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Tag: Duke Lemur Center

To get a fuller picture of a forest, sometimes research requires a team effort

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Film by Riccardo Morrelas, Zahava Production

For some people, the word “rainforest” conjures up vague notions of teeming jungles. But Camille DeSisto sees something more specific: a complex interdependent web.

For the past few years, the Duke graduate student has been part of a community-driven study exploring the relationships between people, plants and lemurs in a rainforest in northern Madagascar, where the health of one species depends on the health of others.

Many lemurs, for example, eat the fruits of forest trees and deposit their seeds far and wide in their droppings, thus helping the plants spread. People, in turn, depend on the plants for things like food, shelter and medicines.

But increasingly, deforestation and other disturbances are throwing these interactions out of whack.

DeSisto and her colleagues have been working in a 750,000-acre forest corridor in northeast Madagascar known as the COMATSA that connects two national parks.

The area supports over 200 tree species and nine species of lemurs, and is home to numerous communities of people.

A red-bellied lemur (Eulemur rubriventer) in a rainforest in northeast Madagascar. Photo by Martin Braun.

“People live together with nature in this landscape,” said DeSisto, who is working toward her Ph.D. in ecology at the Nicholas School of the Environment.

But logging, hunting and other stressors such as poverty and food insecurity have taken their toll.

Over the last quarter century, the area has lost 14% of its forests, mostly to make way for vanilla and rice.

This loss of wild habitats risks setting off a series of changes. Fewer trees also means fewer fruit-eating lemurs, which could create a feedback loop in which the trees that remain have fewer opportunities to replace themselves and sprout up elsewhere — a critical ability if trees are going to track climate change.

DeSisto and her colleagues are trying to better understand this web of connections as part of a larger effort to maximize forest resilience into an uncertain future.

To do this work, she relies on a network of a different sort.

The research requires dozens of students and researchers from universities in Madagascar and the U.S., not to mention local botanists and lemur experts, the local forest management association, and consultants and guides from nearby national parks, all working together across time zones, cultures and languages.

Forest field team members at camp (not everyone present). Photo credit: Jane Slentz-Kesler.

Together, they’ve found that scientific approaches such as fecal sampling or transect surveys can only identify so much of nature’s interconnected web.

Many lemurs are small, and only active at night or during certain times of year, which can make them hard to spot — especially for researchers who may only be on the ground for a limited time.

To fill the gaps, they’re also conducting interviews with local community members who have accumulated knowledge from a lifetime of living on the land, such as which lemurs like to munch on certain plants, what parts they prefer, and whether people rely on them for food or other uses.

By integrating different kinds of skills and expertise, the team has been able to map hidden connections between species that more traditional scientific methods miss.

For example, learning from the expertise of local community members helped them understand that forest patches that are regenerating after clear-cutting attract nocturnal lemurs that may — depending on which fruits they like to eat — promote the forest’s regrowth.

Camille DeSisto after a successful morning collecting lemur fecal samples.

Research collaborations aren’t unusual in science. But DeSisto says that building collaborations with colleagues more than 9,000 miles away from where she lives poses unique challenges.

Just getting to her field site involves four flights, several bumpy car rides, climbing steep trails and crossing slippery logs.

“Language barriers are definitely a challenge too,” DeSisto said.

She’s been studying Malagasy for seven years, but the language’s 18 dialects can make it hard to follow every joke her colleagues tell around the campfire.

To keep her language skills sharp she goes to weekly tutoring sessions when she’s back in the U.S., and she even helped start the first formal class on the language for Duke students.

“I like to think of it as language opportunities, not just language barriers,” DeSisto said.”

“Certain topics I can talk about with much more ease than others,” she added. “But I think making efforts to learn the language is really important.”

When they can’t have face-to-face meetings the team checks in remotely, using videoconferencing and instant messaging to agree on each step of the research pipeline, from coming up with goals and questions and collecting data to publishing their findings.

“That’s hard to navigate when we’re so far away,” DeSisto said. But, she adds, the teamwork and knowledge sharing make it worth it. “It’s the best part of research.”

This research was supported by Duke Bass Connections (“Biocultural Sustainability in Madagascar,” co-led by James Herrera), Duke Global, The Explorers Club, Primate Conservation, Inc., Phipps Conservatory and Botanical Gardens, and the Garden Club of America.

In Drawers of Old Bones, New Clues to the Genomes of Lost Giants

DNA extracted from a 1,475-year-old jawbone reveals genetic blueprint for one of the largest lemurs ever.

By teasing trace amounts of DNA from this partially fossilized jawbone, nearly 1,500 years after the creature’s death, scientists have managed to reconstruct the first giant lemur genome. Credit: University of Antananarivo and George Perry, Penn State

If you’ve been to the Duke Lemur Center, perhaps you’ve seen these cute mouse- to cat-sized primates leaping through the trees. Now imagine a lemur as big as a gorilla, lumbering its way through the forest as it munches on leaves.

It may sound like a scene from a science fiction thriller, but from skeletal remains we know that at least 17 supersized lemurs once roamed the African island of Madagascar. All of them were two to 20 times heftier than the average lemur living today, some weighing up to 350 pounds.

Then, sometime after humans arrived on the island, these creatures started disappearing.

The reasons for their extinction remain a mystery, but by 500 years ago all of them had vanished.

Coaxing molecular clues to their lives from the bones and teeth they left behind has proved a struggle, because after all this time their DNA is so degraded.

But now, thanks to advances in our ability to read ancient DNA, a giant lemur that may have fallen into a cave or sinkhole near the island’s southern coast nearly 1,500 years ago has had much of its DNA pieced together again. Researchers believe it was a slow-moving 200-pound vegetarian with a pig-like snout, long arms, and powerful grasping feet for hanging upside down from branches.

A single jawbone, stored at Madagascar’s University of Antananarivo, was all the researchers had. But that contained enough traces of DNA for a team led by George Perry and Stephanie Marciniak at Penn State to reconstruct the nuclear genome for one of the largest giant lemurs, Megaladapis edwardsi, a koala lemur from Madagascar.

Ancient DNA can tell stories about species that have long since vanished, such as how they lived and what they were related to. But sequencing DNA from partially fossilized remains is no small feat, because DNA breaks down over time. And because the DNA is no longer intact, researchers have to take these fragments and figure out their correct order, like the pieces of a mystery jigsaw puzzle with no image on the box.

Bones like these are all that’s left of Madagascar’s giant lemurs, the largest of which weighed in at 350 pounds — 20 times heftier than lemurs living today. Credit: Matt Borths, Curator of the Division of Fossil Primates at the Duke Lemur Center

Hard-won history lessons

The first genetic study of M. edwardsi, published in 2005 by Duke’s Anne Yoder, was based on DNA stored not in the nucleus — which houses most of our genes — but in another cellular compartment called the mitochondria that has its own genetic material. Mitochondria are plentiful in animal cells, which makes it easier to find their DNA.

At the time, ancient DNA researchers considered themselves lucky to get just a few hundred letters of an extinct animal’s genetic code. In the latest study they managed to tease out and reconstruct some one million of them.

“I never even dreamed that the day would come that we could produce whole genomes,” said Yoder, who has been studying ancient DNA in extinct lemurs for over 20 years and is a co-author of the current paper.

For the latest study, the researchers tried to extract DNA from hundreds of giant lemur specimens, but only one yielded enough useful material to reconstitute the whole genome.

Once the creature’s genome was sequenced, the team was able to compare it to the genomes of 47 other living vertebrate species, including five modern lemurs, to identify its closest living relatives. Its genetic similarities with other herbivores suggest it was well adapted for grazing on leaves.

Despite their nickname, koala lemurs weren’t even remotely related to koalas. Their DNA confirms that they belonged to the same evolutionary lineage as lemurs living today.

To Yoder it’s another piece of evidence that the ancestors of today’s lemurs colonized Madagascar in a single wave.

Since the first ancient DNA studies were published, in the 1980s, scientists have unveiled complete nuclear genomes for other long-lost species, including the woolly mammoth, the passenger pigeon, and even extinct human relatives such as Neanderthals.

Most of these species lived in cooler, drier climates where ancient DNA is better preserved. But this study extends the possibilities of ancient DNA research for our distant primate relatives that lived in the tropics, where exposure to heat, sunlight and humidity can cause DNA to break down faster.

“Tropical conditions are death to DNA,” Yoder said. “It’s so exciting to get a deeper glimpse into what these animals were doing and have that validated and verified.”

See them for yourself

Assembled in drawers and cabinets cases in the Duke Lemur Center’s Division of Fossil Primates on Broad St. are the remains of at least eight species of giant lemurs that you can no longer find in the wild. If you live in Durham, you may drive by them every day and have no idea. It’s the world’s largest collection.

In one case are partially fossilized bits of jaws, skulls and leg bones from Madagascar’s extinct koala lemurs. Nearby are the remains of the monkey-like Archaeolemur edwardsi, which was once widespread across the island. There’s even a complete skeleton of a sloth lemur that would have weighed in at nearly 80 pounds, Palaeopropithecus kelyus, hanging upside down from a branch.

Most of these specimens were collected over 25 years between 1983 and 2008, when Duke Lemur Center teams went to Madagascar to collect fossils from caves and ancient swamps across the island.

“What is really exciting about getting better and better genetic data from the subfossils, is we may discover more genetically distinct species than only the fossil record can reveal,” said Duke paleontologist Matt Borths, who curates the collection. “That in turn may help us better understand how many species were lost in the recent past.”

They plan to return in 2022. “Hopefully there is more Megaladapis to discover,” Borths said.

A fossil site in Madagascar. Courtesy of Matt Borths, Duke Lemur Center Division of Fossil Primates

CITATION: “Evolutionary and Phylogenetic Insights From a Nuclear Genome Sequence of the Extinct, Giant, ‘Subfossil’ Koala Lemur Megaladapis Edwardsi,” Stephanie Marciniak, Mehreen R. Mughal, Laurie R. Godfrey, Richard J. Bankoff, Heritiana Randrianatoandro, Brooke E. Crowley, Christina M. Bergey, Kathleen M. Muldoon, Jeannot Randrianasy, Brigitte M. Raharivololona, Stephan C. Schuster, Ripan S. Malhi, Anne D. Yoder, Edward E. Louis Jr, Logan Kistler, and George H. Perry. PNAS, June 29, 2021. DOI: 10.1073/pnas.2022117118.

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