A new study provides support for Darwin's hypothesis that the struggle for existence is stronger between more closely related species than those distantly related. While ecologists generally accept the premise, this new study contains the strongest direct experimental evidence yet to support its validity.
"We found that species extinction occurred more frequently and more rapidly between species of microorganisms that were more closely related, providing strong support for Darwin's theory, which we call the phylogenetic limiting similarity hypothesis," said Lin Jiang, an assistant professor in the School of Biology at Georgia Tech.
The study was published online on June 14, 2011 in the journal Ecology Letters. The work was supported by the National Science Foundation.
Jiang and his team -- Cyrille Violle, formerly a postdoctoral fellow at Georgia Tech currently at the Centre d'Ecologie Fonctionnelle et Evolutive in Montpellier, France, and Georgia Tech biology graduate student Zhichao Pu -- conducted experiments with 10 common ciliated protist species in artificial, simplified ecosystems called microcosms. Diana Nemergut, an assistant professor in the Institute of Arctic and Alpine Research and the Environmental Studies Program at the University of Colorado at Boulder, helped the team generate a family tree of the 10 microorganisms to determine how closely related the species were.
"We selected bacterivorous ciliated protist microorganisms for this study because they rapidly reproduce, allowing us to examine species co-existence over multiple generations in a closed system during a period of a few weeks, which wouldn't be possible if we were testing the hypothesis with plants or animals," said Jiang.
The researchers set up 165 microcosms that contained either an individual protist species or a pairing of two species, along with three types of bacteria for the organisms to eat. They collected weekly sam
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Georgia Institute of Technology Research News