Abstract
The displacement of species from equatorial latitudes to temperate locations following the increase in sea surface temperatures is among the significant reported consequences of climate change. Shifts in the distributional ranges of species result in fish communities tropicalisation, i.e., high latitude colonisations by typically low latitude distribution species. These movements create new interactions between species and new trophic assemblages. The Senegal seabream, Diplodus bellottii, may be used as a model to understand the population genetics of these invasions. In the last decades, this species has undergone an outstanding range expansion from its African area of origin to the Atlantic coast of the Iberian Peninsula, where now occurs abundantly. Mitochondrial and nuclear markers revealed a striking high haplotypic nucleotide and genetic diversity values, along with significant population differentiation throughout the present-day geographical range of the Senegal seabream. These results are not consistent with the central-marginal hypothesis, nor with the expectations of a leptokurtic distribution of individuals, as D. bellottii seems to be able to retain exceptional levels of diversity in marginal and recently colonised areas. We discuss possible causes for hyperdiversity and lack of geographical structure and subsequent implications for fisheries.
Highlights
The displacement of species from equatorial latitudes to temperate locations following the increase in sea surface temperatures is among the significant reported consequences of climate change
A total of 357 base pairs of the mitochondrial control region were sequenced for 124 individuals, defining 118 haplotypes and 548 base pairs of the S7 first intron were resolved for 96 individuals, defining 69 haplotypes, from five sampling locations (Fig. 1)
High haplotype and nucleotide genetic diversities, and significant population differentiation were consistently found throughout the present-day geographical range of the Senegal seabream
Summary
The displacement of species from equatorial latitudes to temperate locations following the increase in sea surface temperatures is among the significant reported consequences of climate change. It is less common the observation of geographical range expansion of marine species without loss of genetic diversity but, for examples, see[16,20,21]. We used the documented expansion of D. bellottii as an opportunity to assess putative founder effects by looking for evidence of reductions in the number of mitochondrial or nuclear singleton haplotypes (haplotypes seen only once in a sample, i.e. an unshared haplotype) coherent with a predictable loss of overall genetic diversity.
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