Delimitation of 'Sauropus' (Phyllanthaceae) Based on Plastid 'matK' and Nuclear Ribosomal ITS DNA Sequence Data

• Background and Aims: A recent molecular phylogenetic study showed that 'Sauropus' is deeply embedded within 'Phyllanthus' together with its allies, 'Breynia' and 'Glochidion'. As relationships within 'Sauropus' are still problematic and the relationship with Breynia has long been doubted, more molecular data are needed to test/corroborate such a broad definition of Phyllanthus. This study aims to clarify the status and delimitation of Sauropus and establish its position within 'Phyllanthaceae'. • Methods: Plastid matK and nuclear ribosomal ITS DNA sequence data for 'Sauropus' and its allies were used to construct phylogenetic trees using maximum parsimony and Bayesian methods. • Key Results: Within 'Phyllanthus', 'Sauropus' can be split into the mainly south-east Asian 'Sauropus sensu stricto' (s.s.) plus 'Breynia' and the mainly Australian 'Sauropus' (formerly 'Synostemon'). 'Sauropus' s.s. plus 'Breynia' comprise two distinct clades; one is the combination of 'Sauropus' sections 'Glochidioidei', 'Sauropus' and 'Schizanthi' and the other is the combination of 'Sauropus' sections 'Cryptogynium' and 'Hemisauropus' and the monophyletic genus 'Breynia'. • Conclusions: Molecular data indicate that 'Synostemon' should be reinstated at the same level as 'Sauropus s.s.' and that 'Sauropus s.s.' should be united with 'Breynia' under the latter, older name. The molecular data corroborate only two of the five infrageneric groups of 'Sauropus' recognized on the basis of morphological data.