Quadrangle sunset bell (Drymonia quadrangulata) from Andean slopes of southern Colombia and northern Ecuador

NEWS - Quadrangle sunset bell (Drymonia quadrangulata Clavijo & J.L.Clark, sp. nov.) from western Andean slopes of southern Colombia and northern Ecuador has historically been confused with D. killipii which is endemic to Colombia and restricted to the lowlands of the Chocó biogeographic region in the departments of Cauca, Chocó, and Valle del Cauca.

Drymonia Mart. is the third largest genus in the neotropical Gesneriaceae, surpassed only by Columnea with 210+ species and Besleria with 175+ species. Drymonia comprises 87 species mostly concentrated in the northern Andes and the Chocó biogeographic region, especially in Colombia (40 species) and Ecuador (38 species).

D. quadrangulata is a terrestrial herb or shrub, 0.6–1.5 m tall. Stem scandent basally and then erect, usually branched, adventitious roots usually absent, quadrangular in cross-section to strongly angulate, sometimes winged, 4.2–10.5 mm in diameter.

Herbaceous to succulent, green to green with maroon spots, smooth, strigose apically, becoming glabrescent with age, lenticels sometimes present, internodes 2.2–10.2 cm long, reduced toward the apex.

Leaves opposite, decussate, equal to subequal in a pair; petiole (2.2–)5.2–15.0 cm long, green with maroon spots, terete in cross-section, grooved, flattened at base, pairs of petiole bases fused together forming a perfoliate-like flap or wing, 1–2 mm wide, petiole enations present at base of petiole, strigose in apical leaves, glabrescent in basal leaves.

Blade elliptic to ovate, 12.0–26.7 × 5.2–18.5 cm, coriaceous, green adaxially, light green suffused with maroon abaxially, brown-maroon when dried, apex acute to acuminate, base obtuse, rounded or subcordate, margin serrulate to serrate, minutely strigose to glabrescent adaxially, glabrescent abaxially, 5–7 pairs of main lateral veins, minutely puberulent, reticulated, evident on both surfaces but more so abaxially.

Axillary inflorescence, a reduced pair-flowered cyme with 1–6 flowers per inflorescence; bracts usually caducous, 7.0–16.9 × 2.0–3.7 mm, light green suffused with maroon to mostly maroon, lanceolate to oblong, apex acute, base obtuse, margin entire, glabrescent adaxially, strigulose abaxially; peduncle absent.

Flowers non-resupinate; pedicel erect to perpendicular 9.5–42.0 mm long, green, strigulose, enations scattered along the pedicel. Calyx green, green with reddish or maroon margins, or mostly maroon, membranaceous, persistent in fruit.

Calyx lobes 5, 4 nearly equal, nearly free, fused at the base for 0.7–2.0 mm, with margins overlapping at least half their length, lanceolate, apex attenuate, base cordate, margins entire to minutely serrulate, glabrescent adaxially, glabrescent but strigulose at base abaxially, ventral and lateral lobes 25.4–53.2 × 10.3–36.0 mm, dorsal lobe smaller, 25.0–37.6 × 8.4–19.0 mm.

Corolla zygomorphic, protandrous, oblique to perpendicular relative to calyx, tubular, 42.7–64.6 mm long; tube gibbous at base, slightly constricted above base and wider at the middle, 30.8–49.5 mm long, 5.8–9.9 mm wide at constriction above base, 10.7–16.6 mm wide at the middle.

Outside white and puberulous, inside light yellow and glabrescent, with glandular trichomes toward throat on dorsal surface, nectary chamber 4.7–10.2 mm long; throat 9.1–15.1 mm in diameter, outside white and puberulous, inside yellow, ventrally darker and thickened forming a groove, dorsally with glandular trichomes.

Corolla lobes 5, subequal, white to yellow, orbicular, apex rounded, margin incised to short laciniate, glabrous adaxially, glabrous to strigulose abaxially, ventral lobe larger, straight to spreading, 14.2–23.9 × 12.2–33.4 mm, lateral lobes spreading, 12.1–23.1 × 12.7–25.0 mm, upper lobes, 10.3–22.3 × 10.3–21.6 mm.

Androecium of 4 didynamous stamens, included, filaments 29.0–35.0 mm long, adnate to the corolla tube for 5.1–14.0 mm, white, glabrous, coiling after anthesis, staminode absent; anthers oblong, sagittate, coherent by the lateral walls, dehiscence by basal pores that develop into longitudinal slits, 4.2–7.0 × 0.7–2.0 mm.

Gynoecium with a single dorsal nectary gland, oval, apex irregularly acute to obtuse, 1.7–2.7 mm long, white, glabrous; superior ovary, 4.2–10.0 × 2.1–6.7 mm, ovate, yellow to yellow-green, puberulous to velutinous; style included, 23.5–35.1 mm long, puberulous to velutinous, reddish at base, white apically; Stomatomorphic stigma, white.

Fruit a berry, 6.8–17.0 × 5.5–16.5 mm, globose, yellow at maturity. Seeds numerous, 0.8–1.0 × 0.4–0.5 mm, brown, fusiform, longitudinally ridged.

Specimens collected with flowers throughout the year. Fruits picked in May and June. The specific epithet refers to the rectangular to highly angular cross-section of the stem which is sometimes winged.

D . quadrangulata is similar to D. killipii, D. chiribogana and D. lanceolata. This taxon has leafy, almost free, calyx lobes that cover at least half of the corolla tube and sometimes the entire tube. The tips of the calyx lobes are pointed to tapering, with the folded edges extending to outer, and the crown is tubular-infundibuliform.

D. quadrangulata is often misidentified in most herbaria as D. killipii, a narrow endemic species rarely collected in Colombia. However, D. quadrangulata can be distinguished from D. killipii by the strigose indumentum on vegetative and reproductive structures that becomes glabrous with age (vs. hirsutism, becoming glabrous with age).

Stems quadrangular to strongly angular, sometimes winged (vs. terete), petioles (2.2–)5.2–15.0 cm long (vs. 2.0–6.4 cm long), leaf base obtuse to subchordate (vs. cuneate), intersecondary and tertiary venation nettle (vs. indistinct or depressed), petioles and petals lacking glandular trichomes (vs. glandular trichomes present), petal lobes lanceolate (vs. oblong).

Corolla white to yellow (vs. dark purple to maroon), tinged with lemon yellow toward the throat, corolla serrated to short-notched (vs. nearly entire), and indehiscent berries (vs. bivalve fleshy capsules). The fragrant lemon of D. killipii has not been noted in D. quadrangulata.

D. quadrangulata can be distinguished from D. chiribogana by its terrestrial habit (vs. epiphytic), quadrangular to highly angular stems (vs. terete to subquadrangular), smooth stem surface when dry (vs. papyraceous).

Leaf blade green with green midveins adaxially (vs. green with whitish or silvery veins), leaf blade glabrous abaxially (vs. with glandular trichomes sunken into the epidermis), intersecondary and tertiary venation netted (vs. indistinct or depressed).

The calyx lobes are lanceolate (vs. broadly oval), the corolla is 4.3–6.5 cm long (vs. 3.2–4.3 cm long), the corolla lobes are white to yellow (vs. magenta, with red or yellow towards the throat), the corolla lobe margins are notched to shortly notched (vs. almost entirely notched), and the fruit is a berry (vs. bivalve fleshy capsule).

D. quadrangulata has a terrestrial habit, a quadrangular to angular stem, and the fruit is similar to D. lanceolata, distinguished by a smooth stem surface when dry (vs. papyraceous), and the base of the blade is obtuse to subcordate (vs. cuneate to thin).

The leaf veins are slightly puberulent abaxially (vs. strigose to tomentose), the calyx lobes are nearly free with outwardly folded margins (vs. free with flat margins), the corolla lobes are incised to shortly laciniate (vs. long fimbriate), and the stigma is stomatomorphic (vs. deeply bilobed).

Original research

Clavijo L, Clark JL (2024). Resolving the Drymonia killipii (Gesneriaceae) complex results in a new species from the northwestern Andes of South America. PhytoKeys 248: 207-222, DOI:10.3897/phytokeys.248.123248

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