pleroma , according to Cogniaux 1885). Within this group, P. piranii is most similar to species with a branched habit such as Pleroma velutinum ( Naudin 1850: 144) Triana (1872: 42) , and Pleroma blanchetianum ( Cogniaux 1885: 351) Guimarães & Michelangeli in Guimarães et al. (2019: 975).

Pleroma piranii is morphologically similar to P.velutinum due to its shrubby habit (moderately branched), opposite leaves (exclusively), these discolorous, and short petioles. It is also similar in having thyrsoid inflorescences, flower buds surrounded by two elliptical bracteoles, pentamerous flowers, sericeous hypanthia, purple petals, isometric stamens (i.e., the antepetalous and antesepalous cycles differ little in relation to the size of the filaments, connectives, connective appendages, and anthers), purple anthers (light purple on its adaxial surface in P. piranii ), glabrous connectives and appendages, filaments sparsely glandular pilose on its basal portion (sometimes glabrous in P. velutinum ; Freitas et al. 2016). Pleroma piranii differs from P. velutinum by the characters enumerated in the diagnosis, and also by the older branches with a decorticated epidermis (vs. older branches with epidermis non-decorticated in P. velutinum ), indumentum on the adaxial surface of the leaves, which is uniform in size along the adaxial surface and veins in P. piranii (vs. indumentum on the adaxial surface of the leaves longer on the primary veins, especially the portion closer to the base in P. velutinum ). One other difference between P. piranii and P. velutinum is that the former species has trichomes completely covering the ovary (vs. only at the apex in P. velutinum ). Pleroma piranii occurs only in the state of Minas Gerais, on Serra do Cipó and the Planalto de Diamantina , and P. velutinum occurs only in the state of Bahia, on the Chapada Diamantina (northern Cadeia do Espinhaço; Freitas et al. 2016).

Pleroma piranii is also morphologically similar to P. blanchetianum due to the shrubby habit (moderately branched) and leaves with short petioles. They also share thyrsoid inflorescences, flower buds surrounded by two elliptical bracteoles, sericeous hypanthia, purple petals, isometric stamens, purple anthers, glabrous connectives and appendages, filaments sparsely glandular pilose on its basal portion (sometimes glabrous in P. blanchetianum ; Cogniaux 1885, Freitas et al. 2016). Pleroma piranii differs from P. blanchetianum in having the older branches with decorticated epidermis (vs. older branches with epidermis non-decorticated in P. blanchetianum ), larger leaves, with 2.5 7.1 × 1.4 4.7 cm (vs. 1–3 × 0.6–2.5 cm), ovate (vs. orbicular), with opposite branching (vs. more often verticillate, and rarely opposite). Pleroma blanchetianum may have tetramerous (less often) and pentamerous flowers (Freitas et al. 2016), while P. piranii , only has pentamerous flowers; P. piranii also differs by the ovary that is covered with trichomes for its entire length (vs. only at the apex in P. blanchetianum ). Pleroma piranii occurs only in the state of Minas Gerais, on Serra do Cipó and Planalto de Diamantina , and P. blanchetianum occurs only in the state of Bahia, especially on the Chapada Diamantina (the northern portion of Cadeia do Espinhaço; Freitas et al. 2016).

Pleroma piranii also appears to be related to Pleroma clavatum ( Persoon 1805: 476) Guimarães & Michelangeli in Guimarães et al. (2019: 974); they resemble each other in their shrubby habit (little branched in P. clavatum ), oval leaves that are opposite (exclusively), discolorous (slightly discolorous in P. clavatum ), and sericeous on the adaxial surface. They also share the elongated thyrsoids, sericeous hypanthia, purple petals, isometric stamens, purple anthers, glabrous connectives and appendages, filaments sparsely glandular pilose along their basal portions (Guimarães & Oliveira 2009). Pleroma piranii differs from P. clavatum by the older branches with decorticated epidermis (vs. older branches with epidermis non-decorticated in P. clavatum ), brown leaves (in dehydrated specimens) on the adaxial surface (vs. silvery leaves on the adaxial surface), with an acute apex (vs. obtuse), longer petioles that are 3 6 mm long (vs. absent or highly reduced, and 1–2 mm long), and by the ovary completely covered with trichomes (vs. the ovary covered with trichomes only in its apical portion). Another difference between these two species involves habitat. Pleroma clavatum occurs in restinga (vegetation on coastal sandy soils) and Submontane Atlantic Forest along the coast in the states of Santa Catarina, Paraná, São Paulo and Rio de Janeiro ( Guimarães 2022). There is a specimen of P. piranii incorrectly identified as Tibouchina holosericea ( Linnaeus 1753: 390) Baillon (1880: 34) (= P. clavatum ) at K (see Glaziou 19294, on the list of the paratypes). On this collection the branch on the left (K000329046) is mixed with a specimen of P. clavatum (branch on the right, K000329047).

Finally, Pleroma piranii shares some morphological features with Pleroma nodosum ( Wurdack 1959: 9) Guimarães & Michelangeli in Guimarães et al. (2019: 986) - a shrubby habit (moderately branched), older branches with decorticated epidermis, opposite leaves (exclusively), discolorous, short petioles, the thyrsoid inflorescences, flower buds surrounded by two elliptical bracteoles, pentamerous flowers, sericeous hypanthia, isometric stamens, glabrous connectives and appendages, and filaments sparsely glandular pilose along their basal portions. Pleroma piranii differs from P. nodosum by the leaves that are densely sericeous on the adaxial surface (vs. moderately strigose in P. nodosum ), purple petals (vs. light magenta petals), purple anthers (vs. white anthers), and by the ovary completely covered with trichomes (vs. the ovary covered with trichomes only in its apical portion). Pleroma nodosum also has a different distribution pattern. It occurs only in Goiás ( Guimarães 2022), on the Chapada dos Veadeiros ( Cria 2022, Reflora 2022), Serra dos Pireneus ( Versiane et al. 2016), and Serra Dourada ( Machado & Romero 2020).

Chromosome Number:―A chromosome number of n =18 was reported for this species as Pleroma aff . v elutinum by Almeda & Penneys (2022). We provide here a camera lucida drawing of a Telophase I meiotic figure for this species. Meiosis was regular in the several cells examined ( Fig. 4 ). Chromosome numbers are now known for about 18 species of Pleroma , all of which have been reported to have n =18 ( Gadella et al. 1969, Solt & Wurdack 1980, Zhang et al. 2010, Almeda & Penneys 2022). Two species, Pleroma cryptadenum ( Gleason 1952: 426) Guimarães & Michelangeli in Guimarães et al. (2019: 976) and Pleroma urvilleanum ( Candolle 1828: 130) Guimarães & Michelangeli in Guimarães et al. (2019: 991) have n =27 (hexaploid) in addition to n =18 ( Solt & Wurdack 1980, Zhang et al. 2010) so tetraploid and hexaploid races occur in some species of the genus. Most of the species counted to date, however, are tetraploids (n =18) based on x= 9, a common base number in the greater Tibouchina alliance that includes Chaetogastra De Candolle (1828: 131) and Tibouchina ( Almeda & Penneys 2022) . The two latter genera have both diploid and tetraploid species based on x =9 ( Solt & Wurdack 1980, Almeda 2013, Meyer et al. 2018, Almeda & Penneys 2022). Of the five broad patterns of chromosomal evolution now evident across the Melastomataceae ( Almeda & Penneys 2022) Pleroma appears to fit the “interspecific constancy of paleopolyploid origin pattern” with x² =18 and to a lesser extent the “interspecific polyploidy” pattern with consistently euploid number increases based on tetraploidy. Polyploidy is common in the tribe Melastomateae but an overwhelming trend in the family is the prevalence of tetraploidy which appears to have conferred some advantage in the chromosomal evolution of Melastomataceae ( Almeda & Penneys 2022) .

Figures

FIGURE 1. Pleroma piranii. A. Branch. B. Details of the trichomes that cover the branches. C. Leaf with obtuse base, abaxial surface. D. Leaf with obtuse base, adaxial surface. E. Details of the cordate base of the leaf (abaxial surface). F. Flower at anthesis in lateral view. G. Petal, abaxial surface. H. Antesepalous stamen. I. Antepetalous stamen. J. Hypanthium and calyx lobes in lateral view. K. Gynoecium. L. Bracteole with indumentum distributed only in the central portion of the abaxial surface, glabrous at the margin. M.Adaxial surface of the bracteole shown in L. N. Bracteole with indumentum distributed along the entire abaxial surface to the margin. O. Adaxial surface of the bracteole shown in N. [A-D and F-O drawn based on Almeda et al. 7762 (CAS); E based on Almeda et al. 7762 (HUFU).]

FIGURE 2. Photos of the inflorescence, flowers, and some floral parts of live specimens of Pleroma piranii. A. Partial inflorescence. B. Detail of androecium and gynoecium. C. Senescent flower, in the initial period of fruiting, without petals and stamens. D. Flowers with petals, stamens, and style. Voucher: Almeda et al. 7762. (All photos by Frank Almeda).

FIGURE 3. Distribution map of Pleroma piranii.A. Brazil. B. State of Minas Gerais. C. Distribution of P.piranii. D. Rupestrian grasslands on Serra do Cipó, one of the places where the species occurs. (Photo D by Soizig Le Stradic).

FIGURE 4. Drawing of chromosomes of Pleroma piranii in Telophase I (drawn with camera lucida).