Two new Pleroma species and an updated key: Melastomateae from the Serra da Canastra National Park, Minas Gerais, Brazil

Rosana Romero; Rodrigo Pereira Silva; Paulo José Fernandes Guimarães

doi:10.3897/phytokeys.247.130040

Abstract

Here we describe and illustrate Pleroma canastrense sp. nov and Pleroma viscosa sp. nov. two new species of the Melastomateae tribe from Serra da Canastra National Park, Minas Gerais, Brazil. We also provide an updated identification key for the members of the tribe that occur in this Protected Area. Pleroma canastrense sp. nov. has coriaceous leaves, broadly ovate to orbicular leaf blade, entire and adpressed-strigose margin, 11–17 basal acrodromous veins, and flowers with white petals. Pleroma viscosa sp. nov. has the younger branches, both side of the leaf blade, bracteoles, hypanthium, and sepals, densely covered by viscous trichomes, as well as prominent secondary veins on the abaxial surface of the blade. Both species have stamens with a short pedoconnective and an inconspicuous ventral appendage. In addition to the descriptions of new species, we present comments, geographic distribution data, conservation status and images of plants in the field. We recommend that P. canastrense and P. viscosa should be included as of ‘Least Concern’ (LC) in the IUCN Red List.

Resumo

Descrevemos e ilustramos aqui Pleroma canastrense sp. nov e Pleroma viscosa sp. nov., duas novas espécies da tribo Melastomateae do Parque Nacional da Serra da Canastra, Minas Gerais, Brasil. Fornecemos também uma chave de identificação atualizada para os membros da tribo que ocorrem nesta área protegida. Pleroma canastrense sp. nov. apresenta folhas coriáceas, lâmina foliar amplamente oval a orbicular, margem inteira e estrigosa, 11–17 nervuras acródromas basais e flores com pétalas brancas. Enquanto Pleroma viscosa sp. nov. apresenta os ramos mais jovens, ambas as faces da lâmina foliar, bractéolas, hipanto e sépalas densamente cobertos com tricomas viscosos, além de nervuras secundárias proeminentes na face abaxial da lâmina. As duas espécies apresentam estames com pedoconectivo curto e apêndice ventral inconspícuo. Além das descrições das novas espécies, apresentamos comentários, dados de distribuição geográfica, estado de conservação e imagens das plantas no campo. Recomendamos que P. canastrense e P. viscosa sejam incluídas na categoria ‘Pouco Preocupante’ na Lista Vermelha da IUCN.

Key words

Campo rupestre, endemism, Melastomateae, pedoconnective, Svitramia, taxonomy

Palavras-chave

Campo rupestre, endemismo, Melastomateae, pedoconectivo, Svitramia, taxonomia

Introduction

The Serra da Canastra National Park, located in southwestern Minas Gerais (IBAMA 2005), is considered the second-largest conservation unit in the state (Romero and Martins 2002; Machado and Romero 2014; Romero and Versiane 2014) and the sixth-largest area protected in Brazil (IBAMA 2005). The Park has a diverse flora with 101 families of Angiosperms and at least 17 endemism areas with 45 endemic species (see Romero and Nakajima 1999). However, these numbers must be higher since dozens of new species endemic to the region have been described in the last 30 years (e.g., Versieux and Wanderley 2008; Batista et al. 2010; Chautems et al. 2010; Feres 2010; Romero and Versiane 2014; Oliveira et al. 2016; Romero and Rocha 2017; Oliveira et al. 2019; Echternacht et al. 2021).

Among the most diverse families in this National Park, Melastomataceae Juss. stands out with 105 species in 21 genera (see Romero and Martins 2002; Silva and Romero 2008; Romero and Versiane 2014). The pantropical Melastomateae Bartl. tribe is represented in the National Park by 24 species distributed in Pleroma (18 spp.), Chaetogastra (3 spp.), and Macairea, Pterolepis, and Tibouchina (with one species each) (see Romero and Martins 2002; Silva and Romero 2008; Romero and Versiane 2014; Alves 2022; Silva 2023).

The phylogenetic study of the tropical specimens of Melastomateae recognized 17 genera (Michelangeli et al. 2013; Veranso-Libalah et al. 2022), and the most significant implication was the segregation of Tibouchina Aubl. This genus was previously considered the largest within the tribe, with 310 species (Guimarães et al. 2019). Then, Tibouchina was redefined into four monophyletic and easily distinguishable genera (Guimarães et al. 2019). The narrower circumscription of Tibouchina led to the reinstatement of Pleroma and Chaetogastra DC., along with the description of a new genus, Andesanthus P.J.F.Guim. & Michelang., with Pleroma also including Itatiaia Ule, Microlepis Schrad. ex Nees, and Svitramia Cham.

The six species previously recognized in Svitramia occur in the Serra da Canastra National Park: S. pulchra Cham. [=Pleroma bandeirae (Cham.) P.J.F.Guim. & Michelang.], S. hatschbachii Wurdack [=P. gertii (Wurdack) P.J.F.Guim. & Michelang.], S. integerrimum R.Romero & A.B.Martins [=P. integerrimum (R.Romero & A.B.Martins) P.J.F.Guim. & Michelang.], S. minor R.Romero & A.B.Martins [=P. minus (R.Romero & A.B.Martins) P.J.F.Guim. & Michelang.], S. petiolata R.Romero & A.B.Martins [=P. petiolatum (R.Romero & A.B.Martins) P.J.F.Guim. & Michelang.], and S. wurdackiana R.Romero & A.B.Martins (=P. wurdackianum (R.Romero & A.B.Martins) P.J.F.Guim. & Michelang.] (see Romero 2000; Romero and Martins 2003). Here, we describe two new species of Pleroma, initially referred to as Svitramia sp. nov. 1 and Svitramia sp. nov. 2 in the previous Melastomataceae checklist for Serra da Canastra National Park (see Romero and Martins 2002). We compare the new species with morphologically similar species and provide illustrative plates, field images, and an occurrence map of the new species. In addition, the identification key for the species of Melastomateae in the Serra da Canastra National Park is provided.

Methods

This study was based on the examination of Chaetogastra, Pleroma, Pterolepis, Macairea, and Tibouchina specimens from Serra da Canastra National Park deposited at the HUFU with duplicates at CESJ, HUEFS, K, NY, OUPR, P, R, RB, SP, SPF, UB, UEC, UFG, VIC herbaria (Thiers 2024, continuously updated) and field observations. We also examined specimens with available images on Global Plants on Jstor (https://plants.jstor.org/), speciesLink (https://specieslink.net/), and Reflora Virtual Herbaria (http://reflora.jbrj.gov.br/reflora/herbarioVirtual). The vegetative and reproductive structures of the examined samples of the new species were measured in a stereoscopic microscope and with a digital caliper. Morphological terminology followed Radford (1986). The area of occupancy (AOO) was estimated using GeoCAT software (Bachman et al. 2011), and preliminary assessments of conservation status followed IUCN criteria (2001, 2022).

Results

Taxonomic treatment

Pleroma canastrense R.Romero, R.Pereira & P.J.F.Guim., sp. nov.

urn:lsid:ipni.org:names:77349019-1

Figs 1, 2, 3

Type

Brazil • Minas Gerais. Parque Nacional da Serra da Canastra. São Roque de Minas: campo rupestre do morro próximo à sede administrativa do parque; 26 June 1994; fl. fr., R. Romero & J.N. Nakajima 1039 (holotype HUFU!; isotypes: BHCB!, RB!, UEC!).

Figure 1.

Pleroma canastrense R.Romero, R.Pereira & P.J.F.Guim.: A flowering branch B adaxial leaf surface C detail of the leaf blade margin D flower E hypanthium and sepals F detail of the hypanthium surface G petal, abaxial view H petal margin detail I stamens, in lateral view J gynoecium K stigma detail L cross section of the ovary M fruit N seed (Illustration by Klei Souza based on the holotype (R. Romero & J. N. Nakajima 1039).

Diagnosis

The coriaceous leaf blade, broadly ovate to orbicular, entire and adpressed-margin, with 11–17 basal acrodromous veins, the stamens with a short pedoconnective and an inconspicuous ventral appendage together with the white petals, distinguish this species from another Pleroma.

Figure 2.

Pleroma canastrense R.Romero, R.Pereira & P.J.F.Guim. A rocky outcrop at Serra da Canastra National Park, Minas Gerais, Brazil, the type locality of Pleroma canastrense B subshrub in campo rupestre near the road C flowering specimen showing the beautiful leaf architecture D flower E fruiting branch. Photos: Rosana Romero.

Description

Subshrubs or shrubs, 0.6–1.8 m tall, decumbent. Stem terete to subterete, glabrous, or with setose trichomes in the basal portion. Younger branches quadrangular, flattened at the apex, with spherical glands, or glabrous, older branches terete, glabrous, internodes 2–5 cm long. Leaves sessile, decussate, horizontal, isomorphic in size at each node; blade 2.5–6.5 × 2–5 cm, discolorous (when fresh and dry), coriaceous, adaxial surface darker, broadly ovate to orbicular, obtuse to acute at the apex, rarely rounded, with a terminal trichome, 0.5–1 mm long, base cordate, semiamplexicaul, margin entire, adpressed-strigose, marginal trichomes 2–4 mm long, both surfaces glabrous, acrodromous veins 11–17, basal, principal vein lighter, conspicuously visible on both surfaces and secondary veins tenuous on the abaxial surface. Panicles of simple or compound dichasium, reduced or not, terminal; bracts two, 5–12.5 × 3–8.5 mm, caducous, leafy, sessile, coriaceous, largely ovate to orbicular, elliptic-lanceolate, obtuse to acute at the apex, base truncate, semiamplexicaul, margin strigose-ciliate, trichomes 0.3–1 mm long, both surfaces glabrous; bracteoles two, 3–7.5 × 2–6.7 mm, caducous, brownish, cucullate, membranaceous, both surfaces covered with spherical glands, margin glandular-ciliate, mainly at the apical portion. Flowers 5-merous; pedicel 1–2.5 mm long, glabrous; hypanthium 3–7 × 3–6 mm, green or glaucous, cylindrical, glabrous, furfuraceous; calyx tube 0.3 mm long; sepals 2–4 × 1.5–3 mm, green or glaucous, scarious, oblong, rounded at the apex, margin glandular-ciliate, furfuraceous; petals 8–14 × 9–12 mm, white, largely ovate, rounded or slightly retuse at the apex, base attenuate, margin entire, inconspicuously glandular-ciliate; androecium subisomorphic, stamens 10; filaments 4–7 mm long, white, filiform, glabrous or with sparse glandular trichomes in the basal portion; anthers 3–5 mm long, cream, oblong, straight, pore inclined ventrally, pedoconnective ca. 0.2 mm long, ventral appendage ca. 0.1 mm long, slightly bilobed, dorsal appendage ca. 0.1 mm long, lobed, glabrous; ovary 5-locular, half-inferior, free apical portion densely sericeous; style ca. 9 mm long, cream, filiform, slightly curved at the apex, glabrous, stigma truncate. Fruits loculicidal, capsules coated by persistent cupuliform hypanthium, 6–8.3 × 5–6.8 mm, brownish, oblong. Seeds ca. 0.5 × 0.3 mm, brown, numerous, cochleate, testa papillose.

Distribution and habitat

So far, we know Pleroma canastrense only from the Serra da Canastra National Park, where it is probably endemic (Fig. 3). The beautiful populations with white flowers occur exclusively in campo rupestre.

Figure 3.

Geographical distribution of Pleroma canastrense and Pleroma viscosa in the Serra da Canastra National Park, Minas Gerais, Brazil [Adapted from Alves (2022)]. White line refers to the area of Serra da Canastra National Park.

Conservation status

Pleroma canastrense has an area of occupancy (AOO) of 48 km². Although this species has a distribution restricted to Serra da Canastra, we indicate it preliminarily here as “Least Concern” (LC), according to the IUCN categories (2012, 2022). This assessment is because most individuals are in a conservation unit with complete federal protection, established almost 50 years ago, with no significant threats to the populations. Furthermore, we have not identified a continued decline in occupancy over the past 30 years (R. Romero, pers. obs.).

Phenology

Pleroma canastrense was collected in flower from April to August and in fruit from June to October.

Etymology

The specific epithet refers to the restricted occurrence of this species in the campo rupestre of Serra da Canastra, Minas Gerais state, Brazil. The name “Serra da Canastra” is due to the similarity presented by the immense plateau, which, when viewed from afar, resembles a canastra, a term of Greek origin used to name a type of rustic chest with a rectangular shape.

Discussion

Pleroma canastrense resembles P. wurdackianum (R.Romero & A.B.Martins) P.J.F.Guim. & Michelang., which also occurs in the Serra da Canastra National Park (Romero and Martins 2003). Both species share a subshrubby or shrubby habit, terete to subterete stem, glabrous and sometimes with setose trichomes on the basal portion, sessile leaves, discolorous leaf blade, cordate at the base, semiamplexicaul, and entire and adpressed-strigose margin with spiny trichomes. However, P. wurdackianum has pink petals (vs. white in P. canastrense), hypanthium and leaf blade with spherical glands (vs. glabrous). Pleroma canastrense is also similar to P. integerrimum (R.Romero & A.B.Martins) P.J.F.Guim. & Michelang., known only from Serra Preta in Delfinópolis (Romero and Martins 2003), since both have flowers with white petals. However, P. integerrimum differs in having a chartaceous and concolorous leaf blade (vs. coriaceous and discolorous in P. canastrense), glabrous at the margin (vs. adpressed-strigose).

Thirty years ago, John Julius Wurdack (1921–1998) wrote the following note on the sheet Romero & Nakajima 1039 from HUFU herbarium: “Svitramia sp. aff. S. hatschbachii Wurdack (currently as Pleroma gertii P.J.F.Guim. & Michelang.), but leaf cilia shorter, blade relatively broader and scarcely puncticulate, calyx lobes shorter, corolla white and larger, anthers longer.” Pleroma canastrense resembles P. gertii, the latter occurring preferentially in campo rupestre and more rarely in campo limpo and sujo in the south and southwest of Minas Gerais, i.e., a distribution that exceeds the limits of the Serra da Canastra National Park. However, P. gertii has elliptic, elliptic-lanceolate, or ovate to ovate-lanceolate leaf blade (vs. broadly ovate to orbicular in P. canastrense) with 7–9 basal acrodromous veins (vs. 11–17), and purple petals (vs. white).

The specimen G.J. Shepherd et al. 7032 (UEC055432) deposited at UEC was first named as Svitramia alba by Angela Borges Martins (1945–) & João Semir (1937–2018) and this sheet annotated as holotype, but this name was never published by them.

Additional specimens examined (paratypes)

Brazil • Minas Gerais. Parque Nacional da Serra da Canastra. Capitólio: Reserva de Furnas; 20 February 1978; (fl), G.J. Shepherd et al. 7032 (UEC055432-online image!) • Morro do Chapéu; 24 July 1993 (fl, fr); R. Simão-Bianchini & S. Bianchini 413 (HUFU!, SP!) • Paraíso perdido, córrego Quebra-Anzol; 29 September 2005 (fr); J.N. Nakajima 3737 (HUEFS!, HUFU!, VIC!) • estrada de Capitólio para Passos; 1 October 2005 (fl, fr); R. Romero 7264 (HUFU!) • estrada para Pedreira Souza; 7 November 2005 (fl); J.N. Nakajima et al. 4053 (HUFU!) • estrada atrás do Paraíso Perdido; 12 July 2006 (fr); R. Romero et al. 7794 (HUFU!, RB!, SPF!, OUPR!, UEC!) • estrada para pedreira; 21 March 2007 (fr); P.H.N. Bernardes et al. 45 (HUFU!, OUPR!, VIC!) • morro atrás da pousada do Rio Turvo; 21 May 2007 (fl, fr); P.H.N. Bernardes et al. 140 (HUFU!, P!, UB!) • estrada para Cachoeira Feixo da Serra; 13 July 2007 (fl, fr); R. Romero et al. 7795 (HUFU!, NY!, SPF!, RB!, UB!, UEC!, UFG!) • Chapadão de Furnas; 18 May 2013 (fr); M.J.R. Rocha 985 (HUFU!, BHCB!) • Delfinópolis: estrada para a Babilônia; 24 May 1996 (fl, fr); R. Romero & J.N. Nakajima 3438 (HUFU!) • Cachoeirinhas; 27 February 2000 (fr); A.C.B. Silva 302 (HUFU!, SPF!, R!) • 2 May 2001 (fl, fr); A.C.B. Silva 881 (HUFU!, SPF!, R!) • s.d. (fl, fr); A.C.B. Silva 422 (HUFU!, SPF!, R!) • trilha Casinha Branca; 11 April 2002 (fl); R.A. Pacheco et al. 101 (HUFU!) • trilha do Zé Carlinho, subida para a Serra do Cemitério; 9 October 2002 (fr); J.N. Nakajima et al. 3193 (HUFU!, OUPR!, VIC!) • Paraíso Selvagem; 11 March 2003 (fl); R. Romero et al. 6707 (HUFU!) • trilha do S. Cannyon; 16 May 2003 (fl, fr); R. Romero et al. 6921 (HUFU!, UB!, UEC!) • estrada para Pedreira Souza; 30 September 2005; J.N. Nakajima et al. 3946 (HUFU!, K!, OUPR!, P!) • estrada para Pedreira Souza; 17 February 2006; R. Romero et al. 7704 (CESJ!, HUFU!, UFG!) • trilha Cachoeira Águas Claras; 23 June 2010 (fl); P.O. Rosa et al. 1306 (HUFU!, K!, P!, VIC!) • São Roque de Minas: Parque Nacional da Serra da Canastra; 20 August 1994 (fl, fr); R. Romero & J.N. Nakajima 1118 (HUFU!, SPF!, UFG!) • 15 October 1994 (fr); J.N. Nakajima et al. 452 (HUFU!, OUPR!, UB!) • estrada São Roque de Minas para Sacramento; 16 October 1994 (fr); R. Romero & J.N. Nakajima 1268 (HUFU!, VIC!) • Cachoeira Casca D’Anta; 17 October 1994 (fr); J.N. Nakajima & R. Romero 554 (HUFU!, UEC!) • córrego dos Passageiros; 11 May 1995 (fl); R. Romero et al. 2206 (CESJ!, HUFU!, NY!, OUPR!) • estrada para Cachoeira Casca D’Anta; 12 May 1995 (fl); J.N. Nakajima et al. 1026 (HUEFS!, HUFU!, K!, P!, RB!, SPF!, UEC!, VIC!) • Parque Nacional da Serra da Canastra; 15 July 1995 (fl, fr); R. Romero et al. 2384 (HUEFS!, HUFU!, OUPR!, RB!, SPF!, UEC!) • Cachoeira da Casca D’Anta; 17 July 1995 (fl, fr); R. Romero et al. 2505 (CESJ!, HUFU!, NY!, OUPR!) • caminho para a Cachoeira Casca D’Anta; 18 July 1995 (fl, fr); J.N. Nakajima et al. 1258 (HUEFS!, HUFU!, RB!, VIC!) • paredão da Cachoeira dos Rolinhos; 26 May 1996 (fl); J.N. Nakajima & R. Romero 1775 (HUFU!, P!, UB!, UFG!) • Chapadão do Diamante; 9 July 1996 (fl); J.N. Nakajima et al. 1929 (HUFU!, UEC!) • estrada para Cachoeira Casca D’Anta; 10 July 1996 (fl); J.N. Nakajima et al. 1939 (HUFU!, UB!, UFG!) • 10 July 1996 (fl, fr); J.N. Nakajima et al. 1947 (HUEFS!, HUFU!, K!, P!, US) • córrego dos Passageiros; 11 July 1996 (fl, fr); J.N. Nakajima et al. 2011 (CESJ!, HUFU!, K!, NY!, US) • próximo à sede administrativa; 11 July 1996 (fl, fr); J.N. Nakajima et al. 2043 (HUFU!, RB!, UEC!, VIC!) • Cachoeira Casca D’Anta; 10 August 1996 (fl); J.N. Nakajima et al. 1948 (CESJ!, HUEFS!, HUFU!, OUPR!) • trilha do paredão da Serra da Canastra; 17 April 1997 (fl); R. Romero et al. 4142 (HUFU!, SPF!, US!) • estrada para Fazenda do Fundão; 25 June 1997 (fl, fr); R. Romero et al. 4265 (HUFU!, NY!, OUPR!, UEC!) • Cachoeira dos Rolinhos; 29 June 1997 (fl, fr); R. Romero et al. 4369 (CESJ!, HUFU!, OUPR!) • Chapadão do Diamante; 29 June 1997 (fl); R. Romero et al. 4330 (HUFU!, UB!, UFG!) (fl, fr), R. Romero et al. 4336 (CESJ!, HUFU!, UFG!) • estrada para o sítio João Domingos; 20 August 1997 (fl); J.N. Nakajima et al. 2635 (CESJ!, HUFU!, UB!, UFG!) • estrada para o Vale dos Cândidos; 22 August 1997 (fr); J.N. Nakajima et al. 2708 (HUFU!, NY!, US!) (fr), J.N. Nakajima et al. 2696 (HUFU!, RB!, UB!, VIC!) • Guarita de São Roque de Minas; 23 June 2001 (fl); R. Romero et al. 6140 (CESJ!, HUFU!, UFG!) • parte alta da Cachoeira Casca D’Anta; 14 May 2007 (fl); A.P.M. Santos & J.F. Silva 403 (HUEFS!, HUFU!) • morro próximo à sede administrativa; 23 July 2009; (fl), P.J.F. Guimarães et al. 402 (RB!) • alto da Casca D’Anta; 29 May 2014 (fl); A.F.A. Versiane et al. 647 (HUFU!, NY!).

Pleroma viscosa R.Romero, R.Pereira & P.J.F.Guim., sp. nov.

urn:lsid:ipni.org:names:77349020-1

Figs 3, 4, 5

Type

Brazil • Minas Gerais. Parque Nacional da Serra da Canastra. São Roque de Minas: campo rupestre próximo à sede administrativa; 16 April 1994 (fl); R. Romero et al. 845 (holotype: HUFU!; isotypes: BHCB!, RB!, UEC!, US!).

Figure 4.

Pleroma viscosa R.Romero, R.Pereira & P.J.F.Guim.: A flowering branch B adaxial leaf surface C detail of the abaxial surface and margin of the leaf blade D flower E detail of the hypanthium surface F hypanthium and sepals G petal, abaxial view H petal margin detail I stamen, in lateral view J gynoecium K stigma detail L cross section of the ovary M fruit N seed (Illustration by Klei Souza based on the holotype (R. Romero et al. 845).