Revision of Chassalia (Rubiaceae) in Borneo

The genus Chassalia in Borneo is revised based on a morphological survey of herbarium specimens using classical taxonomic methods. The tribal placement and probable paraphyly of Chassaliaas currently delimited is reviewed. Previously four described species of Chassalia were known from Borneo with only one endemic species Chassalia psychotrioides . 12 new species are described in this study, all of them endemic to Borneo. A key is given to the 16 species of the genus now recognised from Borneo in this study. Circumscriptions and discussions are given of all Bornean species recognised. A morphological glossary for Asian Chassalia species is provided. Three separate species groups are recognized. A new informal group ‘Involucrate group’, is proposed and circumscribed Proposals for further work on Asian Chassalia are given.