Classification of the cormorants of the world.

Relationships among the 40 or so extant species of cormorants (family Phalacrocoracidae) have been obscured by their morphological similarities, many of which have recently been shown to be the result of convergent evolution. Previous attempts to derive an evolutionarily justifiable classification for this group of birds using osteological and behavioral data have been hampered by these similarities. We present a well-resolved evolutionary tree for some 40 cormorant taxa based on the results of extensive genetic work that produced over 8000 bases of mitochondrial and nuclear DNA sequence. This tree implies a novel classification for the cormorants, which reflects their evolutionary history and can be implemented using some 7 genera. Some of the relationships among the species are well-known but many are previously unrecognized. Nevertheless, much of the classification makes sense in terms of biogeography.