This is undoubtedly one of the most confused groups in Amphiprion, with much disagreement regarding their evolutionary history. Early morphological efforts united A. mccullochi with the melanopus group and A. akindynos within a broad concept of the clarkii group, but genetic data has firmly supported these two as being sister species. There are even photographs that illustrate likely hybrids of the two.
What stands out most noticeably about the three species recognized here is their restricted distribution in the subtropical waters of Australia and the Coral Sea. The true A. akindynos is a dark fish with thin bars and occurs primarily from the Capricorn Reefs south to New South Wales, while a distinct but still nearly identical population, A. cf akindynos, exists at New Caledonia. Similar specimens observed in the isolated islands of the Northern Coral Sea have been observed paired with A. cf chrysopterus “New Guinea”, but these are most likely examples of that species’ “dark morph”.
A. akindynos likely hybridizes with the confusingly similar A. cf clarkii found just to the north in the Great Barrier Reef. These two species make for a fascinating evolutionary story, illustrating the homogenizing effects hybridization can have on distantly related taxa. Existing CO1 data fails to differentiate the two.
The evolution of the highly restricted A. mccullochi is also of considerable interest, as initial study has indicated regular periods of genetic introgression from outside its current distribution. Phenotypically similar specimens with a single bar have been observed outside the known range along the Australian coastline, which may represent rare westerly waifs, hybrids or atavistic mutations.
Another important question is in regards to where these fishes fit within the greater evolutionary history of Amphiprion. Molecular data has suggested a position near A. chrysopterus, which makes sense given that both of these groups tend to produce dark-brown fishes. However, there is a noticeable difference in the habitat preferences of these two lineages, with the chrysopterus group hailing from throughout the warm waters of the Central Pacific while A. akindynos, A. cf akindynos and A. mccullochi are primarily known from subtropical climes. It’s hard to reconcile this discrepancy, especially in light of the similarly restricted range observed in A. latezonatus, a species known from essentially the exact same regions as this group. Perhaps the most likely explanation is that the akindynos group is a unique clade all its own, which has more recently become introgressed with its tropical relatives in the clarkii and chrysopterus groups.
Amphiprionology 