Decalobanthus peltatus

Staples, G., 2022, A synoptic revision of the golden glories, genus Decalobanthus (Convolvulaceae), Blumea 67 (1), pp. 37-70 : 59-65

16. Decalobanthus peltatus (L.) A.R.Simões & Staples — Fig. 12 , 13 , 14 , 15 ; Map 11

Decalobanthus peltatus (L.) A.R. Simões & Staples (2017) 571. — Convolvulus peltatus L. (1753) 1194. — Ipomoea peltata (L.) Choisy (1834) 452. — Merremia peltata (L.) Merr. (1917) 441. — Lectotype (designated by Merrill (1917) 441, see notes): [icon] ‘ Convolvulus laevis Indicus major ’ in Rumphius, Herb. Amboin. 5 (1747) t. 157 ( Fig. 13 ). Epitype (designated here): Robinson 401 (epi US [ US 03147977]; isoepi L [L.2722073], P [P00600280]), ( Indonesia,) Amboina (Ambon) .

Ipomoea nymphaeifolia Blume (1825) 719, non Griseb. (1866) 203. — Merremia nymphaeifolia (Blume) Hallier f. (1896) 127. — Lectotype (designated by Van Ooststroom 1939b: 355): C.L. Blume 1505 ‘304’ (lecto L [ L 0866915 ]), ( Indonesia,) Java, Salak.

Ipomoea menispermacea Domin (1928) 535. — Type: Domin 7928 (holo PR, accession 530538), ( Australia,) ‘ Nordost-Queensland : Regenwälder bei Harveys Creek’.

Stems and branches glabrous, not lenticellate. Leaves peltately attached (small leaves below inflorescences sometimes basally attached), broadly ovate to orbicular, 7–30 cm long, bases rounded or retuse; secondary veins 7–10 on either side of the midvein. Inflorescences 1 or 2 in leaf axils, paniculate, several-flowered or flowers solitary; peduncles 5–15 cm long. Flower buds ovoid, acute; sepals subequal, concave, broadly ovate, 1.8–2.5 cm long; corollas 4–6 cm long, limb 5-sided, dimorphic: Morph 1: campanulate, ± waxy, white or bright yellow; stamens included; Morph 2: broadly bowl-shaped, diaphanous, white or pale yellow; stamens protruding; anthers strongly spiralled, connectives long hairy (or glabrous); pistil exceeding stamens. Fruiting calyxes accrescent, cupping fruit, black-brown. Capsules broadly ovoid, 2.5–3 cm long; valves 4, splitting lengthwise into several segments. Seeds trigonous, c. 6–8 mm long, brown hairy, margins long tomentose.

Previously published illustrations — Heine (1984: pl. 12, 13); Bosser & Heine (2000: pl. 7); Staples (2010: colour plate LI, f. 4); Staples & Syahida-Emiza (2015: 294, pl. 40D, 295, pl. 41A, B).

Distribution — Wide-ranging throughout the tropical Indo-Pacific from eastern tropical Africa (Pemba island), to Madagascar, Réunion, Mayotte, Seychelles, Andaman Islands, Nicobar Islands, peninsular Thailand, Malaysia (peninsular, Sabah, Sarawak), Singapore, Indonesia (Java, Kalimantan, Maluku, Sulawesi, Sumatra), Philippines (Bohol, Luzon, Mindanao, Mindoro, Palawan, Sulu), New Guinea (Indonesian, Papua, New Ireland), Solomon Islands (Guadalcanal, San Cristoval, Vanikoro), New Caledonia, Vanuatu (Efate, Epi, Erromanga, Espiritu Santo, Vanua Lava), Australia (Queensland), eastward throughout the Pacific Islands ( Cook Islands, Fiji, French Polynesia, Micronesia, Niue, Palau, Samoa, Tonga, Wallis and Futuna) as far north as Hawai‘i (naturalized on Kaua‘i).

Habitat & Ecology — Decalobanthus peltatus has an enormous ecological amplitude and tolerates, or even thrives with, human disturbance. It has been reported by collectors in the following natural habitats and ecosystems: evergreen forest; primary alluvial lowland forest; riverbanks; in Inocarpus­Hibiscus forest; and the edges of closed broadleaf rainforest. Collectors record it from a wide array of disturbed places such as: logged over dipterocarp forest; secondary forest regrowth; roadsides and logging roads; belukar scrub and edges of alang­alang ( Imperata , Poaceae ) fields; margins of palm and pine plantations; old taro cultivation areas; covering deforested areas on slopes; in disturbed Hibiscus­Psidium forest scrub; margins of mangroves; and along stony railway embankments. Soil types are diverse and include: coral and karst limestones; well-drained alluvial flats; clay loam; sandy loam; lava fields; orange soil on dolerite; gneiss; quartzite; forest soil on basalt; and in the pioneer vegetation stages on talus. Elevations reported range from sea level to 600(–1200) m.

This species is becoming a serious weed in the Pacific. Its distribution now reaches as far east as the Hawaiian Islands, where D. peltatus was recently documented as naturalized on the island of Kaua‘i (Wood 2012). There is a growing literature advocating weed removal and control methods for D. peltatus on numerous Pacific islands ( Bacon 1982, Paynter et al. 2006). It is a curious fact that only plants with white, campanulate corollas are implicated as weedy invasive species (see Notes).

Vernacular names — Federated States of Micronesia (Chuuk): Fitay (C.Y.C. Wong 288); (Kosrae): pala (Fosberg 26572). Fiji: see compilation by Smith (1991: 50 as Merremia peltata ). Indonesia (Java): Aroy tjaraü-úng (Blume ‘ 64 ’) – (Sumatra): Andor bararoeng (Rahmat si Boeea 1645) – (Kalimantan): Belaran (Samboja, Slik FS­9). Madagascar: see compilation by Deroin (2001: 114). Malaysia: (Akar) laran (Kadir A­2540) – (Sabah): (akar) larau ( Brunei; Cuadra A2233), bagon (Suluk; Anthony A775), balaan (Murut Pansiangan; Anthony A775); biloran (Puasa FMS­36752); kachabung (akar) (Dusun; Cuadra A2233). Malesian region: Van Ooststroom (1939b: 356) provides a comprehensive catalogue of vernacular names used throughout the Malesian region. Micronesia: see the compilation by Fosberg & Sachet (1977: 27). Papua New Guinea: Bamul (Weiblen WS2A2061), bohurèh (Orokaiva language, Mumuni; Hoogland 3354). Philippines: Bulakan (Luzon island; Sulit PNH 7060), boracan (Madulid et al. 7180), burac-buracan (Palawan island; Vidal 3353bis). Samoa: Fue lau tetele, fue to (Bristol 2268). Solomon Islands: Abiu (Whitmore 6293). Tahiti: Pohue (Fosberg 63680), pohue tafifi (Moore 211). Thailand: อ็นลื่น (transliteration: en lûn; Kerr 15681); ย่านเอ็นเหลือง (yaan en luang; Staples 2010); ยานขี้เดือน (yan khi duean; Khunwasi 43); ย่านเหล็น (yan len; Kerr 17112). Vanuatu: Nafélé, tavélé (Drake 5), nosiviliau (Cabalion 3045). Wallis & Futuna: Faliava (Yen X­73).

Uses — Fosberg & Sachet (1977: 27) report that the leaves and seeds are used as an abortifacient in Ponape. On the island of Chuuk ( Truk) “the leaves are pounded and placed in breadfruit poi to make it taste good (C.C.Y. Wong 288). In Papua New Guinea the latex is applied to wounds and the stems are used for tying bundles of firewood (Weiblen WS2A2061).

Typification — There is a pernicious error in the literature regarding the typification for Convolvulus peltatus L.: Merrill (1917: 441) designated Rumphius’ plate 157, f. 1 and 2 as the ‘type’ and according to the modern ICN (Turland et al. 2018) this constitutes effective lectotypification. In the thorough translation of Rumphius’ Herbarium Amboinensis that is now available ( Beekman 2011) we see that Rumphius made a clear and detailed verbal distinction in his text accompanying plate 157 ( Fig. 13 ) between two quite different plants: plate 157 f. 1 purports to show a purple-flowered plant, which he contrasts with f. 2, showing the white-flowered ‘Haylale’. Only the white-flowered plant is consistent with what we know today as D. peltatus . As Merrill (1917) rightly points out, however, the two figures are ‘not clearly separable’ and Merrill assumed that both figures refer to one species, despite what Rumphius’ text says. This lectotypification clearly fixes the application of the epithet peltatus . It is therefore terribly unfortunate that Linnaeus, when he published Convolvulus peltatus ( Linnaeus 1753: 1194) , actually cited Rumphius’ plate 159, which shows the plant we know today as Ipomoea pes­caprae (L.) R.Br. Merrill (1917) corrected this error made by Linnaeus; unfortunately, Merrill’s correction escaped the notice of several authors for late twentieth century floras: beginning with Verdcourt (1963: 50) and continuing through Heine (1984: 38), Bosser & Heine (2000: 18), and Deroin (2001: 114), all of whom perpetuated the incorrect plate number 159.

Contrasting with the white-flowered plant long interpreted as M. peltata is the yellow-flowered taxon distinguished by Hallier (1896, 1913) as M. nymphaeifolia . I located five sheets in L that appear to be original material (syntypes) for Ipomoea nymphaeifolia ( Blume 1825) ; one of the sheets was labelled by Van Ooststroom as the ‘type’ and this one can be confirmed now as the lectotype.

Note — Living plants of D. peltatus display two different corolla morphologies, each with two colour forms. One morphotype has a campanulate, more or less waxy, corolla with a reflexed limb that may be bright yellow or white ( Fig. 14 ); the other morphotype has a broadly bowl-shaped, thinly membranous corolla with wide-spreading limb that may be white or pale yellow ( Fig. 15 ). These differences are not evident on herbarium specimens but they are very obvious in the field. It is not possible, at the present state of knowledge, to separate discrete taxa and the variability has been maintained (as has long been the case) under one scientific name. Recently even slight variations in floral morphology, when backed up with field observations that corroborate differences in natural history and ecology, have been used for recognition of discrete ‘cryptic’ species teased out of morphologically variable ones ( Santos et al. 2019). It is possible that future scrutiny will demonstrate multiple taxa can be distinguished from the polymorphic concept of D. peltatus that is kept up here. Herbarium specimens are totally inadequate for this purpose: field study combined with appropriate molecular tools need to be applied.

One final morphological anomaly should be pointed out to indi- cate a need for future study: Deroin (2001: 114) has highlighted three collections from a remote valley (vallée de la Lokoho) in north-eastern Madagascar that have basally attached leaves; in other respects, such as calyx and corolla morphology and size, these specimens can be accommodated in D. peltatus where he kept them. Whether these non-peltate specimens represent a genetic mutation or an edaphic adaptation, as Deroin postulated, or whether they represent an unidentified taxon in Decalobanthus remains to be discovered.

One of the distinctive features of D. peltatus on herbarium specimens (shared with D. elmeri ) is the tufts of long hairs usually (but not always) present on the anther connectives ( Fig. 14 , 15 ). The purpose of these extraordinary, long trichomes is unknown; possibly they play some role in pollination. Why some flowers have them and others do not is also a mystery.

Figures

Map 11 Distribution of Decalobanthus peltatus (L.) A.R.Simões & Staples (Y = yellow corollas; W = white corollas; ● = fruiting specimens or corolla colour not indicated; E = plants with basally attached leaves that are non-peltate).

Fig. 12 Decalobanthus peltatus (L.) A.R.Simões & Staples. a. Habit of leaves and flowers; b. mature flower bud, opened; c. calyx and stamens; d. stamen with dense hair tuft covering anther; e. pistil; f. opened capsule, two views; g. seed. Painted by Charles de Alwis. Reproduced with permission, courtesy of Singapore Botanic Gardens Archives.

Fig. 13 Decalobanthus peltatus (L.) A.R.Simões & Staples. Plate 157 by Rumphius, chosen as lectotype by Merrill (1917: 441); see comments in text.

Fig. 14 Decalobanthus peltatus (L.) A.R.Simões & Staples. Variations in corolla morphology and colouration, 1: a–c: Campanulate corolla, waxy texture, bright yellow colour, included stamens; d, e, campanulate corolla, white colour, included stamens (a, b: Rachun Pooma, Peninsular Thailand, voucher:Pooma et al. 6529 in BKF; c: Imin Kamin, Peninsular Malaysia, voucher: Imin K. et al. FRI­74568 in KEP; d: Joju P. Alappatt, Andaman Islands, no voucher); e: Jean- François Butaud, Tahiti, no voucher).

Fig. 15 Decalobanthus peltatus (L.) A.R.Simões & Staples. Variations in corolla morphology and colouration, 2: a. Cauline leaf showing peltate attachment of petiole; b. Borneo form with white and pale yellow corollas collected from same population (or same plant) showing broadly rotate corollas with thinly mem- branous texture and spreading limb (at mid-morning); c. flower from same plant as A, Borneo form with white corolla, thinly membranous texture, reflexed corolla limb and protruding stamens (at mid-afternoon), note the prominent hair tufts on the exserted anthers; d. New Guinea plant showing corolla with broad rotate shape and very short tube, protruding stamens; e. Sumatra plant with broadly rotate corolla, pale yellow colour, and thinly membranous texture (at midafternoon) (a, c: George Staples, voucher: Sugau et al. SAN­152853 in SAN; b: George Staples, voucher: Sugau et al. SAN­152876 in SAN; d: Serena Lee, voucher: S. Lee et al. SL­346 in SING; e: George Staples, voucher: Nurainas et al. 2535 in ANDA).