Polystichum kenwoodii Lorence & W. L. Wagner, 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 : 14-16

4. Polystichum kenwoodii Lorence & W. L. Wagner sp. nov. Figs 6 14E

Latin.

A Polytsicho marquisensi E. D. Br. longioribus et angustis rhizomatibus, stipitis squamis 20-35 mm, squamis prope stipitis basin congregates, soris indusiatis differt.

Type.

Marquesas Islands: Ua Huka: Vaikivi summit region and drainage, 8°54'S, 139°31'W, 600 m, 16 June 2004, K. R. Wood 10759 (Holotype PTBG-044161!, PTBG-044162!, PTBG-044163! [3 sheets]; Isotypes BISH!, P!, PAP!, US!).

Description.

Terrestrial ferns; rhizomes erect or suberect, 7-20 cm long, 5-15 cm in diameter including bases of stipes (from collector’s notes); rhizome scales 20-35 × 2-2.5 mm, linear-oblong, concolorous, medium brown, margins entire, cells narrow linear, in sinuous files, mixed with slender hairlike scales. Fronds clustered; stipes 55-90 cm long, 5-6 mm in diameter medially, 2/5 as long as or equaling length of the blade, adaxially grooved, pale brown, basally densely clothed with reddish brown, linear to linear-oblong scales 10-30 × 1.5-3 mm, similar to rhizome scales, stipes distally with progressively smaller and finer scales mixed with matted hairlike scales or glabrescent; blades narrowly ovate to oblong-ovate, 50-83 × 30-32 cm, tripinnate at least in lower pinnae, with 20-28 pinnae on a side; rachises stramineous, moderately to densely scaly with reddish brown hairlike scales to 8 mm long; pinnae linear-oblong, apices long-acuminate, largest pinnae 8-26 × 4.5-7 cm, lowermost2(-3) pinnae pairs slightly reduced, costules adaxially grooved; largest pinnae with up to 32 pairs of pinnules, pinnules deeply incised acro- and basiscopically forming 1-2 free, obovate lobes or blades tripinnate in large fronds, pinnule apices obtuse, tips abruptly acuminate-aristate, both margins serrate-crenate, blades stiffly chartaceous to subcoriaceous, adaxially glabrous except for a few hairlike scales basally, abaxially with whitish or tan hairlike scales with expanded lacerate-ciliate bases on costules and veins; veins forking, scarcely visible adaxially, slightly prominulous abaxially. Sori with a peltate indusium 0.5-0.7 mm in diameter, tan, thin and fugacious, with scattered marginal projections, not confluent at maturity. Spores dark brown.

Distribution.

Marquesas Islands, known from Ua Huka, Hiva Oa, and Tahuata.

Habitat.

This new species occurs at 600-884 m elevation in diverse montane wet forest and shrubland dominated by Freycinetia sp., Hibiscus tiliaceus, and Weinmannia marquesana var. marquesana with other associates including Alstonia marquisensis M. L.Grant, Boehmeria virgata (G. Forst.) Guill., Cheirondendron bastardianum (Decne.) Frodin, Crossostylis biflora, Cyclophyllum barbatum , Ficus prolixa var. prolixa, Metrosideros collina, Myrsine grantii Fosberg & Sachet, Reynoldsia marchionensis F. Br., Xyolosma suaveolens subsp. pubigera, and often growing with numerous other pteridophytes.It also occurs in transitional mesic to wet forest with Alsophila tahitensis , Crossostylis biflora , Freycinetia sp., Metrosideros collina, Pandanus tectorius , and Weinmannia marquesana var. marquesana. Polystichum kenwoodii grows terrestrially in forest understory or sometimes along boulder-strewn stream beds.

Etymology.

We take pleasure in naming this new species for its collector Kenneth R. Wood (1953-), whose excellent collections have contributed greatly to our knowledge of the Marquesas flora.

Conservation status.

Proposed IUCN Red List Category: Endangered (EN): B2a, B2b ( i–iii): B2: total area of occupancy less than 500 km2 (ca. 460 km2); B2a, severely fragmented with only three populations known; b ( i–iii), habitat continuing decline inferred. The suitable habitat for Polystichum kenwoodii on Ua Huka (ca. 83 km2), Hiva Oa (ca. 315 km2), and Tahuata (ca. 61 km2) is indicated as an endangered environment, threatened by human activity (deforestation and fire), feral animals, and invasive plants, reducing the extent of the forest.

Specimens examined.

Marquesas Islands: Hiva Oa: Hanamenu region, up Hanamenu valley to the drainages below and west of Temetiu, 9°76'S, 139°0'W, 884 m, K. R. Wood 10232 (BISH, P, PAP, PTBG [3 sheets], US). Tahuata: Amatea region, around Haaoiputeomo satellite dish, 9°92'S, 139°8'W, 884 m, K. R. Wood 10257(BISH, P, PAP, PTBG [3 sheets], US).

Discussion.

Polystichum rapense E. D. Br. from Rapa Iti (Austral Islands) resembles this new species but differs in having very dark brown, almost black scales 3-4 mm wide on the rhizome and base of stipe and much smaller, bipinnate fronds (stipes 6-10 cm long, blades 11-14 × 8-10 cm). Polystichum stokesii , also from Rapa Iti, has similar dark brown to blackish, lustrous scales on the rhizome and base of stipe and shorter fronds with stipes to 20 cm long and blades to about 50 × 40 cm compared with Polystichum kenwoodii .

Figures

Figure 6. Polystichum kenwoodii Lorence & W. L. Wagner. A blade B stipe and part of rhizome C lower surface of fertile pinnule showing sori and scales D sorus with indusium and scales E rhizome scale F part of rhizome scale, detail of cells G lower surface of sterile pinnule showing scales. Drawn from type collection (Wood 10759) and field images.

Figure 14. A Blechnum pacificum, habit, habit, fertile and sterile fronds (Fatu Hiva, Lorence 6171) B-D Dryopteris macropholis B frond (Ua Huka, Wood 10489, type) C habit, D rhizome and stipe bases (C, D Hiva Oa, Wood 10045) E Polystichum kenwoodii, rhizome and stipe bases (Hiva Oa, Wood 10232) F Polystichum uahukaense, habit (Ua Huka, Wood 10552).