Heliotropium marchionicum Decne., Voy. Venus, Bot. [Alt.] 21. 1864.

Lorence, David H. & Wagner, Warren L., 2015, Heliotropium (Boraginaceae) in the Marquesas Islands (French Polynesia) with description of a new species, PhytoKeys 47, pp. 49-57 : 52-53

Heliotropium marchionicum Decne., Voy. Venus, Bot. [Alt.] 21. 1864.

Type.

Iles Marquises [Marquesas Islands], Noukahiva [Nuku Hiva], “toutemanou”, pl. herbacee sur le sommet du montagne, Le Bastard 76 (Holotype P, digital image!). Figure 2.

Description.

Shrubs or suffrutescent perennials 1-2 m tall, stems erect or decumbent, sympodially branched, with usually only a single lateral branch 30-120 cm long developing adjacent to inflorescence, terete, 1.5-3 mm diam., most parts densely silvery white strigillose with ascending white trichomes 0.2-0.5 mm long. Leaves subopposite to alternate, blade elliptic to narrowly elliptic or obovate-elliptic, 1-5 × 0.5 -1.5 cm, apex acute, obtuse or rounded, often apiculate, base acute to narrowly cuneate, sometimes attenuate, chartaceous to subcoriaceous, both surfaces strigillose to densely white strigillose with appressed white trichomes 0.2-0.4 mm long, smooth or sometimes pustular, secondary veins 2-3 pairs arising in basal half of lamina; petiole 3-15 mm. Inflorescences terminal and later displaced by growth of one axillary bud, or sometimes leaf-opposed, scorpioid-cymose, densely white strigillose as for stems and leaves, 4-7 cm long, forked once, peduncle 1-2 cm long, primary branches 2.5-7 cm long, each with 17-35 flowers. Flowers sessile or subsessile, calyx lobes 5, densely white strigillose, free to the base, subequal, ovate to lanceolate, 1.7-2.2 × 0.7-1.2 mm, acute to acuminate; corolla shortly funnelform, 2.6-3.2 mm, tube 2.0-2.2 mm, externally strigillose except at base, internally with pubescent lines below the lobes, lobes 5, subcircular, 1.2-1.7 × 0.8-1.3 mm × 0.8 mm, margins crisped, dorsally strigillose medially; stamens 5, attached below middle of tube, basifixed, anthers linear-oblong, 0.6-0.7 mm long, glabrous, not connate; ovary ovoid, densely strigillose, 0.5 mm long, style terminal, 0.3-0.6 mm long, glabrous, stigmatic column 0.4-0.5 mm, cylindrical-conical, papillose, apex strigillose, base annular. Fruit broadly ovoid, 1.5-2.0 × 2.0 mm, shallowly 4-lobed, externally strigillose, dry, splitting into 4 wedge-shaped nutlets. Nutlets 1.4-1.6 × 0.8-1.0 mm, apiculate, dorsally densely strigillose, ventrally glabrous, dark brown.

Distribution.

Marquesas Islands, known only from Nuku Hiva.

Habitat.

This species usually occurs inland on basaltic cliffs and dry ridges, sometimes near waterfalls, in dry land forest with Sapindus saponaria L., Cerbera manghas L., and introduced invasive species including Tecoma stans (L.) Kunth and Leucaena leucocephala (Lam.) De Wit. The label on one collection notes it is a low elevation littoral plant (Brown 542, BISH).

Conservation status.

Proposed IUCN Red List Category Endangered (EN): B1ab (i, ii, iii) + 2ab (i, ii, iii): B2: total area of occupancy less than 500 km² (ca. 50 km²). B1a, severely fragmented; B1b (1-iii), habitat quality continuing decline inferred. The suitable habitat for Heliotropium marchionicum on Nuku Huka (ca. 340 km²) is indicated as an endangered environment, threatened by human activity (deforestation), feral animals, and invasive plants, thus reducing the extent of the suitable habitat.

Discussion.

Heliotropium marchionicum is apparently closely related to H. permanii but differs by the characters noted above. A single collection from Taiohae, Nuku Hiva (Florence 8394, BISH, CHR, K, NY, P, US) resembles Heliotropium marchionicum superficially but differs in having stems and petioles pilose with hairs to 1 mm long, inflorescence axis pilose, very small flowers (calyx lobes 1-1.1 mm long, corolla 1.1-1.3 mm long) and ribbed fruits 1.1-1.2 × 1.8 mm, covered with bulbous-tuberculate scales, splitting into 4 nutlets. Further collections are needed to determine whether it represents an undescribed taxon or alternatively a naturalized species. It closely resembles H. angiospermum Murr., native to North America and the Caribbean and was identified by M. Strong (US) as this species.

Specimens examined.

Marquesas Islands. Nuku Hiva: Hakaui, 20 July 1921, F.B.H. Brown 542 (BISH); Moyenne vallée de Hakaui, flanc droit, 125 m, latitude 08°54'S, longitude 140°10'W, 18 May 1984, J. Florence 6695 (BISH, P); Hakaui Valley, 107 m elevation, 26 June 1988, S. P. Perlman 10005 (AD, BISH, F, MO, MU, NY, OS, P, PAP, PTBG, US); Matatekouaehi Valley, about 2 miles in from coast, by 100 ft. waterfall, 1 July 1988, S. P. Perlman 10026 (BISH, PTBG, US); Taiohae, flanc gauche de la baie, S du CJA, 150 m, latitude 08°56'S, longitude 140°05'W, 26 Jul 1987, J. Florence 8394 (BISH, CHR, K, NY, P, US),W shore, 200 m elevation, 20 Oct 1922, W.B. Jones 1591 (BKL); slope on ridge, 18 Oct 1922, E.H. Quayle 1591 (A, BISH); without precise locality, 1841, R. Hinds s.n. (P), Mathias 96 (GH), 1847, M.P. Mercier s.n. (P, US).