Simaba tocantina Devecchi & Pirani, 2015

Devecchi, Marcelo Fernando & Pirani, José Rubens, 2015, A new species of Simaba sect. Grandiflorae (Simaroubaceae) from Jalapão region, Tocantins, Brazil, Phytotaxa 227 (2), pp. 167-174 : 168-171

Simaba tocantina Devecchi & Pirani , sp. nov. ( Figs. 1 , 2 )

Diagnosis: A Simaba salubris , cui affinis, foliorum rachi laevi (striata), inflorescentia laevis (striata) ramis lateralibus elongatis (brevibus) provisa, floribus 2.1–2.5 cm longis (3.1–3.5 cm), gynophoro 2,4– 2.9 mm longo (1.6–2 mm) otpime distincta.

Type: — BRAZIL. TOCANTINS: Mateiros, Parque Estadual do Jalapão, Estrada para Boa Esperança, arredores do Morro do Porco, cerrado, campo sujo, 10°19’55”S, 46°37’31”W, fl. fr., 20 September 2014, G.M. Antar et al. 528 (holotype SPF!, isotype RB!).

Shrubs, 0.3–0.8 m tall, with a thickened underground system; aerial branches 1–3, glabrous or finely pubescent; bark glossy, breaking into irregular plates. Leaves imparipinnate or sometimes paripinnate, clustered near apex; petiole cylindrical, 4.3–8.2(–10.5) cm long, puberulent to pubescent, intumesced at base; rachis cylindrical 12–25 cm long, smooth, pubescent along the adaxial surface, with short, hooked trichomes; petiolules 1–2 mm long, intumescent and wrinkled; leaflets (13–)15–17(–21), opposite or subopposite; lamina of the terminal and lateral-distal leaflets 4.5–7.3 × 1.3–2.4 cm, obovate to elliptic-obovate in the terminal leaflet, oblong-obovate to narrowly elliptic in the lateral ones, apex acute, base cuneate, coriaceous to subcoriaceous, margin not revolute, discolor, adaxial surface dark green and glossy, abaxial surface light green and dull, glabrous except along the midvein in the upper side, with short, hooked trichomes; venation brochidodromous; midvein prominent on the abaxial surface, slightly to sharply sulcate on the adaxial surface, secondary and tertiary veins prominulous or slightly sulcate on both sides; superficial glands laminar present at the basal half of the lamina on abaxial surface, sometimes also on adaxial surface, apical gland generally present at the apex, not conspicuously developed. Inflorescence a terminal thyrse, the main axis 45–60 cm long, lateral axes poorly developed, up to 10 cm long, puberulent, provided with scattered glandular trichomes; bracts 1.5–2.5 × 1.6–2.6 mm, spathulate to spheroid, reddish-green, puberulent, intumesced with a small hole in the upper side. Flowers: pedicel 2.4–3.2 mm long, pubescent, with glandular trichomes; calyx green turning reddish towards the apex, externally pubescent, internally glabrous, length ratio between tube and lobes 1:1, sepals 5, apex obtuse or acute; petals 5, slightly imbricate, cream to greenish, 21–25 × 3.5–3.9 mm, oblanceolate, apex rounded, glabrous internally, puberulent externally; stamens 10; filaments 18–20 mm long, flattened, provided with an adaxial appendage 16–17 mm long, villous at apex and margins, forming a pseudo-tube by the intertwining of trichomes, the adnate portion length of the appendages relative to the free portion 6:1; anthers dorsifixed, ca. 1.7 mm long, white to cream; gynophore subterete, slightly sulcate, 2.4–2.9 mm long, puberulent; ovary ca. 2 mm long, tomentose; style subterete, 13–15 mm long, bristly near the base; stigma slightly 5-lobed. Fruits with 1–2 drupaceous mericarps (drupelets), immature 14–17 × 11–13 mm, widely elliptic to obovate, greenish, pubescent, with a single seed.

Additional specimens examined (paratypes): — BRAZIL. TOCANTINS: Mateiros, Parque Estadual do Jalapão, estrada para Boa Esperança , Brejo do Guará , campo sujo, 10°19’55”S 46°37’31”W, 420 m, fl., 18 June 2002, T.B. Cavalcanti et al. 2928 ( CEN!) ; ibidem, 10°20’43”S 46°37’34”W, 468 m, sterile, 25 March 2014, M.F. Devecchi et al. 293 ( NY!, RB!, SPF!) ; Ponte Alta do Tocantins, estrada entre Ponte Alta do Tocantins e Mateiros , cerrado, 10°30’58”S 46°53’17”W, 440 m, sterile, 15 July 2014, M.F. Devecchi 312 ( HTO!, SPF!) .

Phenology:— Simaba tocantina has been collected with flowers in June and September, and with immature fruits in September.

Distribution and ecology:— Simaba tocantina is endemic to cerrado and campo sujo on sandy soils of the Jalapão region. Only two populations are known so far: one inside the limits of the Jalapão State Park in the municipality of Mateiros, and the other in the municipality of Ponte Alta do Tocantins ( Fig. 3 ). The geoxylic habit of the new species may be seen as a putative drought and fire-resistant trait. As well as in several taxa from other families, this kind of life-form usually has been considered to have evolved as an adaptation to drought, or nutrient-deficient soils, or to fire regimes (e.g. Rachid 1947; Rizzini & Heringer 1961; Simon & Pennington 2012). We have some morphological evidence that even though the aerial parts of individual plants of the S. tocantina may be completely burned out during a fire event, the protected buds on top of the underground stem can sprout new branches and leaves afterwards, with blooming following these events.

Etymology: —The epithet refers to the state of Tocantins, where the species is known to occur.

Conservation status:—Critically endangered (CR– B1b [i,ii,iv]). The species is probably endemic to the small area of Jalapão, where only three subpopulations are known. According to the performed GeoCAT analysis and the IUCN (2012, 2014) criteria, the species may be classified as critically endangered. EoO = 71 km 2; AoO = 12 km 2.

Notes: The presence of large and sparsely branched inflorescences, producing 2.1–2.5 cm long flowers, with staminal appendages covered by intertwined trichomes forming a pseudotube around the gynoecium places the new species in Simaba sect. Grandiflorae Engler (1874: 209) . Even though Simaba tocantina is very similar to S. salubris in having a shrubby habit, with short branches sprouting from a thickened underground system, it is distinct from the latter by the presence of a smooth leaf rachis (vs. striate), the presence of glandular trichomes in the inflorescence axis (vs. absence thereof), the shorter flower length (2.1–2.5 cm vs. 3.1–3.5 cm long), the gynophore size (2.4–2.9 mm vs. 1.6–2 mm tall), and by the ratio of the adnate and free part to the stamina appendages (6: 1 vs. 10: 1 or more). The other species belonging to S. sect. Grandiflorae are shrubs or small trees with conspicuous aerial stems. They also differ from the new species mainly by the following characters: the staminal appendages are 18–20 mm long in S. tocantina , while in S. cedron , S. pohliana Boas (1913: 337) and S. trichilioides Saint-Hilaire (1823: 279) they are shorter (11–17 mm long); the ovary is tomentose in S. tocantina , but villous to velutinous in the three other species. All distinctive features are depicted in Table 1, and a key to the species of S. sect. Grandiflorae is also provided below.

Figures

FIGURE 1. Simaba tocantina. A. Habit, on top right a detail of a portion of the inflorescence rachis showing glandular trichomes. B. Sterile individual. C. Pinnate leaves with ascending leaflets and petioles covered by sand. D. Distal part of the inflorescence main axis, with floral buds and flowers at anthesis. E. Habitat of the new species, an open campo-cerrrado at Jalapão State Park, Tocantins, Brazil. Pictures A and D by Guilheme Antar; B, C and E by the first author.

FIGURE 2. Simaba tocantina. A. Habit with a subterranean steam and the leaves crowded at the apex. Note the leaflet midvein prominent and the secondary veins slightly sulcate. B. Flower. The filament appendage of the stamens forming a pseudo-tube by the intertwining of trichomes. C. Stamen with filament appendage and dorsifixed anther. D. Gynoecium with a long, subterete gynophore and an elongated style. E. Transverse section of the gynoecium showing five carpels free from each other. F. Fruit, a drupaceous mericarp (drupelet), subtended by an intumesced glandular bract (an extrafloral nectary). G. Leaflet apex with an apical nectary. H. Detail of a glandular bract subtending a flower, with a small cavity in the upper side. (A–H. Antar 528). Drawings by Marcelo Kubo.

FIGURE 3. Distribution map of Simaba tocantina.