Mammal ancestors bided their time
in Life Science, Diversity of Organisms, and Biological Populations Change Over Time
Modern mammals waited for the right time to diversify: Photo of Hopi chipmunk by Mdf courtesy Wikipedia Commons.Results from a new study of mammalian diversity and origins show that most species of mammals alive today waited several millions of years after dinosaurs died out to diversify and take over the world left by their reptilian predecessors.
The conclusion comes from an international research team studying the evolutionary connections between some 4,500 species of mammals. In the process the researchers also developed a “supertree” of mammal relationships. Supertrees are created using numerous smaller studies to summarize the evolutionary history of a large group of organisms.
Some mammals did flourish in the bio vacuum created by the Mass Extinction Event (MEE) that took place at the end of the Cretaceous 65 million years ago - credited to a large asteroid colliding with the Earth - but most of those mammals later became extinct themselves. The ancestors of mammals alive today, including rodents, hoofed animals, primates and humans, existed some 20 million years before the dinosaurs’ demise, but appear to have waited in the shadows before diversifying and expanding.
"Our research has shown that for the first 10 or 15 million years after the dinosaurs were wiped out, present day mammals kept a very low profile, while these other types of mammals were running the show,” said professor Andy Purvis of Imperial College London’s Division of Biology, one of the study’s leaders.
“It looks like a later bout of 'global warming' may have kick-started today's diversity – not the death of the dinosaurs,” he added.
The diversification took place in the Eocene Period and seems to coincide with what is known as the Paleocene-Eocene thermal maximum, a time of peaking global temperatures during the Cenozoic era. But whether the high temperatures caused of biological expansion is not known.
The findings not only counter the widely held idea that ancestors of modern mammals evolved and spread quickly to fill the void left by the mass extinctions of dinosaurs, but also add invaluable insight into other aspects of mammalian evolution.
"Not only does this research show that the extinction of the dinosaurs did not cause the evolution of modern-day mammals, it also provides us with a wealth of other information,” said Dr. Kate Jones from the Zoological Society of London. “Vitally, scientists will be able to use the research to look into the future and identify species that will be at risk of extinction. The benefit to global conservation will be incalculable.”
The research appeared in the journal Nature.
STORY IN MINNEAPOLIS STAR TRIBUNE
MORE ON THE CRETACEOUS
MORE ON THE EOCENE PERIOD
MORE ON MASS EXTINCTIONS
MORE ON MAMMALS
MORE ON DINOSAURS
Tags : An international team of more than 80 marine biologists has surveyed a coral reef in the Philippines and discovered thousands and thousands of species -- one of the most diverse spots on Earth. So far, over 100 have been confirmed as new to science, though the team estimates there could be several thousand new species in their study. (What makes this all the more amazing is that coral reefs grow in the tropical oceans -- one of the most hostile environments on the planet!)
Prairie grasses: This experimental plot contains four species of prairie plants. The nearby plots, going clockwise, contain eight species, four species, and 16 species. (Photo courtesy David Tilman, University of Minnesota)
Scientists at our very own U of M have made some exciting new discoveries about the prospect of using biofuels for energy! They found that planting a diverse mix of native prairie species is more efficient than corn or soybeans, even on degraded soil. Amazingly, their most diverse plots, with 18 different species, produced 238% more bioenergy than the plots with only 1 species.
While there is still a lot of research needed to make this system useable on a wide scale, these findings are encouraging for a few reasons. Unlike all of our other forms of fuel, including corn ethanol or biodiesel from soy beans, the native plants actually absorb more carbon from the atmosphere than is released when used for fuel. Because of the vast root network associated with prairie plants (which allow them to withstand Minnesota’s hot and dry summers), much carbon is stored below ground and is not harvested for fuel. Also, these environmentally friendly crops can be grown on land that is unusable for traditional food crops. They do not need to be fertilized, a benefit to growing a native species, and thus can be grown in nutrient poor areas. Fertilizer runoff from traditional agriculture is a big contributor to water quality problems. Additionally, because native prairie species are perennial crops, they can help prevent erosion. For much of the year, particularly during the rainy months in the spring, corn or soybean fields are bare. This leaves the ground vulnerable to soil loss. Planting a native mix, particularly on steep slopes or along riverbanks, which are less suitable to traditional crops anyway, could mitigate many environmental issues. Plus, we could increase the amount of prairie habitat for native wildlife!
For more information on sustainable agriculture and the latest research check out Sustainable Agriculture Research and Education and the Minnesota Institute for Sustainable Agriculture.
Seed bank:: Through a new facility being built in Norway north of the Arctic Circle, seeds from all over the world will be kept safe to be used in the event of catastrophic natural disasters. (Photo from U.S. Agriculture Department)What could be a safer place than the frigid temperatures of the Artic along with roaming polar bears to protect the world’s rich diversity of seeds? That’s the conclusion that scientists have come to I planning a way to save our most precious seeds.
Work started this week on a northern Norway island to build a seed vault. Carved into an Arctic mountain, the vault will hold a supply of food crop seeds. Run by the Global Crop Diversity Trust (GCDT), the vault will protect the seeds from being lost forever if some natural catastrophe should sweep the Earth or parts of it.
GDTC currently has about 1,400 crop gene banks spread across every corner of the globe except Antarctica.
The new vault will be imbedded into permafrost and rock above the Arctic Circle and be covered with a layer of ice. Eventually, seeds from every nation will be stored there. It will have the capacity to hold up to 1 million seeds.
Seeds will be kept in watertight foil packaging and will be stored in an area that doesn’t need artificial refrigeration. Temperatures on the island of Spitsbergen never get over 27 degrees Fahrenheit. The island is only a couple hundred miles from the North Pole.
So what kind of seeds to you think should be put in the vault? What kind of conditions do you think it should take to get seeds out of the vault?
By the way, the Science Museum of Minnesota has its own project involving old, saved seeds. The Three Sisters Garden in the Big Back Yard grows corn, beans and squash that have been stored for hundreds of years by Native Americans.
Prairie grasses: This experimental plot contains four species of prairie plants. The nearby plots, going clockwise, contain eight species, four species, and 16 species. (Photo courtesy David Tilman, University of Minnesota)
Ecosystems containing many different plant species are more productive and better able to deal with stresses such as climate extremes, pests, and disease. Those are the findings, published in last week’s issue of Nature, of University of Minnesota ecologist David Tilman and colleagues Peter Reich and Johannes Knops.
It sounds familiar, doesn’t it? The debate about whether or not diversity stabilizes ecosystems has been going on for 50 years! But Tilman’s experiment is the first to collect enough data, over enough time and in a controlled environment, to confirm the hypothesis.
Tilman, Reich, and Knops spent 12 years studying 168 9-meter-by-9-meter experimental plots at the Cedar Creek Long-Term Ecological Research (LTER) site near Cambridge, Minnesota. Each plot was randomly planted with 1-16 perennial grasses and other prairie plants. Over the 12 years of the study, temperatures and rainfall varied, but the plots with more species and more root mass did better than the others. (Why root mass? Roots store nutrients and provide a buffer against climate variations. And perennial prairie plants have far more root mass than annual plants, such as corn and other crops.)
Experimental plots: This aerial photo shows the individual nine-meter by nine-meter plots. (Photo courtesy David Tilman, University of Minnesota)
So what does it mean?
Two things. First, biodiversity does matter when it comes to healthy ecosystems. Second, biodiversity is decreasing worldwide as human populations increase and forests and prairies have been replaced with farm fields, buildings, and roads. Tilman thinks that increasing diversity may be the key to both restoring ecosystems and meeting the energy needs of people around the world.
In a National Science Foundation press release, Tilman said:
”Diverse prairie grasslands are 240 percent more productive than grasslands with a single prairie species. That’s a huge advantage. Biomass from diverse prairies can, for example, be used to make biofuels without the need for annual tilling, fertilizers, and pesticides, which require energy and pollute the environment. Because they are perennials, you can plant a prairie once and mow it for biomass every fall, essentially forever.”
This experimental plot contains four species of prairie plants. The nearby plots, going clockwise, contain eight species, four species, and 16 species. (Photo courtesy David Tilman, University of Minnesota)
Please contact us if you have questions about the rights on this image.
This aerial photo shows the individual nine-meter by nine-meter plots. (Photo courtesy David Tilman, University of Minnesota)
Please contact us if you have questions about the rights on this image.
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