Taxonomic Study of Nelsonioideae (Acanthaceae) in Thailand Thiamhathai Choopan* and Paul J. Grote
School of Biology, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima, Thailand
E-mail: firstname.lastname@example.org Abstract A taxonomic revision of the subfamily Nelsonioideae (Acanthaceae) (7 genera and 168 species worldwide) in Thailand is in progress. The detailed study on the three genera recorded, Nelsonia (1 sp.), Ophiorrhiziphyllon (1 sp.), and Staurogyne (ca. 25 spp.) is now well under way. Nelsonioideae is a subfamily of herbs, with opposite, elliptic, entire leaves. The flowers are arranged in small dense spikes (Nelsonia) or terminal racemes (Ophiorrhiziphyllon, Staurogyne). The calyx consists of a tube with 4-5 lobes. The corolla is purplish rose, yellowish white, or white and consists of a slender tube with 5 lobes. Two or four stamens are inserted (Nelsonia, Staurogyne) or exserted (Ophiorrhiziphyllon). The ovary is 2-celled, with ovules arranged in two rows. The capsule is oblong, acute with numerous orbicular seeds, without retinacula. The investigation is based on both herbarium specimens and field observations. Diagnostic characters for distinguishing species are the arrangement of flowers in inflorescence, the shape of leaves, sepals, petals and their trichomes. The members of Nelsonioideae have been collected from several localities in Thailand, especially in the protected areas, i.e., national parks, wildlife sanctuaries, and reserved forests. The ecology, distribution and utilization of the species are being investigated.
KEY WORDS: Nelsonioideae, Acanthaceae, Thailand, taxonomy