Two new species of Tetrastigma (Miq.) Planch. (Vitaceae) from Thailand

Two new species of Tetrastigma from Thailand, T. calcicola Kochaiph. & Trias-Blasi sp. nov. and T. jaichagunii C.L.Li ex Kochaiph. & Trias-Blasi sp. nov. are described and illustrated. Tetrastigma calcicola sp. nov. is a slender climber restricted to the open areas on limestone mountains at high elevation in the northern part of Thailand. The other species, T. jaichagunii sp. nov., is similar to T. harmandii Planch., but differs from it by having more densely verrucose young branches, broader leafl ets, 4-lobed thick discs, bigger globose berries and oblongoid seeds. This species occurs along streams or in forest margins in evergreen forest and it is widely distributed in several parts of Thailand.


Introduction
Tetrastigma Planch. (Vitaceae) is a genus comprising approximately 95 species, distributed in tropical and subtropical Asia with a few of them reaching Australia (Planchon 1887;Latiff 1983;Trias-Blasi et al. 2012;Wen 2007). It can be easily distinguished from other genera of Vitaceae by its polygamo-dioecy, 4-merous fl owers, 4-lobed or 4-parted stigma, and absent or very short styles. Twenty-six species have been recorded in Thailand (Kochaiphat et al. 2014), of which fi ve are endemic.
During preparation of the revision of Tetrastigma for the Flora of Thailand account, the first author came across several specimens collected from Doi Tung and Tham Luang Khun Nam Nang Non Forest Park (Chiang Rai province) with a unique combination of characters that did not match any previously described species.

Diagnosis
Tetrastigma calcicola sp. nov. is most closely aligned to T. pachyphyllum (Hemsl.) Chun, but differs in having a 4-lobed disc adnate to the lower part of the ovary, and small berries with a smooth surface (Table 1).

Etymology
The specifi c epithet refers to the habitat of this species, which is only found on limestone mountains.

Ecology and phenology
In open area on limestone mountain, dry evergreen forest, altitude 1,300-1,450 m; fl owering: February-March; fruiting: July-October.

Conservation status
We suggest to treat this species as Data Defi cient (DD) according to IUCN (2012), as this species is only known from a few herbarium specimens and only two localities have been recorded: Doi Tung and Tham Luang Khun Nam Nang Non Forest Park in Chiang Rai Province. Although the species seems to occur only in limestone mountains at high elevation, the number of populations and their sizes are not known so far.

Diagnosis
This species is similar to T. harmandii Planch., but differs from it by having more densely verrucose young branches, broader leafl ets, 4-lobed thick discs, bigger globose berries and oblongoid seeds ( Table 2). Some specimens were misidentifi ed as T. hookeri Planch., an Indian species, but T. hookeri has narrow leaves and an inconspicuous disc in female fl owers.

Etymology
We think that Prof. C.L. Li selected the specifi c epithet 'Jaichagunii' in honour of Mr Manit Jaichagun, from the CITES Scientifi c Authority in Thailand.

Ecology and Phenology
Along streams or in forest margins in evergreen forest; altitude 0-1,500 m; fl owering: January-April; fruiting: June-January.