Data from: Human-mediated extirpation of the unique Chatham Islands sea lion and implications for the conservation management of remaining New Zealand sea lion populations

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.

尽管全球范围内陆地巨型动物群灭绝事件已得到充分表征，但我们对海洋巨型动物群种群衰退的认知仍十分有限。本研究针对新西兰偏远查塔姆群岛出土的公元1450年至1650年史前海狮标本开展古代DNA（ancient DNA）分析，以此评估人类定居活动对海狮种群动态的影响。数据显示，波利尼西亚人定居该群岛时期，当地曾存在一支专属的大型海狮种群；这一独特的线粒体谱系（mitochondrial lineage）因过度捕猎在200年内快速灭绝，其灭绝过程与同期规模相当的特有大陆海狮种群的局部灭绝情况高度一致。全线粒体基因组（mitogenome）分析证实，史前海狮谱系间存在丰富的种内多样性。种群动态模型结果表明，即便极低的捕获率也可能驱动这些谱系快速灭绝。本研究显示，现存的新海狮属（Phocarctos）种群是曾经兼具多样性与分布广度的海狮类群的残存后裔，凸显了人类活动对特有海洋生物多样性的剧烈影响。此外，我们的研究结果还表明，商业渔业中捕获的新海狮属副渔获物可能是其种群持续衰退的重要诱因之一。