Plastid rbcL sequence data indicate a close affinity between Diegodendron and Bixa

Diegodendron humbertii Capuron (Diegodendraceae Capuron) is endemic to Madagascar. The family is monospecific, and whereas various affinities have been suggested, its phylogenetic position has remained unclear. Analysis of rbcL sequence data indicates a close relationship to Bixa. Together these taxa form a monophyletic group with a somewhat more distant relationship to other groups of Malvales s.l. including Cochlospermaceae. Cochlospermaceae (Cochlospermum and Amoreuxia) should be maintained as a family distinct from Biraceae but if Biraceae are expanded to include Cochlospermaceae they should also include Diegodendron. DNA extraction from herbarium specimens, involving modifications to the standard extraction and amplification techniques, is described.