| Summary: | While terrestrial megafaunal extinctions have been well characterized worldwide, our understanding of declines in marine megafauna remains limited. Here, we use ancient DNA analyses of prehistoric (<1450–1650 AD) sea lion specimens from New Zealand's isolated Chatham Islands to assess the demographic impacts of human settlement. These data suggest there was a large population of sea lions, unique to the Chatham Islands, at the time of Polynesian settlement. This distinct mitochondrial lineage became rapidly extinct within 200 years due to overhunting, paralleling the extirpation of a similarly large endemic mainland population. Whole mitogenomic analyses confirm substantial intraspecific diversity among prehistoric lineages. Demographic models suggest that even low harvest rates would likely have driven rapid extinction of these lineages. This study indicates that surviving Phocarctos populations are remnants of a once diverse and widespread sea lion assemblage, highlighting dramatic human impacts on endemic marine biodiversity. Our findings also suggest that Phocarctos bycatch in commercial fisheries may contribute to the ongoing population decline. BEAST Dloop phylogenetic analysis with Birth Death speciation priorChatham_sealions_Dloop_Birth_Death.xmlBEAST Dloop phylogenetic analysis with Yule speciation priorChatham_sealions_Dloop_Yule.xmlIndividual Based Model for anthropogenic mortality estimatesIBM script.rSequence alignment of Chatham Island sea lionsSequence alignment of Chatham Island sea lion mtDNA D-loop including all Chatham Islands individuals (NRO number, location, haplotype - C1 to 9), exemplar haplotype sequences of subantarctic individuals (SA1-3), exemplar haplotype sequences of prehistoric New Zealand individuals (NZ1-14), and outgroups (Australian sea lion, South American sea lion, New Zealand furseal). Please see Suppl. Info. Table S1 for numbers of New Zealand and subantarctic individuals for each haplotype.Chatham Island sealions_final.fasBEAST mitogenome phylogenetic analysis with ...
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