Tibouchina longisquamata F.S.Mey., 2023

Meyer, Fabrício Schmitz, Diniz, Danielle De Oliveira, Ziemmer, Juliana Klostermann & Goldenberg, Renato, 2023, Two new species of Tibouchina (Melastomataceae) from the Brazilian Cerrado, Phytotaxa 599 (1), pp. 51-64 : 58-62

Tibouchina longisquamata F.S.Mey. sp. nov. ( Figures 6 , 7A , 8 ).

Type:— BRASIL, Tocantins, Almas, Estaç „o Ecológica Geral do Tocantins, Serra da Muriçoca , 11º13’13”S, 46º53’17”W, 14 January 2020, G. Martinelli, E. Fernandez, G.B. Cosac & D.L. Estevam 21535 (holotype: UPCB0052654!; isotypes: HUFU00079992 online image!, RB01441065 online image!) .

Diagnosis:— Tibouchina longisquamata differs from T. llanorum Wurdack (in Maguire & Wurdack 1964: 142) by the subcylindrical branches (vs. 4-6 angulose in T. llanorum ), narrower leaves, 2.9–5.1 cm wide (vs. 4–6 cm wide), with the adaxial surface moderately strigose, exclusively covered with trichomes (vs. covered with flattened and proximally attached scales; sensu Wurdack 1986; Figure 7C ).

Description:—Shrubs 1–1.5 m tall; younger and older branches subcylindrical; younger branches and inflorescence axes densely covered with whitish scales 0.9–2.2 mm long, oblanceolate, appressed, ciliate along the entire margin and at the apex (cilia up to 0.1mm long), the same scales on the nodes, somewhat longer, 2.5–4 mm long, older branches decorticant. Leaves with petioles 4.3–9 mm long, densely covered with the same scales as the nodes and inflorescence axes, somewhat shorter, 2.8–3.3 mm long; blade 5.5–10.5 × 2.9–5.1 cm, ovate, flat, patent, apex acute, base obtuse to slightly cordate, acrodromous veins 5(–7), the first and second lateral pairs confluent near the base, submarginal pair tenuous, adaxial surface lacking scales but moderately strigose, whitish trichomes 0.9–1.2 mm long, unbranched, appressed, eglandular, the base swollen, immersed in the leaf tissue, not forked to 1-3 forked, abaxial surface densely to moderately covered with whitish scales 0.6–1.2 mm long, lanceolate, appressed, fimbriate along the entire margin and at the apex (the fimbria up to 0.5 mm long); the fimbriate margin simulating a tomentose indumentum; Figure 8D ), primary and secondary veins with the same scales as on the younger branches and inflorescence axes, somewhat longer, 1.5–3 mm long, leaf margin with the same scales as on the primary and secondary veins, somewhat longer, 1.4–3.5 mm long. Inflorescences in short cymes, 3.5–5 × 3.2–5 cm, with 13–21 lax flowers; bracts 2, foliaceous, petiole 3.6–5 mm long, blade 3.4–5.4 × 1.4–2.1 cm, ovate, flat, patent, apex acute, base obtuse to slightly cordate, late deciduous, acrodromous veins 5, the first and second lateral pairs confluent near the base, the same scales and trichomes as on the leaves on both surfaces and margins; bracteoles 2, sessile, blade 2.4–4.1 × 1.6–2.3 mm, deltoid, apex acute, base obtuse, slightly concave, early deciduous, adaxial surface glabrous, abaxial surface densely covered with whitish scales 0.8–1.8 mm long (the longer ones on its central portion), lanceolate, appressed, ciliate along the entire margin and at the apex (cilia up to 0.2 mm long). Flowers 5–merous, pedicels 1.6–2.4 mm long; hypanthium 7.8–8.3 × 6–6.4 mm, campanulate, abaxial surface densely covered with whitish scales 1.7–2.2 mm long, lanceolate, inclined (with an angle of 45° in relation to the surface) or patent, ciliate along the entire margin and at the apex (cilia up to 0.2 mm long); between the sepals sparsely covered with the same scales as the abaxial surface of the hypanthium, somewhat longer, 2.2–2.8 mm long; sepals 3.3–4.3 × 2.4–2.7 mm, triangular, apex acute, adaxial surface glabrous, abaxial surface covered with the same scales as the abaxial surface of the hypanthium, somewhat shorter, 0.8–1.8 mm long (the longer on its central portion), margin moderately covered with the same scales as the abaxial surface of the sepals, somewhat shorter, 0.3–0.9 mm long; petals purple, 18.7–19.3 × 17.8–19 mm, obovate, apex truncate or obtuse, margin moderately pilose, whitish trichomes 0.2–0.4 mm long, unbranched, erect, glandular, the base slender, not immersed in the leaf tissue; stamens 10, slightly dimorphic in size, the antesepalous with filaments 11.9–12 mm long, sparsely to moderately villose on its middle portion, whitish trichomes 1–2.4 mm long, unbranched, twisted, glandular, the base slender, not immersed in the leaf tissue, pedoconnective 2.6–2.8 mm prolonged below the thecae, glabrous, ventral appendages bilobed, apex obtuse, ca. 0.5 mm long, moderately villose, whitish trichomes 1.2–2.6 mm long, unbranched, twisted, glandular, the base slender, not immersed in the leaf tissue, thecae 10.5–11 × ca. 0.8 mm, falcate, apex attenuate, the antepetalous with filaments 10.1–11.2 mm long, with trichomes similar to the antesepalous, pedoconnective ca. 1 mm prolonged below the thecae, glabrous, ventral appendages bilobed, apex obtuse, ca. 0.4 mm long, with trichomes similar to the antesepalous, thecae 8.4–8.8 × ca. 0.7 mm, falcate, apex attenuate; ovary superior, 5–locular, ca. 6.1 × 3.9 mm, apex densely sericeous, whitish trichomes 0.7–2 mm long, unbranched, appressed, eglandular, the base slender, style ca. 19.2 mm, filiform, apex curved, glabrous, stigma truncate. Fruits and seeds not seen.

Paratypes:— BRAZIL. Tocantins, Municipality of Almas, Estaç „o Ecológica Serra Geral do Tocantins, 14 January 2020, G. Martinelli et al. 21511 (RB01441041, UPCB0053111 !) .

Distribution and habitat:—This species grows in “Veredas” (= palm swamps), which is one of the phytophysiognomies of the Cerrado biome, in flat and humid areas. The “Veredas” are rich in herbaceous, shrubby, and arboreal, hygrophilous species, marked by the presence of the palm Mauritia flexuosa Linnaeus (1782: 454) , popularly known as “buriti” ( Nunes et al. 2022). The species also occurs in Cerrado vegetation associated with rocky outcrops. Tibouchina longisquamata is known from only two samples, both from Serra da Muriçoca, within the limits of the “Estaç„o Ecológica Geral do Tocantins ” ( Figure 5 ).

Phenology:—The only two samples of the species indicates that it flowers in January; we have not found collections with fruits until the moment.

Conservation status:—According to our assessments, Tibouchina longisquamata should be considered as in the Data Deficient (IUCN 2022). It is very likely that it is an endangered species, especially because of its apparent restricted distribution. There are few collection efforts in the places where T. longisquamata occurs, and it is not possible to accurately estimate the distribution and the conservation status for the species.

Etymology:—The epithet “ longisquamata ” refers to the large scales that cover the hypanthium of the species.

Notes:— Tibouchina longisquamata is morphologically similar to Tibouchina llanorum by the oval, slightly discolorous leaves, with a conspicuous petiole (4.3–9 mm in T. longisquamata , and 6.5–8.7 mm in T. llanorum ), and the hypanthium covered with larger and lanceolate scales, these patent or inclined. In addition to the characters indicated in the diagnosis, T. longisquamata also differs from T. llanorum by the surface of the hypanthium densely covered with scales (vs. sparsely covered with scales, or “loose hypanthial scales” according to Maguire & Wurdack 1964), shorter inflorescences 3.5–5 cm long (vs. inflorescences 4–20 cm long), with 13–21 flowers (vs. 49–63 flowers), and these lax (vs. congested). There is no overlap in their distributions: Tibouchina longisquamata occurs in Brazil, only in the state of Tocantins, in Cerrado, while T. llanorum occurs in Colombia, Venezuela and Brazil; in Brazil, it occurs in the states of Amazonas and Pará, in Amazonian savanna.

Tibouchina exasperata ( Naudin 1850: 154) Cogniaux (1885: 377) is also morphologically related to T. longisquamata : both have oval leaves, with conspicuous, but short petioles (4.3–9 mm in T. longisquamata , and 2–3 mm long in T. exasperata ), blades with 5 veins (more rarely up to 7 veins in T. longisquamata ), the hypanthium covered with patent or inclined scales, these lanceolate, and glabrous style. Tibouchina longisquamata differs from T. exasperata by the larger leaves 5.5–10.5 × 2.9–5.1 cm (vs. 3–5 × 2–2.5 cm in T. exasperata ), with the adaxial surface covered with trichomes (vs. covered with flattened and proximally attached scales; sensu Wurdack 1986; Figure 7B ). While both are endemic to Brazil, T. longisquamata occurs in the state of Tocantins, and T. exasperata occurs in the state of Goiás (Guimar„es 2022). Tibouchina longisquamata seems to be restricted to Estaç„o Ecológica Serra Geral do Tocantins, and T. exasperata exclusive to Serra dos Pirineus ( Cogniaux 1885).

Finally, T. longisquamata shares some morphological features with Tibouchina araguaiensis Guimar „es (2014: 44): the shrubby habit (plants 1– 1.5 m tall in T. longisquamata , and up to 3 m tall in T. araguaiensis ), ovate leaves with conspicuous petioles (4.3–9 mm in T. longisquamata , and 7–9 mm in T. araguaiensis ), flowers arranged in terminal inflorescences, and stamens with villose pedoconnective appendages. It differs from T. araguaiensis by the leaves with 5(–7) veins (vs. 3 veins in T. araguaiensis ), and by the hypanthium covered with longer scales, 1.7–2.2 mm long (vs. scales ca. 0.5 mm long).

Figures

FIGURE 5. Distribution map of Tibouchina falcifolia (orange triangles) and Tibouchina longisquamata (yellow triangles).Abbreviations: DF: Distrito Federal; GO: Goiás; TO: Tocantins; MA: Maranh„o; PI: Piauí; BA: Bahia; MG: Minas Gerais.

FIGURE 6. Plate with photos from the holotype of Tibouchina longisquamata. A. Branch. B. Adaxial surface of the leaf. C. Abaxial surface of the leaf. D. Bracteole, abaxial surface. E. Floral bud. F. Detail of the scales on the abaxial surface of the hypanthium. G. Antepetalous stamen. H. Antesepalous stamen. I. Gynoecium. [All images from Martinelli et al. 21535 at UPCB].

FIGURE 7. Indumentum on the adaxial surface of the leaves of Tibouchina longisquamata and putative related species. A. Tibouchina longisquamata. B. Tibouchina exasperata. C. Tibouchina llanorum (A from Martinelli et al. 21535 at UPCB; B from Meyer 2055 at UPCB; C from Monteiro & Ramos 76-838 at UPCB).

FIGURE 8. Scanning Electron Microscopy of vegetative and reproductive organs of T. longisquamata. A. Scales on young branches. B. Trichomes on the adaxial surface of the leaves. C. Scales on the abaxial surface of the leaves. D. Detail of the scale on the abaxial surface of the leaf. E. Scales on the primary veins of the leaves on the abaxial surface. F. Scales on the abaxial surface of the hypanthium. G. Detail of the base and margin of the scales from the hypanthium. (All images from Martinelli et al. 21535 at UPCB).