Population genetic variation of the Southern Ocean krill, Euphausia superba, in the Western Antarctic Peninsula region based on mitochondrial single nucleotide polymorphisms (SNPs)

P.G. Batta Lona¹, A.Bucklin¹, P.W. Wiebe², N.J. Copley², and T. Patarnello³

¹Department of Marine Sciences, University of Connecticut, Groton, CT, USA;

²Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA;

³Department of Public Health, Comparatitve Pathology, and Veterinary Hygiene, University of Padova, Padova, Italy

Population genetic diversity and structure of the Antarctic krill Euphausia superba was examined for collections from the Western Antarctic Peninsula (WAP) region made during US GLOBEC cruises in austral Fall, 2001 and 2002. The molecular markers used were allele frequencies at single nucleotide polymorphism (SNP) sites in the gene encoding mitochondrial cytochrome B (CytB). Four 4-fold degenerate SNP sites were selected, and allelic variation was detected using a multiplexed single-base extension PCR protocol for a total of 585 E. superba, including all 6 furcilia larval stages, juveniles, and adults). Confirmation of species identification was done using a competitive multiplexed species-specific PCR (SS-PCR) reaction based on mitochondrial cytochrome oxidase I (mtC0I) sequences. A total of 22 SNP haplotypes (i.e., strings of alleles at the four SNP loci) was observed; haplotype diversity (Hd) = 0.811 (s.d. = 0.008; Var = 0.00006). Analysis of molecular variation within and among samples, areas (i.e., Marguerite Bay, Crystal Sound, shelf, offshore), and collection years revealed no difference between 2001 and 2002 collections as a whole, although 2001 and 2002 collections from Marguerite Bay explained 7.4% of the variance (Fsc = 0.072; P = 0.002 + 0.001). Most of the variation (96.3%) occurred within samples each year, with no differentiation among areas. There was small, but significant differentiation among samples within areas in 2001 (4.6%; Fsc = 0.045; P = 0.015 ± 0.003) and 2002 (6.3%; Fsc = 0.062; P = 0.000 ± 0.000). Separate analysis of furcilia larval life stages revealed large and significant variation among samples each year: in 2001, among-sample variation was 25.6% (Fsc = 0.225; 0.095 ± 0.010) for F3 furcilia; 73.0% for F4, 15.8% for F5, 12.2% for F6; in 2002, among-sample variation was 191.% for F1 and 92% for F2 stages. For 2001 collections from Marguerite Bay, 20.6% of the variation (Fsc = 0.199; 0.000 ± 0.0000) was found among life stages within samples. The significant differentiation among life stages within and among samples and between years is interpreted to suggest multiple sources of recruitment of E. superba in the WAP region, consistent with advective transport and production of both offshore and shelf habitats. In light of climate change and global warming, as well as an expanding commercial krill fishery, further population genetic analysis at sub-regional scales is needed to understand and eventually predict population dynamic processes (e.g., recruitment, migration, retention, and over-wintering) of the Southern Ocean krill.

STATUS UPDATE

09/04/09: Manuscript submitted.