When morphology is not reflected by molecular phylogeny: the case of three ‘orange-billed terns’ Thalasseus maximus, T. bergii and T. bengalensis (Charadriiformes: Laridae).

In order to elucidate genetic structure within the Royal Tern Thalasseus maximus, genetic analyses and phylogenetic reconstructions were performed on Royal Terns T. m. albididorsalis from the West African breeding population and compared with sequences from American populations T. m.maximus. The analysis shows that Royal Tern as currently defined is a paraphyletic species: West African Royal Tern is genetically distinct from American breeding populations of the nominate subspecies and forms part of a genetic cluster with Lesser Crested Terns (of all subspecies) and Greater Crested Terns T. bergii. This represents the first published analysis of the genetic relationship between the two subspecies of Royal Terns, suggests that the West African population should be treated as a distinct species, and provides support to previous studies suggesting that morphological and genetic similarities are poorly correlated in the genus Thalasseus. Conservation and taxonomic implications are discussed.