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Bird louse study shows how evolution sometimes repeats itself

University of Illinois at Urbana-Champaign


IMAGE: The lice that live on parrots look very different from one another, but they are more closely related to one another than to similar-looking lice on other types of birds.... view more

Credit: Vincent Smith, The Natural History Museum, London

CHAMPAIGN, Ill. -- Birds of a feather flock together and - according to a new analysis - so do their lice.

A study of the genetic heritage of avian feather lice indicates that their louse ancestors first colonized a particular group of birds (ducks or songbirds, for example) and then "radiated" to different habitats on those birds - to the wings or heads, for instance, where they evolved into different species. This finding surprised the researchers because wing lice from many types of birds look more similar to one another than they do to head or body lice living on the same birds.


Wing lice are long and narrow and insert themselves between the feather barbs of a bird's wings. This allows them to avoid being crushed or removed by a bird when it preens, said Kevin Johnson, a University of Illinois ornithologist with the state Natural History Survey. Johnson conducted the new analysis with Vincent Smith, of the Natural History Museum in London, and Illinois graduate student Scott Shreve.

"If you were just guessing at their ancestry based on external traits, you would think the wing lice on different birds were more closely related to one another than they were to head or body lice on the same bird," Johnson said. "But that's just not the case."



"The similarities between the lice living in specific habitats on the bodies of birds are really striking," Johnson said. "But it appears that those similarities are the result of what we call 'convergent evolution': The lice independently arrived at the same, or similar, solutions to common ecological problems. This occurred only after they had colonized a particular type of bird."




"Here we see how evolution repeats itself on different bird types," he said. "The lice are converging on similar solutions to the problem of survival in different microhabitats on the bird."




The paper, "Repeated Adaptive Divergence of Microhabitat Specialization in Avian Feather Lice," is available online.
