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For the first time, climate change adaptation is discovered at the genetic level

Climate change forces life on earth to adapt or face extinction. These adaptations generally happen in two ways. One is by moving to different geographical areas, the other is by evolving genetically.

While the geographical shifts of species can be easily observed and recorded, proving genetic evolution over time is much more challenging.

A breakthrough study by researchers at Colorado State University (CSU) now presents one of the first documentations of climate adaptation at the genetic level. The subject of their study was the Southwestern Willow Flycatcher. It is an endangered migratory bird.

The researchers discovered an increase in genetic variation within this species. This is believed to be linked with the bird’s enhanced tolerance for wetter and more humid conditions.

How the Southwestern Willow Flycatcher study was conducted

Leading this pioneering study was Sheela Turbek, a postdoctoral researcher in CSU’s Department of Biology. She and her team conducted an extensive examination of the Willow Flycatcher’s genome over a span of more than a century. They compared the DNA from specimens preserved since the late 1800s with samples obtained today.

The researchers discovered notable increases in genetic variation within the Willow Flycatcher population in San Diego, California. They deduced that these genetic changes have been enabling the birds to adapt better to the changing climates. Remarkably, the shift seems to have started as far back as the 19th century.

Climate change adaptation on a genetic level

Turbek initially hypothesized that the changing climate in San Diego—characterized by increasingly wetter and more humid weather—would trigger genetic shifts in wildlife populations.

“We used over 200 contemporary samples from the Willow Flycatcher to scan the genetic material for specific regions of the genome associated with important environmental variables,” Turbek explained. “This includes things like monthly precipitation and monthly maximum temperature.”

After identifying the regions of the DNA potentially involved in climate adaptation, the team extracted the genetic data from those regions in both the historical and contemporary San Diego samples.

Discoveries about the Southwestern Willow Flycatcher

The results were groundbreaking. There had been an increase in genetic variation in Willow Flycatchers over the years. The genetic regions associated with humidity and precipitation in the birds had evolved in a way consistent with climate adaptation.

This research was made possible by advances in genome sequencing technology over the last decade. Turbek’s focus on the Southwestern Willow Flycatcher was driven by the bird’s endangered status and the existing preliminary research by Kristen Ruegg. This suggested the birds had adapted to different climate conditions across their habitats.

The Willow Flycatcher is made up of four different subspecies. One of the subspecies has seen a drastic population decline and was listed as federally endangered in 1995.

“So, there’s a lot of interest from government agencies to effectively manage this subspecies and save it from climate induced extinction,” Turbek noted.

Proving genetic adaptation over time is quite tricky. Decades-old samples often contain degraded, contaminated, or low-yield DNA. This is why it has been difficult to provide evidence of genetic adaptation to a sufficient degree of certainty.

Research team confirms the climate change adaptation

But after years of meticulous work sequencing the historical genome and comparing the results with modern samples, the team confirmed the genetic evolution of the Willow Flycatcher.

“We think that it was actually mixing or gene flow into the population from neighboring populations that helped recover the gene pool of the Willow Flycatchers in the San Diego area,” said Ruegg.

The findings of this study validate predictions about how some species will adapt to climate change. As Turbek warned, “Human-induced climate change is really having a drastic effect on the reproductive activities of many species, and it is going to drive a lot of organisms to the brink of extinction.”

However, this research offers a glimmer of hope. “The fact that we can document this amount of adaptation over a century-long time scale is somewhat encouraging in that these birds seem to be responding to the amount of climate change that has already occurred.”

This groundbreaking work was made possible by collaborative effort. Along with Turbek and Ruegg, several other key collaborators contributed to this research. They include Christen Bossu, Christine Rayne, Christian Gruppi, Barbara Kus, Mary Whitfield, Thomas Smith, Eben Paxton, Rachael Bay, and Kristen Ruegg.

Validating predictions of climate change adaptation effects

The research provides valuable insights into how genetic adaptation may enable certain species to survive the growing challenges presented by climate change. However, it also underscores the importance of conserving endangered species like the Southwestern Willow Flycatcher.

According to Turbek, the findings can help us “better predict what’s going to happen in the future, and how species might respond.”

Indeed, understanding how genetic changes may contribute to species survival is critical for preserving biodiversity in a warming world. It allows scientists to build more accurate predictive models, which can inform conservation strategies for vulnerable species.

In conclusion, the research by Turbek and her team marks a significant step forward in our understanding of climate adaptation at the genetic level. The team’s innovative approach to studying the Southwestern Willow Flycatcher offers a roadmap for similar studies in other species.

With ongoing climate change posing a threat to countless species worldwide, this kind of research is more vital than ever. The hope is that the lessons we learn from these small birds can help us protect our planet’s biodiversity for future generations.

More about the Southwestern Willow Flycatcher

The Southwestern Willow Flycatcher (Empidonax traillii extimus) is a small bird and a member of the tyrant flycatcher family, which is one of the largest avian families in the world. This particular subspecies of the Willow Flycatcher is native to the southwestern United States and parts of Mexico.

Here are some key points about the Southwestern Willow Flycatcher:

Physical Description

This bird is relatively small, measuring about 13-16 cm in length, with a wingspan of 18-22 cm. It is predominantly grayish-green with a pale throat and chest, and it has a characteristic two white wing bars and an eye ring that can aid in identification.


The Southwestern Willow Flycatcher typically nests in dense riparian (near rivers or streams) habitats with willows, cottonwoods, or other vegetation types. These habitats are usually found at elevations between 500 and 2,500 meters.


The Southwestern Willow Flycatcher feeds on insects, which it typically catches in mid-air or picks off vegetation.

Breeding and Nesting

Breeding season usually takes place between May and July. The bird constructs its nest in dense riparian vegetation, often near water bodies. The female typically lays 3-4 eggs, which are incubated for about 12-15 days.

Migratory Behavior

The Southwestern Willow Flycatcher is a long-distance migratory bird. It typically spends the winter in Central and South America, before returning to the United States and Mexico to breed in the summer.

Conservation Status

The Southwestern Willow Flycatcher is currently classified as an endangered species. This is due to a combination of factors, including habitat loss, degradation, and fragmentation caused by development, dam construction, water diversions, and other human activities. Predation and brood parasitism (where other birds lay their eggs in the flycatcher’s nest) are also threats.

Conservation Efforts

Several conservation efforts are underway to protect and conserve the Southwestern Willow Flycatcher and its habitat. These include habitat protection and restoration, population monitoring, and research efforts to better understand the bird’s ecology and threats.

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