Impatiens bokorensis (Balsaminaceae), a new species from Cambodia

Abstract Impatiens bokorensis, a new species of family Balsaminaceae from Phnum Bokor National Park in southwestern Cambodia, is described and illustrated. The species is similar to Impatiens patula, but is readily distinguished by the orbicular-obovate dorsal petal, shorter pedicels and larger seeds.


Introduction
Balsaminaceae is a family consisting of about 1,000 species mainly distributed in tropical Africa, Madagascar, southern India and Sri Lanka, the eastern Himalayas and southeastern Asia and is absent from Australia and South America (Song et al. 2003, Yuan et al. 2004, APG III 2009. This family includes annual or perennial herbs (more or less succulent) to sub-shrubs. It is distinguished from other families by strongly zygomorphic flowers with a spur on the adaxial sepal and a fleshy explosive-dehiscent capsule (Chen et al. 2007, APG III 2009. It comprises two genera: Hydrocera Blume ex Wight & Arn. (monotypic) and Impatiens L. with the most species.
Except for I. balsamina and I. cardiophylla, most species in Cambodia have been considered endemic species, with I. relaxata, I. vagans and I. zygosepala restricted to a local area with only a very small number of specimens. There is a need to re-evaluate and resurvey areas of the previous collection of specimens through a detailed taxonomic study of each species.
During the recent floristic survey, one species of Impatiens was collected at Bokor National Park in Southwestern Cambodia that does not appear to be similar to previously reported species (Figures 1 & 2). It is most similar to Impatiens patula Craib from Thailand (Craib 1926, Shimizu 1970, but a comparison with the type specimens and descriptions revealed that it differs from I. patula and is therefore described here as a new species.  Diagnosis. Impatiens bokorensis is most similar to the Thailand endemic species I. patula Craib in habit but is readily distinguished from the latter by the orbicularobovate dorsal petal, shorter pedicels and larger seeds (Table 1).
Distribution and habitat. Impatiens bokorensis grows on sandstone tables in evergreen forest margins at 1,050 m a.s.l.. Endemic to southwestern Cambodia, I. bokorensis is at present known only in the type locality.
GenBank Accession No. Cho et al. CB-3432: KX171761 (ITS).  Conservation status. Impatiens bokorensis was collected in Phnum Bokor National Park in southwestern Cambodia. Until now, only one population, consisting of ca. 200 individuals, has been discovered in the park area; therefore, it is preliminarily classified as data deficient (DD) according to the IUCN Red List criteria (IUCN 2001).