A new paper in Evolution Letters by lab postdoc Jennifer Walsh studies multiple independent cases of adaptation to salt marsh environments, evaluating weather adaptations are species-specific or convergent. The study focuses on four species of North American sparrows that represent four independent, post‐Pleistocene colonization events by an ancestral, upland subspecies and a derived salt marsh specialist. The authors leverage whole genome sequencing to identify both parallel and novel targets of putative selection that may underlie solutions to osmotic stress.
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Organisms that inhabit salt marshes are faced with extreme challenges and must cope with harsh, open environments as well as daily influxes of salt water into the system. Our whole‐genome comparisons among four species of sparrows demonstrate the important interplay between species‐specific and parallel signatures of selection in driving adaptation across an ecological gradient. Several lineage‐specific adaptations to salt marshes, particularly related to salt tolerance, suggest that selection of independent pathways may be important for allowing increased osmoregulatory function in salt marsh environments. Our results highlight the utility of a comparative genomics approach in characterizing the genomic basis of local adaptation and may aid in informing conservation strategies for threatened salt marsh endemics through the characterization of evolutionary potential.
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