The team observed viruses as they evolved over hundreds of generations to infect bacteria. They found that when the bacteria could evolve defences, the viruses evolved at a quicker rate and generated greater diversity, compared to situations where the bacteria were unable to adapt to the viral infection.
The study shows, for the first time, that the American evolutionary biologist Leigh Van Valen was correct in his 'Red Queen Hypothesis'. The theory, first put forward in the 1970s, was named after a passage in Lewis Carroll's Through the Looking Glass in which the Red Queen tells Alice, 'It takes all the running you can do to keep in the same place'. This suggested that species were in a constant race for survival and have to continue to evolve new ways of defending themselves throughout time.
Dr Steve Paterson, from the University's School of Biosciences, explains: "Historically, it was assumed that most evolution was driven by a need to adapt to the environment or habitat. The Red Queen Hypothesis challenged this by pointing out that actually most natural selection will arise from co-evolutionary interactions with other species, not from interactions with the environment.
"This suggested that evolutionary change was created by 'tit-for-tat' adaptations by species in constant combat. This theory is widely accepted in the science community, but this is the first time we have been able to show evidence of it in an experiment with living things."
Dr Michael Brockhurst said: "We used fast-evolving viruses so that we could observe hundreds of generations of evolution. We found that for every viral strategy of attack, the bacteria would adapt to defend itself, which triggered an endless cycle of co-evolutionary change. We compared this with evolution against a fixed target, by disabling the bacteria's ability to adapt to the virus.
"These experiments showed us that co-evolutionary interactions between species result in more genetically diverse populations, compared to instances where the host was not able to adapt to the parasite. The virus was also able to evolve twice as quickly when the bacteria were allowed to evolve alongside it."
Erich Feldmeier on 09 Jan 12"Wissenschaftler der San Francisco State University (USA) berichten jetzt im Fachjournal PLoS ONE von einer Fliegenart, die bisher nur als Parasit von Hummeln bekannt war. Diese Parasiten nisteten sich aber auch in Honigbienen ein, die daraufhin ihren Bienenstock verlassen, zu einem Rundflug aufbrechen und sterben. Bislang wurde die Fliege (Apocephalus borealis) in Kalifornien und South Dakota bei Bienen nachgewiesen. Wenn sie ein neuer Parasit sei, "könnte sie Bienenkolonien in ganz Nordamerika bedrohen", schreiben die Forscher. Ganz unwahrscheinlich sei das nicht. "Honigbienen gehören zu den am besten untersuchten Insekten auf der Welt", wird Hafernik in einer Mitteilung seiner Universität zitiert. "Also sollte man annehmen, dass wir diesen Parasit schon kennen, wenn er schon lange existiert.""
