Pleroma carajasense K.Rocha, R.Goldenb. & F.S.Mey., 2017

Rocha, Keila Cristina De Jesus, Goldenberg, Renato, Viana, Pedro Lage & Meyer, Fabrício Schmitz, 2017, Pleroma carajasense (Melastomataceae), a new species endemic to ironstone outcrops in the Brazilian Amazon, Phytotaxa 329 (3), pp. 233-242 : 234-240

Pleroma carajasense K.Rocha, R.Goldenb. & F.S.Mey. sp. nov. ( Figures 1–4 .)

Type:— BRAZIL. Pará: Parauapebas, Floresta Nacional de Carajás, Serra dos Carajás, N 8, solo de canga, 6°10’48’’S, 50°08’37’’W, 721 m, 26 March 2016 (fl.), K. C. J. Rocha, A. M. Giulietti, R. M. Harley & J. Meirelles 88 (holotype: MG!, isotypes: HCJS!, NY!, RB!, UPCB!).

Diagnosis:— Pleroma carajasense differs from Tibouchina caatingae Freitas (2013: 418) by the chartaceous leaves (versus coriaceous in T. caatingae ), with cuneate to obtuse base (vs. obtuse to subcordate), hypanthium 4–7 × 1.2–4 mm (vs. 10–15 × 3–5 mm), and antepetalous stamens with shorter anthers (4–7.5 vs. 8–15 mm long).

Shrubs 0.6– 3 m. Branches terete, exfoliating, moderate to densely sericeous when young, the whitish trichomes 0.5–3 mm long, non glandular, erect, straight or rarely curved, slightly broadened or not at the base. Leaves opposite, congested at the apex of the branches; petioles 3–17 mm long, terete, covered with the same indumentum as the young branches; blades 2–6.5 × 1–3.5 cm, elliptic to ovate, chartaceous, discolorous, base cuneate to obtuse, apex acute to acuminate, margin entire or slightly repand, main nerves 5, plus a shorter marginal pair that do not reach the leaf apex, acrodromous, basal, confluent (the nerves from the outermost pair reaching the ones from the innermost pair 1–10 mm above the midrib, the transversal veins forming an oblique angle in relation to the main veins), prominent on the abaxial surface, impressed on the adaxial surface, the adaxial surface slightly to densely strigose to strigosesericeous, the trichomes 0.3–1.5 mm long, non glandular, appressed, narrow to slightly broadened at the base, abaxial surface moderate to densely sericeous, the trichomes 0.5–1.5 mm long, non glandular, appressed, narrow at the base. Inflorescences shortened thyrsoids 1.9–6.5 × 0.9–6 cm, with 7–25 flowers, axis terete, covered with the same indumentum as the young branches; bracts early deciduous, with petioles 2–6 mm, blades 8–15 × 2–8 mm, elliptic, leafy, apex acute to acuminate, base rounded to acute, margin entire, indumentum similar to the leaves on both sides; bracteoles two, sessile, blades 3.8–5 × 1.2–3 mm, lanceolate to oblanceolate, apex acute to acuminate, base obtuse, margin entire, abaxial surface densely sericeous, trichomes 1.3–2.7 mm long, non glandular, erect, narrow at the base, adaxial surface glabrous. Flowers 4–6-merous, on pedicels 0.8–2 mm; hypanthium 4–7 × 1.2–4 mm, campanulate, densely sericeous, the whitish trichomes 0.5–2.2 mm long, non glandular, erect, narrow at the base; sepals 1–4 × 1–2.5 mm, persistent, triangular, apex acute-attenuate, margins ciliate, abaxially with the same indumentum as the hypanthium; petals 7–15 × 2–9 mm, obovate, purple, whitish at the base, apex obtuse, truncate or retuse; stamens 8–12, dimorphic, the antesepalous with filaments 6.2–10 mm long, glabrous or sparsely to moderately pilose, trichomes 0.2–1 mm long, glandular, curved, slightly enlarged at the base, connectives prolonged 1.7–3 mm below the thecae, glabrous, appendages 2, ventral, 0.5–1.1 mm long, glabrous, anthers 6–8.5 mm long, purple, the antepetalous with filaments 5–8 mm long, glabrous or sparse to moderately pilose, trichomes 0.1–0.8 mm long, glandular, curved, slightly enlarged at the base, connectives prolonged 0.5–2.3 mm below the thecae, glabrous, appendages 2, ventral, 0.3–1 mm long, glabrous, anthers 4–7.5 mm long, purple; ovary 3–5.5 × 2–3.2 mm, 5-locular, the apex densely sericeous, the trichomes 0.8–1.8 mm long, non glandular, erect, slightly enlarged at the base; style purple, 10–18 mm long, terete, curved at the apex, glabrous or sparse to moderately sericeous on the basal 1/3–2/3, the trichomes 0.5–2 mm long, non glandular, erect, slightly enlarged at the base. Capsules (with persistent sepals) 3.5–7 × 2–4.5 mm, longitudinally costate, greenish when immature, brown when mature. Seeds 0.7–1 × 0.5–0.8 mm, cochleate, testa papillose (see Figure 4 G-H).

Distribution and habitat:— Pleroma carajasense seems to occur exclusively on ironstone outcrops of the Serra dos Carajás range, in large populations. It was collected in several plateaux at the Serra Norte (N1, N2, N4, N5, N6 and N8 plateaux), Serra Sul (S11A, S11C, S11D), Serra Arqueada, Serra Leste, and Serra de Campos ( Figure 3 ). The plants have been found growing on shallow clefts on the “canga”, sometimes close to forest borders.

Phenology:—It was collected with flowers from February to May, September and November. Fruits were recorded from March to May and December.

Etymology:—The specific epithet refers to the “Serra dos Carajás”, where the species seems to be endemic.

Conservation status:— Pleroma carajasense should be classified as Endangered (EN), according to IUCN criteria B2ab(i,ii,iii): area of occupancy less than 500 km 2, severely fragmented populations, and continuing decline projected in extent of occurrence, area of occupancy, and quality of habitat. The estimated extent of occurrence calculated for this species is 6,587 km 2, the area of occupancy is 208 km 2, and the areas where it occurs are threatened by ongoing and future iron mining in the region.Although most known populations of the species were recorded inside a natural reserve (Carajás National Forest, or FLONA de Carajás, Figure 3 ), this category of reserve allows sustainable exploration of its natural resources (MMA 2014). Some populations of this species have already been removed by mining activities within the FLONA, such as the ones represented by older collections (e.g. A.S.L. Silva 1792, R.S. Secco 122 and M.G. Silva 2924). The areas outside the FLONA de Carajás where the species was recorded, such as Serra de Campos (São Felix do Xingu municipality) and Serra Arqueada (Ourilândia do Norte municipality), include expressive areas of canga and are potential candidates for becoming full protection natural reserves.

Affinities:—Most species of Pleroma have fruits with caducous sepals, an important diagnostic feature for the genus ( Michelangeli et al. 2013, Oliveira et al. 2014). The fruits of Pleroma carajasense have persistent sepals, representing a problem for its generic placement. Despite this we are certain of its position in Pleroma by the shrubby habit (not subshrubby as in most species in Chaetogastra ), branches and leaves coated by trichomes [not scales as in Tibouchina sensu stricto and Tibouchina sect. Lepidotae Cogniaux (1885: 372) ], and both stamen cycles with purple anthers (not yellow, as usually in one or both cycles in Chaetogastra and Tibouchina sect. Lepidotae ). Additionaly, stamen appendages are glabrous in Pleroma , and villose in Tibouchina sensu stricto ( Michelangeli et al. 2013, Meyer & Goldenberg 2016, Meyer et al. 2016). The main differences between P. carajasense and these morphologically related taxa [ Tibouchina caatingae , Pleroma fothergillii ( Candolle 1828: 108) Triana (1871: 42) and T. lithophila Wurdack (1981: 305) ] are summarized in Table 1.

Some floristic checklists focusing the cangas of the Serra dos Carajás ( Silva 1991, Silva et al. 1996) listed Tibouchina aspera Aublet (1775: 446) and Tibouchina spruceana Cogniaux (1885: 376) . Several herbarium specimens cited here as paratypes were incorrectly identified as T. aspera or T. spruceana . Both differ from P. carajasense by the scales covering the branches, petioles, abaxial surface of the leaves, hypanthium and sepals (vs. trichomes in P. carajasense ) and by the persistent bracts (vs. early deciduous in P. carajasense ). These characters also define

Tibouchina sensu stricto, which means that these two species should remain in this genus after the generic realignments indicated by Michelangeli et al. (2013).

Paratypes:― BRAZIL. Pará: Canaã dos Carajás, Serra Sul, 6 December 2007, P. L. Viana 3351 ( BHCB!) ; 10 September 2008, L. V. C. Silva 520 ( BHCB!) ; Serra Sul, 17 March 2009, P. L. Viana 4088 ( BHCB!) ; 5 May 2010, R.D. Ribeiro 1487 ( RB!) ; 22 May 2010, L. V. C. Costa 911 ( BHCB!) ; 24 April 2012, A. J. Arruda 1077 ( BHCB!) ; 13 May 2014, R. S. Santos 214 ( MG!) ; 22 March 2015, L. C. Lobato 4391 ( MG!) ; 12 April 2015, L. M. M. Carreira 3351 ( MG!) ; 12 April 2015, L. M. M. Carreira 3352 ( MG!) ; 20 April 2015, fl, L. M. M. Carreira 3447 ( MG!) ; 2 December 2015, R. Goldenberg 2237 ( MG!) ; 23 March 2016, K. C. J. Rocha 71 ( MG!) ; 4 May 2016, L. V. Vasconcelos 769 ( MG!). Curionópolis, Serra Leste, 19 May 2016, A. L. Hiura 101 ( MG!). Marabá, Serra Norte, 20 April 1970, P. B. Cavalcante 2674 ( MG!, NY!) ; 22 April 1970, M. G. da Silva 2670 ( MG!, NY!) ; 29 March 1977, M. G. da Silva 2924 ( MG!, MO!, NY!) ; 12 May 1982, R. S. Secco 122 ( FLAS!, MG!, MO!, NY!) ; 14 March 1984, A. S. L. da Silva 1792 ( MG!). Ourilândia, Serra Arqueada, 3 May 2016, P. L. Viana 6181 ( MG!). Parauapebas, Serra Norte, 12 May 1982, C. R. Sperling 5606 ( MG!, NY!) ; 24 February 1987, C. M. Araújo 28 ( IAN!, RB!) ; 7 March 2010, L. C. B. Lobato 3831 ( MG!) ; 15 April 2010, L. C. B. Lobato 3896 ( MG!) ; 13 March 2011, R. C. V. Martins-da-Silva 45 ( IAN!) ; 19 April 2012, A. J. Arruda 910 ( BHCB!, MG!) ; 30 Novembro 2013, L. C. B. Lobato 4282 ( MG!) ; 18 March 2015, L. C. Lobato 4347 ( MG!) ; 24 March 2015, A. E. S. Rocha 1820 ( MG!) ; 26 March 2015, P. L. Viana 5574 ( MG!) ; 26 March 2015, P. L. Viana , 5575 ( MG!) ; 26 March 2015, P. L. Viana 5582 ( MG!) ; 27 April 2015, N. F. O. Mota 2927 ( MG!) ; 18 May 2016, A. L. Hiura 79 ( MG!). São Félix do Xingu, Serra de Campos , 1 May 2016, P. L. Viana 6118 ( MG!) .

Figures

FIGURE 1. Images based on the holotype (A, C, E, F, G, H, I and K) and paratypes (B, D, J and L) of Pleroma carajasense. A. Branch. B, C, D. Variation in size and shape of the leaves, with corresponding variation of indumentum on both leaf surfaces (adaxial surface: B1, C1, D1, and abaxial surface B2, C2, C2). E. Indumentum on the branch. F. Variation in size and shape of the bracteoles (abaxial surface). G. Flower bud. G1. Detail of the indumentum on the hypanthium, abaxial surface. H. Hypanthium, adaxial surface. I. Stamens with glabrous filaments. I1. Appendages of the antesepalous stamens. I2. Appendages on the antepetalous stamens. I3. Filaments of the antepetalous stamens. J. Stamens with sparsely pilose filaments. J1. Appendages of the antesepalous stamens. J2. Appendages of the antepetalous stamens. J3. Filaments of the antepetalous stamens. K. Gynoecium. K1. Stigma. K2. Detail of the ovary apex. L. Fruit. (A, C, E, F, G, H, I and K: Rocha 88; B and J: Rocha 71; D: Mota. 2927; L: Goldenberg 2237).

FIGURE 2. Living plant photos of Pleroma carajasense. A-C. Habitat and habit of flowering plants. D-E. Inflorescences. F. Flower with a pilose style base. G. Flower with a glabrous style. H. Fruiting plant. I. Mature fruits with persistent sepals. A-G by Pedro Viana, H-I by Renato Goldenberg.

FIGURE 3. Distribution map of Pleroma carajasense. Records indicated by triangles.

FIGURE 4. SEM images of trichomes and seeds of Pleroma carajasense. A-C. Trichomes on the leaf adaxial surface. D-F. Trichomes on the leaf abaxial surface. G. Seed, lateral view. H. Seed, raphal view. (A, E: Lobato 3896; B, D, F: Rocha 71; C: Silva1792; G, H: Goldenberg 2237).