Poirier Maude, Listmann Luisa, Roth Olivia
GEOMAR Helmholtz Centre for Ocean Research Kiel Germany.
Evol Appl. 2017 Apr 19;10(6):603-615. doi: 10.1111/eva.12477. eCollection 2017 Jul.
Habitat stratification by abiotic and biotic factors initiates divergence of populations and leads to ecological speciation. In contrast to fully marine waters, the Baltic Sea is stratified by a salinity gradient that strongly affects fish physiology, distribution, diversity and virulence of important marine pathogens. Animals thus face the challenge to simultaneously adapt to the concurrent salinity and cope with the selection imposed by the changing pathogenic virulence. Western Baltic spring-spawning herring () migrate to spawning grounds characterized by different salinities to which herring are supposedly adapted. We hypothesized that herring populations do not only have to cope with different salinity levels but that they are simultaneously exposed to higher-order effects that accompany the shifts in salinity, that is induced pathogenicity of bacteria in lower saline waters. To experimentally evaluate this, adults of two populations were caught in their spawning grounds and fully reciprocally crossed within and between populations. Larvae were reared at three salinity levels, representing the spawning ground salinity of each of the two populations, or Atlantic salinity conditions resembling the phylogenetic origin of . In addition, larvae were exposed to a . infection. Life-history traits and gene expression analysis served as response variables. Herring seem adapted to Baltic Sea conditions and cope better with low saline waters. However, upon a bacterial infection, herring larvae suffer more when kept at lower salinities implying reduced resistance against or higher virulence. In the context of recent climate change with less saline marine waters in the Baltic Sea, such interactions may constitute key future stressors.
非生物和生物因素导致的栖息地分层引发了种群分化，并导致生态物种形成。与完全的海洋水域不同，波罗的海因盐度梯度而分层，这对鱼类生理学、分布、多样性以及重要海洋病原体的毒力产生强烈影响。因此，动物面临着同时适应盐度变化以及应对致病性变化所带来的选择压力的挑战。波罗的海西部春季产卵的鲱鱼（）会洄游到盐度不同的产卵场，据推测鲱鱼已适应这些盐度。我们假设，鲱鱼种群不仅要应对不同的盐度水平，还要同时面对盐度变化所带来的高阶效应，即在低盐度水域中细菌致病性增加。为了通过实验评估这一点，我们在两个种群的产卵场捕获成年鲱鱼，并在种群内部和种群之间进行完全的正反交。将幼鱼饲养在三个盐度水平下，分别代表两个种群各自产卵场的盐度，或者模拟鲱鱼系统发育起源地的大西洋盐度条件。此外，让幼鱼接触感染。生活史特征和基因表达分析作为响应变量。鲱鱼似乎适应了波罗的海的环境，并且在低盐度水域中表现更好。然而，在受到细菌感染时，饲养在低盐度环境下的鲱鱼幼鱼遭受的痛苦更大，这意味着它们对的抵抗力降低或的毒力增强。在波罗的海海水盐度降低的近期气候变化背景下，这种相互作用可能成为未来的关键压力源。
