Sex -- As We Know It -- Works Thanks to Ever-Evolving Host-Parasite Relationships, Biologists Find

[Elmore Furth]

I'm more from the 'if it feels good, do it' school of evolutionary theory.

Parasites are driving my love life? Damn.

It seems we may have parasites to thank for the existence of sex as we know it. Indiana University biologists have found that, although sexual reproduction between two individuals is costly from an evolutionary perspective, it is favored over self-fertilization in the presence of coevolving parasites. Sex allows parents to produce offspring that are more resistant to the parasites, while self-fertilization dooms populations to extinction at the hands of their biological enemies.

The July 8 report in Science, "Running with the Red Queen: Host-Parasite Coevolution Selects for Biparental Sex," affirms the Red Queen hypothesis, an evolutionary theory who's name comes from Lewis Carroll's Alice in Wonderland text: "It takes all the running you can do, to keep in the same place." The idea is that sexual reproduction via cross-fertilization keeps host populations one evolutionary step ahead of the parasites, which are coevolving to infect them. It is within this coevolutionary context that both hosts and parasites are running (evolving) as fast as they can just to stay in the same place.

The team used the microscopic roundworm Caenorhabditis elegans as a host and the pathogenic bacteria Serratia marcescens to generate a host-parasite coevolutionary system in a controlled environment, allowing them to conduct more than 70 evolution experiments testing the Red Queen Hypothesis. They genetically manipulated the mating system of C. elegans, causing populations to mate either sexually, by self-fertilization, or a mixture of both within the same population. Then they exposed those populations to the S. marcescens parasite. The parasites were either allowed to coevolve with C. elegans or were prevented from evolving. The researchers then determined which mating system gave populations an evolutionary advantage.

"We found that the self-fertilizing populations of C. elegans were rapidly driven extinct by the coevolving parasites, a result consistent with the Red Queen Hypothesis," Morran said. On the other hand, sex allowed populations to keep pace with their parasites. "Sex helped populations adapt to their coevolving parasites, allowing parents to produce offspring that were resistant to infection and ultimately avoid extinction," he noted.

Sex -- As We Know It -- Works Thanks to Ever-Evolving Host-Parasite Relationships, Biologists Find

[napoleon_in_rags]

1. Fundamental lesson of nature: Diversity = Strength.

[WingDinger]

2. iF THEY ARE A LONG LIVED ANIMAL.

Those that evolve quickly enough to stay ahead, can self love.