Publication Date:
2015-11-10
Description:
Antarctic krill (Euphausia superba; hereafter krill) are an incredibly abundant pelagic
crustacean which has a wide, but patchy, distribution in the Southern Ocean. Several
studies have examined the potential for population genetic structuring in krill, but
DNA-based analyses have focused on a limited number of markers and have covered
only part of their circum-Antarctic range. We used mitochondrial DNA and restriction
site-associated DNA sequencing (RAD-seq) to investigate genetic differences between
krill from five sites, including two from East Antarctica. Our mtDNA results show no
discernible genetic structuring between sites separated by thousands of kilometres,
which is consistent with previous studies. Using standard RAD-seq methodology, we
obtained over a billion sequences from 〉140 krill, and thousands of variable nucleotides
were identified at hundreds of loci. However, downstream analysis found that
markers with sufficient coverage were primarily from multicopy genomic regions.
Careful examination of these data highlights the complexity of the RAD-seq approach
in organisms with very large genomes. To characterize the multicopy markers, we
recorded sequence counts from variable nucleotide sites rather than the derived genotypes;
we also examined a small number of manually curated genotypes. Although
these analyses effectively fingerprinted individuals, and uncovered a minor laboratory
batch effect, no population structuring was observed. Overall, our results are consistent
with panmixia of krill throughout their distribution. This result may indicate
ongoing gene flow. However, krill’s enormous population size creates substantial panmictic
inertia, so genetic differentiation may not occur on an ecologically relevant timescale
even if demographically separate populations exist.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
isiRev
Format:
application/pdf
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