Linking specialisation to diversification in the Diplectanidae Bychowsky 1957 (Monogenea, Platyhelminthes).

The hypothesis of a positive correlation between host specificity and taxonomic diversification was tested in a family of fish ectoparasites, the Diplectanidae Bychowsky 1957 (Monogenea). A comparative analysis of correlation of species richness with host specificity was performed using an adapted independent contrasts method. In order to control for phylogenetic effects, a phylogenetic tree of the genera in the Diplectanidae was reconstructed using morphological characters. The current taxonomy is retrieved in this phylogenetic hypothesis, except for the Murraytrematoidinae subfamily, which appears to be paraphyletic. There is no significant correlation between host specificity and taxonomic diversification in the Diplectanidae. The significance of this result is discussed, and different hypotheses which could have led to this observation are presented.