Nav: Home

Salt regulation among saltmarsh sparrows evolved in 4 unique ways

July 16, 2019

thaca, NY--In nature, as in life, there's often more than one way to solve a problem. That includes the evolutionary process. A new study in Evolution Letters finds that different bird species in the same challenging environment--the highly saline ecosystem of tidal marshes along ocean shores--were able to evolve unique species-specific ways to address the same problem.

"For tidal saltmarsh species, the challenge is how to maintain the right balance between water and salt concentrations in their cells," explains lead author Jennifer Walsh, a postdoctoral researcher at the Cornell Lab of Ornithology. "When cells are exposed to salt water, they shrink. If they're exposed to too much fresh water, they expand. Without the right balance, the cells can die."

Walsh and colleagues from eight other universities studied the genomes of four sparrow species: Savannah, Nelson's, Song, and Swamp Sparrow. These were chosen because each of these species has a population living in saltmarsh habitat as well as a separate upland population. This makes it possible to compare the genomes of the two populations and see where they differ. Some of those differences are tied to adaptations evolved in saltmarsh-resident sparrows to control the balance of water and salt concentrations--a process called osmoregulation.

One gene that appears to be important in Savannah Sparrows plays a role in inserting physical channels in the cells. Those channels help the cells resist expansion and contraction from changes in salt levels by allowing exchange of water across the cell wall. Swamp Sparrows show a similar response to salt water, but the genes responsible for forming these channels are completely different. Song Sparrows seem to have adapted through mechanisms that reinforce cell walls so they can expand and contact more quickly in response to salt. The Nelson's Sparrow takes yet another route--evolving a gene that changes its behavior. Their genetic adaption curbs thirst so they only drink the least amount of salt water necessary and salt levels are kept within bounds. The four sparrow species evolved four different, complex mechanisms to deal with salt, each likely governed by many genes working in tandem.

The researchers also found that the osmoregulatory adaptations evolved at a rapid pace, at least on an evolutionary scale--probably over the past 10,000 to 15,000 years--and that New World sparrows have colonized marshes over and over again.

The saltmarsh sparrows also evolved some shared traits across species that may help them survive the hot, salty, harsh conditions of their environment: a larger bill to better dissipate heat, a modified kidney structure, and darker plumage which may provide some UV protection and help feathers withstand abrasive vegetation. But why live in a saltmarsh at all?

"Sometimes birds move into marshes because, if you can adapt to the environment, it's actually a pretty good place to be," Walsh says. "There's no competition because so few species live there, and there is never, ever a shortage of insects for food."
-end-
This research was funded by the National Science Foundation Postdoctoral Research Fellowship in Biology, as well as a seed grant from the Cornell University Center for Vertebrate Genomics. Co-authors are from the University of Montana, University of British Columbia, the Iolani School in Hawaii, University of Connecticut, University of New Hampshire, University of Maine, University of Delaware, and Benedictine College.

Reference:

Jennifer Walsh, Phred M. Benham, Petra E. Deane-Coe, Peter Arcese, Bronwyn G. Butcher, Yvonne L. Chan, Zachary A. Cheviron, Chris S. Elphick, Adrienne I. Kovach, Brian J. Olsen, W. Gregory Shriver, Virginia L. Winder, and Irby J. Lovette. (2019) Genomics of rapid ecological divergence and parallel adaptation in four tidal marsh sparrows. Evolution Letters.

Cornell University

Related Bird Species Articles:

The trouble with being a handsome bird
Male birds often use brightly coloured plumage to be attractive to females.
Bird's eye perspective
Harvard Medical School researchers have now provided the first insight into the perplexing question of how humans developed their daytime vision.
How did bird babysitting co-ops evolve?
It's easy to make up a story to explain an evolved trait; proving that's what happened is much harder.
New species of Brazilian copepod suggests ancient species diversification and distribution
A new species and genus of a tiny freshwater copepod has been found in the Brazilian rocky savannas, an ecosystem under heavy anthropogenic pressure.
Genomic tools for species discovery inflate estimates of species numbers, U-Michigan biologists contend
Increasingly popular techniques that infer species boundaries in animals and plants solely by analyzing genetic differences are flawed and can lead to inflated diversity estimates, according to a new study from two University of Michigan evolutionary biologists.
More Bird Species News and Bird Species Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Teaching For Better Humans
More than test scores or good grades — what do kids need to prepare them for the future? This hour, guest host Manoush Zomorodi and TED speakers explore how to help children grow into better humans, in and out of the classroom. Guests include educators Olympia Della Flora and Liz Kleinrock, psychologist Thomas Curran, and writer Jacqueline Woodson.
Now Playing: Science for the People

#535 Superior
Apologies for the delay getting this week's episode out! A technical glitch slowed us down, but all is once again well. This week, we look at the often troubling intertwining of science and race: its long history, its ability to persist even during periods of disrepute, and the current forms it takes as it resurfaces, leveraging the internet and nationalism to buoy itself. We speak with Angela Saini, independent journalist and author of the new book "Superior: The Return of Race Science", about where race science went and how it's coming back.