Erythroxylum setosum Jara & F. Ávila, 2021

Jara-Muñoz, Orlando Adolfo & Ávila, Fabio Andrés, 2021, A new species of Erythroxylum (Erythroxylaceae) from Colombia and Panama, Phytotaxa 489 (3), pp. 293-298 : 294-297

Erythroxylum setosum Jara & F. Ávila , sp. nov. ( Figs. 1 , 2 )

Type: — COLOMBIA. Chocó: Municipio de Riosucio , Parque Natural Nacional Los Katíos, Peye, alto el Limón, 365 m, 21 May 1976, L. Forero 216 A (holotype MO! [MO-1060425]) .

Erythroxylum setosum can be distinguished from Erythroxylum acuminatum by longer (6.8–14.6 vs. 4–7 mm) and caducous stipules (vs. persistent), longer stipular setae (4.2–4.4 vs. ca. 2.3 mm long), longer calyx (3–3.2 vs. 2–2.5 mm), and also by the underdeveloped anterior ligulae of the stipule.

Shrub 1.2–1.5 m. Branches erect-patent to patent, bark brown without lenticels on the tips, and with gray lenticels on old branches. Stipules early caducous, lanceolate (3.1–) 6.8–14.6 × 1.4–2.3 mm, firmly membranous, densely striate, brown, with 2 apical setae caducous, separating from the adaxial surface of the stipule ca. 1/3 from the base; this free portion of the setae 4.2–4.4 mm long, projected to 1.8–3.7 mm from the stipule apex; apex obtuse with the medial setae thinner and shorter than the laterals, 1.3–1.5 mm long, margin entire. Cataphylls similar to stipules. Leaves persistent along the branches; petioles slightly canaliculated, 3.2–3.9 × 0.6–0.8 mm; blade elliptic, lanceolate-elliptic, or rarely lanceolate-ovate, (5.5–) 6.8–10.2 × (8.5–) 2.4–4.2 mm, firmly membranous, base cuneate, rarely rounded, apex acuminate, acumen 6.7–7.7 mm long, margin plane to undulate, abaxially pale brown when dry, adaxially dark brown to greenish; midvein prominent on both faces; secondary veins impressed adaxially, prominent abaxially, reticulations inconspicuous on both sides. Flowers axillary to cataphylls, on the base of short branches, fascicules of 2-3 flowers; bracteoles 1–1.4 × 0.7–0.8 mm long, 1-keeled, striate, scarious, apex acute with terminal setae of ca. 0.4 mm long, margin entire. Short-styled flowers not seen. Long-styled flowers: calyx 3–3.2 × 2–2.3 mm, ca. ½ divided, lobes 5, valvate, triangular, apex acute, coriaceous, not striate, with margin and apex usually lighter; petals 5, oblong-ovate, concave, membranous, 2–3.3 × 0.9–2 mm, ligulae 0.7–1.1 mm long, anterior auricles 2, not well-formed, not folded, 0.1–0.3 mm long, posteriors auricles 2, 0.4–0.5 mm long, apex crenate, central appendix 0.05–0.25 mm long; stamens 10, basally connate forming an urceolate staminal crown, 1.1–1.8 mm long, margin dentate, filaments alternately unequal, anti-petals 5, 2.3–2.4 mm long, anti-sepals 5, 1.2–1.3 mm long; ovary globose; styles 3, free, 2.9–3.1 mm long; stigma capitate, ca. 0.7 mm long. Drupe ovoid, ca. 10 × 5 mm; endocarp terete.

Additional specimens examined:— COLOMBIA. Chocó. Unguía: Serranía del Darién, 700 m, 7 April 2017, F . Ávila 3638 (CHOCO, COL) ; La Guajira: Sabana Culebra , 340 m, 23 April 1983, E . Carbono 380 ( COL) . PANAMÁ. Darién: Interamerican “highway” ca. 1 mile southeast of Río Tuira , 1 October 1967, J . Duke 14556 ( F) .

Etymology:— The specific epithet refers to the long setae in the stipules, an important character to separate this species from closely related ones.

Habitat and distribution:— Erythroxylum setosum has a disjunct distribution, with records from the Darién Gap region ( Colombia and Panama) and the northern side of the Sierra Nevada de Santa Marta, in the department of La Guajira ( Colombia), separated by nearly 600 km ( Fig. 2 ). The species has been collected on hillsides of the Darién region, with annual precipitation between 730 mm and 3318 mm, representing areas with less precipitation within the Colombian Chocó region ( Poveda et al. 2004), at an elevation range between 365 m and 700 m. Both regions are similar in terms of humidity and elevation, being covered by moist forest, but these are separated by the fragmented patches of the Sinu Valley dry forest of the Colombian Caribbean region, and Guajira-Barranquilla xeric shrub ( Olson et al. 2001).

We believe that the record of Erythroxylum setosum from the foothills of the Sierra Nevada de Santa Marta may have originated from a long-distance dispersal by birds in recent times. The main reason to think this is that the Colombian Caribbean region, including the lower areas of the Sierra Nevada de Santa Marta, has been much better sampled than the Darien Gap, (e.g. Cleef et al. 1984, Dugand 1970, Lozano 1986, Sugden 1982). If there were populations in the Caribbean region, it would be expected that more than one collection would have been made, but this has not happened, while in the few explorations that have been made to the Darién Gap the species was recorded. The verification of this hypothesis will require genetic data that would allow us to infer the phylogeographic history of the species.

Conservation assessment:—We decided to employ the criteria B2, geographic range based on area of occupancy (AOO), because the Extent of Occurrence (EOO) includes mainly dry and xeric forest, in which the presence of the species is unlikely. Using this criterion, Erythroxylum setosum is in the category of endangered (EN), because, 1) the Area of Occupancy is 16 km 2 (<500 km 2), 2) is known to exist in no more than five locations (criteria 2Ba), and 3) there is a continuing decline observed in the quality of habitat, and area of occupancy (criteria 2Bbiii). In fact this region is permanently under land-use pressure because of livestock, illicit coca crops, and transit of immigrants between the Americas.

Taxonomic comments:— The new species is morphologically related to Erythroxylum acuminatum from Ecuador, Peru, Brazil, and Bolivia, by having striated stipules, adaxially impressed veins, and similar calyx shape, but it differs because the new species has longer lateral setae of the stipules, longer and caducous stipules, and poorly developed anterior petaloid ligules. This last character is useful to separate the new species from the widely distributed, E. macrophyllum Cavanilles (1789: 401), along with the triangular and valvate lobes of the calyx (vs. ovate and overlapping in E. macrophyllum) and the longer stipular setae. Erythroxylum setosum belongs to the section Rhabdophyllum Schulz (1907b: 28) because of the striate stipules and the margin of the sepals not overlapping, being probably nested or closely related to the clade III, sensu White et al. (2019), where other species of Rhabdophyllum are included.

Despite the few specimens based on which we describe this species, the distinctive characteristics of the species are present in all specimens and are not found in Erythroxylum acuminatum , so we are reasonably certain that they are fixed phenotypic traits. The presence of these diagnostic traits in populations separated from the distribution of E. acuminatum ( Fig. 2 ) is evidence that these attributes have been inherited; this is compatible with most concepts of species based on traits (e.g. Cracraft 1982, Nixon & Wheeler 1990). We believe that the scarcity of sampling in the area because of logistical difficulties and land-use pressure makes it unlikely that the number of samples will increase in the coming years.

Figures

FIGURE 1. Illustration of Erythroxylum setosum. A. Branch. B. Stipule and setae. C. Flower with removed petals, D. Petal adaxially. E. Gynoecium. Based on L. Forero 216A (MO), by A. Jara.

FIGURE 2. Distribution map of Erythroxylum setosum sp. nov. (red circles) and Erythroxylum acuminatum (dark blue triangles).