Stigmaphyllon caatingicola R.F.Almeida & Amorim, 2014

Almeida, Rafael Felipe De & Amorim, André Márcio, 2014, Stigmaphyllon caatingicola (Malpighiaceae), a new species from Seasonally Dry Tropical Forests in Brazil, Phytotaxa 174 (2), pp. 82-88 : 83-86

Stigmaphyllon caatingicola R.F.Almeida & Amorim , sp. nov. ( Figs. 1 , 2 , 3 )

Type:— BRAZIL. Bahia: Rio de Contas, Distrito de Arapiranga, Estrada para povoado Casa da Telha , 13˚34’24”S, 41˚43’13”W, 23 July 2013, fl., R.F. Almeida 577, M. Alves, L. Moura & E. Chagas (holotype: HUEFS!; isotypes: CEPEC!, MICH!, P!, RB!, SP!) .

This species is morphologically similar to Stigmaphyllon urenifolium , but it is distinguished by showing deciduous leaves when flowering, lamina membranaceous, entire to apically trilobed, abaxially tomentose, with hairs deciduous in patches, sepals with darkish hairs, one latero-anterior petal with reddish macula, styles glabrous, posterior styles ca. 4.5–5.0 mm, stigma foliolate, samaroid mericarps densely sericeous, with dorsal wing horizontally orientated.

Liana, branches longitudinally rugose, with a corky bark, prominent lenticels, glabrous; stipules ca. 2 mm long., triangular, glabrous, deciduous when mature, borne on a prominent ridge at base of leaves. Leaves opposite to subopposite, deciduous when flowering. Laminas 3.3–5.5 × 4.3–7.5 cm, cordiform to apically lobed, membranaceous, dark grey on both sides when dry, apex of lobes obtuse to mucronate, with filiform glands, margin with sessile glands sparse, base lobed, adaxial surface sparsely tomentose when young, soon glabrate, abaxial surface densely tomentose, hairs whitish, twisted, deciduous in patches, actinodromous venation, veins prominent abaxially; petioles 1.3–2.8 cm, canaliculated, densely sericeous, hairs whitish, scamiform, apex with pair of discoid glands abaxially, enlarged at base. Inflorescence in umbels, 9–12 flowered, disposed on a thyrse of dichasia, each dichasia subtended by a pair of soon deciduous reduced leaves, 4.5–5 mm long, sessile, with a pair of conspicuous glands at base, apex with filiform glands, densely tomentose, with scamiform hairs; inflorescence axis 3.0– 8.5 cm long, striated, densely sericeous, with whitish hairs, deciduous in patches when mature; peduncles 5–10 mm long, sericeous, hairs darkish; pedicels 6–10 mm long, sericeous, hairs darkish; bracts 2.0–2.5 × ca. 1.5 mm, ovate, sericeous abaxially; bracteoles 1.5–2.0 × 1.0– 1.5 mm, ovate, sericeous abaxially. Floral bud reddish; sepals ca. 3.0 × 4.0 mm, ovate, sericeous, hairs darkish, apex rounded; elaiophores 10, whitish to light yellow, ca. 1.5 × 2.0 mm, oblong; petals yellow, one latero-anterior petal with reddish macula, margin fimbriate, fimbrie up to 0.5 mm long, latero-anterior petals orbicular, base obtuse, 10–11 × ca. 15 mm, claw ca. 3.0 × 1.0 mm; latero-posterior petals orbicular, base truncate, 10–12 × 11–13 mm, claw ca. 2.0 × 1.0 mm; posterior petal orbicular, base acute, ca. 12 × 12 mm, claw ca. 5.0 × 1.5 mm. Stamens connate at base, heteromorphic, those opposite the posterior-lateral petals with thicker filaments, others with tapered filaments, connectives glandulose, anthers glabrous; stamen opposite the anterior sepal with filament ca. 4.0 × 0.5 mm, anther ca. 1.0 × 1.0 mm; stamens opposite anterior-lateral petals with filaments ca 3.0 × 0.5 mm, anthers ca. 1.5 × 1.0 mm; stamens opposite anterior-lateral sepals with filaments ca. 5.0 × 0.5 mm, anthers ca. 1.0 × 1.5 mm, locules reduced, unequal; stamens opposite posterior-lateral petals with filament 5.0 × 1.0 mm, anthers 2.0 × 2.0 mm; stamens opposite the posterior-lateral sepals with filaments ca. 3.0 × 0.5 mm, anthers ca. 1.0 × 0.75 mm, with locules reduced, unequal; stamen opposite the posterior petal with filament ca. 2.5 × 0.5 mm, anther ca. 1.0 × 1.0 mm. Ovary ca. 1.5 × 1.5 mm, globose, sericeous; styles 4.5–5.0 × ca. 0.5 mm, flattened, glabrous, bearing reduced apical folioles, anterior style straight, posterior style lyrate; foliole of anterior style ca. 3.0 × 1.5 mm, two-sided, umbrella-like; foliole of posterior styles ca. 2.5 × 1.75 mm, one-sided; stigmas lateral, pointing towards the posterior petal. Schizocarp splitting into 3 samaroid mericarps, dorsal wing 2.2–2.5 × 0.8–1.0 cm, horizontally orientated, densely sericeous, hairs deciduous in patches; nut ca. 5.0–8.0 × 4.0–6.0 mm, prominent, with two lateral ridges, densely sericeous, hairs deciduous in patches; areole 6.0–8.0 × 5.0–6.0 mm.

Additional specimens examined (paratypes):— BRAZIL. Bahia: Caturama, entre Caieiras e Tambori , 13˚15’16’’S 42˚12’32’’W, 04 July 2007, fl., A.A. Conceição et al. 2382 (HUEFS). Paramirim, Fazenda Curral Velho, 13˚23’05’’S 42˚18’W, 18 April 2001, fl., T.R. Silva 75, A.M. Giulietti & C. Correia (CEPEC, HUEFS). Rio de Contas , Estrada para Jussiape, perto de um riacho com mata seca, 13˚32’S 41˚52’W, 07 September 2003, fl. fr., R.M. Harley 54684 & A.M. Giulietti (CEPEC, HUEFS). Rio de Contas , Estrada para Jussiape, 26 July 1999, fl., A.M. Giulietti et al. 1508 (HUEFS) .

Distribution, habitat and phenology:— This species is known only from Seasonally Dry Tropical Forests within Caatinga vegetation in the southern portion of Chapada Diamantina , Bahia State, Brazil. The region surrounding the municipality of Rio de Contas is a known center of diversity within the Chapada Diamantina and holds large numbers of endemic flowering plants ( Harley 1995; Rapini et al. 2008). Flowering from April to September. Fruiting from August to September.

Conservation status: —The first collection of Stigmaphyllon caatingicola was recorded two years after the publication of a taxonomic revision of the Neotropical species of Stigmaphyllon by Anderson (1997). This species is represented by only a few records restricted to three municipalities within approximately 90 km of each other, all of them with anthropomorphically modified Caatinga vegetation. Thus, according to IUCN Red List Categories and Criteria (2012), this species should be regarded as Critically Endangered (categories B1a and B1b), due to its range of distribution being less than 100 km 2 and continually declining habitat quality.

Etymology: —The specific epithet refers to its restricted distribution within Caatinga vegetation.

Discussion: — Stigmaphyllon caatingicola is a distinctive leafless species when flowering, a character only known for Stigmaphyllon nudiflorum Diels (1937: 101) from Ecuador, and few other Malpighiaceae species as Diplopterys lutea (Griseb.) W.R.Anderson & C.C.Davis (2006: 10) , and Heteropterys dumetorum (Griseb.) Nied. (1928: 336) . Its leaves are membranaceous, densely tomentose abaxially when young, and seem to grow right after fruit maturing. Stigmaphyllon caatingicola can be mistakenly misidentified as a Cerrado species, Stigmaphyllon urenifolium A.Juss. (1833: 52) , which also occurs within State of Bahia, and States of Minas Gerais and Mato Grosso do Sul. These species differ from each other mostly on leaf, gynoecium and fruit morphology ( Table 1).

Figures

FIGURE 1. Stigmaphyllon caatingicola: A. adaxial leaf surface, B. detail of inflorescence, C. detail of flower, D. samaroid mericarp from S. urenifolium (left) and S. caatingicola (right, scale 1 cm), E. detail of stem surface, F. habitat within SDTF in anthropomorphically modified Caatinga (white arrow shows a tree with S. caatingicola climbing) (R.F.Almeida 577, holotype).

FIGURE 2. Stigmaphyllon caatingicola: A. detail of the abaxial surface of entire leaves, B. detail of the adaxial surface of lobed leaves, C. flowering branches, D. detail of the inflorescence, E. detail of a sepal with oil glands, F. lateral and posterior petals, G. androecium with stamens connate at base and enlarged (androecium opened at the stamen opposite to the anterior sepal), H. detail of the gynoecium, I. detail of the samaroid mericarp (based on R.F.Almeida 577).

FIGURE 3. Map of the distribution of Stigmaphyllon caatingicola (circles) and Stigmaphyllon urenifolium (squares).