Pleroma viscosa R. Romero, R. Pereira & P. J. F. Guim., 2024

Romero, Rosana, Pereira Silva, Rodrigo & Guimarães, Paulo José Fernandes, 2024, Two new Pleroma species and an updated key: Melastomateae from the Serra da Canastra National Park, Minas Gerais, Brazil, PhytoKeys 247, pp. 11-27 : 11-27

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

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!) .

Diagnosis.

The viscosity in the younger branches, leaf blade, bracteoles, hypanthium, and sepals, due to the spherical glands, the prominent secondary veins on the abaxial surface of the blade, and the stamen with a very short pedoconnective (ca. 0.2 mm long), are characteristics that differ from those of other Pleroma species.

Description.

Subshrubs or shrubs, 0.5–1.7 m tall, erect. Stem subquadrangular to quadrangular, sparse to densely covered with spherical glands, glutinous. Younger branches subquadrangular to quadrangular, flattened at the apex, with spherical glands, glutinous, older branches subquadrangular, with spherical glands, glutinous, internodes 2–5 cm long. Leaves sessile, decussate, horizontal, isomorphic in size at each node; blade 2–8 × 3–6 cm, discolorous (when fresh and dry), coriaceous, adaxial surface darker, ovate, ovate-oblong, elliptic-lanceolate to elliptic, obtuse or rounded at the apex, rarely acute, base rounded to subcordate, semiamplexicaul, margin entire, adpressed-strigose, marginal trichomes 1.5–2 mm long, both surfaces densely covered with brownish glands, glutinous, adaxial surface frequently glutinous, 5–7 acrodromous veins, basal, principal and secondary veins prominent on the abaxial surface. Panicles of simple or compound dichasium, reduced or not, terminal, densely covered with spherical glands, glutinous; bracts two, 2.5–9.5 × 4–8.5 mm, caducous, sessile, coriaceous, lanceolate or elliptic-lanceolate, obtuse or rounded at the apex, rarely acute, base truncate, semiamplexicaul, margin strigose-ciliate, trichomes 0.1–1.2 mm long, both surfaces densely covered with spherical, brownish glands, with glutinous aspect; bracteoles two, 4–5.5 × 3.5–4.3 mm, caducous, brownish, cucullate, membranaceous, both surfaces densely covered with spherical glands, with glutinous aspect, margin glandular-ciliate. Flowers 5 - merous; pedicel 3.3–11 mm long, sparse to densely covered with spherical glands; hypanthium 3.3–5 × 3.5–4.5 mm, green or glaucous, cylindrical, with spherical glands; calyx tube 0.3 mm long, sepals 2–4.5 × 1.5–4 mm, green or glaucous, scarious, oblong, rounded at the apex, margin ciliate, rare sparse ciliate, with spherical glands and glutinous aspect; petals 11–17 × 11.5–16.5 mm, purple, obovate, rounded or slightly retuse at the apex, base attenuate, margin entire, glabrous or slightly ciliate; androecium subisomorphic, stamens 10; filaments 3.2–4.5 mm long, purple, filiform, glabrous, sometimes with sparse glandular trichomes; anthers 2.5–3.5 mm long, cream, oblong, slightly curved, pore inclined ventrally, pedoconnective ca. 0.2 mm long, ventral appendage ca. 0.1 mm long, slightly bilobed, dorsal appendage absent; ovary 5 - locular, half-inferior, free apical portion densely sericeous; style ca. 8 mm long, cream, filiform, slightly curved at the apex, glabrous, stigma truncate. Fruits loculicidal, capsules coated by persistent cupuliform hypanthium, 6–8.5 × 5–6.8 mm, brownish, oblong. Seeds ca. 0.5 × 0.3 mm, brown, numerous, cochleate, testa papillose.

Distribution and habitat.

Like P. canastrense , P. viscosa is only known from Serra da Canastra National Park, where it is probably endemic (Fig. 3 ). Its populations also occur in campo rupestre, often associated with rocky outcrops.

Conservation status.

Pleroma viscosa has an area of occupancy (AOO) of 32 km 2. Like P. canastrense , P. viscosa populations are restricted to Serra da Canastra National Park. Therefore, we propose, for the same reasons, the preliminary category of “ Least Concern ” (LC) according to IUCN (2012, 2022). We also did not identify a continuous decline in occupancy of P. viscosa populations over the past 30 years (R. Romero, personal obs.).

Phenology.

Pleroma viscosa was collected in flower from January to July and in fruit from April to October.

Etymology.

The specific epithet refers to the viscous appearance of the plant due to the spherical glands of the younger branches, on both sides of the leaf blade, bracteoles, hypanthium, and sepals. The substance produced by the spherical glands often stains newspapers where they are dried ( Romero 2000).

Discussion.

Pleroma viscosa resembles P. gertii in having an erect stem, sessile leaves, coriaceous and discolorous leaf blade, with the adaxial surface darker than the abaxial surface. In addition, both species have a leaf blade obtuse to rounded at the apex, rounded to subcordate at the base, semiamplexicaul, with entire and adpressed-strigose margin. However, in P. viscosa , the leaf blade is covered with brownish glands (vs. yellowish green in P. gertii ), which give a glutinous appearance mainly on the adaxial surface (vs. non-glutinous). Furthermore, the secondary veins are prominent on the abaxial surface of the leaf blade (vs. inconspicuous in P. gertii ).

Pleroma viscosa also resembles Pleroma minus (R. Romero & A. B. Martins) P. J. F. Guim. & Michelang. , also found in the Serra da Canastra National Park (see Romero and Martins 2003). Both species share coriaceous and discolorous leaf blade, entire and adpressed-strigose margin, both surfaces are covered with brownish spherical glands, and purple petals. However, P. minor can be distinguished by its glabrous or sparsely setose stem in the basal portion (vs. spherical glands in P. viscosa ), ascending leaves (vs. horizontal), smaller leaf blade 0.8–4.5 × 0.5–2.5 cm (vs. 2–8 × 3–6 cm), pedicel ca. 2 mm long (vs. 3.3–11 mm long), petals rounded at the apex, and ciliate at the margin (vs. rounded or slightly retuse, glabrous or slightly ciliate).

The specimen W. A. Araújo 11528 (ESA 066062) deposited at ESA herbarium was first identified by Henrique Lahmeyer Mello Barreto (1892–1962) as Svitramia wilson-araujaei but this name was never published.

Additional specimens examined (paratypes).

Brazil • Minas Gerais Parque Nacional da Serra da Canastra. Araxá: Serra do Taquaral, divisas de Araxá e Sacramento ; W. A. Araújo & H. L. Mello Barreto 11528; 25 May 1943 ( ESA 06606 - image online!) • Delfinópolis: trilha Condomínio de Pedra ; 23 June 2010 (fl); R. Romero et al. 8258 ( HUFU!, RB!) • São Roque de Minas : 20 February 1994 (fl); R. Romero & J. N. Nakajima 625 ( HUFU!, SPF!, UB!, UEC!) • 15 October 1994 (fr), J. N. Nakajima et al. 469 ( HUFU!, UB!, UEC!) • estrada para Sacramento ; 17 October 1994 (fr); J. N. Nakajima et al. 532 ( CESJ!, HUFU!, UFG!) • 10 January 1995 (fl); R. Romero et al. 1642 ( HUFU!, UFG!) • 12 January 1995 (fl); R. Romero et al. 1779 ( HUFU!, VIC!) • morro próximo à sede administrativa; 17 March 1995 (fl); R. Romero et al. 1899 ( HUFU!, K!, NY!, OUPR!, P!, US!) • estrada do Chapadão Diamante ; 18 March 1995 (fl, fr); J. N. Nakajima et al. 821 ( CESJ!, HUFU!) • morro próximo à sede administrativa ; 10 May 1995 (fl, fr); J. N. Nakajima et al. 998 ( HUFU! RB!, SPF!, VIC!) • 15 July 1995 (fl); R. Romero et al. 2383 ( HUFU!) • 11 January 1996 (fl, fr); R. Romero et al. 3250 ( CESJ!, HUFU!, UFG!) • Cachoeira Casca D’Anta ; 13 January 1996 (fl, fr); R. Romero et al. 3293 ( HUFU!, K!, NY!, SPF!, UB!, UEC!) • morro após a nascente do Rio São Francisco ; 20 March 1996 (fl); R. Romero & J. N. Nakajima 3351 ( HUFU!, K!, P), R. Romero & J. N. Nakajima 3352 (HUEFS!, HUFU!, RB!, VIC!) • Serra Brava ; 22 March 1996 (fl); R. Romero & J. N. Nakajima 3393 ( CESJ!, HUFU!, UFG!) • morro próximo à sede administrativa; 24 March 1996 (fl, fr); J. N. Nakajima & R. Romero 1736 ( HUFU!, K!, OUPR!, US!) • Chapadão do Diamante ; 9 July 1996 (fl); J. N. Nakajima et al. 1904 ( CESJ!, HUFU!, OUPR!, UFG!) • morro próximo à sede administrativa; 16 April 1997 (fl); R. Romero et al. 4063 ( HUFU!, OUPR!, P) • Chapadão do Diamante ; 18 April 1997 (fr); J. N. Nakajima et al. 2318 ( HUFU!, RB!) • morro próximo à sede administrativa; 9 January 1998 (fl); R. Romero et al. 4832 ( HUFU!, NY) • estrada a caminho da nascente do Rio São Francisco ; 23 March 1999 (fl); S. I. Elias & G. S. Rolim 341 ( HUFU!) • Garagem de Pedras ; 21 June 2001 (fl, fr); R. Romero et al. 6136 ( HUFU!, SPF!) • ca. de 2 km da sede ; 23 June 2001 (fl); R. Romero et al. 6141 ( HUFU!, UB!, UEC!) • III. 2007 (fl, fr); C. M. Rodrigues 24 ( HUEFS!, HUFU!) • morro próximo à sede administrativa ; 23 July 2009, (fr); P. J. F. Guimarães et al. 400 ( RB!) .

Figures

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.

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).

Figure 5. Pleroma viscosa R. Romero, R. Pereira & P. J. F. Guim., sp. nov. A flowering shrub in campo rupestre at Garagem de Pedras, Serra da Canastra National Park B adaxial leaf surface C abaxial leaf surface D flowering and fruiting branches E flower in frontal view. Photos: Rosana Romero.