Oparanthus tiva W. L. Wagner & Lorence, 2011

Wagner, Warren L. & Lorence, David H., 2011, Two new Marquesan species of the southeastern Polynesian genus Oparanthus (Asteraceae, Coreopsidinae), PhytoKeys 4, pp. 139-148 : 141-142

Oparanthus tiva W. L. Wagner & Lorence sp. nov. Fig. 1 3C

Latin.

Ab O. hivoano foliis tenue coriaceis, 10-19.3 × 6-15.8 cm, testibus 9-14 mm diametro, 10-20 mm altis, paleis flosculorum radiorum 10-11 mm longis, paleis flosculorum discorum 12-13 mm longis, 12-13 achenis sterili disci differt.

Type.

Marquesas Islands: Tahuata, ridge E of trail ridge up to Amatea from Kuaee, E facing slope, 2560 ft (780 m), 18 July 1997, S. P. Perlman, K. R. Wood, and J. P. Luce 16008 (Holotype: PTBG-025572!; isotypes: BISH!, P!, PAP!, US!).

Description.

Trees 3-7 m tall, subglabrous, functionally monoecious, the main trunk to 30 cm in diameter, often with multiple prop roots, bark brown, wood cream colored, the young stems with short internodes. Leaves thinly coriaceous, the blade ovate to very broadly ovate, 10-19.3 × 6-15.8 cm, the young ones often viscous and with a turpentine-like scent, secondary veins 6-18 mm apart, abaxial axils with domatia with small tufts of hairs, margins weakly dentate to subentire, apex bluntly acuminate to obtuse, base obtuse to occasionally truncate, often oblique; petioles 3-9 cm long. Inflorescences terminal, heads in clusters of 3, 9-14 mm in diameter, 10-20 mm high; peduncles 15-76 mm long; involucre campanulate, the bracts 7-9, in 2 series, 7-11 mm long, the external ones wider and thicker; receptacular bracts of ray florets 10-11 mm long, those of disk florets 12-13 mm long; ray florets 8-10 in 1-3 series, white, corolla tube and throat 3-4 mm long, limb 3-3.8 mm long, shallowly toothed; disk florets 18-20, white, corolla tube and throat 3.5-4 mm long, the lobes 3 mm long. Ray achenes 8-9 mm long, narrowly elliptic to lanceolate, winged on both margins, the wings up to 1 mm wide, the wing margin smooth, extending beyond the achene apex; the disk achenes sterile, linear, 12-13 mm long.

Etymology.

We are pleased to name this new species in recognition of its first collector, Steven P. Perlman, known in the Marquesas by his nickname “Tiva”, in recognition of his contributions to our knowledge of the flora of the Pacific region.

Distribution.

Endemic to the Marquesas Islands and restricted to the vicinity of the type locality on Tahuata.

Ecology.

Scattered to locally common in the low wet forest, dominated by species of Alsophila , Crossostylis , Freycinetia , Hibiscus , Metrosideros , Reynoldsia , and Weinmannia , with an understory rich in plants such as Cyrtandra , Dicranopteris , Gahnia , Macropiper , Marattia , Morinda , and Psychotria , from 790 to 900 m elevation, usually on windswept slopes and gulches of summit areas. Known to flower and fruit in July.

Conservation status.

Following the criteria and categories of IUCN (2001) it is assigned a preliminary status of Critically Endangered (CR): B2a, B2b (i-iii); D: B2: total area of occupancy less than 10 km2 (ca. 5 km2). B2a, a single population known; b ( i–iii), habitat continuing decline inferred; D, population estimated to number fewer than 250 individuals. The suitable habitat for Oparanthus tiva on Tahuata (c. 61 km2) is indicated as an endangered environment, threatened feral animals and invasive plants, reducing the extent of the forest. The known habitat is not pristine and non-native plants such as Ageratum conyzoides L., Elephantopus mollis Kunth, Melinis repens (Willd.) Zizka, Paspalum conjugatum P. J. Bergius, Paspalum paniculatum L., Psidium guajava L., Spathoglottis plicata Blume, and Zingiber zerumbet (L.) Sm. were observed in the area.

Specimen examined.

Marquesas Islands: Tahuata: ridge from Amatea to Moteve passing Meikaea, view down is on village of Hanatetena, on E facing slope, Perlman et al. 15977 (BISH, P, PAP, PTBG, US); off trail from Amatea to Moteve, above Haaoipu Bay, to NE of Hanatetena, top of ridge crest, W facing slope, Perlman et al. 15998 (PTBG); Haaoiputeomo summit region, upper drainage to N of satellite dish, [09 56'S, 139 04'W], Wood 6523 (BISH, MO, NY, P, PAP, PTBG [2], US); Amate a region, locations around Haaoiputeomo satelite dish (parabowl), Wood 10263(PAP, PTBG, US), Wood 10265(PAP, PTBG, US).

Discussion.

Oparanthus tiva has domatia (with an associated tuft of hairs) on the abaxial surface of the leaves. Domatia are essentially absent in the family, so domatia in Oparanthus tiva should be investigated further to understand the ecological significance. When domatia were discovered in Oparanthus tiva , we reexamined the other species of the genus and those of the closely related genus Fitchia . We found them only in the closest relative, Oparanthus hivoanus and in the Nuku Hiva species, Oparanthus woodii , but in these without the associated tuft of hairs covering the pit. Oparanthus tiva is a relatively rare species with an estimated 100 individuals known. It is distinguished from Oparanthus hivoanus by the tree habit, leaves thinly coriaceous, 10-19.3 × 6-15.8 cm, larger heads 9-14 mm in diameter, 10-20 mm high, receptacular bracts of ray florets 10-11 mm long, those of disk florets 12-13 mm long, and the sterile disk achenes 12-13.