The San Francisco Bay Area’s temperate climate has long been a magnet for immigrants, both human and animal, with unforeseen consequences for the area’s existing inhabitants.
A recent genomic study of Savannah sparrows (Passerculus sandwichensis) from across California, some collected as far back as 1889 and stored at the Museum of Vertebrate Zoology at UC Berkeley, reveals that over the past 128 years, interbreeding with inland sparrows has diminished the Bay Area’s sparrow’s ability to adapt to saltwater.
This has led to stable genetic diversity among coastal Savannah sparrows in Northern and Central California, but a loss of the genetic variants that enable them to thrive in tidal marshes. This could impact their survival in these marshes, where they rely on saltwater and salty crustaceans, which freshwater birds cannot handle.
The surprising findings, published in the journal Global Change Biology, can be partly attributed to the significant decline in tidal marshes across the state, particularly in the Bay Area, which has reduced the Savannah sparrow population and made them more susceptible to interbreeding with inland sparrows.
“There appears to be an increasing influx of genes from eastern California into places like the Bay Area, possibly due to the local population becoming a sink where the local breeders can’t produce enough offspring to sustain a population,” explained Phred Benham, a postdoctoral fellow at UC Berkeley and the study’s lead researcher. “This creates an opportunity for gene flow to occur into the residents.”
2024-01-24 19:00:05
Link from phys.org