Nav: Home

Missing in action

January 25, 2018

Once abundant in Southern California, the foothill yellow-legged frog inexplicably vanished from the region sometime between the late 1960s and early 1970s. The reasons behind its rapid extinction have been an ecological mystery.

Environmental scientist Andrea Adams set out to crack the case. While pursuing her Ph.D. at UC Santa Barbara, she spent six and a half years reconstructing the missing amphibian's story in an attempt to find out why it disappeared. Her dissertation -- Adams earned her doctorate in 2017 -- explored the importance of discovering a species' past to inform its future. Now, a paper summarizing her findings about Rana boylii appears in the journal Ecology and Evolution.

"As species disappearances from unknown causes go, this one occurred at breakneck speed," said Adams, now a lecturer in UCSB's Environmental Studies Program. "The global trend of amphibian declines points to habitat loss, ultraviolet radiation and pesticides as potential culprits, yet most of these act gradually, slowly chipping away at populations over time. One of the only threats that can cause rapid extirpation -- like that of Rana boylii in Southern California -- is disease."

Chytridiomycosis -- caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd) -- has devastated frog populations all over the world. Adams wanted to know if Bd could have done the same to the foothill yellow-legged frog in Southern California.

As a first step, Adams sampled more than 1,300 historical, archived amphibian specimens from natural history museums. Then she tested an improved protocol to better detect Bd DNA in those specimens. In addition, she looked for Bd DNA in amphibian species that occurred in the Southern California locations common to foothill yellow-legged frogs before, during and after their decline.

Adams also interviewed people who visited Southern California streams before the foothill yellow-legged frog disappeared. "The information I sought didn't exist anywhere but in people's memories and sometimes in field notes stashed away in their garages," she explained. "I used that archived material to determine when foothill yellow-legged frogs were observed and how their population size diminished through time."

Although Bd arrived in the region long before the foothill yellow-legged frog began to decline, Adams found that the pathogen widely advanced as the frogs began to disappear. Many factors could have contributed to the spread: the pressure of a rapidly expanding metropolitan region; increased recreational use of streams; roads extending deeper into natural areas; and the appearance of exotic species. Take the American bullfrog as an example. Brought to Topanga Canyon in big numbers in the early 1900s, the species today is widespread in California and known to harbor and spread Bd via international amphibian trade.

"When I overlaid the historical information with the incidence and prevalence of the chytrid fungus, I found that when the foothill yellow-legged frog started to go extinct corresponded to a spike in the spread of the pathogen in Southern California," Adams said.

"Because this is a retrospective study, we can't say for certain that amphibian chytrid fungus is the cause," said co-author Cherie Briggs, a professor in UCSB's Department of Ecology, Evolution, and Marine Biology. "However, Andrea's doctoral thesis and this paper provide sound supporting evidence for this hypothesis."

University of California - Santa Barbara

Related Pathogen Articles:

From Genome Research: Environmental pressures on opportunistic fungal pathogen
With an estimated one million cases diagnosed worldwide each year, the human pathogen Cryptococcus neoformans, which can cause life-threatening fungal infections in immunocompromised patients, is an important health concern.
Common periodontal pathogen may interfere with conception in women
According to a recent study, a common periodontal pathogen may delay concepcion in young women.
New lab-on-a-chip platform seeks to improve pathogen detection
Researchers from the Fraunhofer Institute have developed a new prototype lab-on-a-chip platform for the easy and versatile detection of molecular pathogens.
Study provides evidence on movement of potato famine pathogen
New North Carolina State University research delves into the movement and evolution of the pathogen that caused the Irish potato famine in the 1840s, which set down roots in the United States before attacking Europe.
A new pathogen in Africa causes anthrax-like disease in wild and domestic animals
A study published in PLOS Neglected Tropical Diseases reports that a related bacillus with distinct genetic and biological characteristics causes anthrax-like disease in chimps, gorillas, elephants, and goats from four different African countries.
Diarrheal pathogen measures human body temperature
Using cutting-edge high-throughput sequencing methods, researchers have mapped all RNA structures of a diarrheal pathogen at once.
Some frogs are adapting to deadly pathogen
Some populations of frogs are rapidly adapting to a fungal pathogen called Batrachochrytrium dendrobatridis (Bd) that has decimated many populations for close to half a century and causes the disease chytridiomycosis, according to a new study.
Fungal pathogen sheds gene silencing machinery and becomes more dangerous
For more than a decade, a rare but potentially deadly fungus called Cryptococcus deuterogatti has taken up residence in the Pacific Northwest and Vancouver Island.
Blueberry types identified for resistance, susceptibility to pathogen
Two extensive experiments with highbush blueberry varieties revealed cultivars that are most susceptible to the soilborne pathogen Phytophthora cinnamomi.
The South American origins and spread of the Irish potato famine pathogen
Using some ancient DNA detective work, a new study led by University of California Berkeley postdoctoral researcher Mike D.

Related Pathogen Reading:

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

Climate Crisis
There's no greater threat to humanity than climate change. What can we do to stop the worst consequences? This hour, TED speakers explore how we can save our planet and whether we can do it in time. Guests include climate activist Greta Thunberg, chemical engineer Jennifer Wilcox, research scientist Sean Davis, food innovator Bruce Friedrich, and psychologist Per Espen Stoknes.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...