Adaptive differentiation between tidal marsh sparrows

Tidal marshes represent a challenge for the animals that live there as they must cope with rising and falling tides on a daily and monthly cycle, along with a high salinity environment. For this reason, tidal marshes are home to some uniquely adapted species which are found no where else in the world. However, these habitats, and the species that rely upon them, are under threat as marshes around our coastlines are lost due to development and rising sea levels.

Saltmarsh and Nelson’s sparrows are two species of songbird that have adapted to cope with this environment. Whilst the Nelson’s sparrow will also breed on inland marshes, the saltmarsh sparrow is only found on salt marshes along the eastern coast of the US, making it particularly vulnerable to habitat loss and sea level rise. These birds must time their egg laying so that they can raise their chicks to fledge between the monthly high (spring) tides, otherwise their chicks will be drowned.

Nest flooding is one of the major reasons that chicks are lost. Photo credit: J. Mielcarek.


Using whole genome sequences from populations of both Nelson’s and saltmarsh sparrows, I am working with Jennifer Walsh Emond and the Saltmarsh Habitat and Avian Research Programme (SHARP) to work out how these birds have adapted to the salt marsh environment. We are working on creating a well-annotated reference genome and then sequencing multiple individuals of each species so that we can determine which genes have been under selection. We are also interested in when and why the two species diverged from one another, and whether hybridisation between them is a recent event.

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