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5 December 2013 11:26 am ,
Vol. 342 ,
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Fungi Had Rocky Relationship
21 June 2001 7:00 pm
The common wisdom of fungus evolution has been flipped on its head by a new study. Researchers were surprised to find that many of today's free-wheeling fungi are descended from species that lived in symbiosis with other organisms as lichens.
A lichen is a collaboration between a fungus and a photosynthetic partner, which can be either green algae, cyanobacteria, or both. The algae or bacteria produce carbohydrates through photosynthesis, some of which are absorbed by the fungi. In return, the fungi provide shelter that allows its partners to survive otherwise intolerable conditions. Up to 20% of fungal species are thought to live as lichens. Scientists assumed lichenization had arisen independently many times, because of the diversity of species that form lichens and also because many branches of the fungus family tree have both lichenized and nonlichenized species.
A new genetic analysis has changed all that. Researchers from the Field Museum of Natural History in Chicago and the University of Reading in the United Kingdom analyzed the Ascomycota fungi--a phylum including 98% of known lichenized species and about 75% of all known fungi. The researchers analyzed RNA from 52 species and found that instead of evolving many times, lichenized fungi arose just a few times in the deep history of the group. On many subsequent occasions, the fungi ditched their photosymbiont partners, the researchers report in the 20 June issue of Nature.
Why do fungi so often turn to a solitary life? Team member Mark Pagel, an evolutionary biologist at the University of Reading, speculates that "symbioses are evolutionarily unstable ... as it's inevitable that natural selection causes the partners to exploit one another." And when one partner is too sorely taken advantage of, it doesn't benefit by continuing the relationship.
Other evolutionary biologists applaud the study. "This is the first solid piece of work to suggest lichen symbiosis is reversible," says David Hibbett, a fungal evolutionary biologist at Clark University in Worcester, Massachusetts. "It's a dynamite study ... which promotes the view that underlying symbioses are conflicts of interest between the partners."