How many genera of Stercorariidae are there?

Abstract

In this contribution I comment on the generic taxonomy of skuas, Stercorariidae, based on the currently available hypotheses of phylogenetic relationships for the group – i.e., the cladograms. Specifically, the different cladograms were examined following Hennig's principle of reciprocal illumination, in which a given hypothesis is evaluated by the extent to which it agrees with competing hypotheses. Currently, all species are often assigned to genus Stercorarius. However, chewing lice- (Insecta, Phthiraptera), behaviour- (territorial display and calls) and molecular-based (mitochondrial DNA) hypotheses of phylogenetic relationships all indicate that Pomarine Skua Stercorarius pomarinus and the species formerly placed in genus Catharacta are monophyletic and sister to a clade comprising Long-tailed S. longicaudus and Parasitic S. parasiticus Skuas. Therefore, contrary to the prevailing view that all species within the family should be placed in a single genus, I argue herein that in a cladistic-based classification by sequencing, both S. parasiticus and S. longicaudus should retain their generic name, whereas S. pomarinus should be transferred to Catharacta, as C. pomarina.