Xyris bituberosa Phonsena & Chantar., 2012

1. Xyris bituberosa Phonsena & Chantar. View in CoL , sp. nov. — Fig. 1 View Fig ; Plate 1a– c View Plate 1 , 2 a, b View Plate 2 ; Map 1 View Map 1

Xyridi tuberosae habitu caule subterranea cormiforme similissima, sed foliis linearibus vel subteretis,nec ensiformibus,caule subterranea bilobata dum in X.tuberosa plerumque elobato sed raro bilobata differt.— Typus: Phonsena

1 Applied Taxonomic Research Center, Department of Biology , Faculty of Science, Khon Kaen University, Khon Kaen 4002, Thailand; corresponding author e-mail: pranom@kku.ac.th .

& Boonsuk 6418 (holo KKU; iso BK, BKF, C, L), Thailand, Bueng Kan, Phu Wua Wildlife Sanctuary , alt. 400 m, 25 Sept. 2009 .

Etymology. The specific epithet refers to the 2-lobed corm.

Solitary perennial herb, 40– 50(–75) cm tall with a 2-lobed corm. Corm -lobes yellowish brown, subglobose, (0.8 –)1–1.5 by (1.2–) 1.5– 2.3 cm, containing starch grains. Leave s (2 –)3 – 4 per plant, linear or subterete, (12–) 25– 37 cm by 2 – 2.3 mm, with a ligule; blade smooth, margin entire, apex bluntly oblique to acute. Scape terete, subterete below the spike, 1–1.5 mm diam. Spike obovoid to ellipsoid, (0.8–)1.2 –1.8 by 0.5– 0.9 cm. Sterile bracts 6 –12, pale brown to reddish brown, ovate to obovate, 4–7 by 3 – 5 mm, margin entire, apex lacerate. Fertile bracts pale brown to reddish brown, ovate to obovate, 6 –8 by 5–7 mm, margin entire, apex lacerate; stomate field triangular, 1.8 – 2.1 by 1.5 –2.5 mm. Lateral s epals hyaline or pale brown, 5 – 6 by 1–1.5 mm, without or with a minute crest. Petal limbs yellow, obovate, 10–12 by 8 –10 mm, margin distally lacerate. Staminodia bibrachiate, branches elongate-penicillate, c. 4 mm long. Anthers oblong, 2–3 mm long, shallowly bifid, deeply sagittate, filaments 1–1.5 mm long. Style terete, 5 – 6 mm long, distally 3-branched, branches c. 3 mm long. Capsule dark brown, obovoid, 3 –3.4 by 2– 2.2 mm. Seeds reddish brown, translucent, ellipsoid, c. 0.6 mm long, 0.2 – 0.3 mm diam, with 13–15 longitudinal ridges and 1–3 transverse ridges between the longitudinal ridges.

Distribution — Endemic to Thailand, known only from North-Eastern: Bueng Kan (Phu Wua Wildlife Sanctuary, Si Wilai).

Habitat & Ecology — On open, sandy soil, wet places in dry dipterocarp forest, at 180 –450 m altitude.

Phenology — Flowering: September to November, between the late rainy season and the beginning of the dry season. The flowers open in the late morning at 11.30 a.m. and persist until 4.30 p.m.

Vernacular name — Kathin phu wua.

Specimens examined. Bueng Kan ( Si Wilai, Na Sing, Ban Na Sai ): Phonsena 6699 ( BK, KEP, KKU, L), 180 m alt., 18°15'N, 103°46'E, 31 Dec. 2010 GoogleMaps ; Phonsena & Boonsuk 6628 ( BKF, C, L), 180 m alt., 28 Nov. 2010 ; Phonsena & Sutthisaksopon 6543 ( KKU), 8 Aug. 2010 ; Phonsena & Sutthisaksopon 6568 ( BM, C, K, KKU, QBG), 8 Oct. 2010 . Bueng Kan ( Bung Khla, Phu Wua Wildlife Sanctuary ): Phonsena & Boonsuk 6418 ( BK, BKF, C, K, KKU, L, QBG), 450 m alt., 18°14'N, 103°58'E, 29 Sept. 2009 GoogleMaps .

Conservation status — Xyris bituberosa is endemic to Thailand, recorded from two localities, one within a wildlife sanctuary, and the other from disturbed dry dipterocarp forest near villages. The habitat outside the sanctuary has been disturbed by farming activities which appear to be causing its rapid decline, but the population within the sanctuary is well protected. A rating of Endangered (EN, IUCN 2001) is merited.

Note — Xyris bituberosa resembles X. tuberosa Ridl. , a species also with a tuber (underground corm-shaped stem), which is distributed in North-Eastern, Eastern and Peninsular Thailand. The latter species, however, differs in having simple (sometimes aggregated) and smaller tubers, and ensiform leaves.