Abstract
Marine environmental variables can play an important role in promoting population genetic differentiation in marine organisms. Although fjord ecosystems have attracted much attention due to the great oscillation of environmental variables that produce heterogeneous habitats, species inhabiting this kind of ecosystem have received less attention. In this study, we used Sprattus fuegensis, a small pelagic species that populates the inner waters of the continental shelf, channels and fjords of Chilean Patagonia and Argentina, as a model species to test whether environmental variables of fjords relate to population genetic structure. A total of 282 individuals were analyzed from Chilean Patagonia with eight microsatellite loci. Bayesian and non-Bayesian analyses were conducted to describe the genetic variability of S. fuegensis and whether it shows spatial genetic structure. Results showed two well-differentiated genetic clusters along the Chilean Patagonia distribution (i.e. inside the embayment area called TicToc, and the rest of the fjords), but no spatial isolation by distance (IBD) pattern was found with a Mantel test analysis. Temperature and nitrate were correlated to the expected heterozygosities and explained the allelic frequency variation of data in the redundancy analyses. These results suggest that the singular genetic differences found in S. fuegensis from inside TicToc Bay (East of the Corcovado Gulf) are the result of larvae retention bya combination of oceanographic mesoscale processes (i.e. the west wind drift current reaches the continental shelf exactly in this zone), and the local geographical configuration (i.e. embayment area, islands, archipelagos). We propose that these features generated an isolated area in the Patagonian fjords that promoted genetic differentiation by drift and a singular biodiversity, adding support to the existence of the largest marine protected area (MPA) of continental Chile, which is the Tic-Toc MPA.
Highlights
Marine environmental landscape parameters play an important role in promoting population genetic differentiation in marine organisms [1]
We described the genetic diversity and population structure of S. fuegensis along the Chilean fjords and we evaluated the effect of marine environmental variables that are related to the causal mechanisms of a population structure
Our results show two genetic clusters in Sprattus fuegensis of the Patagonian fjords: one cluster restricted to Tic-Toc Bay (SC) and the other extending through the rest of the Chilean Patagonia (LC)
Summary
Marine environmental landscape parameters play an important role in promoting population genetic differentiation in marine organisms [1]. Most research on the effects of the environmental marine landscape on the genetics of population structure has been qualitative (e.g., [2,3]). Most studies that used this approach have been performed in terrestrial organisms, leaving marine and freshwater organisms mostly unexplored [6]. Concepts such as seascape genetics or marine landscape genetics have started to appear in studies that evaluate how biotic and abiotic factors promote microevolutionary processes in marine species (i.e. fishes, mollusks, crustaceans [1,3,7]). Different marine habitats (i.e. estuary, open sea, intertidal, pelagic, benthic) could potentially affect the genetic diversity within species, fjord habitats in particular have the potential to greatly affect population genetic diversity due to the complex scenario produced by their heterogeneous geography and environmental characteristics
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