Date Published: May 1, 2017
Publisher: Public Library of Science
Author(s): Diana Catarino, Sergio Stefanni, Per Erik Jorde, Gui M. Menezes, Joan B. Company, Francis Neat, Halvor Knutsen, Tzen-Yuh Chiang.
Population genetic studies of species inhabiting the deepest parts of the oceans are still scarce and only until recently we started to understand how oceanographic processes and topography affect dispersal and gene flow patterns. The aim of this study was to investigate the spatial population genetic structure of the bathyal bony fish Coryphaenoides mediterraneus, with a focus on the Atlantic–Mediterranean transition. We used nine nuclear microsatellites and the mitochondrial cytochrome c oxidase I gene from 6 different sampling areas. No population genetic structure was found within Mediterranean with both marker types (mean ΦST = 0.0960, FST = -0.0003, for both P > 0.05). However, within the Atlantic a contrasting pattern of genetic structure was found for the mtDNA and nuclear markers (mean ΦST = 0.2479, P < 0.001; FST = -0.0001, P > 0.05). When comparing samples from Atlantic and Mediterranean they exhibited high and significant levels of genetic divergence (mean ΦST = 0.7171, FST = 0.0245, for both P < 0.001) regardless the genetic marker used. Furthermore, no shared haplotypes were found between Atlantic and Mediterranean populations. These results suggest very limited genetic exchange between Atlantic and Mediterranean populations of C. mediterraneus, likely due to the shallow bathymetry of the Strait of Gibraltar acting as a barrier to gene flow. This physical barrier not only prevents the direct interactions between the deep-living adults, but also must prevent interchange of pelagic early life stages between the two basins. According to Bayesian simulations it is likely that Atlantic and Mediterranean populations of C. mediterraneus were separated during the late Pleistocene, which is congruent with results for other deep-sea fish from the same region.
Population genetic studies of species inhabiting the deepest parts of the oceans are still scarce compared to shallow or coastal water relatives. The deep-sea is historically described as a stable and homogeneous environment where the existence of barriers to dispersal and gene flow among populations are less evident . Some studies support this pattern since genetic homogeneity over large spatial scales of several deep-sea species seems to prevail, for example the wreckfish (Polyprion americanus ), the hydrothermal vent shrimp (Rimicaris exoculata, ), the black scabbardfish (Aphanopus carbo, ), the blue hake (Antimora rostrata, ) and the orange roughy (Hoplostethus atlanticus, ). Nevertheless, other species such as roundnose grenadier (Coryphaenoides rupestris, ) and the bluemouth rockfish (Helicolenus dactylopterus, ) show a contrasting genetic pattern exhibiting significant levels of genetic divergence across their range. The mixed scenario of genetic patterns across deep-sea species is likely to reflect depth niche, bathyal heterogeneity and ocean currents, as well as differences among species in life histories and dispersal capabilities.