Seamounts and oceanic currents drive the population structure of Octopus insularis in the Southwest Tropical Atlantic

Seamounts and oceanic currents are important oceanographic features that influence genetic diversity of a species along its distribution, acting both as barriers or pathways for species dispersal. There are two important seamount chains in the Tropical Western Atlantic (TWA): the Fernando de Noronha Chain in northeastern Brazil and the Vitoria-Trindade Chain in southeastern Brazil. This region is influenced by the North and South branches of the Southern Equatorial Current (SEC), which flow from the east to west. In order to evaluate how these oceanographic characteristics influence the genetic diversity and population structure of O. insularis along its broad distribution area, we analyzed specimens from sampling sites of the Brazilian coast and oceanic islands, Ascension and Saint Helena archipelago, Mexican Caribbean, and San Blas, Panama. The analyses performed using fragments of 659 bp of the mitochondrial gene (cox1) showed the occurrence of four distinct populations: one from Caribbean to Fernando de Noronha archipelago (Central-North), another from east coast of Brazil to Trindade archipelago (South), and the others restricted to Ascension and Saint Helena, and Sao Pedro and Sao Paulo archipelagos, respectively. Both the seamounts and ocean currents contributed to the genetic structure observed along O. insularis distribution. The bifurcation of the SEC seems to separate Center-North and South populations, while the gene flow within oceanic islands and the coast in each population is explained by the existence of seamounts. Since O. insularis has a broad distribution (mainly the Center-North population) divided into four genetically distinct fisheries, the species fishery needs to be managed accordingly, which might depend on the international policies agreements.