Fighting to exist

The more closely related two species are, the more they're apt to drive one another to extinction.

Jun 14, 2011
Jef Akst

Lin Jiang displays a microscope image of a protist species used in the experimental microcosmsGEORGIA TECH / GARY MEEK

A new study published today (June 14) in Ecology Letters provides experimental evidence for a an assumption of evolutionary biology accepted since Darwin first proposed it in 1859's On the Origin of Species—that competition is greater among closely related species. Researchers at Georgia Tech established 165 experimental microcosms—simplified, laboratory ecosystems—harboring either one or two species of ciliated protists along with three varieties of bacterial prey species. Weekly, the team documented the abundance of each species in each microcosm, and found that after 10 weeks, all individually housed protists species survived. But in more than half of the arenas containing two protist species, one species had grown to dominate the population, driving the other to extinction.

The competition was fiercer when the two species in the microcosm were more closely related. "We found that species extinction occurred more frequently and more rapidly between species of microorganisms that were more closely related," Georgia Tech's Lin Jiang said in a press release. "This study is one step toward a better understanding of how phylogenetic relatedness influences species interactions."