Evolution often bestows the same traits on different organisms in order to help them survive. For example, just within the past 7,000 years – the blink of an eye, evolutionarily speaking – many different species have bleached their backs in order to blend in with the newly formed White Sands region of New Mexico.
However, the vast genetic landscape provided by an organisms DNA often gives several different routes to end up at the same destination. In two different species of lizards in the White Sands region, for example, the same gene was used to create a white back. But that gene was altered in different ways, giving a slight edge to one species whose bleached back became the dominant allele.
For more on that story, check out the press release I wrote for the University of Idaho a few years back.
When different species arrive at the same adaptations independently, it’s called convergent evolution. And now, new research from the University of Illinois has revealed a very surprising example of the phenomenon.
I don’t know very much about lice, except that they itch, I want to avoid them at all costs, and the shampoo treatment to kill them kind of sucks. And I know even less about the lice that ride on the feathers of birds.
But Kevin Johnson, a University of Illinois ornithologist, knows a lot more.
Apparently, different types of lice prey on different parts of a birds body and have evolved striking characteristics to help them do so. For example, lice on the wing are long and narrow, inserting themselves between the feather barbs of a bird’s wings. This allows them to avoid being crushed or removed when the bird preens.
By contrast, the lice on a bird’s head have triangular, grooved heads in order to cling to a single feather barb so they can’t be scratched off.
Of all the bird species in the world, and of all the lice that cling to their bodies, the different species of lice that live on the same body parts of different birds are quite similar. Since all wing lice have the same adaptations and all head lice have the same adaptations, scientists long thought that they were more closely related than the louse species that infect different types of birds.
Just like the defense.
By running the DNA of the different species and creating family trees, the researchers discovered that the lice that live on a single species of bird are much more closely related than those that inhabit similar body parts between species. What this means is that the lice first colonized a new species of bird before branching out to its different body parts. And once they branched out, all the different species evolved the same adaptations to help them thrive.
Convergent evolution at its best.