Altrichthys. — The absence of pelagic larvae and concomitant parental care were subsequently observed in three additional species. After discovering that Amblyglyphidodon azurelineatus (sensu Allen, 1991) shared these traits with Acanthochromis, Allen (1999a) erected Altrichthys to house A. azurelineatus and another species, the newly described A. curatus. A third species, A. alelia, was recently described (Bernardi et al., 2017b). With their limited ability to disperse, all three are confined to the Palawan Province in the Philippines. Allen (1999a) classified the genus as a member of the subfamily Chrominae, noting that Allen (1991) had overlooked the presence of spiniform procurrent caudal rays when assigning azurelineatus to Amblyglyphidodon. However, as mentioned above, Cooper et al. (2009) advised against employing this character for classification because it is unreliable for diagnosing members of Chrominae sensu stricto. They reassigned Altrichthys to Pomacentrinae based on their topology, where Altrichthys landed in a polytomy with Pomacentrus lepidogenys and P. stigma. However, much like the situation with Nexilosus (see above), this unexpected result may have been due to issues with data quality. Unable to obtain fresh samples of Altrichthys, they resorted to sequencing formalin-fixed specimens of A. curatus. Bernardi (2011) acknowledged the limitations of extracting viable DNA from such material. He demonstrated that Cooper et al.’s (2009) sequences do not represent A. curatus and were likely the result of contamination or misidentification involving P. stigma. Perhaps unaware of this discovery, some workers have continued to rely on Cooper et al.’s (2009) data and still misplace Altrichthys inside Pomacentrus (e.g., Litsios et al., 2012b; Frédérich et al., 2013; DiBattista et al., 2016). DiBattista et al. (2016) found Altrichthys to be polyphyletic where Altrichthys azurelineatus was sister to Acanthochromis but Altrichthys curatus was embedded within Pomacentrus. There is robust support (100% bootstrap) for a monophyletic Altrichthys paired with Acanthochromis as its sister group (Fig. 1). This lends further support to the hypothesis that brood care and loss of the pelagic larval stage evolved only once in Pomacentridae (Bernardi, 2011). The relationships discovered within Altrichthys herein match previously published trees (Bernardi, 2011; Bernardi et al., 2017b).

Published as part of Tang, Kevin L., Stiassny, Melanie L. J., Mayden, Richard L. & DeSalle, Robert, 2021, Systematics of Damselfishes, pp. 258-318 in Ichthyology & Herpetology 109 (1) on page 294, DOI: 10.1643/i2020105, http://zenodo.org/record/7846738