One of Charles Darwin's hypotheses posits that closely related species will compete for food and other resources more strongly with one another than with distant relatives, because they occupy similar ecological niches. Most biologists long have accepted this to be true.
Thus, three researchers were more than a little shaken to find that their experiments on fresh water green algae failed to support Darwin's theory — at least in one case.
"It was completely unexpected," says Bradley Cardinale, associate professor in the University of Michigan's school of natural resources & environment. "When we saw the results, we said 'this can't be."' We sat there banging our heads against the wall. Darwin's hypothesis has been with us for so long, how can it not be right?"
The researchers — who also included Charles Delwiche, professor of cell biology and molecular genetics at the University of Maryland, and Todd Oakley, a professor in the department of ecology, evolution and marine biology at the University of California, Santa Barbara — were so uncomfortable with their results that they spent the next several months trying to disprove their own work. But the research held up.
"The hypothesis is so intuitive that it was hard for us to give it up, but we are becoming more and more convinced that he wasn't right about the organisms we've been studying," Cardinale says. "It doesn't mean the hypothesis won't hold for other organisms, but it's enough that we want to get biologists to rethink the generality of Darwin's hypothesis."
The assumptions underlying Darwin's hypothesis are important for conservation policy, since they essentially encourage decision-makers to prioritize species preservation based on how evolutionarily or genetically unique they are. "We don't have enough time, people or resources to save everything," Cardinale says. "A large number of species will go extinct and we have to prioritize which ones we will save.
"Many biologists have argued that we should prioritize for conservation those species that are genetically unique, and focus less on those species that are genetically more similar," he adds. "The thinking is that you might be able to tolerate the loss of species that are redundant. In other words, if you lost a redundant species, you might not see a change."
But if scientists ultimately prove Darwin wrong on a larger scale, "then we need to stop using his hypothesis as a basis for conservation decisions," Cardinale says. "We risk conserving things that are the least important, and losing things that are the most important. This does bring up the question: How do we prioritize?"
The scientists did not set out to disprove Darwin, but, in fact, to learn more about the genetic and ecological uniqueness of fresh water green algae so they could provide conservationists with useful data for decision-making. "We went into it assuming Darwin to be right, and expecting to come up with some real numbers for conservationists," Cardinale says. "When we started coming up with numbers that showed he wasn't right, we were completely baffled."
The National Science Foundation is supporting the work with $2 million over five years, awarded in 2010.
Experiments with green algae
The researchers sequenced 60 species of algae most common in North America and can describe with a high certainty their evolutionary relationships. "We know which ones are ancient and have become genetically unique, and which are new and recently diverged," he says.
Their experiments involved taking closely related species and competing them against one another, and taking evolutionarily ancient distantly related species and similarly pitting them against each other.
Written By: Marlene Cimons
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