Three mitochondrial lineages and no Atlantic-Mediterranean barrier for the bogue Boops boops across its widespread distribution

Abstract

Marine species exhibiting wide distributional ranges are frequently subdivided into discrete genetic units over limited spatial scales. This is often due to specific life-history traits or oceanographic barriers that prevent gene flow. Fine-scale sampling studies revealed distinct phylogeographic patterns in the northeastern Atlantic and the Mediterranean, ranging from panmixia to noticeable population genetic structure. Here, we used mitochondrial sequence data to analyse connectivity in the bogue Boops boops throughout most of its widespread distribution. Our results identified the existence of three clades, one comprising specimens from the Azores and eastern Atlantic/Mediterranean, another with individuals from the Canary Islands, Madeira and Cape Verde archipelagos, and the third with samples from Mauritania only. One of the branches of the northern subtropical gyre (Azores Current) that drifts towards the Gulf of Cádiz promotes a closer connection between the Azores, southern Portugal and the Mediterranean B. boops populations. The Almería-Oran Front, widely recognised as an oceanographic barrier for many organisms to cross the Atlantic-Mediterranean divide, does not seem to affect the dispersal of this benthopelagic species. The southward movement of the Cape Verde Frontal Zone during the winter, combined with the relatively short duration of the pelagic larval stage of B. boops, may be potential factors for preventing the connectivity between the Atlantic oceanic archipelagos and Mauritania shaping the genetic signature of this species.