Contrasting signals from multiple markers illuminate population connectivity in a marine fish

Abstract

Recent advances in molecular biology and bioinformatics have helped to unveil striking and previously unrecognized patterns of geographic genetic structure in marine populations. Largely driven by the pressing needs of fisheries management and conservation, studies on marine fish populations have played a pivotal role in testing the efficiency of a range of approaches to explore connectivity and dispersal at sea. Here, we employed nuclear and mitochondrial DNA markers and parasitic infestations to examine the nature and patterns of population structure in a warm-temperate coastal marine teleost across major putative biogeographic barriers in the Mediterranean Sea and Eastern Atlantic Ocean. We detected deep genetic divergence between mitochondrial lineages, likely caused by dramatic climatic and geological transformations before and during the Pleistocene. Such long-diverged lineages later came into secondary contact and can now be found in sympatry. More importantly, microsatellite data revealed that these lineages, after millions of years of independent evolution, now interbreed extensively. By combining genetic and parasite data, we were able to identify at least five independent demographic units. While the different genetic and parasite-based methods produce notably contrasting signals and may complicate the reconstruction of connectivity dynamics, we show that by tailoring the correct interpretation to each of the descriptors used, it is possible to achieve a deeper understanding of the micro-evolutionary process and, consequently, resolve population structure.

Independence of neutral and adaptive divergence in a low dispersal marine mollusc

“…Contrasting patterns garnered using different tools for unravelling spatial population structure is a relatively common finding, and also increasingly documented in marine populations (Abaunza et al 2008, Sala-Bozano et al 2009, André et al 2011, SalaBozano & Mariani 2011, Yebra et al 2011. When com paring neutral genetic markers with phenotypic features putatively associated with ecological functions (McKay & Latta 2002), the objective is to explore in what way and to what extent neutral and adaptive processes differ in shaping the evolutionary trajectories of species.…”

Mitochondrial DNA and microsatellites reveal significant divergence in the beachflea Orchestia montagui (Talitridae: Amphipoda)

“…1, see also : Blondel et al 2010;Robinson et al 2001). Steady gyres are thought to generate genetic discontinuities in marine species that rely on passive transport to disperse (Sala-Bozano et al 2009). The identified barriers are, however, only moderately supported by the associated bootstrap values.…”

Barriers in the pelagic: population structuring of Calanus helgolandicus and C. euxinus in ­European waters

“…Several other marine species show ge ne tic differentiation between W and E Mediterranean basins (e.g. Bahri-Sfar et al 2000, Sala-Bozano et al 2009), but the exact locations of barriers are usually un known because of insufficient geographic sampling and may actually differ depending on the species biology.…”