Monophyletic origin of brood care in damselfishes

The absence of a pelagic larval stage and brood care has evolved very few times in coral reef fishes. Damselfishes, a widely represented group with more than 380 species, includes only three such species, the monotypic Acanthochromis polyacanthus, and the two Altrichthys species, Altrichthys azurelineatus and Altrichthys curatus. In a recent study, Cooper et al. provided a comprehensive phylogenetic hypothesis for the damselfish family, based on mitochondrial and nuclear sequences, with more than 100 species that included all extant genera (Cooper et al., 2009). A. polyacanthus and sequences from formalin-preserved tissue of A. curatus did not cluster together, indicating that brood care may have evolved independently twice in damselfishes. Here, we use mitochondrial and nuclear molecular markers from fresh specimens of both Altrichthys species. We found that Altrichthys and Acanthochromis are closest relatives, which suggests that brood care may have evolved only once in damselfishes. Due to the limited geographic range of Altrichthys (western Philippines) and the abundant presence of Acanthochromis in that region, we also suggest that brood care may have originated in that region.