Genetic differentiation in the ice‐dependent fish Pleuragramma antarctica along the Antarctic Peninsula

Abstract

Aim Pleuragramma antarctica is an Antarctic notothenioid fish with a pelagic life-cycle. It plays a major trophic role in coastal Antarctic waters as a predator of krill and as prey for penguins and seals. A previous study, using mtDNA to investigate Pleuragramma population structure at multiple Antarctic sites was unable to discriminate between hypotheses of panmixia, with occasional fluctuations of allelic frequencies, and population structure. The aim of the present study was to investigate the population structure of P. antarctica along the Antarctic Peninsula (AP) shelf by microsatellite genotyping.Location Four areas along the AP shelf: Charcot Island, Marguerite Bay, Joinville Island and the Larsen Ice Shelf.Methods A total of 562 individuals from nine population samples were genotyped at 16 expressed sequence tag (EST)-linked microsatellites. Genetic variability, Hardy-Weinberg probabilities and F-statistics were calculated, and a hierarchical analysis of molecular variance was carried out. A Bayesian method was applied to estimate the migration rates between geographical localities.Results We found one genetically homogeneous population with no interannual variability in the south-western AP and one off the northern tip of the AP. Significant differences were recorded between the two geographical regions, which also differed from the eastern AP. The extent of differentiation changed between years and significant genetic differentiation was found between clusters of individuals of different length modes collected at Joinville Island in 2010. Bayesian analysis suggested weak gene flow along the western AP, with a prevailing direction from north to south, following the anticlockwise-flowing Coastal Current.Main conclusions Population genetic structure can be detected in AP shelf samples of P. antarctica. Thus, even in this area characterized by strong oceanographic currents, genetic mixing is not complete. Temporal fluctuations of allelic frequencies and genetic differentiation between individuals of different length collected at the same location suggest the importance of genetic drift in this highly abundant species.

Assemblages of micronektonic fishes and invertebrates in a gradient of regional warming along the Western Antarctic Peninsula

“…This suggests that Pleuragramma from Marguerite Bay and Charcot Island are part of one contiguous population. Genetic analyses performed on fish captured in the present study yielded similar results, with the Marguerite Bay and Charcot Island fish comprising a single, panmictic population that was differentiated from the Joinville Island fish (Agostini et al, 2015). Results of those studies coupled with the results presented here provide three lines of evidence, cluster analyses, otolith microchemical analyses, and genetic analyses, that there is little connectivity between silverfish populations in the northernmost region at Joinville Island and the two southernmost regions at Marguerite Bay and Charcot Island.…”

Spatial structuring and life history connectivity of Antarctic silverfish along the southern continental shelf of the Weddell Sea

“…This was consistent with an earlier review by Kellermann (1996), who suggested that fish spawned in the Bellingshausen Sea were advected over the western Antarctic Peninsula shelf via slope transport in the ACC. Genetics data also indicated connectivity via the AACC between silverfish found in Marguerite Bay and Charcot Island (Agostini et al 2015), which was further supported by reproductive data (La Mesa et al 2015b), otolith chemistry (Ferguson 2012), community spatial distributions (Parker et al 2015), and particle simulations based on a circulation model for the southwestern Antarctic Peninsula shelf (Piñones et al 2011). Additionally, particle simulations combined with otolith age data suggested that larvae sampled off Joinville Island were spawned in Larsen Bay in the western Weddell Sea, before being transported around the northern Antarctic Peninsula and into the Bransfield Gyre via the AACC (La Mesa et al 2015a).…”

Early life history connectivity of Antarctic silverfish (Pleuragramma antarctica) in the Ross Sea

“…In contrast to the AFS, the westward Antarctic Coastal Current (AACC, e.g., Moffat, Beardsley, Owens, & van Lipzig, ; Núñez‐Riboni & Fahrbach, ) is a feature typical of coastal buoyant plumes, with freshwater inputs from precipitation over the ocean, meltwater run‐off from land and sea‐ice and glacial melting (Dutrieux et al., ; Moffat et al., ). The AACC is thought to be involved in the delivery of larvae spawned in the western Weddell Sea to adult assemblages in the Bransfield Strait (La Mesa, Piñones, et al., ), and from Marguerite Bay to Charcot Island (Agostini et al., ; Ferguson, ). It is also located inshore along the Amundsen Sea, flowing around Cape Colbeck and sharply south towards the eastern Ross Ice Shelf (Orsi & Wiederwohl, ; Figure ).…”

“…Due to heavy ice conditions and difficulties of access and sampling, the eastern Ross Sea is understudied compared to western areas. However, multi‐disciplinary approaches combining techniques that include genetics (Agostini et al., ), otolith chemistry (Ferguson, ), age distributions and circulation modelling (La Mesa, Piñones, et al., ), reproduction (La Mesa, Riginella, et al., ), and community studies (Parker et al., ) successfully tested population hypotheses along the Antarctic Peninsula. Spatial heterogeneity between discrete populations contrasts strongly to homogeneity between exported fish and their parent population, providing a useful test around which field sampling can be designed.…”

“…Lipid sequestration in large sacs composed of adipocytes (Eastman & DeVries, ) results in neutral buoyancy and low‐energy behavior in which fish are suspended in the water column to feed (La Mesa & Eastman, ). P. antarctica distribution can be explained by dispersal in regional circulation over the continental shelf (Agostini et al., ; Ferguson, ; Hubold, ; La Mesa, Piñones, Catalano, & Ashford, ; La Mesa et al., ; Parker et al., ). In Terra Nova Bay, the eggs occupy a layer of platelet ice under the fast ice and hatch from mid‐November through December (Vacchi et al., , ).…”