Studying Mouse Lemur Genetics Reveals Ancient Forest Mosaic Environment

Today, Madagascar is home to a mosaic of different habitats--a lush rainforest in the east and a dry deciduous forest in the west, separated by largely open highlands. But the island off the southeast coast of Africa hasn't always been like that--a new study published in the Proceedings of the National Academy of Sciences announces that these two ecologically different portions of the island were once linked by a patchwork of forested areas. And to figure it out, the scientists analyzed the DNA of some of the cutest animals on earth--mouse lemurs.

"For a long time, scientists weren't sure how or why Madagascar's biogeography changed in very recent geological time, specifically at the key period around when humans arrived on the island a few thousand years ago. It has been proposed they heavily impacted the Central Highland forests," says Steve Goodman, MacArthur Field Biologist at The Field Museum in Chicago, who co-authored the study and has been studying Malagasy animals for thirty years. "This study shows the landscape was changing thousands of years before humans arrived."

So scientists wanted to learn about the history of Madagascar's landscape--why study mouse lemurs? The tiny primates are the perfect combination of fast-breeding, hardy, and unique to the island. "They reach reproductive maturity within a year, and that means that a lot of generations are produced very quickly," explains Goodman. "That enables us to see evolution at work faster than we would in an animal that took, say, five years to first reproduce." The lemurs, which are found only on Madagascar, live across much of the island, even forested areas that have been damaged by humans. That means that for scientists studying how the island changed over time, mouse lemurs are a jackpot. "The mouse lemurs are forest dependent--as the forest changes, they change. By studying how mouse lemurs evolved in different areas of the island, we're able to glimpse how the island itself changed and learn whether those changes were caused by humans," says Goodman.

By analyzing DNA from five different mouse lemur species, the scientists were able to tell when the different kinds of lemurs branched out from each other. "We were able to characterize tens of thousands of changes in the genomes of mouse lemurs that are now isolated and form separate species. By analyzing these DNA changes, we were able to understand when the species diverged from each other, and by inference, identify the ecological forces that might have driven them apart," says Anne Yoder, Director of the Duke University Lemur Center and lead author on the paper.

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Implications of lemuriform extinctions for the Malagasy flora

Implications of lemuriform extinctions for the Malagasy flora

Authors:

Federman et al

Abstract:

Madagascar’s lemurs display a diverse array of feeding strategies with complex relationships to seed dispersal mechanisms in Malagasy plants. Although these relationships have been explored previously on a case-by-case basis, we present here the first comprehensive analysis of lemuriform feeding, to our knowledge, and its hypothesized effects on seed dispersal and the long-term survival of Malagasy plant lineages. We used a molecular phylogenetic framework to examine the mode and tempo of diet evolution, and to quantify the associated morphological space occupied by Madagascar’s lemurs, both extinct and extant. Using statistical models and morphometric analyses, we demonstrate that the extinction of large-bodied lemurs resulted in a significant reduction in functional morphological space associated with seed dispersal ability. These reductions carry potentially far-reaching consequences for Malagasy ecosystems, and we highlight large-seeded Malagasy plants that appear to be without extant animal dispersers. We also identify living lemurs that are endangered yet occupy unique and essential dispersal niches defined by our morphometric analyses.

Darwinius' Teeth Suggest More Closely Related to Lemurs Than Monkeys

A famous fossil of an early primate shares more in common with modern lemurs based on how its teeth erupted, according to new model developed at U of T Scarborough.

The model, developed by PhD student Sergi López-Torres and Associate Professors Mary Silcox and Michael Schillaci, re-examined the interpretation of Darwinius, the best preserved fossil primate known to exist.

By looking at the sequence in which adult teeth come in - known as dental eruption - in primates, they found it had more in common with lemurs than squirrel monkeys, the model species used by the researchers who discovered Darwinius.

"Every species has a particular pattern by which their teeth come in and this allows us to estimate the age of fossils that died before their adult teeth could emerge," says López-Torres. "It seems that the pattern of dental eruption for Darwinius is more similar to that of lemurs than to that of monkeys."

Before looking at Darwinius, López-Torres did a large study of 97 living and fossil primates in order to get a clearer picture of how different species compare through patterns of dental development. He found that the three most primitive ancestors - the ancestor to lemurs and lorises, the ancestor to monkeys, apes, and tarsiers, and the ancestor to all primates - share the same eruption sequence with each other. That pattern shares some similarities with the dental eruption sequence found in Darwinius.

"The major difference is we found that anthropoids (ancestors to monkeys, apes and humans) are characterized by a late eruption of the third molar, which is something Darwinius clearly doesn't show," he says. "One idea that still stands links Darwinius to anthropoids, but since it doesn't show this late eruption, it looks more like a modern lemur."

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Lemur Subfossils Found in Flooded Cave in Madagascar

Deep below the surface of a water-filled cave in Madagascar, divers and paleontologists have uncovered a boneyard full of extinct giant lemurs.

Hundreds of bones dot the silty bottom of Aven Cave in Tsimanampetsotse National Park. The remains include exotic species such as the extinct elephant bird, a flightless giant similar to an ostrich, but the most numerous bones are from long-lost giant lemurs.

The largest of the extinct lemurs were as big as gorillas, and paleontologists sometimes refer to the different types as sloth lemurs, koala lemurs, and monkey lemurs to describe their different lifestyles and the living animals they most closely resemble. Sometime between 2,000 and 500 years ago, all these giants disappeared, possibly at the hands of humans.

The underwater caves offer an unprecedented look at these lost species. "The preservation is really incredible," says Brooklyn College anthropologist Alfred Rosenberger, a National Geographic grantee who is leading the project.

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Large Lemurs of Madagascar Were More Vulnerable to Extinction due to Small Population Size

Ancient DNA extracted from the bones and teeth of giant lemurs that lived thousands of years ago in Madagascar may help explain why the giant lemurs went extinct. It also explains what factors make some surviving species more at risk today, says a study in the Journal of Human Evolution.

Most scientists agree that humans played a role in the giant lemurs' demise by hunting them for food and forcing them out of habitats. But an analysis of their DNA suggests that the largest lemurs were more prone to extinction than smaller-bodied species because of their smaller population sizes, according to this team of American and Malagasy researchers.

By comparing the species that died out to those that survived, scientists hope to better predict which lemurs are most in need of protection in the future.

The African island of Madagascar has long been known as a treasure trove of unusual creatures. More than 80 percent of the island's plants and animals are found nowhere else. But not long ago, fossil evidence shows there were even more species on the island than there are today. Before humans arrived on the island some 2,000 years ago, Madagascar was home to 10-foot-tall elephant birds, pygmy hippos, monstrous tortoises, a horned crocodile, and at least 17 species of lemurs that are no longer living -- some of which tipped the scales at 350 pounds, as large as a male gorilla.

Using genetic material extracted from lemur bones and teeth dating back 550 to 5,600 years, an international team of researchers analyzed DNA from as many as 23 individuals from each of five extinct lemur species that died out after human arrival. They looked at a giant ruffed lemur, a baboon lemur, a koala lemur and two sloth lemurs -- all housed in the collections at the University of Antananarivo and the Duke Lemur Center at Duke University. The study also included genetic data from eight extant species, including the three largest lemur species still alive today.

The researchers found that the species that died out had lower genetic diversity than the ones that survived -- a hallmark of small population size.

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Complete Adapid Skeleton to be Unveiled at AMNH

In what could prove to be a landmark discovery, a leading paleontologist said scientists have dug up the 47 million-year-old fossil of an ancient primate whose features suggest it could be the common ancestor of all later monkeys, apes and humans.

Anthropologists have long believed that humans evolved from ancient ape-like ancestors. Some 50 million years ago, two ape-like groups walked the Earth. One is known as the tarsidae, a precursor of the tarsier, a tiny, large-eyed creature that lives in Asia. Another group is known as the adapidae, a precursor of today's lemurs in Madagascar.

Based on previously limited fossil evidence, one big debate had been whether the tarsidae or adapidae group gave rise to monkeys, apes and humans. The latest discovery bolsters the less common position that our ancient ape-like ancestor was an adapid, the believed precursor of lemurs.

Philip Gingerich, president-elect of the Paleontological Society in the U.S., has co-written a paper that will detail next week the latest fossil discovery in Public Library of Science, a peer-reviewed, online journal.

"This discovery brings a forgotten group into focus as a possible ancestor of higher primates," Mr. Gingerich, a professor of paleontology at the University of Michigan, said in an interview.

[...]

Scientists won't necessarily agree about the details either. "Lemur advocates will be delighted, but tarsier advocates will be underwhelmed" by the new evidence, says Tim White, a paleontologist at the University of California, Berkeley. "The debate will persist."

The skeleton will be unveiled at New York City's American Museum of Natural History next Tuesday by Mayor Michael Bloomberg and an international team involved in the discovery.

According to Prof. Gingerich, the fossilized remains are of a young female adapid. The skeleton was unearthed by collectors about two years ago and has been kept tightly under wraps since then, in an unusual feat of scientific secrecy.

Prof. Gingerich said he had twice examined the adapid skeleton, which was "a complete, spectacular fossil." The completeness of the preserved skeleton is crucial, because most previously found fossils of ancient primates were small finds, such as teeth and jawbones.

It was found in the Messel Shale Pit, a disused quarry near Frankfurt, Germany. The pit has long been a World Heritage Site and is the source of a number of well-preserved fossils from the middle Eocene epoch, some 50 million years ago.

Oh wow.

I can't wait to see!

Any chance one our east coasters will live blog this?