Decalobanthus discoidespermus (Donn.Sm.) Staples, 2022

Staples, G., 2022, A synoptic revision of the golden glories, genus Decalobanthus (Convolvulaceae), Blumea 67 (1), pp. 37-70 : 49-50

8. Decalobanthus discoidespermus (Donn.Sm.) Staples , comb. nov. — Fig. 5 ; Map 6

Ipomoea discoidesperma Donn.Sm., Bot. Gaz. 14 (1889) 27. — Operculina discoidesperma (Donn.Sm.) House (1909) 68. — Merremia discoidesperma (Donn.Sm.) C.A. O’Donnell (1941) 495. — Lectotype (first step designated by Standley & Williams(1970) 73,second step designated here;see Typification): Von Türckheim 744 (lecto US [ US 00111388]; isolecto US [ US 00111389]*), Guatemala, Alta Verapaz, Pansamalá.

Operculina populifolia Hallier f. ex Urb. (1912) 342. — Lectotype (designated by Staples et al. (2020) 131): Wright 3083 (lecto MO [MO-150302]), Cuba.

Stems and branches not lenticellate. Leaves basally attached, broadly ovate to suborbicular, 6–14 by 3.5–12 cm, bases rounded to emarginate; secondary veins 5–7 on either side of the midvein. Inflorescences cymose or flowers solitary; bracts caducous. Flower sepals equal, ovate, 20–26 by 10–16 mm, apically rounded to acute; corollas tubular-funnelform, 4.8–6 cm long, bright yellow, glabrous, limb 3–3.5 cm diam, entire or 5-sided; stamens unequal, included, filaments hairy above insertion point, anthers 3–5 mm long; pistil included, equalling or slightly exceeding stamens. Fruiting calyx accrescent, woody, blackish, deciduous. Fruit a utricle, globose, 3–4 cm diam, chartaceous, pale brown, tardily breaking irregularly. Seed 1, quatrefoil, flattened spheroidal, 1.8–2.5 cm diam, bearing a circular hilum on one side and an impressed cross on the reverse, black, velutinous at first, later glabrous and shiny.

Previously published illustrations — Gunn (1977: f. 6, 7). An excellent series of detailed colour photos taken in the field by Reinaldo Aguilar (https://flic.kr/p/2mdpYGA vouchered by Aguilar 17796 in CR) is available online.

Distribution — Pacific and Atlantic coasts of Middle America (southern Mexico, Guatemala, Nicaragua, Costa Rica), and the Greater Antilles ( Cuba, Dominican Republic, Haiti) in the Caribbean. Absent from Belize, El Salvador, and Honduras, whether from low collecting density or lack of suitable habitats is unknown. Reports for Panamá are based solely on drift seeds found on beaches as pointed out by Gunn (1977); the species was not included in the ‘Flora of Panama Convolvulaceae’ ( Austin 1975, 1978).

Habitat & Ecology — A species seemingly always found in forested habitats such as selva alta perennifolia (primaria) (tall evergreen primary forest), lower montane rain forest, cloud forest (broadleaf), and wet somewhat degraded rainforest. Soil types recorded include a limestone fissured ridge and deep laterite (on eruptive). Elevations range from 100–900(–1650) m .

Vernacular names — Cuba: Almorrana ( Alain 1957), terciopelo (Eggers 4981), tomate de mar ( Alain 1957). Guatemala: Boton de terciopelo (Von Türckheim 744), quiebra-cajete ( Standley & Williams 1970). Mexico: Ppak i kaknab (Mayan; Gunn 1977: 237), quiebraplato amarillo (Spanish; Dugés s.n.). Nicaragua: Contra-venano (E.P. Alexander s.n.). English name for the seed: Mary’s-bean ( Gunn 1977).

Uses — The seeds are well documented to drift thousands of kilometres via ocean currents ( Gunn & Dennis 1976, Gunn 1977) in both the North Atlantic and North Pacific. Several ethnobotanical uses are known in places where these seeds wash ashore ( Gunn & Dennis 1976, Gunn 1977).

Typification — John Donnell Smith (1889) did not desig- nate a holotype per se and cited two different specimens, Von Türckheim 744 and S. Watson 412, in the protologue, both of which, under the modern ICN (Turland et al. 2018), are to be considered syntypes. Standley & Williams (1970: 73) made an indirect first step lectotype choice when they stated the ‘type’ was ‘from Pansamalá, Türckheim 744’. Later mentions of the ‘holotype’ by Gunn (1977: 250) and ‘lectotype’ by McDonald (1993: 65) reiterated this choice. However, there are two sheets of Von Türckheim 744 in the US and I have here made a second step lectotypification by choosing the sheet with bar code US 00111388 as the lectotype.

Note — The vegetative and floral morphology of this Neotropical species is congruent with the genus concept for Decalobanthus as proposed here. However molecular sequences extracted from herbarium vouchers proved ambiguous and so the species has not been placed in any molecular phylogenetic arrangement published to date. When conclusive molecular data is available, I fully expect this species will be placed in the Decalobanthus clade. Nevertheless, on a morphological basis alone I am confident that this species belongs in Decalobanthus .

Figures

Map 6 Distribution of Decalobanthus discoidespermus (Donn.Sm.) Staples (wild plants = ■; cultivated plant = ●; seeds on ocean beaches = *).

Fig. 5 Decalobanthus discoidespermus (Donn.Sm.) Staples. a. Habit showing alternate, leathery, entire leaves with basal petiole attachment; b. mature fruit on vine, note absence of calyx and papery, indehiscent pericarp; c. flower in side view showing unequal sepals; d. mature fruit opened to show single seed, initially covered in velvety indumentum; e. corolla opened to expose stamens, note the pubescence on the filaments, pistil to left (a, b, d: Barry Hammel, voucher: B. Hammel et al. 27078 in CR; c, e: Reinaldo Aguilar, voucher: R. Aguilar 17796 in CR).