Increased interbreeding due to loss of tidal marsh habitat caused saltwater-adapted Savannah sparrows to lose their genetic distinctiveness.
The temperate climate of the San Francisco Bay Area has always attracted immigrants — animals and humans — that have had unpredictable impacts on those already living in the area.
For the bay's Savannah sparrow, a subspecies that lives in salty tidal marshes, increased immigration of its inland cousins over the past century has definitely been bad news.
A new genomic analysis of Savannah sparrows (Passerculus sandwichensis) from around the state — many of them collected as far back as 1889, their pelts stored in the Museum of Vertebrate Zoology at the University of California, Berkeley — shows that over the past 128 years, the Bay Area's sparrow's adaptation to salt water is being diminished by interbreeding with inland sparrows adapted to fresh water.
Read more at University of California - Berkeley
Image: Phred Benham, a UC Berkeley postdoctoral fellow who wrote his Ph.D. thesis on genetic variation within saltwater-adapted Savannah sparrows, holds one of his subjects. The subspecies has lost 90% of its tidal marsh habitat over the past 200 years, making the birds subject to outbreeding supression because of interbreeding with more abundant freshwater-adapted Savannah sparrows. (Credit: Phred Benham, UC Berkeley)