Voelker Madelyn R, Schwarz Dietmar, Thomas Austen, Nelson Benjamin W, Acevedo-Gutiérrez Alejandro
Biology Department Western Washington University Bellingham WA USA.
Present address: Ocean Research College Academy Everett WA USA.
Ecol Evol. 2020 Aug 26;10(18):9867-9885. doi: 10.1002/ece3.6638. eCollection 2020 Sep.
Predator-prey interactions are critical in understanding how communities function. However, we need to describe intraspecific variation in diet to accurately depict those interactions. Harbor seals () are an abundant marine predator that prey on species of conservation concern. We estimated intrapopulation feeding diversity (variation in feeding habits between individuals of the same species) of harbor seals in the Salish Sea. Estimates of feeding diversity were examined relative to sex, month, and location using a novel approach that combined molecular techniques, repeated cross-sectional sampling of scat, and a specialization metric (within-individual consistency in diet measured by the Proportional Similarity Index ( )). Based on 1,083 scat samples collected from five haul-out sites during four nonsequential years, we quantified diet using metabarcoding techniques and determined the sex of the scat depositor using a molecular assay. Results suggest that intrapopulation feeding diversity was present. Specialization was high over short periods (24-48 hr, = 0.392, 95% CI = 0.013, R = 100,000) and variable in time and space. Females showed more specialization than males, particularly during summer and fall. Additionally, demersal and benthic prey species were correlated with more specialized diets. The latter finding suggests that this type of prey likely requires specific foraging strategies and that there are trade-offs between pelagic and benthic foraging styles for harbor seals. This differential feeding on prey species, as well as between sexes of harbor seals, indicates that predator-prey interactions in harbor seals are complex and that each sex may have a different impact on species of conservation concern. As such, describing intrapopulation feeding diversity may unravel hitherto unknown complex predator-prey interactions in the community.
捕食者与猎物之间的相互作用对于理解群落如何运作至关重要。然而，我们需要描述饮食中的种内变异，以便准确描绘这些相互作用。港海豹（Phoca vitulina）是一种数量众多的海洋捕食者，以具有保护意义的物种为食。我们估计了萨利希海（Salish Sea）港海豹的种群内觅食多样性（同一物种个体之间觅食习惯的差异）。使用一种新颖的方法，结合分子技术、粪便的重复横断面采样以及一种专业化指标（通过比例相似性指数（PSIndex）衡量的个体饮食内部一致性），研究了觅食多样性估计值与性别、月份和地点之间的关系。基于在四个非连续年份中从五个上岸地点收集的1083份粪便样本，我们使用元条形码技术对饮食进行了量化，并通过分子分析确定了粪便排放者的性别。结果表明存在种群内觅食多样性。在短时间内（24 - 48小时，PSIndex = 0.392，95%置信区间 = 0.013，R = 100,000）专业化程度较高，且在时间和空间上存在变化。雌性比雄性表现出更高的专业化程度，尤其是在夏季和秋季。此外底栖和底层猎物物种与更专业化的饮食相关。后一发现表明，这类猎物可能需要特定的觅食策略，并且港海豹在远洋和底栖觅食方式之间存在权衡。港海豹在猎物物种以及性别之间的这种不同觅食方式，表明港海豹的捕食者 - 猎物相互作用是复杂的，并且每种性别可能对具有保护意义的物种产生不同的影响。因此，描述种群内觅食多样性可能揭示群落中迄今未知的复杂捕食者 - 猎物相互作用。
