The role of the Almería-Oran front in the connectivity between populations of the marine crab Liocarcinus depurator

Abstract

The gene flow between populations of the marine crab Liocarcinus depuratorlocated at the Atlanto-Mediterranean transition depends on the intensity of different oceanographic fronts. These discontinuities are generated by the pattern of marine currents and could change over different seasons and years. In this area, the most important oceanographic discontinuities are the Gibraltar Strait (GS), the Almeria-Oran Front (AOF) and the Ibiza Chanel (IC). To monitor the gene flow variation between the crab populations, we analyzed a 527 pb fragment of COI (Cytochrome oxidase subunit I) mitochondrial gene. The following populations were studied: Cadiz, West Alboran, East Alboran, Alicante, Valencia, Ebro Delta and North Catalonia. They are located at either side of the fronts or well away from them. We studied these populations in a five year period (2014-2018).Depending on the year, GS and IC presented a significant effect which implied a reduction of the gene flow. However, the most important oceanographic barrier is the AOF, although its intensity varies depending on the year. For instance, in 2016 it was displaced to the middle of the Alboran Sea, whereas in 2017 it was strong and located in its classical described position. Finally, in 2018, although it decreased the gene flow its effect was non-significant. Likely, these variations depend on the intensity of the second anticyclonic gyre located in the West Alboran Sea