Distribution of Argostemma Wall. (Rubiaceae), with special reference to Thailand and surrounding areas

Abstract

Argostemma Wall. (Rubiaceae). a disjunct genus (A frica: 2 spp.: SE Asia: > 95 spty .). has 31 taxa in Thailand of which 17 are endemic. Their distributions within the Thai noristic regions are: Northern (N) - II spp. (of which six arc endemic to the region); North-eastern (NE): I sp.;Eastern (E): 3 spp.; South-western (SW): 4 spp. ; Central (C): 3 spp.; South-eastern (SE): 5 spp. (of which one is endemic to the region): Peninsular (PEN): 18 taxa (of which seven are endemic to the region). Some species are endemic to Thailand but have wider distributions 'within the country e.g. A. concinnum (N+E+SE). A. monophyllun (NE+E+C+SE). and A. parvum (E+SE). The 14 non-endemic taxa fall into three categories: (I) "northern" species. also occurring in Myanmar, and India and/or China (Yunnan): (2) "southern" species. also in the Malay Peninsula [and/or S. Myanmar (Tenassermin in). or also on Sumatra or the Andaman Is.]; (3) widespread species (A. neurocalyx only), distributed rrom Borneo. Sumatra, and the Malay Peninsula to Indochina (and also widespread in Thailand: N+C+SE+PEN). An attempt is made to correlate distribution patterns with morphological "species groups" distinguishable within the genus.