Diceratotheca, a new genus of Acanthaceae from Thailand

Summary: A new genus of Acanthaceae, Diceratotheca, is described from Thailand. The genus is characterised by having unique pollen combined with several unusual morphological characters, of which the 2-spurred anther thecae also appear to be unique within Acanthaceae. Phylogenetic analyses show clearly that the genus belongs within the subtribe Ruelliinae. Further analyses, that include the largest available sample of species from other genera, including the species-rich Strobilanthes and Ruellia, demonstrate that the genus is not nested within other genera and a new genus is therefore required. Analyses show that, of the genera sampled, it is most closely related to Pararuellia Bremek., a herbaceous genus with which it appears to have little in common. The only species Diceratotheca bracteolata is known from a single site in NW Thailand and is probably critically endangered. © 2012 The Board of Trustees of the Royal Botanic Gardens, Kew