BEE: Evolutionary Responses to Global Change - Linking Genotype with Phenotype to Model Future Demography and Range Expansions

Climate change is causing drastic environmental shifts throughout the globe, including rapid changes in ocean salinity. This salinity change is caused by alterations in rainfall patterns and enormous volumes of ice melt dumping into the seas. At higher latitudes, rapid salinity decline is imposing incredible amounts of stress on aquatic species, such that many populations are likely to go extinct.

Among aquatic species the most abundant are zooplankton, which are free floating plankton eaten by fish. Among the zooplankton, copepods (small crustaceans) are the most abundant and important for providing the food source for coastal fisheries. This research will examine how copepod populations evolve and specifically how natural selection may rescue particular populations and result in the survival of species even in the face of climate change.

The goal of this project is to use genetic data and mathematical predictions to answer the following questions: (1) How are the genomes of wild populations evolving when faced with rapid changes in salinity and temperature? (2) How will salinity and temperature influence reproduction and growth of wild populations? (3) Will changes in salinity and temperature force populations to migrate or cause them to go extinct? The researchers will address these questions by conducting laboratory evolution experiments to determine which genetic variants (alleles) are favored by natural selection during temperature and salinity change.

The work will also involve mathematical models to understand whether natural selection favors genetic variants, and if this could rescue a population from extinction in the wild. The integration of evolution into predictive mathematical models of demography is crucial for making accurate predictions of the fate of populations and species. Such research is especially important because the focal organisms (small crustaceans) are at the base of the food web and support many important fisheries throughout the world.

One postdoctoral fellow, two graduate students, and several undergraduate students (including members of under-represented groups) will be trained in conducting integrative research

Climate change is currently driving rapid changes in ocean salinity throughout the world. Drastic changes in the global water cycle are causing the freshening of high latitude coastal seas, with acutely severe impacts on estuaries. In such habitats, by the year 2100, salinity is projected to decline by up to 5 PSU, while temperatures are expected to rise by ~2-6°C.

Thus, rapidly declining salinity is predicted to become a potent driver threatening coastal populations. Adaptation is critical for surviving severe environmental stress that exceeds physiological thresholds, but we lack clear understanding of how responses to natural selection translate to population growth rate and demography. This proposal focuses on empirically testing the mostly theoretical concept of evolutionary rescue, where evolution proceeds with sufficient speed to forestall population decline so extirpation and extinction do not occur.

The research will (1) determine the Response to Selection, by conducting laboratory natural selection experiments (experimental evolution) to quantify the genomic responses to salinity and temperature change (i.e., determine the trajectory of alleles and their selection coefficients) and then (2) reconstruct the Genotype-Phenotype Map, by performing genetic association studies, to quantify the effects of beneficial alleles on life history traits that determine absolute fitness, and finally (3) perform Eco-Evolutionary Modeling, by incorporating data on evolutionary trajectories of beneficial alleles (from #1) and fitness effects of those alleles favored by selection (from #2) into models that predict future population demography, including range shifts and probability of extinctions in response to climate change. This study will advance our fundamental understanding of mechanisms of evolutionary adaptation, by elucidating how candidate genes and their interactions could affect demography (linking genotype-phenotype-demography) and by injecting evolutionary data into predictive models of climate change impacts.

Such an integration of evolution into demographic models is crucial for making accurate predictions on limits to future range shifts and probabilities of local and global extinctions.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.