Four new species of Xyris ( Xyridaceae ) from Thailand

Four new species of Xyris (Xyridaceae), X. bituberosa, X. buengkanensis, X. emarginata, and X. thailandica from North-Eastern Thailand are described and illustrated. A provisional conservation assessment for each species is given.


INTRODUCTION
Xyridaceae is a small tropical and subtropical family, comprising c. 385 species in five genera: Abolboda Humb.& Bonpl.( 1813), Achlyphila Maguire & Wurdack (1960), Aratitiyopea Steyerm.& P.E.Berry (1984), Orectanthe Maguire (1958), and Xyris L. (1753).Xyris is the largest genus of the family, with more than 250 species (Kral 2000), and is distributed mainly in tropical and subtropical North and South America, with about 50 species in Africa, and smaller numbers in Asia and Australia.The other four genera are restricted to South America (Dahlgren et al. 1985, Simpson 2006).
The family, as published in the Flora of Thailand (Hansen 1987), comprised 11 species.The family has also been dealt with for the Flora of China with six species, namely X. bancana Miq., X. capensis Thunb., X. complanata R.Br., X. formosa Hayata, X. indica L., and X. pauciflora Willd.(Wu & Kral 2000).During recent studies of Xyridaceae in Thailand and Southeast Asia, additional material was collected, and among these collections there are four hitherto undescribed species from North-Eastern Thailand.
The descriptions below were made from living full-grown plants in flower and/or in fruit and from the cited herbarium specimens.Leaf widths were measured in the middle of the blade.Sepal, petal, stamen and pistil morphology were measured in fully open flowers in the living state, as the flowers are so delicate that pressed material is of little use.Seed morphology was investigated by scanning electron microscopy (SEM) and light microscopy (LM).Conservation assessments follow the criteria set out by IUCN (2001).Regions follow floristic regions in the Flora of Thailand.The vernacular names were provided by the first author.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.

Xyris buengkanensis
Etymology.The specific epithet refers to Bueng Kan, the newest province of Thailand, where the type specimens were collected.
Caespitose perennial herb, 20 -50 cm tall.Conservation status -Xyris buengkanensis is endemic to Thailand, and is so far known from only one locality.Its extent of occurrence is estimated as to be less than 100 km 2 .Its habitat has been disturbed by farming activities and its occurrence is declining.A rating of Critically Endangered (CR, IUCN 2001) is merited.

Xyris emarginata
Distribution -Endemic to Thailand, North-Eastern: Bueng Khong Long, only known from the type locality.It may be assumed that it has a wider distribution in nearby areas along the Mekong basin of Laos and Thailand.
Habitat & Ecology -On open, sandy soil, in wet places in dry dipterocarp forest, at 180 m altitude.
Phenology -Flowering and fruiting: October to December, between the late rainy season and the beginning of the dry season.The flowers open in the morning at 08.30 a.m. and persist until 12.30 p.m.
Note -The fertile bracts of X. emarginata resemble those of X. lobbii Rendle in its emarginate apex, but differ in its lacerate margin (entire in X. lobbii).The margin of the fertile bracts also resemble those found in X. complanata, but the new species differs from the latter in the leaf margin and the scape being smooth, not rough with tubercles.Phonsena & Chantar., Seeds reddish brown, translucent, narrowly ellipsoid, 0.9-1.1 mm long, 0.3 -0.4 mm diam, with 14 -15 longitudinal ridges and with 1-4 transverse ridges between the longitudinal ridges.Distribution -Endemic to North-Eastern Thailand, known only from a restricted area in Phu Kradueng National Park and Phu Ruea National Park.

Xyris thailandica
Habitat & Ecology -On open places, among grasses in lower montane pine-oak forest at 1187-1280 m altitude.
Phenology -Flowering: September to November, between the late rainy season and the beginning of the dry season.The flowers open in the afternoon at 2.00 p.m. and persist until 5.00 p.m.
Vernacular name -Kathin phu.Conservation status -Xyris thailandica is endemic to Thailand, recorded only from Phu Kradueng National Park and Phu Ruea National Park.Its extent of occurrence is estimated to be less than 50 km 2 , but the population in these national parks are well protected.A rating of Endangered (EN, IUCN 2001) is merited.
Note -Xyris thailandica is similar to X. linifolia by having a bulbous underground stem, but differs in its flat, linear leaves (terete in X. linifolia) and in its papillose margin of the leaves (entire in X. linifolia).Xyris thailandica is a montane species, occurring above 1 000 m altitude whereas X. linifolia occurs in the lowland, between 180 -200 m altitude.