In East Africa, five known Pomacanthus hybrids are known to occur involving four main parent species. In the photo above, a breakdown of the individual hybrids can be seen. They are
"“ P. semicirculatus x P. chrysurus,
"“ P. semicirculatus x P. maculosus,
"“ P. maculosus x P. chrsurus,
"“ P. chrysurus x P. imperator and
"“ P. imperator x P. semicirculatus.
P. semicirculatus is the most promiscuous species and in East Africa, forms hybrids with three species. In at least one of them, namely P. semicirculatus x P. maculosus, hybrids are not rare and are regularly seen in the wild and in the trade. In basic combinatorics, the formula nCr can be used where "œn" represents the four parent species and "œr" for any two of the four. As it takes two species to hybridise, then 4C2=6 will result in six different hybrid permutations. That is assuming all species are compatible to begin with. So far we have seen five, and the only hybrid yet to be seen is P. maculosus x P. imperator.
*Note that these six permutations are of standard one way crosses. Offspring can appear differently if the male and females were to be switched between species. For example, a male P. semicirculatus crossing with a female P. maculosus may look very different from a female P. semicirculatus crossing with a male P. maculosus. However in both ways the offspring is still considered a hybrid of two species and so we take that as one out of six permutations from four species.
There is a likelihood that the last pairing between P. imperator and P. maculosus isn't viable, but based on what we can see above, its existence is entirely plausible. Considering hybrids have been documented from all four species, even in the extremely rare P. imperator x P. chrysurus, there is a chance we might see one in the future. Perhaps if it were to exist it would be a result of an accidental fertilisation where sperm and eggs were to mix unintentionally.
