Postglacial recolonization of the Southern Ocean by elephant seals occurred from multiple glacial refugia

The Southern Ocean is warming more rapidly than other parts of our planet. How this region’s endemic biodiversity will respond to such changes can be illuminated by studying past events, through genetic analyses of time-series data sets including historic and fossil remains. Archaeological and subfossil remains show that the southern elephant seal (Mirounga leonina) was common along the coasts of Australia and New Zealand in the recent past. This species is now mostly confined to sub-Antarctic islands and the southern tip of South America. We analysed ancient seal samples from Australia (Tasmania), New Zealand, and the Antarctic mainland to examine how southern elephant seals have responded to a changing climate and anthropogenic pressures during the Holocene. Our analyses show that these seals formed part of a broader Australasian lineage, comprising seals from all sampled locations from the south Pacific sector of the Southern Ocean. Our study demonstrates that southern elephant seal ..., Control Region Sequence Analysis: Partial control region (HVR1) sequences were successfully amplified from modern and ancient samples. A data set with representative sequences from various populations was constructed. Genetic diversity metrics were calculated, and FST values were used to measure genetic differentiation. AMOVAs were performed to infer geographic structure. A time-sensitive haplotype network was constructed.
Mitochondrial Genome Assembly: DNA extraction was performed on selected ancient samples for mitochondrial genome assembly. Libraries were prepared, quantified, and enriched using hybridization capture with bait from a closely related species. PCR amplification and pooling of samples were performed and sequenced using the Illumina MiSeq platform.
Data Processing: Sequence data were processed using specific scripts to trim adapters, merge overlapping read pairs, and filter low-quality reads. The processed reads were mapped to a reference mitochondrial genome using BWA a..., , # Postglacial recolonization of the Southern Ocean by elephant seals occurred from multiple glacial refugia

[https://doi.org/10.5061/dryad.xwdbrv1q9](https://doi.org/10.5061/dryad.xwdbrv1q9)

## Description of the data and file structure

### Files and variables

#### File: SES.ControlRegion.fasta

**Description:** Alignment of 628 previously published and newly generated ancient and modern mitochondrial control region sequences of southern elephant seals (*Mirounga leonina*) from all known living and extinct populations around the Southern Ocean. Each sequence name has a dollar sign followed by an age category (this info is for the temporal haplotype network and can be deleted).

#### File: SES.Mitogenomes.fasta

**Description:** Alignment of 23 previously published and newly generated ancient and modern mitogenomes of southern elephant seals (*Mirounga leonina*) from living and extinct populations from Victoria Land Coast (Antarctica), Macquarie Island, Tasmania and New Zealand. This...