10.24.08
Mass extinction and unique plants
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http://www.ens-newswire.com/ens/oct2008/2008-10-21-01.asp
Genetically Unique Plants Matter Most in Current Mass Extinction
SANTA BARBARA, California, October 21, 2008 (ENS) – The sixth mass extinction of both plants and animals is underway, scientists say, warning that nearly 50 percent of all species could disappear within the lifetimes of people now living on Earth.
Some species are more critical than others in preserving the functions of ecosystems and scientists researching grasslands around the world have found that the most valuable species are those that are genetically unique.
“The current extinction event is due to human activity, paving the planet, creating pollution, many of the things that we are doing today,” said scientist Bradley Cardinale, assistant professor of ecology, evolution and marine biology at the University of California-Santa Barbara.
“The Earth might well lose half of its species in our lifetime,” he said. “We want to know which ones deserve the highest priority for conservation.”
Cardinale and his team are attempting to determine which species must be saved. Their international study of grassland ecosystems with flowering plants, is published this week in the Proceedings of the National Academy of Sciences.
The paper reviews 40 studies of grassland ecosystems around the world and reconstructs the evolutionary history of 177 flowering plants used in these studies by comparing the genetic makeup of the plants.
“These 40 studies are showing the same thing for all plants around the world,” said Cardinale. “This study is very robust. It includes studies of plants that are found throughout the U.S., Europe, and Asia. We can have a high degree of confidence in the results. And the results show that genetic diversity predicts whether or not species matter.”
“Given that we are losing species from ecosystems around the world, we need to know which species matter the most and which we should pour our resources into protecting,” said first author Marc Cadotte, a postdoctoral fellow at the university’s National Center for Ecological Analysis and Synthesis.
Cadotte explained that the buttercup is a very unique species, evolutionarily. Losing the buttercup, where it occurs in grasslands, would have a much bigger impact on the system than losing a daisy or a sunflower, for example.
A daisy and a sunflower are closely related species with similar genetic makeup. Each could, therefore, help fill the niche of the other, if one were to be lost, the scientists reason.
Recent studies show that ecological systems with fewer species produce less biomass than those with more species. Less plant biomass means that less carbon dioxide is absorbed from the atmosphere and less oxygen is produced.
So, as the biomass of plants shrinks around the globe, the composition of gases in the atmosphere that support life could be profoundly affected. There will be fewer plants for herbivorous animals to eat. Entire food chains can be disrupted, which can impact the production of crops and fisheries.
The loss of species that are not closely related to other species in the ecosystem reduces productivity more than the loss of species with close relatives. And the more genetically distinct a species is, the more impact it has on the amount of biomass in an ecosystem.
“Losing a very unique species may be worse than losing one with a close relative in the community,” said co-author Todd Oakley, associate professor of ecology, evolution and marine biology at UC Santa Barbara. “The more evolutionary history that is represented in a plant community, the more productive it is.”
The last mass extinction near the current level took place 65 million years ago, called the Cretaceous Tertiary extinction event. Scientists believe it was the result of a meteor hitting the Earth. It is best known for the extinction of non-avian dinosaurs, but large numbers of plant species also became extinct at that time.