Thelypteris marquesensis 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 : 26-28

12. Thelypteris marquesensis Lorence & K. R. Wood sp. nov. Figs 13 15F

Latin.

Species Thelypteri quayleii affinis, sed minori habitu, laminis cum 1-3 paribus inferis deminutisque pinnarum, et pinnarum abaxiali superficie sine sessilibus glandis differt.

Type.

Marquesas Islands: Hiva Oa; Temetiu, windswept ridges and drainages, 3280 ft [999 m], 9°48'S, 139°4'W, 26 August 1995, K. R. Wood 4408 (holotype PTBG-038499!; isotypes, P!, PAP!, US!).

Description.

Small ferns, usually lithophytic, forming colonies over wet basalt rock faces (rarely mossy tree trunks); rhizomes slender, decumbent to suberect, unbranched, radial, 1.5-7 cm long, 0.4-1.2 cm in diameter, densely clothed by stipe bases, sparsely covered in red - brown, unicellular acicular hairs; fronds 7-9 per rhizome; stipes 1 –5(– 8.5) cm long, medium brown, moderately covered in unicellular acicular, red-brown hairs 0.5-0.7 mm long and scales, the scales sparsely scattered, those near base ovate-falcate, red-brown to brownish black, 1-2 × 0.5-0.7 mm, margins entire or with sparse short projections; blades 1-pinnate-pinnatifid, 2.5-8.5 × 1.2-2.8 cm, oblong-elliptic, rachises medium to red-brown, moderately covered with light brown, curved acicular hairs 0.3-0.7 mm long, apex pinnatifid, pinnae 5-12 pairs, largest pinnae 0.6-1.4 × 0.3-0.5 cm, apex obtuse, lobed (1/3-) ½ toward costa, lobes crenate, margins with acicular hairs 0.3-0.6 mm long, costules to 2 mm apart, lower pinnae slightly reduced and lower 2(-3) pairs deflexed, basal acroscopic pinnule 1 mm longer than next, veins 2-3 pairs in basal lobe, 1-2 pairs in middle lobes, abaxial surface of rachises and costae hirtellous with brown acicular hairs 0.2-0.7 mm long, adaxial surfaces glabrous or with occasional short acicular hairs 0.2-0.5 mm, sessile glands absent. Sori medial, 1(-2) per segment; indusia reniform to subcircular, margins with sessile glands, otherwise glabrous.

Distribution.

Known only on Hiva Oa, Marquesas Islands, from a single population in the vicinity of Mt. Temetiu, on the island’s central summit crest.

Ecology.

Thelypteris marquesensis occurs at 1000-1200 m elevation in low, windswept, montane wet forests and shrublands with Alsophila tahitensis , Cheirodendron bastardianum , Crossostylis biflora , Cyrtandra spp., Freycinetia spp., Leptochloa marquisensis, Melicope spp., Metrosideros collina , Psychotria spp., Weinmannia marquesana var. marquesana, and abundant pteridophytes in the understory. This new species is rare and localized, although in one area it occurs in dense colonies of hundreds of plants that completely cover wet banks and rock faces in and around shallow depressions or grottos, with fronds often appressed to the rock face (K. Wood, pers. obs.). Threats to this species include rooting by feral pigs and invasion by aggressive alien plant species, notably Elephantopus mollis , Psidium guajava , and Syzygium cumini .

Etymology.

This new species is named for the Marquesas Islands, where it is known currently known only from Hiva Oa.

Conservation status.

Proposed IUCN Red List Category Critically Endangered (CR): B2a, B2b i–iii): B1, extent of occurrence estimated to be less than 100 km2; B2, area of occupancy estimated to be less than 10 km2 (ca. 9 km2), and B2a, a single population known; b ( i–iii), habitat continuing decline inferred. The suitable habitat for Thelypteris marquesensis on Hiva Oa (ca. 315 km2), confined to Mt. Temetiu and vicinity, is indicated as an endangered environment, threatened by human activity (deforestation and fire), feral animals (pigs), and invasive plants, reducing the extent of the forest.

Discussion.

This new species differs from Thelypteris quaylei in its much smaller habit (although some specimens of Thelypteris quaylei from the Ua Huka summit are atypically small), fronds with 1-3, gradually reduced basal pairs of pinnae, and lack of sessile glands on the lamina surfaces (but present on indusial margins), a feature it shares with Thelypteris fasciculata Ching from New Caledonia, New Guinea, and the Celebes ( Holttum 1977). Although Thelypteris marquesensis may occur in the vicinity of Thelypteris quaylei (Lorence et al. 8942, PTBG), the latter species tends to grow in wet forest understory either terres trially or on mossy boulders, although it is sometimes found in shady depressions on steep ridge slopes either as individuals or forming small colonies.

Specimens examined.

Marquesas Islands: Hiva Oa: Temetiu, windswept ridges and drainages, 3900 ft, 9°48'S, 139°4'W, Wood 4392 (P, PAP, PTBG, UC, US); chemin d’Atuona a Hanamenu par Feani, pente vers Hanamenui, Schäfer 5195 (US); Atuona–Feani trail, crest of Feani ridge, Sachet & Decker1127 (US), 1192 (US).

Figures

Figure 13. Thelypteris marquesensis Lorence & K. R. Wood. A habit B lower surface fertile pinnae showing sori C lower surface of fertile pinna showing sori and hairs D rhizome scale. Drawn from the type collection (Wood 4408) 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).