Biogeography of Forcipiger. This genus is remarkable for the dichotomizing distributions of two species. F. flavissimus is the most widespread butterflyfish in its genus and family, adopting a nearly completely circumtropical distribution. F. wanai, on the other hand, is restricted to only Cenderawasih Bay and the surrounding region of West Papua. Photo credit: Gerry Allen and John Randall.
Of the butterflyfishes that have evolved long snouts in tandem with their dietary needs, none are more impressive, or quirky, than those in the genus Forcipiger. This genus boasts some of the most iconic members of the family, easily identified in the field by even the most amateur of divers. My mother, for one, surprised me one day by identifying it correctly in a travel brochure (the fish was featured in a dive resort advertisement). Considering that she knows as much about marine fish as I do folk dancing, it comes as no surprise then, that Forcipiger has managed to attain more or less a symbolic status even amongst the general public. The genus comprises three species, of which, two are remarkable for their dichotomizing and polarizing biogeography. F. flavissimus is the most widespread butterflyfish, not only in its genus, but in the entire family. Conversely, F. wanai is localized to the reefs of Cenderawasih Bay and regional West Papuaa – a tiny locale in the Indonesian Archipelago. The nearly circumtropical distribution of F. flavissimus is extremely remarkable, where it can be found from the East African coast all the way to Baja California in North America. Aside from crossing into the Eastern Pacific, it has also managed to colonize Norfolk Island in New Zealand. F. flavissimus is absent in the Atlantic, due to its inability to cross the Cape of Good Hope in South Africa. The strong, cold currents present here separates the Indian Ocean from the Eastern Atlantic and prevents species such as F. flavissimus from attaining a fully circumtropical distribution (although there is no doubt that it will proliferate in the Atlantic given a chance – alien introduction). The reason for Forcipiger’s success is its long larval phase, allowing them to drift significant distances to colonize new ground. F. flavissimus is reported to settle out of its larval phase at 7 centimeters, after which it quickly adopts the usual yellow coloration and begin its life as a juvenile. This is comparatively similar to Moorish Idols of the monotypic genus Zanclus, and, in comparison to Zanclus’ biogeography, you’d notice that it too, attains a nearly circumtropical distribution.… More:
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