A Molecular and Morphological Survey of Generic Limits of Acsmithia and Spiraeanthemum (Cunoniaceae).

A phylogenetic analysis was conducted on the tribe Spiraeanthemeae (Cunoniaceae) to clarify relationships of and . Three molecular markers, one plastid region ( intron and intergenic spacer) and two nuclear single copy genes ( and ), were sequenced for this purpose. The independent analysis of the three markers and a combined analysis all showed that is paraphyletic since is nested within it. A morphological survey of all species in the tribe confirmed the existence of two groups within . One comprises the species from Australia, New Guinea, and from New Caledonia and is characterised by multiple ovules per carpel. The other group contains all the remaining New Caledonian species plus from Fiji and is characterized by a single ovule per carpel. The study shows that characters previously used to distinguish and , phyllotaxy and sexual system, are homoplasious as in several other groups of Cunoniaceae. A broad circumscription of the genus is adopted here that includes the species formerly placed in . Two new combinations are proposed: and . is considered a synonym of .