Posavi Marijan, Gulisija Davorka, Munro James B, Silva Joana C, Lee Carol Eunmi
Department of Integrative Biology, University of Wisconsin, Madison, WI, USA.
Department of Biology, University of New Mexico, Albuquerque, NM, USA.
Mol Ecol. 2020 Dec;29(24):4835-4856. doi: 10.1111/mec.15681. Epub 2020 Nov 20.
Saline migrants into freshwater habitats constitute among the most destructive invaders in aquatic ecosystems throughout the globe. However, the evolutionary and physiological mechanisms underlying such habitat transitions remain poorly understood. To explore the mechanisms of freshwater adaptation and distinguish between adaptive (evolutionary) and acclimatory (plastic) responses to salinity change, we examined genome-wide patterns of gene expression between ancestral saline and derived freshwater populations of the Eurytemora affinis species complex, reared under two different common-garden conditions (0 versus 15 PSU). We found that evolutionary shifts in gene expression (between saline and freshwater inbred lines) showed far greater changes and were more widespread than acclimatory responses to salinity (0 versus 15 PSU). Most notably, 30-40 genes showing evolutionary shifts in gene expression across the salinity boundary were associated with ion transport function, with inorganic cation transmembrane transport forming the largest Gene Ontology category. Of particular interest was the sodium transporter, the Na /H antiporter (NHA) gene family, which was discovered in animals relatively recently. Thirty key ion regulatory genes, such as NHA paralogue #7, demonstrated concordant evolutionary and plastic shifts in gene expression, suggesting the evolution of ion transporter function and plasticity during rapid invasions into novel salinities. Moreover, freshwater invasions were associated with the evolution of reduced plasticity in the freshwater population, again for the same key ion transporters, consistent with the predicted evolution of canalization following adaptation to stressful conditions. Our results have important implications for understanding evolutionary and physiological mechanisms of range expansions by some of the most widespread invaders in aquatic habitats.
从咸水栖息地迁移到淡水栖息地的物种是全球水生生态系统中最具破坏性的入侵物种之一。然而，这种栖息地转变背后的进化和生理机制仍知之甚少。为了探究淡水适应的机制，并区分对盐度变化的适应性（进化性）和适应性（可塑性）反应，我们研究了亲缘水蚤物种复合体的祖先咸水种群和衍生淡水种群在两种不同的共同培养条件下（0与15 PSU）全基因组的基因表达模式。我们发现，基因表达的进化变化（咸水和淡水近交系之间）比盐度适应性反应（0与15 PSU）变化更大、更广泛。最值得注意的是，30 - 40个在盐度边界上显示出基因表达进化变化的基因与离子转运功能相关，无机阳离子跨膜转运形成了最大的基因本体类别。特别有趣的是钠转运蛋白，即Na /H反向转运蛋白（NHA）基因家族，它是最近在动物中发现的。30个关键的离子调节基因，如NHA旁系同源物#7，在基因表达上显示出一致的进化和可塑性变化，这表明在快速入侵到新盐度环境的过程中离子转运蛋白功能和可塑性的进化。此外，淡水入侵与淡水种群中可塑性降低的进化有关，同样是针对相同的关键离子转运蛋白，这与适应压力条件后预期的发育稳态进化一致。我们的研究结果对于理解水生栖息地中一些分布最广泛的入侵物种范围扩张的进化和生理机制具有重要意义。
