Abstract
Ongoing climatic changes, with predictable impacts on marine environmental conditions, are expected to trigger organismal responses. Recent evidence shows that, in some marine species, variation in mitochondrial genes involved in the aerobic conversion of oxygen into ATP at the cellular level correlate with gradients of sea surface temperature and gradients of dissolved oxygen. Here, we investigated the adaptive potential of the European sardine Sardina pilchardus populations offshore the Iberian Peninsula. We performed a seascape genetics approach that consisted of the high throughput sequencing of mitochondria’s ATP6, COI, CYTB and ND5 and five microsatellite loci on 96 individuals coupled with environmental information on sea surface temperature and dissolved oxygen across five sampling locations. Results show that, despite sardines forming a nearly panmictic population around Iberian Peninsula, haplotype frequency distribution can be explained by gradients of minimum sea surface temperature and dissolved oxygen. We further identified that the frequencies of the most common CYTB and ATP6 haplotypes negatively correlate with minimum sea surface temperature across the sampled area, suggestive of a signature of selection. With signatures of selection superimposed on highly connected populations, sardines may be able to follow environmental optima and shift their distribution northwards as a response to the increasing sea surface temperatures.
Highlights
Ongoing climatic change translates into a series of environmental fluctuations with the potential to transform the current distribution of global biodiversity
Under and intense fishing pressure, the capacity for the European sardines to positively respond to ongoing climatic shifts must be resolved before developing practices of sustainable exploitation
We focused on the European sardine stocks around the Iberian Peninsula and provided additional evidence for the existence of an apparent near panmictic population with a high degree of connectivity
Summary
Ongoing climatic change translates into a series of environmental fluctuations with the potential to transform the current distribution of global biodiversity. As biological responses fall in the spectrum of “adapt, move or go extinct”, the range shifts, biological invasions and re-shaping of entire ecosystems, are expected to increase in frequency [1]. The marine environment is susceptible to climatic shifts [1], and phenomena such as rising sea surface temperatures, increases in CO2 concentrations (ocean acidification) and depletion of O2 in deep oceanic waters, translate into tropicalization of fish assemblages in temperate zones [2,3] and hypoxia in coastal regions and estuaries [4,5]. Investigating the adaptive potential of species to cope with environmental shifts relies on the identification of phenotypic or molecular changes, expected to emerge as evolutionary responses [6]. Coupled with the extensively available environmental data that exists in marine regions, seascape genetic approaches are frequently being used to identify signatures of evolutionary processes [8,9]
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