Role of environmental factors in the genetic structure of a highly mobile seabird

Aim: Environmental features can act as selection pressures and barriers to gene flow between populations. The genetic structuring of highly mobile but philopatric seabirds creates a paradox, and the role of oceanographic and geographic variables is still poorly understood. In this study, we investigate the influence of environmental and geographic variables in the genetic and phenotypic diversity of a pantropical seabird breeding in islands and archipelagos separated by different geographic distances, up to thousand kilometers, and which differ in environmental characteristics. Location: Islands and archipelagos in the southwestern Atlantic Ocean. Taxon: Sula dactylatra, Lesson, 1831 (masked booby). Methods: The population structure of the species was accessed through mitochondrial and nuclear DNA. To test Isolation by Environment (IBE) vs. by Distance (IBD), sea surface temperature, primary productivity, and salinity, as well as isotopic niche based on carbon and nitrogen, and distances between colonies and from the continent, were used. We also tested the correlation between the genetic structure and the morphometry of individuals in each colony. Results: We identified the presence of low genetic structure between populations. Nevertheless, differences were identified between inshore and offshore colonies, with the influence of landscape characteristics of these two types of environment. The morphometric and isotopic niche variations are consistent with this segregation. Main conclusions: Environmental variables of coastal and oceanic environments seem to influence the genetic structure of masked boobies, even though it is low in the SW Atlantic Ocean, highlighting the role of environmental heterogeneity in shaping biodiversity.

研究目的：环境特征可作为选择压力与种群间基因交流的障碍。兼具高移动性与恋巢习性(philopatry)的海鸟，其种群遗传结构构成了一个难解的悖论，而海洋学与地理变量在其中的作用仍不甚明晰。本研究针对一种泛热带海鸟展开调查，该物种在地理距离可达数千公里、环境特征各异的岛屿与群岛上繁殖，旨在探究环境与地理变量对其遗传多样性与表型多样性的影响。
研究区域：西南大西洋海域的岛屿与群岛。
研究类群：蒙面鲣鸟(Sula dactylatra, Lesson, 1831, masked booby)。
研究方法：通过线粒体DNA与核DNA解析该物种的种群结构。为检验环境隔离(Isolation by Environment, IBE)与距离隔离(Isolation by Distance, IBD)假说，本研究采用了海表温度、初级生产力、盐度，以及基于碳、氮同位素的同位素生态位指标，同时纳入了繁殖群落间的距离及各群落与大陆的距离。此外，我们还检验了各繁殖群落的种群遗传结构与个体形态计量学特征间的相关性。
研究结果：我们发现种群间仅存在微弱的遗传结构。尽管如此，近岸与远海繁殖群落间仍存在显著差异，且受到两类生境景观特征的影响。形态计量学与同位素生态位的变异与这一分化模式相一致。
主要结论：尽管西南大西洋海域的蒙面鲣鸟种群遗传结构较弱，但近岸与海洋环境的变量似乎对其遗传结构存在调控作用，这凸显了环境异质性在塑造生物多样性进程中的关键作用。