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

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.

Automated summary

With climate change, habitat salinity is rapidly shifting globally. Invasive species from saline habitats have recently invaded freshwater habitats. The copepod Eurytemora affinis species complex has independently invaded freshwater habitats multiple times from saline estuaries on three continents. Surprisingly, natural selection has favored the same alleles across independent freshwater invasions, which is unexpected for polygenic adaptation. Factors such as population structure and genome architecture may contribute to rapid adaptation and parallel evolution. The findings from this study can provide valuable insights into mechanisms in other systems and adaptation in a changing planet.