Erycibe sangiheensis Kochaiph. & Utteridge, 2021

Kochaiphat, Phongsakorn, Traiperm, Paweena & Utteridge, Timothy M. A., 2021, Three new species of Erycibe (Convolvulaceae) from Malesia, Phytotaxa 494 (1), pp. 103-112 : 104-106

1. Erycibe sangiheensis Kochaiph. & Utteridge sp. nov. ( Figs. 1 and 2 )

Type:— INDONESIA. North Sulawesi Province: Sangihe Island , site 2, camp 1 (‘Kalumelahana’), on spur leading to caldera ridge, 3°30’N, 125°32’E, 730 m, 8 April 1999 (fl.), Hicks, Talangamin & Epraing 196 (holotype K [ K.000271421]!; isotypes BO, Manado) .

Diagnosis:—Unique in the genus Erycibe by the combination of the climbing habit, inflorescences with numerous flowers, anthers with an acuminate apex, and especially by the dense indumentum of brown furry stellate hairs with 2–3(–5) subequal to unequal branches 0.375–0.5 mm long on all parts of the plant, particularly on the abaxial surface of the lamina and inflorescence.

Climber; stems terete, young branches densely brown-hirsute, hairs 2–3(–5)-branched usually subequally or unequally branched on vegetative parts or with a longer central branch on the corolla, hairs 0.375–0.5 mm long. Leaves simple, petioles 1.3–1.5 cm long, densely hairy as branches; laminas chartaceous, elliptic, 12–17 × 5.5–7.5 cm, base obtuse, apex attenuate, margin entire, adaxially nearly glabrous, rarely with 2-branched hairs, abaxially densely covered with 2–3 branched hairs, hairs up to 0.5 mm long; midrib sunken adaxially, prominent abaxially; veins 7–10 on either side, inconspicuous adaxially, prominent abaxially; intercostal veins reticulate, inconspicuous adaxially, prominent abaxially. Inflorescences axillary, paniculate, (1.5–) 15 cm long, 10–100-flowered; floral bracts lanceolate, up to 4 mm long; pedicels 3–4 mm long, densely stellate-hairy. Sepals orbicular, 2.5–4 × 3–4 mm, abaxially densely covered with stellate hairs, the two inner sepals glabrous near margin abaxially, glabrous adaxially, margin ciliate; corolla tube c. 0.5 mm long, midpetaline bands densely stellate-hairy abaxially with unequally 2–5-branched hairs, longitudinal veins inconspicuous, lobule c. 1.5 × 1.5 mm, margin undulate; stamens c. 1.5 mm long, filaments broader at the base, anthers dark brown when dry, c. 1.2 mm long, base cordate, apex acuminate; ovary (dry) ovoid, c. 1 × 1.5 mm, glabrous, stigma 5-ridged, twisted, c. 0.7 mm long. Fruits not seen.

Distribution:— Endemic to Sangihe Island, Indonesia; currently only known from the type collection.

Habitat:— “Hill rainforest with palms. Steep slopes with some forest trails ascending to the ridge and edges threatened by agricultural conversion”; elevation 730 m.

Phenology:— Flowering in April.

Conservation assessment:— Data Deficient (DD) category of the IUCN (2012). Erycibe sangiheensis is only known from one specimen collected from Sangihe Island and there is no additional information to assess the population size. Although the island has a rugged topography because of its volcanic origin, it had been deforested by the 1920s and now only isolated fragmentary patches of natural forest remain—it is now dominated by mixed plantations, including coconut, nutmeg, clove, sago and banana ( Riley & Wardill 2001). The specimen was collected from the slopes of Mt Sahendaruman—the region with the most extensive remaining forest areas on Sangihe ( Riley 1997) but, as recorded on the label, the forest edges are threatened by agriculture. The island is still extremely poorly known and further collections and/or observations on the plant communities of the island are required to better understand the conservation status of the island’s flora and of E. sangiheensis .

Etymology:— The specific epithet refers to Sangihe Island where this species is found.

Notes:— Erycibe sangiheensis is unique in the genus in the combination of its climbing habit, the dense indumentum throughout and the many-flowered inflorescences. This species is most similar to E. hainanensis Merr. ( Merrill 1922: 353) , known from southern China and Vietnam, in the branches and abaxial leaf surface being densely brown-hairy but differs in having 2–3(–5) subequally or unequally branched hairs, while E. hainanensis has extremely unequally 2-branched hairs.

Using the Flora Malesiana account of Hoogland (1953c), Erycibe sangiheensis would key out to E. strigosa Prain (1896: 536) and E. subsericea Hoogland (1953a: 318) based on the acuminate anthers, sepals hairy on the outside, many-flowered inflorescences and hairy abaxial surface of the lamina. Erycibe strigosa is endemic to Peninsular Malaysia but has sparsely hairy (‘strigose’) leaves and axillary inforescences, whilst E. subsericea is endemic to Borneo and has short-sericeous hairs on the abaxial surface of the lamina and a densely hairy (‘strigose’) ovary.

The Sangihe Islands are biogeographically close to northern Sulawesi and the Philippines. The only species of Erycibe recorded from Sulawesi is E. malaccensis C.B. Clarke (1883: 182) , with a disjunct distribution between the Malay Peninsula and the Philippines and Sulawesi (and perhaps Java), but absent from Sumatra and Borneo. Erycibe malaccensis differs from E. sangiheensis in several characters especially the leaves which are soon glabrescent, the relatively smaller laminas 5–16 × 2.5–6.5 cm ( E. sangiheensis 12–17 × 5.5–7.5 cm), the fewer 4–6(–7) secondary veins ( E. sangiheensis 7–10 secondary veins), the inflorescences with up to c. 20 flowers at maximum ( E. sangiheensis with up to c. 100 flowers), and the hairs with a distinctly longer central branch ( E. sangiheensis hairs subequally or unequally branched). The only species in the Philippines with leaves that can be hairy abaxially are E. malaccensis (as previously discussed), E. sericea Hoogland (1953a: 317) and E. tomentosa Blume (1826: 1048) . The laminas of all of these species are soon glabrescent abaxially but, in addition, E. sericea has a densely hairy ovary, and the hairs of E. tomentosa are up to 1.5 mm long.

Field notes record that the flower buds are dull green, and the stem and leaves are ‘with brown furry indument’. The leaves have substantial and prominent insect damage with numerous sub-spherical to elliptic holes and leaf-miner damage (omitted from the line drawing to show venation more clearly).

Figures

FIGURE 1. Distribution of Erycibe sangiheensis (star), E.trichocarpa (triangle), E.brunneopilosa (circle).Map made using Simplemappr (https://www.simplemappr.net).

FIGURE 2. Erycibe sangiheensis Kochaiph. & Utteridge. A Habit, flowering branch B Adaxial surface of lamina and midrib C Abaxial surface of lamina and midrib D Lamina hairs, side view E Flower bud F Sepal, abaxial view G Sepal, adaxial view H Corolla and lobules, adaxial view I Corolla showing midpetaline band, abaxial view J Hair from midpetaline band K Stamen L Ovary and stigma. Drawn by Naoko Yasue from Hicks et al. 196 (K).