Data from: Assessing the trophic ecology of top predators across a recolonisation frontier using DNA metabarcoding of diets

Top predator populations, once intensively hunted, are rebounding in size and geographic distribution. The cessation of sealing along coastal Australia and subsequent recovery of Australian Arctocephalus pusillus doriferus and long-nosed A. forsteri fur seals represents a unique opportunity to investigate trophic linkages at a frontier of predator recolonisation. We characterised the diets of both species across 2 locations of recolonisation, one site an established breeding colony, and the other, a new but permanent haul-out site. Using DNA metabarcoding, high taxonomic resolution data on diets was used to inform ecological trait-based analyses across time and location. Australian and long-nosed fur seals consumed 76 and 73 prey taxa, respectively, a prey diversity greater than previously reported. We found unexpected overlap of prey functional traits in the diets of both seal species at the haul-out site, where we observed strong trophic linkages with coastal ecosystems due to the prevalence of benthic, demersal and reef-associated prey. The diets of both seal species at the breeding colony were consistent with foraging patterns observed in the centre of their geographic range regarding diet partitioning between predator species and seasonal trends typically observed. The unexpected differences between sites in this region and the convergence of both predators’ effective ecological roles at the range-edge haul-out site correlate with known differences in seal population densities and demographics at these and other newly recolonised locations. This study provides a baseline for the diets and trophic interactions for recovering fur seal populations and from which to understand the evolving ecology of predator recolonisation.曾遭到高强度捕杀的顶级捕食者种群，其种群规模与地理分布范围正逐步恢复。澳大利亚沿海地区禁捕海狗的举措，以及随后澳洲海狗（Arctocephalus pusillus doriferus）与长鼻海狗（A. forsteri）种群的恢复，为研究捕食者重新定殖前沿地带的营养联系提供了独特契机。我们针对两处重新定殖区域的两种海狗的食性展开了表征分析：一处为成熟繁殖种群聚集地，另一处则为新建但长期存在的上岸休憩站点。本研究借助DNA元条形码（DNA metabarcoding）技术获取的高分类学分辨率食性数据，开展了跨时间与空间维度的生态性状分析。澳洲海狗与长鼻海狗的捕食猎物类群分别为76种与73种，其猎物多样性均高于此前已有报道的水平。我们在该上岸休憩点的两种海狗食性中，发现了猎物功能性状的意外重叠；由于底栖、近底栖与岩礁关联猎物占据较高比例，该站点与沿岸生态系统存在紧密的营养联系。两处繁殖聚集地的两种海狗食性，与其地理分布核心区域的觅食模式相符：既包括捕食者间的食性分化，也涵盖了已被广泛观测到的季节动态特征。该区域不同站点间存在的意外差异，以及两种捕食者在分布边缘上岸休憩点所展现出的趋同生态功能，与这些站点及其他新定殖区域的海狗种群密度、种群结构差异存在显著关联。本研究为恢复中海狗种群的食性与营养相互作用提供了基准数据，同时也为理解捕食者重新定殖过程中的动态生态学特征奠定了研究基础。