Sloanea cayapensis J.Jaram. & J.E. Guevara, 2020

Guevara Andino, Juan Ernesto & Fernandez-Fernandez, Diana, 2020, A new rare and endemic species of Sloanea (Elaeocarpaceae) from the Choco region of Ecuador, PhytoKeys 160, pp. 131-139 : 131

Sloanea cayapensis J.Jaram. & J.E. Guevara sp. nov. Figs 1 , 2 , 3 , 4

Diagnosis.

Sloanea cayapensis resembles S. grandiflora Smith and S. fragrans Rusby, the most morphologically similar taxa, but can be differentiated from them by having short petioles (2-7.5 cm), obovate-spatulate leaves, 6-8 free sepals, shorter thick and acute-obtuse anthers (1.5-2 mm), densely hirsute filaments and styles and by having capsules with large, flexible, curled bristles (2.8-6 cm).

Type.

Ecuador. Esmeraldas: Borbón-Río Cayapas, 78°50'W, 1°5'S, 10 m elev., 3 May 2003, Jaime Jaramillo, A. Sola, S. Yandun 24200 (holotype [2 sheets]: QCA7007914! (fl, fr); QCA7007917!; isotypes QCA7007915!,QCA7007916! (fl), QCA204513!).

Medium-sized trees up to 15-18 m tall. Trunk striated, bark rough, brownish. Branchlets glabrous, quadrangular and covered by ovoid, cream-coloured lenticels. Leaves alternate; petioles 2-7.5 cm long, semi-terete, striated, shortly pubescent, thickened at the insertion with the blade; blades (18.8-)42-52(-61.8) cm long, (9.5-)17-26(-32) wide, coriaceous obovate-spatulate, attenuate-subcordate or rounded at base, obtuse-retuse at apex, the margins entire, slightly revolute; foliaceous stipules persistent at the top of the individual branchlets, 3.9-13 cm long, 2.1-3.9 cm wide, elliptical with acuminate apex, the margin entire or shallowly sinuate; primary vein prominent on the adaxial surface, very prominent and angular on the abaxial surface, secondary venation eucamptodromous, 11-20 secondary veins, prominent on the abaxial surface and ascendant (angle> 45°), flat on the adaxial surface, tertiary veins prominent on the abaxial surface, slightly flat on the adaxial surface. Inflorescence axillary, racemose; peduncles 2-6 cm long; rachis 5-18.5 cm long, slightly pubescent, deeply striated and quadrangular; pedicels 1-7 cm, stout, shortly pubescent, finely striate and quadrangular, pedicels, 1-1.5 cm long, navicular bracts at the base of individual pedicels, 4-4.5 mm long, dense appressed pubescence on both abaxial and adaxial surfaces, apex acute, commonly deciduous. Flowers with the receptacle large, expanded; sepals 6-8, free, 3-5 mm long, 2.5-3 mm wide, greenish coloured, ovate, apex acute-acuminate, margins entire, slightly involute, yellow on the outer surface, not covering the reproductive organs before anthesis. Stamens 5-6 mm long, yellow with orange anthers; filaments 3-3.5 mm long, densely hirsute, striated and angulate; anthers 1.5-2 mm long, densely hirsute, thick, the connective thin on the abaxial surface of the anther sacs, extended as an acute or obtuse awn, very short, up to 0.5 mm long; anther sacs not opening widely along entire length. Ovary 2-4 mm long, 1.5-2.7 wide, with four locules, 4-angled, ovoid, densely hirsute; placentation axillary; style to 8 mm long, densely hirsute at the base, becoming sparsely hirsute towards the apex. Fruits globose capsules 1.2-2.5 cm long, 1-2 cm wide, rounded, opening by 4 rigid valves; bristles 2.8-6 cm long, curled, contorted and flexible, laterally flattened, densely hirsute at the base, more sparse and appressed pubescence towards the apex, easily detached. Seeds not studied.

Specimens examined.

Paratypes. Ecuador: Esmeraldas: La Chiquita, bosque secundario, 45 m elev., Jaime Jaramillo 24422 (QCA-236170!); Esmeraldas: Localidad Borbón, entre Punta Piedra y Maldonado, 78°58'W, 1°4'S, 60 m elev., febrero 13 de 1993, Jaime Jaramillo 15016 (QCA-204514!).

Distribution and habitat.

Sloanea cayapensis is a medium-sized tree only known from two localities on high alluvial terraces along the Cayapas River in the Lowland Evergreen Forests of Equatorial Chocó ( Ministerio del Ambiente del Ecuador 2013). This area lies in the Chocó floristic province, where forest structure is characterised by a canopy 25-30 m high, with occasional emergent trees reaching 40 m. High levels of endemism and dominance of families, such as Moraceae , Fabaceae , Meliaceae , Myristicaceae and Lecythidaceae , have been reported for this area ( Gentry 1982; Ministerio del Ambiente del Ecuador 2013) and the label of the type specimen indicates that S. cayapensis co-occurs with the following tree species: Terminalia amazonia ( Combretaceae ), Swartzia littlei ( Fabaceae ), Matisia cordata ( Malvaceae ) and Cordia alliodora ( Boraginaceae ). The climate of this area is rainy near the Ecuador-Colombia border and becomes more seasonal to the south, where it transitions into the Lowland Seasonal Evergreen Forests of the Equatorial Chocó ( Ministerio del Ambiente del Ecuador 2013).

Etymology.

From the Spanish word Cayapa, with reference to the Chachi indigenous group that inhabits a great portion of the evergreen lowland forests of the Equatorial Chocó in Ecuador. The word Chachi means ‘pure’ in the Cha’palaachi language. The species name was first proposed by the late Ecuadorian botanist J. Jaramillo as a written annotation on herbarium specimens, but was never validly published.

Conservation status.

Sloanea cayapensis may be catalogued as Endangered (EN) following IUCN (2012) criterion A2c, which indicates: "An observed, estimated, inferred or suspected population size reduction of ≥ 50% over the last 10 years or three generations, whichever is the longer, where the reduction or its causes may not have ceased or may not be understood or may not be reversible" and criterion B1ab(iii), which indicates: "Extent of occurrence (EOO) estimated to be less than 5,000 km2 and estimates indicating continuing decline, observed, inferred or projected, in area, extent and/or quality of habitat". The analysis using the GeoCat tool for geospatial conservation assessment determined an EOO of 2000 km2 ( Bachman et al. 2011). Sloanea cayapensis is only known from two localities on the banks of the Cayapas River, in the lowland evergreen forest of the Equatorial Chocó. The area has suffered extensive clear-cutting in the last 30 years, leading to a drastic reduction of native forests and expansion of oil palm plantations and illegal logging, these being the major threats faced by the species. Since collection of the types in 2003, no other specimens of this species have been recorded despite the fact that subsequent field trips have sampled the same habitat occupied by this species. Over the last 26 years, the annual rate of deforestation in the lowland evergreen forest of the Equatorial Chocó in Ecuador has been 1.7-2.9% and the remnant forests in this area cover just 24% of their original extent ( Sierra 2013). Consequently, the habitat occupied by this species in Ecuador has been drastically reduced. However, the species is likely to occur in similar habitats in the Colombian Chocó where the dynamic of deforestation is less drastic but a cause for concern.

Figures

Figure 1. Map of the geographic distribution of Sloanea cayapensis J. Jaramillo ex J. E. Guevara, sp. nov. (red squares), Sloanea fragrans Rusby (black circles) and Sloanea grandiflora Sm. (grey inverted triangles).

Figure 2. Sloanea cayapensis. Image from the holotype at QCA (J. Jaramillo 24200).

Figure 3. Sloanea cayapensis. Image from the holotype at QCA (J. Jaramillo 24200).

Figure 4. Sloanea cayapensis A detail of ovary and sepals B dorsal view of stamen C ventral view of stamen (A-C from J. Jaramillo 24200 QCA).