Blechnum pacificum Lorence & A. R. Sm.

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: 6-10

publication ID

http://dx.doi.org/10.3897/phytokeys.4.1602

publication LSID

lsid:zoobank.org:pub:39581BBC-24A2-42D6-B92B-0E83D499FCF8

persistent identifier

http://treatment.plazi.org/id/D37E08AC-8C8C-15BA-1E55-8AAEC7235AC9

treatment provided by

PhytoKeys by Pensoft

scientific name

Blechnum pacificum Lorence & A. R. Sm.
status

sp. nov.

1. Blechnum pacificum Lorence & A. R. Sm.   sp. nov. Figs 1 View Figure 1 2 View Figure 2 14A View Figure 14

Latin.

Species Blechno venoso Copel. affinis, sed stipitis squamis non tan numerosis, deciduis, leviter castaneis usque ad castaneis, sterilibus pinnis cum axialibus glabris et paulatim prominentibus venis, fertilibus pinnis cum viridi expansa textura prope basin differt.

Type.

Marquesas Islands: Ua Pou: Poumaka Summit Trail, 690 m elevation, 9°23'33"S, 140°04'59"W, 19 June 2004, L. M. Dunn and D. H. Lorence 481 (Holotype: PTBG-041866!, PTBG-041867! [2 sheets]; Isotypes BISH!, P!, PAP!, US!).

Blechnum capense   sensu E. D. Br. & F. B. Br., non Burm. f., non (L.) Schltdl.

Description.

Large terrestrial ferns; rhizomes erect or suberect, rarely decumbent and dorsiventral, short, stout, (10 –)15– 20 mm in diameter (excluding scales), apex covered with scales; scales of rhizome and bases of stipes linear-subulate to oblong-ovate, 20-30 ×1–3(– 5) mm, thin, light brown to brown, concolorous but somewhat thicker and darker basally and in center, basifixed, base rounded or truncate, apex sinuate, margins entire or subentire, cells linear, arranged in vertical rows. Fronds clustered near apices of rhizomes, usually dimorphic but both fertile and sterile pinnae occasionally occurring on the same blade; stipes 41-102 cm long, 4-10 mm in diameter, stout, light to dark brown when fresh, drying stramineous, densely scaly toward the bases, sparsely so distally, eventually glabrescent, smooth, grooved adaxially. Sterile blades 1-pinnate, oblong-ovate to oblong-elliptic, (35 –)50– 100 × (20 –)30– 60 cm, coriaceous to subcoriaceous, stiff, rachises stramineous or sometimes dark brown, proximal pinnae only slightly or not at all reduced, apices acute, each blade with a conform terminal pinna, when young the rachises, costae, costules, and veins scaly with thin, scurfy, brown to pale brown, oblong-ovate to subulate, contorted-sinuate scales to 10 mm long with margins subentire or sometimes lacerate basally; pinnae 19-30 on a side, with a slightly swollen, mammiform aerophore at the base each pinna, basal pinnae opposite and shortly stipitate (to 2 mm), the distal ones becoming subopposite to alternate, sessile with basiscopic base often adnate to rachis, terminal pinna free, conform, medial pinnae 11-30 × 1.5-2.5 cm, linear, margins serrulate, often decidedly undulate, apices acute or acuminate, serrulate, acroscopic bases oblique-cuneate, basiscopic base truncate or rounded, the veins prominulous, simple or 1-forked, free, each ending in a marginal tooth; fertile fronds subequal to or slightly smaller than sterile, with up to 40 pinnae pairs (sometimes the proximal pinnae sterile and distal pinnae fertile on the same frond), fertile pinnae approximately the same length as sterile pinnae but narrower, 2.5-5 mm wide, the margins strongly revolute, the sori covering most of the abaxial surface but usually with some expanded green tissue at the base, adaxially glabrate. Sori linear, abaxial surface of pinnae bordered or partly covered by the reflexed, scarious, erose blade margins except on expanded green bases. Spores subellipsoidal, 67 × 47 µm including a perispore 8-12 µm wide.

Distribution.

Known from the Marquesas Islands (Nuku Hiva, Ua Pou, Hiva Oa, Tahuata, and Fatu Hiva), Society Islands (Moorea, Raiatea, and Tahiti), and Austral Islands (Rapa Iti).

Ecology.

This new terrestrial species occurs in clearings or shade from 380 to 1500 m elevation in lowland to montane mesic and wet forests, shrubland or fernland, in valleys, on slopes or ridge crests and rocky banks. In the Marquesas associated species include Crossostylis biflora   J. R. Forst. & G. Forst., Dicranopteris linearis   (Burm. f.) Underw., Freycinetia impavida (Gaudich. ex Hombr.) B. C. Stone, Metrosideros collina (J. R. Forst. & G. Forst.) A. Gray, Pandanus tectorius Parkinson, Santalum insulare Bertero ex A. DC., and other native tree, shrub, and pteridophyte species. Threats include competition from alien plant species and damage from feral ungulates. Although this is the most widely distributed of the new species, it is clearly at risk due to habitat loss and degradation.

Etymology.

The epithet refers to the Pacific distribution of this new species.

Conservation status.

IUCN Red List Category: Vulnerable (VU): B1: total area of occupancy less than 20,000 km2 (ca. 750 km2); b ( i–iii), habitat continuing decline inferred; B2: total area of occupancy less than 2000 km2 (ca. 750 km2); B2b ( i–iii), habitat continuing decline inferred. The suitable habitat for Blechnum pacificum   on most islands of occurrence is indicated as a declining or endangered environment, threatened by human activity (deforestation, fire), feral animals, and invasive plants, reducing the extent of the forest.

Specimens examined.

Austral Islands: Rapa Iti. Perau–Mamuere summit, eastern peaks, 27°S, 144°W, 10-100 ft (3-30 m), Wood & Faraire 9777 (NY, PTBG [4 sheets]), Fosberg 11567 (UC), Fosberg 11601 (UC), Fosberg 11605 (UC); St. John & Fosberg 15293 (UC). Society Islands: Moorea: Mt. Rotui, 149°50'18W, 17°30'38S, 916 m, Nitta & Vinette 212 (PAP, UC); Mt. Tohiea, 149.819°, 17.553°, 994 m, Nitta & Vinette 320 (PAP, UC). Tahiti. Pirae–Maoua Aorai trail, Quayle 105A (BISH, UC); Orofena, east side of south ridge, ravine in rain forest, St. John & Fosberg 17114 (BISH); Mt. Marau road, crest between Tapaerui and Punaruu valley, 1250 m, Fosberg 62647 (PTBG [2 sheets], US); Orofena, south ridge, moist thicket on exposed ridge, 1600 m, St. John & Fosberg 17082 (UC); Mahina, Ahonu-tuauru, 2875 ft (876 m), Grant 4394 (UC); Aorai, in summit shrubs, 6700 ft (2042 m), M. L. Grant 3791 (UC); Faaa, Mt. Marau, 3 km below TV tower, 1300 m, Hodel 1375 (UC); Fautaua, below Diadem, 2830 ft (863 m), Grant 3546 (UC). Raiatea: Temehani Plain, Moore 175 (BISH [2 sheets]). Marquesas Islands: Nuku Hiva: Toovii, 1000 m, Brown & Brown 528 (BISH); Toovii Plateau, spur of Mt. Ooumu, 790 m, Gagné 1039 (US); Tauamaka, Toovii plateau, 1000 m, Mumford & Adamson 576 (BISH, UC); without precise locality, 1000 m, Quayle 1284 (BISH), Quayle 1298 (BISH). Ua Pou: Mt. Tekahoipu, 800 m, Quayle 1138 (BISH [2]); Tekohepo, summit, 2500-3000 ft (762-914 ft), 09°24'31"S, 140°04'21"W, Wood & Perlman 6455 (PTBG [2 sheets], US); Drainage northwest of Teavahaakiti, 700 m, Wood 10458 (P, PAP, PTBG, US). Hiva Oa: road from Atuona to Puamau, just below Ootua, 625-700 m, Sachet & Decker 1904 (PTBG, US); Puamau, along Puamau–Atuona trail, 500-650 m, Decker 1190 (PTBG, US); Feani, 800 m, Brown 877 (BISH [3]); Atuona–Feani Trail, ridge crest, 1200-1300 m, 24-26 Sep. 1963, Sachet & Decker 1160 (US [2]); Montagnes NW du Temetiu, entre la haute vallée de Hanamenu et la crête de Temetiu–Feani, 850 m, Schäfer 5932 (US); Vaiata, NW slopes of Mt. Ootua, 800 m, Mumford & Adamson 355 (BISH); Feani ridge to upper slopes of dry side of island, 1150 m, Oliver & Schäfer 3130 (US [2]); Temetiu, 1100 m, Pacific Entomol. Surv. 156 (BISH); above Atuona, 800 m, Pacific Entomol. Surv. Ex 355 (BISH); Hanaiapa, 700 m, Jones 1613 (BISH [2 sheets]); without precise locality, 800 m, Brown 16 (BISH). Tahuata: de Hamatea [Amatea] à la crête centrale de l’île, 750-850 m, Thibault 64 (US); Mt. Amatea, 1000 m, Jones 1796 (BISH). Fatu Hiva: ‘Omo’a-Ouia-Mounanui Trail, 690 m, Gagné & Montgomery 2323 (BISH); trail from ‘Omo’a along Punaitai ridge crest to base of Tekou peak, 550-840 m, Lorence et al. 6171 (BISH, PAP, PTBG); Hanavave, 600 m, Jones 1826 (BISH); Sentier d’Ouia, W du col, lieu-dit Tahuna, 620 m, Schäfer 5803 (US).

Discussion.

The name Blechum capense   Burm. f. has been erroneously applied to this new Polynesian species ( Brown and Brown 1931; Copeland 1932). The true Blechnum capense   is confined to southern Africa and some nearby islands ( Burrows 1990; Roux 2001). This southern African species has also been treated under the name Blechnum sylvaticum   Schelpe (Schelpe 1979; Jacobson 1983), on the false assumption that the type of Blechnum capense Burm. f. was a mixed collection of two species ( Jacobson 1983). However, there seem to be good reasons for placing Blechnum sylvaticum   in synonymy under Blechnum capense   (Roux 1982; Schelpe and Anthony 1986; Burrows 1990; Roux 2001).

The name Blechnum procerum   G. Forst. has also been incorrectly applied to the Polynesian plants. Quoting Nicolson and Fosberg (2004: 125-126), who stated that the type of Blechnum procerum   is from New Zealand: "Tindale (1960b: 254) published a photo (t. 7) of the Goettingen material [Nova Zeelandia, Forster 295, GOET] as 'Type specimen’ and referred to BM and K specimens as 'Forster material.' Chambers and Farrant (1998a: 4), without discussion, said 'T. Noua Zeelandia, Forster; lecto (here chosen): K; isolecto: BM, GOET (photo seen). ’” Nicolson and Fosberg (2004: 126) further stated "There is considerable confusion about the names applied to this taxon and the following quotation from Brownsey and Smith-Dodsworth (2001) summarized it well: 'The name Blechnum minus   was used incorrectly by Allan (1961) and Crookes (1963) for the plant we call Blechnum procerum   . The true Blechnum minus   , or swamp kiokio, is only doubtfully distinct from the common kiokio (previously known as Blechnum capense   ). ’” Blechnum procerum   has lower pinnae only slightly reduced (not less than half the length of the median pinnae), fertile fronds are up to 50% longer than sterile fronds, and the fertile pinnae show no expanded green tissue at the base in the type as in Blechnum pacificum   . Clearly, the name Blechnum procerum   does not apply to the Polynesian plants.

In New Zealand, closest relatives appear to be Blechnum novae-zelandiae   T. C. Chambers & P. A. Farrant and Blechnum minus   (R. Br.) Ettingsh., neither of which is conspecific with our Polynesian plants. Blechnum novae-zelandiae   is superficially similar but differs in having reduced proximal pinnae and distinctive “black-spot” rhizome and stipe scales with dark brown or black centers and pale margins (Chambers and Farrant 1998). From evidence presented in a recent paper on the phylogeny of New Zealand Blechnaceae   by Shepherd et al. (2007, Fig. 2), it seems likely that if Blechnum pacificum   were sampled, it would fall somewhere in the clade containing Blechnum wattsii   Tindale and Blechnum novae-zelandiae   .

Several species from New Caledonia, all considered endemic, form a confusing array of species somewhat similar to Blechnum pacificum   . These include Blechnum confusum   (E. Fourn.) Brownlie, Blechnum chauliodontum   Copel., and Blechnum subcordatum   (E. Fourn.) Brownlie. Brownlie’s (1969) illustration and characterization of Blechnum subcordatum   suggests that it differs in having smaller fronds with less scaly stipes and rachises, fewer pinnae pairs (5-15), and sterile pinnae not so undulate at the margins. Blechnum confusum   differs in its strongly ascending, more sharply serrulate and less scaly pinnae (sterile blades are nearly glabrous). The closest species in Malesia (excluding Papua New Guinea) appears to be Blechnum vestitum   (Blume) Kuhn, nom. cons., non Blechnum vestitum   T. Moore (see Chambers and Farrant 2001; Chambers 2004; McNeill et al. 2006: 438). The Papua New Guinea species Blechnum dilatatum   (Brause) T. C. Chambers & P. A. Farrant is similar to Blechnum pacificum   in having fertile pinnae with an expanded basal sterile region, but in the latter the margins are never revolute and the rhizome scales are thin, concolorous, and pale to medium brown. No names of taxa with types from Fiji apply to the new species, the closest species there being Blechnum milnei   (Carruthers) C. Chr. (historically also called Blechnum procerum   ), which differs in having very large fronds with generally broader, less coriaceous pinnae and a less scaly rachis and costae on the sterile blades, and fertile pinnae lacking expanded green tissue at the base.

Among the Polynesian species of Blechnum   , Blechnum pacificum   seems most closely related to Blechnum venosum   Copel. from Rapa Iti in the Austral Islands. In addition to having copious, shiny, dark brown, almost blackish scales on the stipes as noted in the diagnosis, the veins of Blechnum venosum   are very prominent and strongly raised above the surface on the abaxial side of blades, whereas the veins in Blechnum pacificum   are visible abaxially but scarcely, if at all, raised. This gives Blechnum venosum   a much harsher, more cartilaginous appearance. Also, in Blechnum venosum   , there are very short hairs on the veins abaxially and some hairs are even present between the veins on laminar tissue, but Blechnum pacificum   lacks such hairs. In Blechnum venosum   , some of these hairs on the veins and laminar tissue appear multicellular (septate, but uniseriate), and glandular or gland-tipped. Also, pinna margins in Blechnum pacificum   are more crenulate (scalloped) than in Blechnum venosum   which has entire margins.