Pleroma miconiifolium F.S.Mey. & R.Goldenb., 2022

Goldenberg, R., Gonella, P. M. & Meyer, F. S., 2022, Four new species of Pleroma (Melastomataceae) from campos rupestres and vegetation on granitic inselbergs in Eastern Minas Gerais, Brazil, Edinburgh Journal of Botany 79 (624), pp. 1-30 : 15-19

3. Pleroma miconiifolium F.S.Mey. & R.Goldenb. , sp. nov.

Pleroma miconiifolium differs from P. leopoldinense L.Kollmann & R.Goldenb. by its leaves with shorter petioles, 4.6–9.1 mm long (versus 15–45 mm long in P. leopoldinense ), pustulate on the adaxial surface (versus pustulate-strigose on the adaxial surface); and stamens in both cycles with the appendages covered with sparse glandular trichomes (versus appendages glabrous in both cycles). – Type: Brazil, Minas Gerais, Santa Rita do Itueto, A.P.A. Municipal Pedra do Paredão , Pedra de Santa Rita , na encosta do topo da pedra, 19°22′22.72′′S, 41°21′28.70′′W, 1060 m, 6 v 2021, P.M. Gonella, D.P. Cordeiro, G.A. da Silva, P.R. Bartholomay & L. Medeiros 2722 (holotype UPCB, isotype MBML). Figures 7 , 8 .

Erect shrubs 1–1.5 m tall, with sympodial growth, moderately branched. Younger branches terete, not winged, glabrous; older branches terete to quadrangular, not winged, glabrous, and basally decorticant; nodes slender. Leaves opposite; chartaceous, with distinct petioles, 4.6–9.1 mm long; blades 5.2–8.5 × 1.5–3.5 cm, chartaceous, slightly discolorous, elliptic, base obtuse, apex acute, margins smooth or slightly crenulated, 5 acrodromous nerves, the midrib and the first lateral pair slightly suprabasal, basally joined on the abaxial surface by a minute membrane and resulting in a pair of pocket domatia, adaxial surface flat, dark green in dry specimens and in fresh material, sparsely pustulate, the minute trichome-like projections less than 0.1 mm long, unbranched, erect, the base linear, not immersed, not forked, and nested within a tuft of minute, glandular, sessile projections, abaxial surface flat, yellowish green or light brown in dry specimens, light green in fresh material, sparsely strigose on the primary veins, trichomes 0.3–1.3 mm long, unbranched, eglandular, appressed, the base linear, not immersed, not forked, sparsely strigose on the surface, tertiary and quaternary veins, the minute trichome-like projections 0.1–0.3 mm long, unbranched, eglandular, appressed, the base linear, not immersed, not forked, and nested within a tuft of minute, glandular, sessile projections. Thyrsoids 5–12.5 × 5–8.5 cm, terminal, c.29–51 flowers, axis terete, glabrous, yellowish green to burgundy green; bracts late deciduous, leafy, with conspicuous petioles, 2.4–9.5 mm long, blade 39.1–81.3 × 10.8–28.8 mm, elliptic, indumentum the same as on the leaves; bracteoles early deciduous, 3.4–8.9 × 1.9–4.2 mm, ovate, apex acute or obtuse, not covering the apex of the flower bud, margins entire, ciliate, both surfaces glabrous. Flowers 5-merous, pedicels 1.1–2.2 mm long; hypanthium 4.4–6 × 4.3–5 mm, obovate, not costate, sparsely pustulate, trichomes less than 0.1 mm long, unbranched, glandular, erect, the base linear, not immersed, not forked; sepals late deciduous, 3–4.1 × 2.2–3 mm, triangular, margins ciliate, apex acute, both surfaces glabrous; petals purple with a white base (during anthesis) or purple with a red base (in senescent flowers), 17–18.8 × 9.9–10.9 mm, obovate, apex obtuse or truncate, ciliate; stamens 10, slightly dimorphic, antesepalous with the filaments white on its lower half, and purple on its upper half (during anthesis) to totally purple or reddish (in senescent flowers), 7.6–8.4 mm long, glabrous, pedoconnective purple, 0.9–1.3 mm prolonged below the thecae, glabrous, ventral appendages bilobed, apex acute or cuspidate, c. 0.4 mm long, sparsely setulose, trichomes c. 0.3 mm long, unbranched, glandular, erect, the base linear, not immersed, not forked, thecae 8–8.2 × 0.9–1.1 mm, falcate, purple, antepetalous with the filaments white on its lower half, and purple on its upper half (during anthesis) to totally purple or reddish (in senescent flowers), 7–7.3 mm long, glabrous or sparsely setulose on its upper half, trichomes c. 0.2 mm long, unbranched, glandular, curved to erect, the base linear, not immersed, not forked, pedoconnective purple, 0.5–0.8 mm prolonged below the thecae, glabrous, ventral appendages bilobed, apex acute or cuspidate, c. 0.3 mm long, sparsely setulose, trichomes c. 0.3 mm long, unbranched, glandular, erect, the base linear, not immersed, not forked, thecae 7.6–7.8 × 0.7–0.8 mm, falcate, purple; ovary 4.5–4.9 × 3.2–3.7 mm, 5-locular, apex sparsely setulose, trichomes 0.1–0.4 mm long, unbranched, eglandular, erect to curved, the base linear, not immersed, not forked; style purple, white only in the upper apical portion (during anthesis) and totally purple or reddish (in senescent flowers), 15.3–17 mm long, apex curved, glabrous, stigma truncate. Capsular fruits 7.7–9.1 × 5.6–6.7 mm, sepals early deciduous, epicarp undivided when mature, ecostate.

Distribution and habitat. Pleroma miconiifolium was collected at the Environmental Protection Area Pedra do Paredão, a granitic inselberg with rupicolous vegetation surrounded by dense forests in the municipality of Santa Rita do Itueto (see Figure 3 ). Individuals matching the morphology of the new species were also photographed at another inselberg named Palestina (Lucian Medeiros, Santa Rita do Itueto [Minas Gerais], personal communication), in the municipality of Pocrane (around 19°29′44.73′′S, 41°38′6.18′′W; a distance of 32 km to the west); because these individuals were not collected, we did not include them in the distribution map or conservation assessment. At both sites, the species was found in small populations with scattered individuals. Pleroma miconiifolium is rupicolous, growing on shallow pockets of soil over exposed rock at elevations around 1000 m. At the type locality, the species is syntopic with another endemic and recently described species, the bromeliad Orthophytum santaritense Leme, S.Heller & Zizka ( Bromeliaceae ; Leme et al., 2017).

Phenology. Collected and photographed with flowers in April and May.

Proposed IUCN conservation category. Critically Endangered: CR B2ab(iii). Although this species has been collected only once, we avoided considering it Data Deficient (DD), because one of the authors (P.M.G.) had collected the single specimen at Pedra do Paredão. The author’s in loco assessment found the species to be under severe threat by the same factors listed for the Pleroma brevicomosum and P. caetanoi , that is, several anthropic activities (fires, motocross, trampling) and co-occurrence with invasive species, all of which occur in a landscape that is already greatly fragmented.

Etymology. The specific epithet, miconiifolium , refers to the similarity of the leaves of this species to those of the genus Miconia Ruiz & Pav. ( Melastomataceae ), which often have pocket domatia on their abaxial surface (see Bacci et al., 2016).

Pleroma miconiifolium is morphologically closely related to P. leopoldinense ; both have leaves with 5 nerves, and with domatia on the abaxial surface at the junction between the main nerves; additionally, the flowers in both have glabrous hypanthia, filaments and styles, and the petals are purple with a white base. Pleroma miconiifolium differs from P. leopoldinense by the characters described in the diagnosis, and also by its elliptic leaves (versus ovate to ovate-lanceolate leaves in P. leopoldinense ); weakly dimorphic stamens, the antesepalous with shorter thecae, 8–8.2 mm long (versus strongly dimorphic stamens, the antesepalous with thecae 11.5–12 mm long); and shorter style, 15.3–17 mm long (versus 20–22 mm long).

Pleroma miconiifolium is also related to P. vimineum (D.Don) D.Don , both having elliptic, 5-nerved leaves, weakly dimorphic stamens with glabrous pedoconnectives, and glabrous style. Pleroma miconiifolium differs from P. vimineum by its leaves sparsely pustulate on the adaxial surface (versus moderately strigose in P. vimineum ), with a pair of domatia on the abaxial surface (versus lacking domatia), sparsely pustulate hypanthia (versus moderately strigose), and glabrous filaments (versus basally moderately setulose).

Figures

Figure 3. Distribution in Minas Gerais (MG), Brazil, of the four new species described in this article. BA, Bahia; ES, Espírito Santo; RJ, Rio de Janeiro.

Figure 7. Pleroma miconiifolium F.S.Mey. & R.Goldenb., sp. nov. A, Branch with inflorescence; B, surface of a young branch; C, leaf (adaxial surface); D, leaf (abaxial surface); E, detail of the adaxial surface; F, detail of the leaf indumentum (abaxial surface); G, detail of the leaf base (abaxial surface), with the two pocket domatia indicated by arrows; H, bracteole (adaxial surface); I, hypanthium and style in an old flower (the caducous calyx has already fallen at this stage); J, antesepalous stamen; K, antepetalous stamen; L, detail of the connective of the same antesepalous stamen shown in J, with two glandular trichomes attached; M, detail of the connective of the same antepetalous stamen shown in K, with two glandular trichomes attached; N, ovary, detached from the hypanthium; O, ovary apex, with sparse and short trichomes; P, immature capsule. All from the holotype, Gonella et al. 2722 (UPCB). Photographs: F. S. Meyer.

Figure 8. Pleroma miconiifolium in the field. A, Plant growing on granitic substrate; B, leaf (adaxial surface); C, leaf (abaxial surface); D, cyme, partial inflorescence; E, partial inflorescence; F, flower with damaged stamens, probably chewed by bees. Photographs: P. M. Gonella.