Waltheria glabribracteata T.S. Coutinho & M. Alves, 2020

Coutinho, Thales Silva & Alves, Marccus, 2020, Waltheria glabribracteata (Byttnerioideae, Malvaceae), a new species with elongate-plumose stigmas from South America, Phytotaxa 430 (4), pp. 294-299 : 295-298

Waltheria glabribracteata T.S. Coutinho & M. Alves , sp. nov. ( Figure 1 ).

Type:— BRAZIL. Mato Grosso: Vila Bela da Santíssima Trindade, Serra de Ricardo Franco, topo da Cachoeira do Jatobá, 650 m elev., 14º55’06’’S, 60º04’36’’W, 21 March 2014, M. F. Simon, G. Pereira-Silva, J. L. Barros, M. Mendonza & T. S. Reis 2232 (holotype: CEN!, isotype: RB!, NY [digital image]!).

Diagnosis: — Waltheria glabribracteata is morphologically close to Waltheria rotundifolia Shrank (1828: 65) , differing by its discolorous leaf blades (vs. concolorous), glabrous adaxial surface of the bracts (vs. pilose), lanceolate to ovate bracts (vs. linear), calyx 6–7 mm long (vs. 4–5 mm long), oblanceolate and glabrous corolla lobes (vs. spatulate and sericeous), and elongate-plumose stigmas in longistylous flowers (vs. fan-plumose).

Description: —Shrubs 0.80–1.80 m tall. Branches terete, strigose, the trichomes stellate and sessile; trunk not resinous, not lenticellate. Stipules ca. 4 × 0.7 mm, lanceolate, adaxial surface pubescent, abaxially scabrous, the apex acute, the margins ciliate. Leaves simple, alternate, spirally arranged; petioles 0.7–1 × 0.26–0.36 cm, compressed, scabrous, the trichomes similar to those on the branches; leaf blades 5.3–8 × 4–7.5 cm, circular to oblate, discolorous, chartaceous to subcoriaceous, strigose, the trichomes stellate and sessile; venation actinodromous, 7–8 pairs of secondary veins, 2 basal, tertiary veins reticulate, the base cordate, the apex rounded to truncate, the margins irregularly and finely serrate, teeth 2.2–3 × 1–1.5 mm. Inflorescences cymose, axillary, the peduncle 5–20 mm long, strigose; bracts 4, 3–3.5 × 0.9–2.2 mm, lanceolate to ovate, the apex acute to acuminate, adaxial surface glabrous, abaxial sericeous, longitudinally nerved. Flowers potentially distylous, ca. 9 mm long, sessile, in pairs, surrounded by bracts. Calyx 5-merous, gamosepalous, 6–7 × 3.2–3.5 mm, 10-ribbed, externally sericeous, trichomes stellate, internally glabrous, pubescent on the free lobes, trichomes simple, lobes free, 2–3.2 × 1.1–1.7 mm, the apex acute to acuminate; veins not reaching the margins; nectary ca. 0.3 mm long, on the base of the internal surface. Corolla 5-merous, gamopetalous, yellow, tube ca. 1.8–2 mm long, claw 1–1.4 mm long, limb ca. 6–7.5 × 2.2–2.5 mm, oblanceolate, glabrous, the apex rounded. Longistylous form: stamens 3.8–5.5 mm long, staminal tube adnate to corolla, ca. 3.5 mm long, glabrous, free filaments 0.5–1.1 mm long, papillate, anthers dithecous, 1.2–1.3 mm long, dehiscence longitudinal; pistil ca. 6–7 mm long, the ovary 1.5 × 0.8 mm, sericeous, the style 3.2 mm long, tortuose basally, pubescent, the stigma 1.5–2.1 × 0.8 mm, penicillate, elongate-plumose. Brevistylous form: not observed. Capsule ca. 4 × 3 mm, obovoid, membranaceous on the lower third, chartaceous on the upper third, the dehiscence loculicidal, sericeous, the trichomes concentrated apically, long-simple and short-stellate, the apex truncate; seed 1, ca. 2.8 × 1.7 mm, obovoid, glabrous, black, brownish basally, crenulate at the base.

Etymology: —The specific epithet refers to the glabrous adaxial surface of the bracts, a unique character among Waltheria species.

Distribution and Habit: — Waltheria glabribracteata is known from a few collections in Brazil (Mato Grosso state, in the municipally of Vila Bela da Santíssima Trindade) and Bolivia (Santa Cruz department, province of José Miguel de Velasco) ( Figure 2 ). In both countries, W. glabribracteata is found in protected areas within the Serra Ricardo Franco State Park ( Brazil) and Noel Kempff Mercado National Park ( Bolivia), which are on the border of both countries.

The species occurs in transitional vegetation among Amazonian forest, Cerrado and Pantanal ( Killeen 1998, IBGE 2004), at 600 to 900 m elevation.

In Serra Ricardo Franco State Park, this is the first record of the genus Waltheria (speciesLink 2019), whereas in Noel Kemp National Park, W. glabribracteata occurs sympatrically with W. indica Linnaeus (1753: 673) and Waltheria sp. , erroneously identified as W. polyantha Schumann (1886: 60) , however, this latter species is restricted to Minas Gerais state in Brazil.

Phenology: —Collected with flowers in March to May and August, fruits in May.

Conservation status: — Waltheria glabribracteata is known only from a few collections in the two localities previously indicated. The State Park Serra de Ricardo Franco is officially a fully protected area comprising ca. 158,000 ha. However, the locality is also the target of deforestation for cattle breeding, as well as exploitation of its natural resources. These anthropogenic actions may cause a decrease in population size in the short term, promoting ultimately the total elimination of these individuals. Because of this, W. glabribracteata should be classified as Critically Threatened (CR), B1b (i, ii, iii, iv), C2a (i), according to GeoCat data and IUCN Criteria 2012 ( IUCN 2019).

Additional specimens examined (Paratypes): — BOLIVIA. Santa Cruz, José Miguel de Velasco , 21 April 1993, T. J. Killeen 5413 ( CTES!) . BRAZIL. Mato Grosso, Vila Bela da Santíssima Trindade, Córrego da Cascata, 18 August 1997, G. Hatschbach , A. Schinini & E. Barbosa 66985 ( MBM!) ; topo da Cachoeira do Jatobá, 14º55’06”S, 60º04’26”W, 17 May 2013, J. E. Q. Faria , M. R. V. Zanatta & D. Villarroel 3484 ( RB!, UB!) ; Serra Ricardo Franco , 15ºS, 60ºW, 22 March 1978, P. G. Windisch 1739 ( RB!, UEC!) ; ibidem, 25 May 1978, P. G. Windisch 1939 ( CTES!, RB!, UEC!) .

Discussion: — Waltheria glabribracteata can be recognized mainly by the fact that it is the only species of the genus having bracts with a glabrous adaxial surface ( Fig. 1 d-e). In the taxonomic revision of Waltheria, Saunders (1995a , unpublished) cites the adaxial surface of the bracts of Waltheria collina Schumann (1828: 63) as “essentially glabrous but with 1–2 branched trichomes… and sessile glandular trichomes”, so in this species cannot be considered glabrous, but sparsely pilose according to our own data. Regarding its morphology, the new species shares with Waltheria rotundifolia the stellate and sessile trichomes, the leaf blade shape, with finely serrate margins, but differs by its pedunculate inflorescences (vs. sessile to subsessile in W. rotundifolia ), lanceolate to ovate bracts (vs. linear), glabrous adaxial surface of the bracts (vs. pilose), glabrous corolla lobe apex (vs. densely ciliate) and elongate-plumose stigma (vs. fan-plumose) ( Table 1). Comparing with Waltheria ackermanniana Schumann (1886: 61) , W. glabribracteata is similar in the strigose indument, pedunculate inflorescences and circular leaf blades (in some individuals), however the latter species can present a broad variation of leaf blade shape, varying from elliptical, widely elliptical, circular to ovate ( Table 1). However, W. glabribracteata lacks glandular trichomes (vs. present in W. ackermanniana ), glabrous adaxial surface of the bracts (vs. sparsely pilose), bracts not exceeding 3.5 mm long (vs. reaching 12.5 mm long) and elongate-plumose stigma (vs. fan-plumose). Other characters are shown in Table 1.

Concerning geographic distribution, Waltheria glabribracteata is allopatric to W. rotundifolia and W. ackermanniana . While Waltheria grabribracteata is restricted to Mato Grosso state ( Brazil) and Santa Cruz department ( Bolivia), W. rotundifolia occurs in Mexico and Brazil (restricted to the Northeast region - Piauí, Ceará, Rio Grande do Norte, Paraíba, Pernambuco, Alagoas, Sergipe and Bahia states), while W. ackermanniana was previously restricted to the states of the Bahia, Minas Gerais and Rio de Janeiro, and here in this study it is also recorded in Pernambuco state (Coutinho et al. 335 and Coutinho et al. 344, UFP herbarium).

According to Silva-Coutinho et al. (2019), seven species of the Waltheria occur in the Mato Grosso state. Waltheria glabribracteata differs of them specially by circular to oblate leaf blade and absence of trichomes on the adaxial surface of the bracts.

Figures

FIGURE 1. Waltheria glabribracteata. A. Flowering branch. B. Detail of the branch and indumenta. C.Adaxial surface of the leaf blade. D. Bracts with two flowers removed. E. Adaxial surface of the bract. F. Flower. G. Internal view of the calyx. H. Free lobe of the calyx with trichomes removed. I. Corolla lobe. J. Staminal tube and stigma elongate-plumose. K. Internal view of the staminal tube. L. Pistil. M. Capsule. N. Seed. (A–N: M.F. Simon et al. 2232).

FIGURE 2. Geographic distribution map of Waltheria glabribracteata.