Pteris hivaoaensis Lorence & K. R. Wood, 2011

Lorence, David H., Wagner, Warren L., Wood, Kenneth R. & Smith, Alan R., 2011, New pteridophyte species and combinations from the Marquesas Islands, French Polynesia, PhytoKeys 4, pp. 5-51 : 18-19

6. Pteris hivaoaensis Lorence & K. R. Wood sp. nov. Figs 8 15B

Latin.

Ab aliis Marquesas speciebus laminis 1-pinnatis usque ad 1-pinnato-pinnatifidis, apice cum 6-7 loborum paribus distalibus falcatis, glabris vel glabrescentibus stipitibus differt.

Type.

Marquesas Islands: Hiva Oa: Temetiu, windswept ridges and drainages, 9°49'S, 139°4'W, 930 m (3050 ft), 24 August 1995, K. R. Wood 4374(Holotype PTBG-038496!; Isotypes BISH!, P!, PAP!, US!).

Description.

Lithophytic ferns; rhizomes erect, clumping together, 3-7 cm long,15-22 mm in diameter, clothed in very narrow, golden-brown acicular hairlike scales 1-2 mm long. Fronds erect or arching-pendent, to 30 cm long, clustered at rhizome apex; stipes ca. ½ length of frond, up to 1 mm in diameter medially, atrocastaneous, grooved adaxially, sparsely pustulate-tuberculate, glabrous except for a few linear to linear-lanceolate, falcate scales 2-3 × 0.1-0.5 mm at bases, tan-brown, margins subentire; blades chartaceous, glabrous, narrowly ovate to lanceolate, 10-16 × 5-9 cm; proximal 2-3 pinnae consisting of subopposite, subequal pairs, 1-pinnate-pinnatifid for most of length, sessile or stalked up to 2 mm, non-articulate, bearing 2-3 pair of falcate lobes of increasing size proximally with maximum size at basiscopic lobe of lowest pinnae, lobes linear-oblong or linear-triangular 0.3-2.5 × 0.3-11 mm, apices rounded to acute, crenate to dentate, basal pinnae slightly reduced, blade distally pinnatifid, lanceolate, the apex pinnatifid, with 6-7 pairs of falcate lobes 5-8 mm wide above their bases, dilated basiscopically, margins mostly entire, tapering gradually to acute apices with crenate-dentate margins, single terminal lobe falcate or tapering to narrowly linear crenate margin; margins of sterile pinnae finely dentate with one tooth per vein ending; costae and costules grooved adaxially, rounded abaxially, similar to stipe in color; veins netted with 1-2 rows of areoles. Sori occasionally interrupted at sinuses and absent at apices of segment; indusia tan-brown with entire margins. Spores tan-brown.

Distribution.

Known only from Hiva Oa, Marquesas Islands.

Ecology.

This rare species is known only from the type location at 930 m on wet stream walls adjacent to wet forest dominated by Cheirodendron bastardianum , Crossostylis biflora , Metrosideros collina , Weinmannia marquesana var. marquesana and other associates including Alsophila tahitensis , Cyrtandra spp., Freycinetia sp., Leptochloa marquisensis (F. Br.) P. M. Peterson & Judz., Melicope spp., and Psychotria spp., interspersed with a rich pteridophyte understory. The main threats to this habitat are feral pigs and invasives plants including Elephantopus mollis Kunth, Psidium guajava , and Syzygium cumini (L.) Skeels.

Conservation status.

Proposed IUCN Red List Category 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 mature individuals. The suitable habitat for Pteris hivaoaensis on Hiva Oa (ca. 315 km2) is indicated as an endangered environment, threatened by human activity (deforestation, fire), feral animals, and invasive plants, reducing the extent of the forest. D, the rarity of this species is supported by the lack of collections and the small extant area within a commonly collected island, i.e. with a single collection.

Etymology.

This new species is named for its only known island of occurrence.

Discussion.

Pteris hivaoaensis is quite distinct from the other Marquesan Pteris species, differing by its pinnate to pinnate-pinnatifid blades with glabrous or glabrescent stipes and the apex pinnatifid with 6-7 pairs of falcate lobes.

Figures

Figure 8. Pteris hivaoaensis Lorence & K. R. Wood. A habit B lower surface of fertile pinna C sterile pinnule, detail of venation D lower surface of fertile pinnule showing sori E rhizome scale. Drawn from the type collection (Wood 4374) and field images.

Figure 15. A Polystichum uahukaense, frond (Ua Huka, Wood 10518) B Pteris hivaoaensis (Hiva Oa, Wood 4374) C, D Pteris marquesensis C frond D rhizome and stipe bases (both Hiva Oa, Wood 10871) E Pteris tahuataensis (Tahuata, Wood 10083) F Thelypteris marquesensis, habit, colony on wet rock face (Hiva Oa, Wood 4408).