Large-scale genetic panmixia in the blue shark (Prionace glauca): a single worldwide population, or a genetic lag-time effect of the “grey zone” of differentiation?

The blue shark Prionace glauca, among the most common and widely studied pelagic sharks, is a top predator, exhibiting the widest distribution range. However, little is known about its population structure and spatial dynamics. With an estimated removal of 10 to 20 million individuals per year by fisheries, the species is classified as “Near Threatened” by International Union for Conservation of Nature. We lack the knowledge to forecast the long-term consequences of such a huge removal on this top predator itself and on its trophic network. The genetic analysis of more than 200 samples collected at broad scale (from Mediterranean Sea, North Atlantic and Pacific Oceans) using mtDNA and nine microsatellite markers allowed to detect signatures of genetic bottlenecks but a nearly complete genetic homogeneity across the entire studied range. This apparent panmixia could be explained by a genetic lag-time effect illustrated by simulations of demographic changes that were not detectable throu...蓝鲨（Prionace glauca）是全球最常见且被广泛研究的远洋鲨鱼之一，作为顶级捕食者，其分布范围最为广泛。然而学界对其种群结构与空间动态却知之甚少。据估算，每年因渔业捕捞被移除的蓝鲨个体达1000万至2000万只，该物种已被国际自然保护联盟（International Union for Conservation of Nature, IUCN）列为"近危（Near Threatened）"物种。目前我们尚不明确如此大规模的捕捞移除，会对这一顶级捕食者本身及其营养网络造成何种长期影响。研究团队对地中海、北大西洋及太平洋大范围采集的200余份样本，采用线粒体DNA（mtDNA）与9个微卫星（microsatellite）标记开展遗传分析，结果在整个研究区域内检测到了遗传瓶颈的特征，但同时发现近乎完全的遗传同质性。这种表观泛交（panmixia）现象可通过遗传滞后效应加以解释，该效应由人口统计变化的模拟实验所阐释，但此类变化目前尚无法通过[原文未完整表述的检测手段]完成检测。