Data from: Phylogeography of the snake pipefish, Entelurus aequoreus (Family: Syngnathidae) in the northeastern Atlantic Ocean

The snake pipefish, Entelurus aequoreus, is a widespread marine species occurring in pelagic and coastal environments in the northeastern Atlantic Ocean. Recently, the snake pipefish underwent a short-lived, yet substantial, increase in abundance and range expansion into arctic waters. However, little is known about the species’ population structure or if different ecotypes contributed to this outbreak. Specimens (n=178) were sampled from 25 locations from six regions spanning 1.9 million km2. A fragment of the mitochondrial cytochrome b gene and control region was used to assess population structure and genetic diversity. Both loci showed high haplotype diversity (Hd) and low nucleotide diversity (π) over all sampled locations. A genetic signature of population expansion was evident through mismatch distributions and tests for recent population expansion (Fu’s Fs, Tajima’s D, and R2). Effective population size analyses (Bayesian Skyline Plot) suggest an ancient expansion (50-100 thousand years ago). However, we found neither significant population differentiation (AMOVA) among regions, nor evidence of genetically distinct ecotypes. This lack of structure is likely due to a pelagic life style, fast development and long distance dispersal aided by ocean currents. Our work highlights the need for further research to better understand the recent outbreak and how this species may respond to future environmental challenges.

蛇形海龙（Entelurus aequoreus）是一种广布性海洋物种，分布于东北大西洋的远洋与近岸海域。近年来，该物种曾出现短暂却显著的种群数量增长，且分布范围扩张至北极海域。然而，目前对该物种的种群结构，以及不同生态型是否参与了此次种群暴发，仍知之甚少。本研究共采集178号标本，采样覆盖6个区域的25个采样点，总面积达190万平方公里。通过线粒体细胞色素b基因片段与控制区序列，本研究分析了其种群结构与遗传多样性。在所有采样点中，两个分子标记均呈现出较高的单倍型多样性（Hd）与较低的核苷酸多样性（π）。通过错配分布分析与近期种群扩张检验（Fu’s Fs、Tajima’s D及R2统计量），可观测到种群扩张的遗传信号。有效种群大小分析（贝叶斯天际线图，Bayesian Skyline Plot）显示，该物种的种群扩张发生在5至10万年前的远古时期。但研究并未发现区域间存在显著的种群分化（分子方差分析，AMOVA），也未找到遗传分化明显的生态型证据。这种缺乏种群结构的现象，可能与其远洋生活型、快速发育以及借助洋流实现的长距离扩散有关。本研究强调，需开展更多研究以深入理解此次近期的种群暴发事件，以及该物种将如何应对未来的环境挑战。