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]