The oceans are harsh environments where insects are not expected to thrive, yet a few skaters of the genus Halobates Eschscholtz, 1822 (Hemiptera: Heteroptera: Gerridae) have completely adapted to life on the open seas. There are five oceanic Halobates species that have well-established and distinct distributions, but little is known about their population dynamics and intraspecific genetic variation. Moreover, existing knowledge on most species has been largely based on limited sample sizes. We examined the phylogeographic patterns and inferred past population dynamics of three Halobates species (H. micans Eschscholtz, 1822, H. sobrinus White, 1883 and H. splendens Witlaczil, 1886) based on an unprecedented large number of specimens (73–199 individuals each) collected from the Eastern Tropical Pacific (ETP) Ocean. These species have distinct biogeographies, with H. sobrinus occurring mostly along coastal Mexico, H. micans in the ETP north of the equator, and H. splendens largely south of the equator in the cold tongue of water derived from the Peru (Humboldt) current. We did not find evidence for sub-population structure within each species over distances as far as 6000–7000 km. Populations of all three species were found to deviate from neutrality, with evidence of past population growth. Genetic diversity and haplotype genealogies varied between species, implying distinct evolutionary trajectories. Coalescent analyses using Bayesian skyline plots suggested that H. splendens underwent a population expansion ~ 1 Ma, whereas H. sobrinus and H. micans experienced demographic growth ~ 120 Ka to 100 Ka, respectively. The period of population expansion of H. splendens roughly corresponds to the establishment of cool, productive waters in the cold tongue starting ~ 1 Ma and reaching modern temperatures ~ 800 Ka. Population expansions of both H. micans and H. sobrinus north of the equator occurred mostly during the last interglacial period, characterized by increased frequency and dominance of El Niño conditions, and a relatively southerly position of the Intertropical Convergence Zone of high rainfall. Intensification of El Niño conditions between ~ 75 and 125 Ka may have produced a warmer, low wind and nutrient-depleted habitat favoring population growth for both H. micans and H. sobrinus. Key insights drawn from the results of this study, alongside future resolution of evolutionary relationships among Halobates species, will complete our understanding of how these remarkable insects conquered the high seas where no other insect could.

海洋是恶劣的环境，昆虫预计不会繁衍生息，但1822 年的Halobates Eschscholtz属（半翅目：异翅目：Gerridae）的一些滑冰者已经完全适应了公海的生活。有 5种海洋Halobates物种具有完善和独特的分布，但对其种群动态和种内遗传变异知之甚少。此外，关于大多数物种的现有知识主要基于有限的样本量。我们检查了系统地理学模式并推断了三种Halobates物种（H. micans Eschscholtz, 1822, H. sobrinus White, 1883 和H. splendensWitlaczil, 1886) 基于从东热带太平洋 (ETP) 海洋收集的前所未有的大量标本（每个标本 73-199 只）。这些物种具有不同的生物地理分布，H. sobrinus主要分布在墨西哥沿海地区，H. micans位于赤道以北的 ETP 和H. splendens大部分位于赤道以南，来自秘鲁（洪堡）洋流的冰冷水舌。我们没有发现每个物种在 6000-7000 公里范围内的亚种群结构的证据。发现所有三个物种的种群都偏离中立，并有过去种群增长的证据。物种之间的遗传多样性和单倍型谱系各不相同，这意味着不同的进化轨迹。使用贝叶斯天际线图的聚结分析表明，H. splendens经历了约 1 Ma 的种群扩张，而H. sobrinus和H. micans 分别经历了约 120 Ka 到 100 Ka 的人口增长。H. splendens种群扩张期大致对应于在冷舌中建立凉爽、多产的水域，从约 1 Ma 开始并达到现代温度约 800 Ka。赤道以北的H. micans和H. sobrinus 的种群扩张主要发生在最后一个间冰期，其特征是厄尔尼诺条件的频率和优势增加，以及高降雨量的热带辐合带的相对偏南位置。厄尔尼诺现象在约 75 到 125 Ka 之间的加剧可能产生了一个温暖、低风和营养耗尽的栖息地，有利于H. micans和H. sobrinus 的人口增长。从这项研究的结果中得出的关键见解，以及未来对Halobates物种之间进化关系的解决，将完成我们对这些非凡昆虫如何征服其他昆虫无法征服的公海的理解。