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Decoded genome may help tortoise win race to survive

May 31, 2017

Slow and steady wins the race.

While that may have been true in one of Aesop’s classic fables, the Mojave Desert tortoise may need to adapt more quickly than it has in decades past. The species is facing serious threats to its survival, from invasive plants to man-made changes in the landscape.

But researchers from Arizona State University’s School of Life Sciences and their collaborators may have a new tool to help conserve this iconic desert reptile. For the first time, they have decoded the animal’s genome; their findings appear in the current issue of the journal PLOS ONE.

The breakthrough could help the animal survive an increasing number of threats.

Tortoise habitat
Mojave Desert tortoise habitat is negatively affected by power lines, development, highways and changes across the landscape. Photo by Sandra Leander/ASU

“There is more and more development across deserts, as well as a surge of renewable energy development,” said Todd Esque, a research ecologist and tortoise expert with the U.S. Geological Survey. “Highways and power lines disturb the tortoise habitat. We are also considering impacts to tortoise habitat from changes across the landscape. 

“And, in the last 100 years, we’ve had invasive grasses come in with livestock, probably mostly accidental. Red brome and Mediterranean grass are the two primary invasive grasses we have here. A diet of primarily red brome is really a bad diet for little tortoises and their survivorship is much lower.” While Esque was not involved in the project, the study’s findings may assist tortoise conservation efforts.

Government agencies and other researchers have been monitoring tortoise populations in the Southwest for more than two decades. The Mojave Desert tortoise population has seen considerable decline in its habitat that includes California, Nevada, Utah and Arizona. This species is listed as ‘threatened’ under the U.S. Endangered Species Act and is considered ‘vulnerable’ by the International Union for Conservation of Nature (IUCN). 

Marc Tollis, lead ASU investigator on the project, said the genome is an important resource for the conservation of the Gopherus agassizii tortoise, particularly because this population is suffering from a serious disease. Researchers don’t yet fully understand its cause or what makes tortoises susceptible to it.

“We don’t know how the tortoise is handling the fact that it’s also being threatened by an upper respiratory disease,” Tollis said. “Decoding this genome will help us catalog which tortoise genes are evolving quickly enough to help them overcome this threat.” 

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Kristina Drake, biologist with the U.S. Geological Survey, monitors desert tortoise populations in the Mojave Desert. Photo by Sandra Leander/ASU

Tollis, a postdoctoral researcher, along with the paper’s senior author Kenro Kusumi, obtained the genetic data for a particular tortoise specimen, assembled and annotated the genome and learned about the evolutionary history of tortoises.

“Decoding a genome has gotten technically a lot easier,” said Kusumi, senior investigator for the project and professor with the ASU School of Life SciencesThe School of Life Sciences is in the College of Liberal Arts and Sciences.. “What’s challenging now is decoding the information in the tortoise genome. We can use clues from similarities with the mouse and human genomes. Finding the proverbial ‘needle in the haystack’ would be to identify the genes that direct the immune response to infectious disease, as well as the ability to survive the harsh conditions of the Mojave Desert.” 

Kusumi added that it’s important for the research team to learn where tortoise diversity is located across its geographic range. Identifying hotspots of genetic diversity helps manage the species from a conservation standpoint and preserve tortoise populations that could respond better to unknown challenges in the years ahead.

Greer Dolby, co-author and ASU postdoctoral associate, is analyzing the genetic differences between this tortoise and its sister species, the Sonoran Desert tortoise.

Dolby said: “My hope is that this study will enable other agencies to ask new questions, questions they would not have been able to ask without this research. For instance, ‘What immune genes do tortoises have to fight pathogens? How does their immune system function in an environment with lots of threats? And, how might a changing environment impact this?’ These are important questions to answer in managing the species. Now, we can begin investigating.” 

Adapted for life in a harsh desert

Many tortoises living in the study site are fitted with small GPS units. This allows biologists to know where they are and how much they’ve traveled over a certain season. Scientists regularly check the tortoises for things such as overall health, body condition and signs of disease or stress. 

Beginning in mid-October through November, the tortoises hibernate, only coming out of their burrows to drink water when it rains. When the weather warms up in March, they become active again and will mate during the spring. Females will lay a clutch of eggs up to three times per year depending on the weather. 

Incredibly, desert tortoises can live up to 50 years in the wild, with lifespans estimated between 30 to 50 years. Tortoises in captivity have been known to live as long as 100 years.

Predators include ravens and coyotes, but other factors such as climate change, invasive grasses and human activity also negatively affect tortoise populations.

Using genome information in conservation

The future is uncertain for the desert tortoise, as it continues to face multiple threats. 

“In a best-case scenario, the work we do with ASU will help us understand how to inform the scientific methods designed to increase conservation and perpetuate the survival of this species,” Esque added. 

The genome provides a starting point for a number of studies focusing on disease resistance, adaptations to the desert environment, distribution of genetic diversity across its range and hybridization with its sister species.

Ultimately, insights from the decoded tortoise genome should help guide how this threatened species is managed and may improve its chances of long-term survival.

 

 

Arizona State University’s College of Liberal Arts and Sciences and the U.S. Marine Corps (Natural Resources and Environmental Affairs, Marine Corps Air Ground Combat Center/Marine Air Ground Task Force Training Command) funded the research project. Collaborators include the University of Arizona; U.S. Marine Corps; and Royal Ontario Museum.

Top photo: Red brome and Mediterranean grass are invasive grasses in the Mojave Desert. A diet of red brome is bad for little tortoises and their survivorship is low. Photo by Sandra Leander/ASU

Sandra Leander

Manager, Media Relations and Marketing , School of Life Sciences

480-965-9865

 
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Kids in high-achieving schools: Addiction down the road?

May 31, 2017

New study led by ASU professor shows the link between growing up in affluent communities and drug and alcohol addiction

They have what most would want — affluent upwardly mobile parents, living in comfortable homes in the suburbs, going to an elite high school and being groomed for the nation’s best colleges. And they appear to thrive in this setting — popular among their peers, performing exceedingly well in school, highly regarded by peers and teachers, and accomplished at a various extracurricular activities. 

But these “privileged” American high schoolers can be at high risk for problematic substance abuse across early adulthood, according to new research from Arizona State University.

Suniya Luthar

“We found alarmingly high rates of substance abuse among young adults who we initially studied as teenagers,” said Suniya Luthar, a Foundation Professor of psychology at Arizona State University and a professor emerita at Columbia University’s Teachers College, who led the research. “Results showed that among both men and women and across annual assessments, these young adults had substantial elevations, relative to national norms, in frequency of several indicators — drinking to intoxication and of using marijuana, stimulants such as Adderall, cocaine and club drugs such as ecstasy.”

The paper, “Adolescents from upper middle class communities: Substance misuse and addiction across early adulthood,” appears in the current issue of Development and Psychopathology. It is co-authored by Phillip Small, an ASU graduate student in clinical psychology, and Lucia Ciciolla, an assistant professor at Oklahoma State University.

In the article, the authors describe a study of two groups of students in affluent communities in the Northeast U.S. as part of the New England Study of Suburban Youth (NESSY). The researchers assessed these youngsters as high school seniors and then annually across four college years (NESSY-Y, for the younger cohort), and across ages 23 to 27 (NESSY-O, for the older cohort).  

“We found rates of addiction to drugs or alcohol among 19 to 24 percent of women in the older cohort by the age of 26, and 23 to 40 percent among men. These rates were three and two times as high respectively, as compared to national norms,” Luthar said. “Among the younger cohort by the age of 22 years, rates of addiction were between 11 and 16 percent among women (close to national norms) but 19 to 27 percent among men, or about twice as high as national norms.”

Luthar said a look into the lives of these adolescents provide some clues to the cause of these high rates of addictions. 

When the NESSY groups were first assessed, they all attended the best schools in the region — suburban schools with very high standardized test scores, rich extra-curricular offerings and high proportions of their graduates heading off to highly selective universities. In general, kids at such schools experience enormous pressures to achieve, and many come to live by the dual credos of “I can, therefore I must” and “We work hard and we play hard” with the playing involving parties with drugs and alcohol. 

Also implicated is affluence in the school community.

“Not all of these students were from wealthy families but most were, as parents typically had advanced educational degrees and median incomes much higher than national norms,” Luthar said. “And without question, most of the parents wanted their kids to head off to the best universities, as did the kids themselves.” 

With affluence comes ease in acquiring drugs, she added. “Many kids in these communities have plenty of disposable income with which they can get high-quality fake IDs, as well as alcohol and both prescription and recreational drugs.”

"These ostensibly privileged youth, many of who start experimenting early and often with drinking and drugs, could well be among the groups at highest risk for alcoholism and addiction in adulthood.”   

— Suniya Luthar, ASU Foundation Professor of psychology

Other factors that exacerbate the risks, Luthar said, include widespread peer approval for substance use, and the fact that parents can be lulled into a false sense of security, believing that as their kids continue to perform well in school there could not be any serious underlying issues. As a result, they can become somewhat laissez-faire about detected alcohol or marijuana use. 

So what can be done to reverse this trend?

“This is a problem that derives from multiple levels of influence, so we’re going to need interventions at multiple levels to tackle it,” Luthar said.

“At the level of the kids themselves and their parents, it will be important to disseminate research findings — based on rigorous scientific data — that messing with drugs and alcohol really should not be trivialized as just something all kids do,” Luthar said. “The earlier children start to use and the more frequently they do, the more likely it is that they will develop addictions down the line.”

Luthar pointed to strategies like sex-education programs conveying the “bottom line” of risks involved, such as “it only takes once” to contract a sexually transmitted disease.

“For high-achieving and ambitious youngsters, it could actually be persuasive to share scientific data showing that in their own communities the statistical odds of developing serious problems of addiction are two to three times higher than norms,” Luthar said. “And that it truly just takes one event of being arrested with cocaine, or hurting someone in a drunken car accident, to derail the high-profile positions of leadership and influence toward which they are working so hard for the future.”

On a second level is reducing the enormous pressure these kids are under trying to get into only the most selective universities.

“As long as university admissions processes continue to be as they are — increasingly smaller number of admits per applications and requiring impossible resumes — these young people will continue to be frenetic in pursuing those coveted spots and many will continue to self-medicate as a result,” Luthar said. “An alternative approach, suggested by my colleague Barry Schwartz, could be to have these highly selective universities institute a lottery system for final admittance, given all other qualifications and resumes being equal.

A second important measure would be showing the kids there are role models of adults who did not go to an elite university, but who picked a college because it felt right for them and who were highly successful in life. 

“It shows that there is, in fact, life, wisdom, financial solvency, creativity and, yes, happiness beyond the walls of the Ivy Leagues,” Luthar said.

A third factor is for leaders in science, public health and social policy to take seriously the fact that youth at high-achieving schools could be a population that is at inordinately high risk for addiction. Decades ago, developmental researchers established that children growing up in chronic poverty were at high risk for maladjustment, and this led, laudably, to a plethora of studies trying to figure out how best to minimize risks and foster resilience among these youth by addressing different aspects of their environments. 

“We now need the same dedicated research on kids who grow up in pressure-cooker, high-achieving schools,” Luthar said. “Paradoxical though it may seem, these ostensibly privileged youth, many of who start experimenting early and often with drinking and drugs, could well be among the groups at highest risk for alcoholism and addiction in adulthood.”

Associate Director , Media Relations & Strategic Communications

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