Gone with the currents: lack of genetic differentiation at the circum-continental scale in the Antarctic krill Euphausia superba.

• Published in: BMC Genetics
• Main Authors: BORTOLOTTO E, BUCKLIN A, MEZZAVILLA M, ZANE, LORENZO, PATARNELLO, TOMASO
• Other Authors: Bortolotto, E, Bucklin, A, Mezzavilla, M, Zane, Lorenzo, Patarnello, Tomaso
• Format: Article in Journal/Newspaper
• Language: English
• Published: BIOMED CENTRAL LTD, MIDDLESEX HOUSE, 34-42 CLEVELAND ST, LONDON, ENGLAND, W1T 4LB 2011
• Subjects: krill; Population Genetic; Antarctica; Antarctic; Antarctic Ocean; Southern Ocean; The Antarctic; Antarc*; Antarctic Krill; Euphausia superba
• Online Access: http://hdl.handle.net/11577/146854; https://doi.org/10.1186/1471-2156-12-32

BACKGROUND Southern Ocean fauna represent a significant amount of global biodiversity, whose origin may be linked to glacial cycles determining local extinction/eradication with ice advance, survival of refugee populations and post-glacial re-colonization. This pattern implies high potential for differentiation in benthic shelf species with limited dispersal, yet consequences for pelagic organisms are less clear. The present study investigates levels of genetic variation and population structure of the Antarctic krill Euphausia superba using mitochondrial DNA and EST-linked microsatellite markers for an unprecedentedly comprehensive sampling of its populations over a circum-Antarctic range. RESULTS MtDNA (ND1) sequences and EST-linked microsatellite markers indicated no clear sign of genetic structure among populations over large geographic scales, despite considerable power to detect differences inferred from forward-time simulations. Based on ND1, few instances of genetic heterogeneity, not significant after correction for multiple tests, were detected between geographic or temporal samples. Neutrality tests and mismatch distribution based on mtDNA sequences revealed strong evidence of past population expansion. Significant positive values of the parameter g (a measure of population growth) were obtained from microsatellite markers using a coalescent-based genealogical method and suggested a recent start (60 000 - 40 000 years ago) for the expansion. CONCLUSIONS The results provide evidence of lack of genetic heterogeneity of Antarctic krill at large geographic scales and unequivocal support for recent population expansion. Lack of genetic structuring likely reflects the tight link between krill and circum-Antarctic ocean currents and is consistent with the hypothesis that differentiation processes in Antarctic species are largely influenced by dispersal potential, whereas small-scale spatial and temporal differentiation might be due to local conditions leading to genetic patchiness. The signal of recent ...