Aeschynanthus elmeri Mendum (2001: 439)

Naive, Mark Arcebal K., 2023, Recollection and new data on the distribution of Aeschynanthus elmeri (Gesneriaceae) from the island of Mindanao, Southern Philippines, Phytotaxa 606 (2), pp. 164-168 : 166-167

Aeschynanthus elmeri Mendum (2001: 439) .

Type:— PHILIPPINES. Eastern Mindanao , Province of Agusan , Cabadbaran, Mt. Urdaneta, elev. 5000 ft., October 1912, A.D.E. Elmer 14154 (lectotype E00062816-image seen!, designated here; isolectotype L 0003311-image seen!). Fig. 1 .

Scandent, epiphytic, pendulous herb. Stem terete, 2–4 mm in diameter, sparsely pubescent when young, becoming glabrous as it matures, green, internodes up to 9 cm long. Leaves opposite; petiole terete, 9–11 mm long, 1.5–2.0 mm in diameter, sparsely pubescent, purplish when young, becoming glabrous, green as it matures; lamina lanceolate, 7–10 cm long by 2.2–3.2 cm wide, coriaceous, glabrous both sides when mature, densely pubescent when young, adaxially green, abaxially pale green, margin entire, apex acute to attenuate. Inflorescences terminal, bearing two flowers; peduncle short, terete, 1.2–1.4 cm long, 2.0– 2.5 cm in diameter, glabrous, pale green; bracts persistent, ovate, 2.0– 2.1 cm long by 1.3–1.4 cm wide, pale green, adaxially glabrous, abaxially sparsely pubescent, margin sparsely ciliate, apex acute; pedicel terete, 1.0– 1.4 cm long, 2.0– 2.5 mm in diameter, glabrous, greenish yellow. Calyx cupuliform, with a long tube and free lobes, tube not clasping the corolla, erect to slightly falcate, lemon yellow, pubescent when young, glabrous except the lobes margin when mature, 3.5–4.0 cm long, tube 3.8–4.0 cm long, 1.0– 1.1 cm in diameter, lobes 5, ovate, lobules 6–7 mm long, porrect, margin incrassate, sparsely ciliate, apex subacute. Corolla tubular, 6.5–7.0 cm long, red suffused with yellow inside; upper lobe erect, slightly convex, broadly oblong, 10.0– 10.5 mm long by 10.5–11.0 mm wide, inside glabrous, outside with glandular hairs, margin entire, apex emarginate, lobules rounded; lateral lobes spreading, broadly ovate, 10.5–11.0 mm long by 10.0– 10.5 mm wide, inside glabrous, outside with glandular hairs, margin entire, apex rounded; lower lobe elliptic to oblong, 9–10 mm long by 8.0– 8.5 mm wide, inside glabrous, outside with glandular hairs, margin entire, apex rounded. Stamens 4, exerted, fused in 2 pairs; staminode ca. 1–2 mm long; anthers 3–4 mm long by 1.5–2.0 mm wide, dark red to pale red; filaments 2.0– 2.5 cm long, glabrous, greenish yellow with red tip; pollen yellow or ochre. Disk rotate, 2–3 mm long, yellowish red, minutely papillose, with glandular hairs. Pistil 7.5–7.8 cm long; ovary ca. 1.5 mm long, glabrous, lemon yellow; style 7.0– 7.5 cm long, green except the apical portion which is suffuse with red, apical ¼ with glandular hairs. Fruit not seen.

Distribution: Endemic to the island of Mindanao, southern Philippines. This species is only known from its type locality (Cabadbaran City, Province of Agusan del Norte) which is east of Mindanao Island and was recently found and collected in Zamboanga Peninsula (Zamboanga del Norte and Zamboanga City) of western Mindanao ( Fig. 2 ).

Habitat: The species was found growing as an epiphyte together with ferns and orchid species clinging to a jackfruit tree ( Artocarpus sp. ) at the peak of Mt. Timolan with direct lit from sunlight at an elevation of 1000–1200 m. Elmer (1915) discovered this species growing 10 ft above ground among other vines on the summit of Mt. Cawilanan peak at an elevation of 5000 ft (1524 m).

Phenology: Observed flowering in the wild in January, February and July.

Etymology: Named in honour of Adolph Daniel E. Elmer, the first person to collect the species in Mt. Urdaneta, Cabadbaran, Agusan Province.

Vernacular name: According to Elmer (1915), the species was locally known to the Manobos as ‘ babayranon ’. There is no recorded local name within Zamboanga Peninsula.

Proposed conservation status: Based on the IUCN red list categories and criteria (IUCN Standards and Petitions Committee, 2022), Aeschynanthus elmeri is herein provisionally assessed as Endangered (EN B2ab(iii), D). Although found in two of the protected areas within Zamboanga peninsula, the area of occupancy (AOO) is estimated to be 12 km 2 with less than 50 mature individuals.

Specimen examined: PHILIPPINES. Western Mindanao, Zamboanga del Sur, Tigbao, Mt. Timolan Protected Landscape , elev. 1150 m, 30 January 2022, MAK Naive 132 ( HNUL!, new provincial record); Zamboanga City, La Paz, Pasonanca Natural Park , Tabu tabu BMS, elev. 1300 m, 20 October 2022, MAK Naive 135 ( HNUL!, new provincial record) .

Notes: Aeschynanthus elmeri was originally described as Trichosporum grandiflorum by Elmer in 1915 based on his collected specimen from Mt. Urdaneta of Agusan del Norte. At present, only two sheets of the type gathering is known and we here designate E00062816 as the lectotype since Elmer (1915) did not specify where and how many specimens were preserved and duplicates may therefore yet surface.

According to Elmer (1915), the species is comparable to Aeschynanthus truncatus (Elmer) Schlechter (1923: 264) from the Cuernos Mountains of Negros Oriental. However, Elmer did not mention the specific characters that distinguish the two species from each other. Based on our recent investigation, A. elmeri differs significantly in having these following characters: stem sparsely pubescent when young, glabrous as it matures (vs. glabrous in A. truncatus ), petiole 9–11 mm long (vs. 4–7 mm long in A. truncatus ), leaf lamina lanceolate, densely pubescent when young, glabrous as it matures with acute to attenuate apex (vs. ovate to oblongish, glabrous with short obtuse apex in A. truncatus ), calyx lemon yellow, 3.5–4.0 cm long, pubescent when young, glabrous except the lobes of the margin when mature (vs. shining deep purple red, 3 cm long, glabrous in A. truncatus ) and corolla 6.5–7.0 cm long, red suffused with yellow inside (vs. 5 cm long, lighter red or purple in A. truncatus ).

Figures

FIGURE 1. Aeschynanthus elmeri A. Leaf (left: abaxial, right: adaxial) B. Bract (left: adaxial, right: abaxial) C. Inflorescence D. Detail of corolla lobes (front view) E. Corolla (profile view) F. Pistil G. Apical portion of style and disk H. Pedicel, stipe and ovary. From MAK Naive 132. Photos by: MAK Naive.

FIGURE 2. Map showing the distribution of Aeschynanthus elmeri (red dot, type locality).