Questions raised by amoebae 'cheats' that thrive

The experiment was conducted by Lorenzo Santorelli, in collaboration with evolutionary biologists David C. Queller and Joan E. Strassmann of Rice University, and others.

Santorelli, who was then a graduate student and has since moved to Oxford University, had worked with advisors at Washington University in St. Louis, where Queller is professor of biology and Strassmann professor of biology.

The cheat in question, the researchers found, was putting more than the clone's fair share of cells into a communal spore body, so that its genome dominated the next generation of amoebae.

The dominant idea in scientific studies, that cheating clones pay a price in the form of reduced evolutionary fitness in some other chapter of their lives, was thus questioned, the journal BMC Evolutionary Biology reports.

Scientists tested the fitness of a knockout mutant (an amoeba with one disabled gene) called CheaterB.

When mixed with equal parts of a wild-type clone, the cheater clone contributed almost 60 percent of the cells in the spore body, 10 percent more than its fair share, according to a Rice statement.

Scientists ran CheaterB cells through exhaustive tests of their ability to grow, develop, form spores and germinate.

CheaterB did just as well in these tests as its ancestor wild strain.

Under lab conditions, at any rate, CheaterB didn't seem to be paying a fitness cost for cheating.

This study raises important questions about the tension between cooperation and cheating, and asks why breaking something that is presumably functional (by knocking out a gene) might confer an advantage, in the first place.