Ceratostema limonensis M. M. Jiménez & H. Garzón, 2025

Jiménez, Marco M., Iturralde, Gabriel A., del Pozo, Diego Gutiérrez, Lapo-González, Nadia, Kuethe, J. R. & Garzón-Suárez, Henry X., 2025, Ceratostema limonensis (Ericaceae), a new species from the Province of Morona-Santiago, Ecuador, PhytoKeys 263, pp. 37-47 : 37-47

Ceratostema limonensis M. M. Jiménez & H. Garzón sp. nov.

Figs 1 , 2 , 4

Diagnosis.

Ceratostema limonensis is morphologically similar to C. gualaquizensis , but differs by the longer ( 4.8–5.1 mm vs. 1 mm long), subterete (vs. obconical) rhachis; the shorter ( 1.4–1.8 mm vs. 3.4–4.7 mm long), ovate-deltate (vs. narrowly lanceolate) calyx lobes; the shorter corolla ( 2.9 cm vs. 4.5–4.7 cm long) with narrower lobes ( 2.3 mm vs. 3.7–4.0 mm wide), that have the same colour as the rest of the corolla (vs. black at the apex and inside); and the shorter ( 3.1–3.3 cm vs. 4.6–4.7 cm long), pilose (vs. glabrous) filaments.

Type.

Ecuador • Morona-Santiago: Cerca de Limón , 1298 m alt., 28 April 2025, H. Garzón 293 ( holotype: HUTPL!) .

Description.

Pendant, epiphytic shrubs; indumentum consisting of short, white, almost persistent, eglandular trichomes of 0.2–0.7 mm long, trichomes arranged unevenly, sparsely to densely on younger branches, petioles, leaf blades, inflorescences and flowers, including stamens and style; axonomorphous roots with well-developed lignotubers, lignotubers fusiform, 6.0–7.3 × 2.1–2.8 cm. Stems terete to subterete, 5–8 cm long, glabrous, slightly arching, arising from the lignotuber, the older stems dark brown, cracking longitudinally and exfoliating; younger branches subterete, up to 18 cm long, 0.8–1.3 mm wide, pendant, subflexuous, dark brown, pilose, becoming glabrous and striate when old or after exfoliation; axillary buds emerging 1 mm below the leaf node. Leaves spirally arranged, subsessile, pendulous to almost horizontal; petioles subterete, 0.9–1.9 × 1.0 mm, pilose, pale green; blades lanceolate, 5.5–7.8 × 1.8–2.0 cm, thinly-coriaceous, convex with the basal margins folded to conceal flowers and fruits, base cordate to obtuse, apex acuminate, dark green adaxially, pale green abaxially, lustrous and pilose adaxially, dull and pilose abaxially, becoming glabrous with age, 5–7 - plinerved from near the base, the mid-vein raised along almost its length adaxially, thickened in the proximal 12 mm, impressed and hollow abaxially, the secondary veins raised adaxially, weakly impressed abaxially, branching, anastomosing distally with reticulate veinlets, slightly raised adiaxally, obscure abaxially. Inflorescence axillary, 1–2 - flowered, sessile; rachis subterete, constricted in the middle, 4.8–5.1 mm long, 1.4 mm thick, subverrucose, covered at the base by several bracts; bracts deltate, 0.4–0.6 mm long, minute, persistent, whitish-green, pilose, acute; floral bracts narrowly ovate, ca. 0.6 × 0.2 mm, suffused with pink, pilose, attenuate; pedicel subclavate, 5.1–5.5 mm long, 2.6–2.8 mm thick, subverrucose, slightly arcuate, pale green, pilose, articulate with the calyx; bracteoles 2, ovate-triangular, 0.5–0.7 × 0.3–0.5 mm, minute, whitish-green, pilose, attenuate, located near the base and opposite. Flowers pentamerous rarely tetramerous, descending to pendulous; calyx pilose, 5.1–6.0 × 4.5–5.0 mm, green; hypanthium obconic, 2.7–3.8 × 4.6–5.0 mm, obscurely 5 - ridged, truncate; limb open, 1.9 × 4.2–4.5 mm, erect; lobes 5, ovate-deltate, 1.4–1.8 × 1.8–2.1 mm, small, shortly acuminate, the sinuses acute. Corolla tubular, slightly narrowing distally, 2.9 cm long (including the lobes), thick-carnose, bistratose, pubescent and bluntly 5 - angled along its length, pubescent in the internal apical half, 5 mm in diameter at the base, 4 mm in diameter at the throat, magenta, paler at the angles; lobes 5, narrowly linear-triangular, 14.0–15.7 × 2.3 mm, spreading, acuminate, slightly incurved, glabrous, channelled and subverrucose internally. Stamens 10, nearly equalling the corolla in overall length, each pair unequal, 3.1–3.3 cm long; filaments connate forming a tubular staminal tube, slightly dilated distally, 8.9–9.6 mm long, white with a touch of pink, pilose externally in the proximal half; anthers 2.3–2.7 cm long, thecae conspicuously granulose, 6.2–6.8 mm long, prognathous, each pair of thecae unequal, 4.8–5.0 mm long; tubules distinct, 1.8–2.2 cm long, slightly unequal, seemingly connate in almost its length, straight, glabrous, dehiscing by terminal pores, 0.6 × 0.3 mm. Style exserted, 2.9–3.4 cm long, sparsely pilose at the middle, pale green, stigma truncated. Fruits not seen.

Distribution and habitat.

Ceratostema limonensis is currently known only from the vicinity of Limón in southern Morona-Santiago Province, where it was found on the south-eastern slopes of the Ecuadorian Andes (Fig. 3 ). It has been observed at elevations between 1100 and 1400 m in habitats characterised by mature, lower montane forests (Fig. 4 ). These forests are part of the “ Bosque siempreverde piemontano del sur de la Cordillera Oriental de los Andes ” (code BsPn 04), as defined by the Ecuadorian Ministry for Environment ( Ministerio del Ambiente del Ecuador 2013). The forest at the type locality is multi-stratified with a semi-open forest canopy and few lower forest glades with a maximum height of ca. 20 m. The most dominant species are Alchornea grandis Benth. , Ficus cf. trapezicola Dugand , Metteniusa tessmanniana (Sleumer) Sleumer and Otoba parvifolia (Markgr.) A. H. Gentry. Specimens of C. limonensis were found sympatric with other flora, such as Evodianthus funifer Lindm. , Maxillaria mapiriensis (Kraenzl.) L. O. Williams , Ronnbergia campanulata Gilmartin & H. Luther and Stenospermation sp.

Etymology.

This species is named after the Municipality of Limón in the Province of Morona-Santiago, the township near to which the new species was discovered.

Conservation status.

The very limited distribution of Ceratostema limonensis suggests that this species is a narrow endemic to south-eastern Ecuador. Its low abundance, combined with its restricted occurrence, does not allow for assessment of the AOO or EOO at this stage. Conservation threats to this species are excessive farming and mining activities which already occurring near the type locality. Due to the absence of more known specimens belonging to this species, a tentative classification of Data Deficient (DD) has been given ( IUCN 2024).

Taxonomic discussion.

Ceratostema limonensis is primarily distinguished from all other species within the genus Ceratostema by its subflexuous young branches and axillary inflorescences, characterised by an entire, subterete rachis and pedicel. The inflorescences likely produce a second successive flower, a trait observed in related species, such as C. alexportillae A. Doucette, H. Medina & J. Portilla , C. gualaquizensis M. M. Jiménez & H. Garzón , C. loucianae Cornejo, G. Tello & Luteyn and C. rauhii Luteyn ; however, further data on the floral production of this new species are necessary. These species also share several morphological features, including an epiphytic, pendant growth habit; spirally arranged, subsessile, plinerved, acuminate leaves; subsessile inflorescences with minute floral bracts and bracteoles; dark-coloured corollas with lobes that are narrowly triangular to narrowly linear-triangular, acuminate and recurved; and an exserted style ( Luteyn 1992; Cornejo and Luteyn 2024; Cornejo et al. 2024; Jiménez et al. 2024 b; Doucette et al. 2025 a).

Amongst these, Ceratostema limonensis most closely resembles C. gualaquizensis , as both possess non-amplexicaul, plinerved leaves folded at the base to enclose magenta flowers. Their hypanthia are similarly obconic and subtly 5 - ridged, adorned with acuminate calyx lobes. However, they differ in the characteristics set out in the diagnosis and, in addition, in that C. limonensis has foliar veins raised adaxially, whereas in C. gualaquizensis , the veins are impressed in the proximal 4 mm. Additionally, the corolla lobes of C. limonensis comprise approximately 50 % of the total corolla length, compared to about 30 % in C. gualaquizensis . C. limonensis also shares similarities with C. alexportillae , lianoid branches and notably convex, lanceolate leaves folded at the base ( Jiménez et al. 2024 b; Doucette et al. 2025 a). A comparative summary of morphological differences amongst these species is provided in Table 1 .

Figures

Figure 1. Lankester Composite Dissection Plate (LCDP) of Ceratostema limonensis. A. Lignotuber; B. Fertile branch with a close-up of the node (B 1) and rachis of the inflorescence (B 2); C. Complete flower with a ventral view of the corolla lobes (C 1); D. Flower with a longitudinal section of the corolla showing stamens and the corolla without stamens (right); E. Calyx, pedicel and style with a close-up of the ovary (E 1) and the bracteole (E 2); F. Stamens with a close-up of the pores of the tubule (F 1), anther thecae (F 2) and external surface of the filament (F 3). Prepared by N. Lapo-González from photographs of the holotype.

Figure 2. Leaves of Ceratostema limonensis with close-ups of the indumentum. A. Adaxial view with a close-up of the margin (A 1) and mid-vein (A 2); B. Abaxial view with a close-up of the basal portion of the leaf (B 1). Prepared by N. Lapo-González from photos by H. X. Garzón-Suárez.

Figure 3. Distribution of Ceratostema limonensis in the south-eastern region of Ecuador.

Figure 4. Ceratostema limonensis in situ. Photos by Henry X. Garzón-Suárez.