Cyclosorus (Sphaerostephanos) castaneus A. R. Sm. & Lorence, 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 : 23-24

9. Cyclosorus (Sphaerostephanos) castaneus A. R. Sm. & Lorence sp. nov. Fig. 11

Latin.

A Cyclosoro heterocarpo (Blume) Ching numerosis, nitidis, castaneis, falcatis pilis 0.3-1.5 mm longis super rachides, costis et costulis abaxialibus, parva indusia 0.4-0.6 mm diametro, magis marcatis aerophoribus, fortasseque longioribus, magisque bene-formatis caudicibus differt.

Type.

Marquesas Islands: Nuku Hiva: Toovii region, trail along ridge from near l’Economie Rurale complex to Ooumu peak, 860-1080 m, 17 July 1988, D. Lorence (with W.L. Wagner, J. Florence and S. Perlman) 6115 (holotype PTBG!; isotypes BISH!, PAP!, US!).

Description.

Terrestrial ferns; rhizomes erect, caudices 15-60 cm long; fronds clustered, 7-10 per rhizome; base of stipes to first large pinnae 40-50 cm, distal part of stipes bearing 7-10 pairs of reduced pinnae 3-5 cm apart, 1 –7(– 35) mm long, the largest ones sometimes trifid; rachises reddish brown, bearing numerous reddish, often curved hairs; proximal large pinnae narrowed at their bases; blades, excluding reduced proximal pinnae, 50-70 cm long; largest pinnae 11-16 × 1.5-2 cm, at their bases each with a swollen, tuberculiform aerophore (most developed and scalelike, to 4 mm long in young fronds), pinnae bases not auricled, apices caudate-acuminate, lobed 2/3-3/4 toward the costae (2-3 mm from costae), lobes slightly falcate, rounded at tips; costules ca. 3-5 mm apart; veins to ca. 8-9 pairs per segment, the basal pair from adjacent segments anastomosing and producing an excurrent vein 1-1.5 mm long to the sinus, the next acroscopic vein to sinus-membrane; abaxial surface of costae with very short, hyaline, spreading to distally curved hairs 0.1 mm long and much longer and stouter falcate hairs to 0.3-1.5 mm on costae, scales lacking or costae with a few adpressed, tan, amorphous scales to 2 × 0.1 mm; yellowish sessile glands borne on abaxial laminar surfaces, often dense, absent or very sparse on adaxial laminar surfaces; stout reddish, falcate hairs adaxially on costae and costules to 1 mm long, with short, falcate hairs ca. 0.2-0.3 mm long sometimes on veins and between veins, especially below sinuses. Sori medial; indusia reddish brown to tan, ca. 0.4-0.6 mm in diameter, glabrous or with a few short hairs 0.1-0.2 mm long; sporangia with sessile, yellow glands on the capsules.

Distribution.

Known only from Nuku Hiva, Marquesas Islands.

Ecology.

This new species occurs in montane rain forest with fern understory. All three specimens seen were collected on Nuku Hiva on or near Ooumu Peak in the Toovii area and probably represent a single population.

Conservation status.

Proposed IUCN Red List Category Endangered (EN): B2a, B2b i–iii): B2: total area of occupancy less than 500 km2 (ca. 50 km2). B2a, a single population known; b ( i–iii), habitat continuing decline inferred. The suitable habitat for Cyclosorus castaneus on Nuku Huka (ca. 340 km2) is indicated as an endangered environment, threatened by human activity (deforestation), feral animals, and invasive plants, reducing the extent of the forest.

Etymology.

Named for the castaneous, curved hairs that are borne on the costae abaxially.

Specimens examined.

Marquesas Islands: Nuku Hiva: Toovii Plateau, trail behind L’Economie Rurale toward Ooumu peak; 3100 ft (945 m), S. Perlman 10125 (BISH, PTBG); Toovii, Ooumu area, top of Tapueahu Valley off new Hwy, 0851 S 14019 W, 3500-3700 ft (1067-1128 m), K. Wood 4578 (BISH, PAP, PTBG, US).

Discussion.

The three known specimens were previously determined as Sphaerostephanos (Cyclosorus) heterocarpus (Blume) Holttum, a related species known from Southeast Asia, Malesia, Australia (Queensland), Melanesia (Fiji, Vanuatu), and Samoa. From that species Cyclosorus castaneus differs in the numerous shiny, castaneous, falcate hairs 0.3-1.5 mm long, on the rachises, costae, and costules abaxially. These hairs vary in length, but are frequently longer than 0.5 mm on the costae. Cyclosorus heterocarpus shows considerable variation in indument (both length and disposition of hairs); however, the hairs in Cyclosorus heterocarpus are always hyaline, not so decidedly curved, and are generally much shorter than those in Cyclosorus castaneus . Holttum (1982) recognized many unnamed forms of Cyclosorus heterocarpus and produced a key to them based primarily on the depth of pinna lobing, presence/absence of sessile glands on the laminae adaxially, width of fertile pinnae, and presence/absence of hairs on the laminae adaxially. Cyclosorus heterocarpus also has larger indusia than Cyclosorus castaneus , often 1 mm in diameter or more, and the indusia envelop the sporangia when young. Some variants of Cyclosorus heterocarpus have sessile glands adaxially (rare in Cyclosorus castaneous ) and less deeply incised pinnae ( Holttum 1982). Aerophores in Cyclosorus heterocarpus appear to be much less developed, only a lunate, slightly raised area, or mammiform hump. In Cyclosorus castaneus , the aerophores are tuberculiform, peglike, or even scalelike, to 4 mm long. A single specimen from Ua Pou (Anakooma river valley just ESE of Oave peak, 470 m, Lorence 9117, PTBG) resembles Cyclosorus castaneus in having reddish hairs on the costae abaxially, but the hairs are less deeply colored and spreading, not falcate. Most sporangia seem empty, and what spores are formed are irregular, so it is possible this is a hybrid involving Cyclosorus castaneus and Cyclosorus florencei . However, neither parental species has been found on Ua Pou. Further study is clearly needed.

Figures

Figure 11. Cyclosorus castaneus A. R. Sm. & Lorence. A frond B upper surface of pinna C lower surface of fertile pinnules showing sori, hairs, and glands D detail of lower surface of fertile pinnule with sorus, hairs, and glands. Drawn from the type collection (Lorence et al. 6115).