Breaking News: Biologists experimentally trigger adaptive radiation - News Paper

When naturalist Charles Darwin stepped onto the Galapagos Islands in 1835, he encountered a bird that sparked a revolutionary theory on how new species originate. From island to island, finches had wildly varied beak designs that reflected their varied diets. The so-called Darwin's finches are an emblem of adaptive radiation, which describes when organisms from a single lineage evolve different adaptations in response to competitors or predators.

The changes in colour are as light as the lightest species and as dark as the darkest species
in the entire genus - and this genus has been evolving for millions of years
[Credit: Adapted from Bush et. al. 2019]

Scientists think that adaptive radiation generates much of the biodiversity on Earth, yet most studies focus on groups that have already diversified. A new study took the opposite approach.

University of Utah biologists experimentally triggered adaptive radiation; they used host-specific parasites isolated on individual pigeon "islands." The scientists showed that descendants of a single population of feather lice adapted rapidly in response to preening, the pigeons' main defense.

The biologists painted the backs of feather lice, half with black paint, and half with white paint, and put them
on black, gray and white pigeons. Lice painted the 'wrong' colour - black lice on white feathers
and vice versa - were 40 percent more likely to be preened than cryptically coloured lice
[Credit: Adapted from Bush et. al. 2019]

They found that preening drives rapid and divergent camouflage in feather lice (Columbicola columbae) transferred to different coloured rock pigeons (Colombia livia). Over four years and 60 generations, the lice evolved heritable colour differences that spanned the full colour range of the lice genus found on 300 bird species worldwide.

"The changes in colour that we saw are as light as the lightest species and as dark as the darkest species in the entire genus--and this genus has been evolving for millions of years," said Sarah Bush, associate professor in biology at the U and lead author of the paper. "The changes and selection that happens day to day are the same patterns that we see over millions of years."

Pigeons defend themselves against lice by preening. Conspicuous lice are more
likelyto be picked off by prying beaks [Credit: Sydney Stringham]

This is the first study to show that the evolutionary changes that occurred within a single species (microevolution) echoed changes in colour among different species that diverged millions of years ago (macroevolution).

"People have been trying to bridge micro- and macro- evolution for a long time," said Dale Clayton, professor in biology at the U and co-author of the paper. "This study actually does it. That's a big deal."

The study has been published in the journal Evolution Letters.

Source: University of Utah [March 05, 2019]



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Breaking News: Biologists experimentally trigger adaptive radiation - News Paper