TWO NEW SPECIES OF FERNS FROM THAILAND (S. LINDSAY, D. J. MIDDLETON & S. SUDDEE)
Cyclosorus thailandicus S.Linds., sp. nov. Rhizoma suberectum; stipes 4.5–6 cm longi. Lamina 34.5–37 x 9.5–12 cm; pinnae 11–14-jugatae, infimae redactae. Sori binati. Typus: Thailand, Phetchaburi [Amphoe Kaeng Krachan, Kaeng Krachan National Park, trail from KU Camp along Phetchaburi River, 12°51’N, 99°18’E, 27 March 2003, Middleton, Hemrat, Lindsay, Suddee & Suwanachat 1748 (holotype BKF; isotype A)]. Fig. 1. Map 1.
Small terrestrial fern with delicate fronds. Rhizome suberect with closely spaced fronds; scales pale brown, narrowly triangular, 3–4.5 x 0.5–0.8 mm, uniformly coloured, minutely pubescent, margins entire. Stipe purplish, 1–6 cm long, scaly at base only. Lamina decrescent at base, widest slightly above the middle, 34.5–37 x 9.5–12 cm; 11–14 pairs of lateral pinnae; terminal pinna largest, apex acuminate, 11–12.5 x 1.4–2.5 cm, incise T– way towards costa; 4–5 pairs of basal pinnae, gradually reduced, butterfly-shaped, ca 1 x 1 cm; lateral pinnae sessile, ca 2 cm apart, oblong, base truncate, first acroscopic pinnule somewhat larger, apex acuminate, incised Tway towards costule, 3.5-8.3 x 0.8-1.2 cm; rachis and costae pubescent above with acicular hairs, costae and lamina minutely pubescent all over beneath; veins 5–6 pairs, of which lowest pair anastomose, the second pair have the distal vein anastomosing with the intercostule vein, the proximal vein runs to sinus. Sori mostly very closely paired, confluent, in a single row in lower parts of pinnae, sometimes 2 or 3 in upper parts, situated where the first pair of veins anastomose below the sinus in lower parts, also on second or third veins in upper parts; indusium densely pubescent, reniform. Spores monolete & ellipsoidal, with short low ridges.
Distribution.— Only known from the type from Kaeng Krachan National Park in Phetchaburi.
Ecology.— Collected in primary evergreen forest in sandy-stony soil beside river in deep shade at 330 m altitude.
IUCN Conservation Status Assessement.— Data Deficient (DD). The species is currently only known from the type specimen which was collected in a river bed, a habitat that could be subject to sudden and catastrophic change. However, it is unknown to what extent the species also occurs in the very extensive and protected surrounding forest.
Notes.— In the Flora of Thailand treatment Tagawa & Iwatsuki (1988) used broad delimitations for the genera in Thelypteridaceae rather than the very much narrower genus concept employed by Holttum (1982). We have chosen the intermediate position employed by Smith (1990) and Smith et al. (2006) and have thereby described this species in Cyclosorus. It is similar to Christella zeylanica (Fe´e) Holttum (which has no combination in Cyclosorus), from Sri Lanka and the Nicobar Islands (Panigrahi, 1975; Shaffer-Fehre, 2006), but differs in the position of the sori on the veins, the prescence of paired sori, and the very much more densely pubescent indusia. It is also similar to the Cyclosorus subpubescens (Blume) Ching complex (the limits of the species in this complex are very fluid – see Holttum 1954, 1976, 1982; Tagawa & Iwatsuki 1988), and most similar to Cyclosorus latipinna (Benth.) Tardieu, but no species in the complex are known to have as many pairs of basal butterfly- shaped reduced pinnae or to have such pinnae almost to the base of the rachis.