Evolutionary origin of the Atlantic Cabo Verde nibbler (Girella stuebeli), a member of a primarily Pacific Ocean family of antitropical herbivorous reef fishes

Nibblers (family Girellidae) are reef fishes that are mostly distributed in the Indo-Pacific, with one exception: Girella stuebeli, which is found in the Cabo Verde Archipelago, in the Atlantic Ocean. We capitalized on this unusual distribution to study the evolutionary history of the girellids, and determine the relationship between G. stuebeli and the remaining nibbler taxa. Based on thousands of genomic markers (RAD sequences), we identified the closest relatives of G. stuebeli as being a clade of three species endemic to the northwestern Pacific, restricted to the Sea of Japan and vicinity. This clade diverged from G. stuebeli approximately 2.2 Mya. Two alternative potential routes of migration may explain this affinity: a western route, from the Tropical Eastern Pacific and the Tropical Western Atlantic, and an eastern route via the Indian Ocean and Southern Africa. The geological history and oceanography of the regions combined with molecular data presented here, suggest that the eastern route of invasion (via the Indian Ocean and Southern Africa) is a more likely scenario.

Automated summary

Nibblers, reef fishes mostly found in the Indo-Pacific, have an interesting distribution pattern with Girella stuebeli being an exception in the Cabo Verde Archipelago in the Atlantic Ocean. Through studying genomic markers, it was discovered that G. stuebeli is closely related to a clade of three endemic species in the northwestern Pacific, diverging approximately 2.2 million years ago. The most likely migration route between these species is through the Indian Ocean and Southern Africa, based on geological history, oceanography, and molecular data analysis.