Genetic Structure in a Small Pelagic Fish Coincides with a Marine Protected Area: Seascape Genetics in Patagonian Fjords

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.

Genetic analysis redraws the management boundaries for the European sprat

“…In a broader context, pelagic species such as the European sardine, Sardina pilchardus, Walbaum 1792 sampled from NE Spain to south of Morocco reflected a single evolutionary unit with mtDNA yet showed weak but significant genetic differentiation depicting an IBD pattern when using microsatellites (González & Zardoya, 2007). In contrast to sardine and in line with our results, the sprat congener Sprattus fuegensis (Jenyns 1842) in Patagonian Chile display two highly differentiated genetic clusters, potentially the result of larval retention via combination of oceanographic mesoscale processes combined with local geographical configuration (i.e., embayment areas, islands, archipelagos) (Canales-Aguirre, Ferrada-Fuentes, Galleguillos, & Hernández, 2016).…”

Population genetic structure of Patagonian toothfish (Dissostichus eleginoides) in the Southeast Pacific and Southwest Atlantic Ocean

“…The two well-differentiated clusters are located (i) on the South American continental shelf (i.e., SAC) and around to the South Georgia Island. Along the South American continental shelf, two biogeographic breaks have been described consequence of the currents (e.g., 41°S) and upwelling patterns (e.g., ∼30°S and 36°S) of these areas which has been correlated with changes in species composition (see review by Camus, 2001 ; Fenberg et al, 2015 ) and genetic isolation of marine taxa (e.g., Tellier et al, 2009 ; Brante, Fernández & Viard, 2012 ; Canales-Aguirre et al, 2016 ). These patterns do not seem to play a role in the population structure of D. eleginoides and its distribution on the South American continental shelf (i.e., SAC).…”

Peer Review #2 of "Population genetic structure of Patagonian toothfish (Dissostichus eleginoides) in the Southeast Pacific and Southwest Atlantic Ocean (v0.2)"

“…~30° S and 36 ° S) of these areas which has been correlated with changes in species composition (see review by Camus, 2001;Fenberg et al, 2014) and genetic isolation of marine taxa (e.g. Tellier et al, 2009;Brante, Fernández & Viard, 2012;Canales-Aguirre et al, 2016). These patterns do not seem to play a role in the population structure of D. eleginoides and its distribution on the South American continental shelf (i.e.…”