Researchers at Cornell University have traced the success of non-native starlings to rapid evolution. The experts set out to investigate how the European starling has become one of the most abundant bird species in North America.
After just 80 individuals were released in New York City’s Central Park in 1890, the starling population exploded to an estimated 200 million breeding adults spread across the continent of North America.
“The amazing thing about the evolutionary changes among starling populations since they were introduced in North America is that the changes happened in a span of just 130 years in parallel with a huge expansion in the bird’s range and population size,” said study lead author Natalie Hofmeister. “For a long time we didn’t think that was possible – that it took millions of years for genetic mutations to change a genome.”
According to the researchers, the genetic differences found among North American starlings are very subtle. DNA sequencing showed that the genomes of birds from different regions of the United States were all remarkably similar.
The experts identified specific genetic signatures representing changes in areas of the genome that control how starlings adapt to variations in temperature and rainfall. The study authors concluded the birds had undergone “rapid local adaptation” to quickly adjust to conditions not found in their native European range.
Movement played a major role in the evolution of starlings. They established new populations as they spread westward, and each population had to adapt to the new environmental conditions. These adaptations may not have required new mutations, but instead resulted from an existing genetic variations.
“A genetic variation that might not have been useful in one environment could turn out to be very beneficial in another,” said Hofmeister. “So, a variation related to temperature and rainfall that enhanced survival became more common in a new environment.”
The massive size of the total starling population across North America meant these gene variants were passed down from the original birds across generations.
“What I think is really cool is that the starlings in North America appear to have adapted to different conditions across the range,” said Hofmeister. “So, it wasn’t just that they reproduced really quickly, and then just kept reproducing. It’s that they specialized once they arrived in new areas.”
Despite their success, the European starlings are currently in a state of decline. The population is now half the size it was 50 years ago throughout North America, and is also declining in Europe.
The study is published in the journal Molecular Ecology.