Genes Influence Birds' Response to Climate Change

A yellow warbler during breeding season.| Joe Ellis

Some subpopulations of yellow warblers may be genetically better equipped to adapt to climate changes than others, according to a new study in the January 5 issue of Science. In particular, genes associated with exploratory and migratory behavior appear to influence successful climate adaptation.

Climate change is having a dramatic impact on Earth's biodiversity, by causing rapid fluctuations in temperature and precipitation that alter species' environments. How well species can adapt to these changes will determine their long-term survival, scientists suggest.

Rachel Bay of the University of California, Los Angeles and her colleagues were interested in studying how migratory birds, which travel thousands of miles each year between their breeding and wintering grounds, might be equipped to deal with climate change. "Yellow warblers are an ideal species for this because they are common across most of the U.S. and Canada during the summer, so different birds must inhabit very different climates," explained Bay. The species lives in environments ranging from marshes and forests to urbanized areas.

The team analyzed genetic data from 229 yellow warblers living in 21 sites across North America, looking at how well-suited the genetic variation of individual birds was for their respective environments. For example, some variations of a gene are better suited for a dry climate, while other variations of that same gene are better suited for wetter environments. The researchers then looked at the climate projections and measured how well these genes would be adapted to future conditions.

If birds at a particular location have the "wet-adapted" genes and their location will be very dry in the future, there would be a mismatch. Warblers with more genes mismatched for their future predicted environment can be described as more genetically vulnerable to climate change.

Researcher Kristen Ruegg in the field. | Jasmine Rajbhandary

"Being able to map this vulnerability provides valuable information for making decisions about how to conserve the species in the future," Bay said.

The scientists found that two genes associated with migration, DRD4 and DEAF1, were influential in determining how well the species respond to climate change. The authors note that DRD4 in particular, a dopamine receptor gene, has been extensively studied for its involvement in novelty-seeking behavior in primates, fish and birds.

The researchers also found that a substantial amount of genetic variation among individual warblers is associated with the different precipitation levels of their respective environments. Bay proposed that precipitation-related genetic variation may have to do with the birds' resources. "For example, regions with more or less precipitation may have different vegetation patterns, which can alter the abundance of insects, the primary food resource for these birds," she said.

Although the study does not directly identify a link between this type of variation and current climate change vulnerability, these precipitation-linked variables could be a source of vulnerability in the future, Bay and her colleagues noted.

Unfortunately, the results of this study suggest that some yellow warbler populations that are most genetically vulnerable to climate change have already been declining over the past half-century, says Bay. "This suggests that the impacts of climate change are happening now — these populations have already experienced negative effects and those effects are likely to become more severe in the future."

Next, Bay and her team aim to explore the genetic vulnerability of other migratory bird species. These efforts might help identify regions where multiple species are vulnerable, hinting at hotspots that might be particularly beneficial for conservation.

[Credit for associated image: Daniel Karp]