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1. Comparative Proteomics of Salinity Stress Responses in Fish and Aquatic Invertebrates

   https://doi.org/10.1002/pmic.202400255  

   Leprêtre, Maxime; Hamar, Jens; Urias, Monica B; Kültz, Dietmar (February 2025, PROTEOMICS)

   ABSTRACT Fluctuating salinity is symptomatic of climate change challenging aquatic species. The melting of polar ice, rising sea levels, coastal surface and groundwater salinization, and increased evaporation in arid habitats alter salinity worldwide. Moreover, the frequency and intensity of extreme weather events such as rainstorms and floods increase, causing rapid shifts in brackish and coastal habitat salinity. Such salinity alterations disrupt homeostasis and ultimately diminish the fitness, of aquatic organisms by interfering with metabolism, reproduction, immunity, and other critical aspects of physiology. Proteins are central to these physiological mechanisms. They represent the molecular building blocks of phenotypes that govern organismal responses to environmental challenges. Environmental cues regulate proteins in a concerted fashion, necessitating holistic analyses of proteomes for comprehending salinity stress responses. Proteomics approaches reveal molecular causes of population declines and enable holistic bioindication geared toward timely interventions to prevent local extinctions. Proteomics analyses of salinity effects on aquatic organisms have been performed since the mid‐1990s, propelled by the invention of two‐dimensional protein gels, soft ionization techniques for mass spectrometry (MS), and nano‐liquid chromatography in the 1970s and 1980s. This review summarizes the current knowledge on salinity regulation of proteomes from aquatic organisms, including key methodological advances over the past decades. 

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2. Ion Transporter Gene Families as Physiological Targets of Natural Selection During Salinity Transitions in a Copepod

   https://doi.org/10.1152/physiol.00009.2021  

   Lee, Carol Eunmi (November 2021, Physiology)

   Salinity is a key factor that structures biodiversity on the planet. With anthropogenic change, such as climate change and species invasions, many populations are facing rapid and dramatic changes in salinity throughout the globe. Studies on the copepod Eurytemora affinis species complex have implicated ion transporter gene families as major loci contributing to salinity adaptation during freshwater invasions. Laboratory experiments and population genomic surveys of wild populations have revealed evolutionary shifts in genome-wide gene expression and parallel genomic signatures of natural selection during independent salinity transitions. Our results suggest that balancing selection in the native range and epistatic interactions among specific ion transporter paralogs could contribute to parallel freshwater adaptation. Overall, these studies provide unprecedented insights into evolutionary mechanisms underlying physiological adaptation during rapid salinity change. 

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3. Linking individual animal behavior to species range shifts under climate change

   https://doi.org/10.1016/j.tree.2025.06.002  

   Wrensford, Kwasi C; Angert, Amy L; Gaynor, Kaitlyn M (August 2025, Trends in Ecology & Evolution)

   Climate change has led animal species to shift their ranges to greater elevations, latitudes, and depths, tracking their preferred abiotic niche. However, there is extensive variation in these shifts, and some species have not shifted their ranges at all. Some of this variation arises because species’ distributions not only align with the abiotic environment but are also shaped by biotic factors and movement. Through facilitating rapid adaptive responses to climate-mediated changes to abiotic, biotic, and movement factors, behavioral plasticity allows populations to survive environmental change by persisting in place, while also enabling successful establishment in novel habitats when shifting in space. 

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4. Genome architecture underlying salinity adaptation in the invasive copepod Eurytemora affinis species complex: A review

   https://doi.org/10.1016/j.isci.2023.107851  

   Lee, Carol Eunmi (October 2023, iScience)

   With climate change, habitat salinity is shifting rapidly throughout the globe. In addition, many destructive freshwater invaders are recent immigrants from saline habitats. Recently, populations of the copepod Eurytemora affinis species complex have invaded freshwater habitats multiple times independently from saline estuaries on three continents. This review discusses features of this species complex that could enhance their evolutionary potential during rapid environmental change. Remarkably, across independent freshwater invasions, natural selection has repeatedly favored the same alleles far more than expected. This high degree of parallelism is surprising, given the expectation of nonparallel evolution for polygenic adaptation. Factors such as population structure and the genome architecture underlying critical traits under selection might help drive rapid adaptation and parallel evolution. Given the preponderance of saline-to-freshwater invasions and climate-induced salinity change, the principles found here could provide invaluable insights into mechanisms operating in other systems and the potential for adaptation in a changing planet. 

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5. Local Adaptation Despite Gene Flow in Copepod Populations Across Salinity and Temperature Gradients in the Baltic Sea and North Sea Region

   https://doi.org/10.1111/ddi.70176  

   Diaz, Juanita A; Stern, David B; Lee, Carol Eunmi (May 2026, Diversity and Distributions)

   ABSTRACT AimClimate change is threatening aquatic populations with rapid changes in habitat salinity and temperature. Locally adapted alleles along environmental gradients, along with low but sufficient gene flow, could provide crucial genetic variation to adapt to future climate change and rescue populations from extinction. Thus, we explored whether planktonic populations exhibit genomic signatures of selection and gene flow across salinity and temperature gradients in the Baltic Sea and North Sea region. LocationBaltic Sea, North Sea region. MethodsWe performed whole‐genome sequencing of 11 populations of the copepodEurytemora affinisproper along salinity and temperature gradients. We determined signatures of population structure, admixture, and natural selection by analysing single nucleotide polymorphism (SNP) frequencies across populations using TreeMix, PoPoolation2, poolfstat, and BayPass. ResultsWe found significant population genomic signatures of selection associated with salinity and temperature gradients using BayPass X^TX and environmental association tests, consistent with local adaptation. Several ion transport functional categories (GO terms) were significantly associated with the salinity gradient across all populations, whereas only one GO term, ‘prostaglandin biosynthetic process’, was significantly associated with the temperature gradient in the North Sea region. We found clear population structure with PoPoolation2 and TreeMix. We also found signals of admixture between populations with poolfstat and TreeMix, consistent with the presence of gene flow. Site‐frequency spectra (SFS) of candidate SNPs tested against simulated SFS distributions revealed an excess of intermediate frequency alleles within a few populations. Main ConclusionsThe interplay between local adaptation and gene flow had not been fully explored in passive holoplankton dispersers. Many of the same ion transporter genes showed signatures of selection as in our prior studies, but in this case across a metapopulation ofE. affinisspanning a broad geographic range. The presence of locally adapted alleles along with gene flow across environmental gradients could provide genetic substrate for natural selection, enabling populations to adapt to future climate change. 

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