visited by Charles Darwin in 1835, the Galapagos Islands, he found that they were a number of songbirds, the finches were later named after him, Darwin. From island to island the finches different beaks, pointed shaped, sometimes round, sometimes delicate, or strong. Darwin suspected – revolutionary at the time – an adaptation to the environment: While, for example, of the big reason Fink, preferably in its natural habitat seeds pecks and a massive Beak needs, had the tips of the Beak to the Warbler Finch, in the course of many generations, in order to better insect hunt.
This principle, called “adaptive Radiation” brought Darwin to a cornerstone of his teaching of evolution – it says that species are spreading through natural selection pressure, evolutionarily to new environmental conditions. A large part of the diversity of species on the planet can probably be explained by the fact.
However, the observations are based mostly on species that have developed a long time ago apart, in front of hundreds of thousands or millions of years. Now, biologists have embarked on for the first time, the reverse – path and the adaptive Radiation simulated experimentally and in real-time.
In the journal “Evolution Letters” describes Lingen, a Team from the American University of Utah, a four-year-long experiment with pigeons spring – these are lice-like parasites, which colonize the pigeon, the Plumage of the house and from the springs to feed. The pigeons try these lice get rid of by brushing and the parasites wegpicken.
colorized back
In the experiment, the researchers played specifically with the colors of pigeons and Pigeon lice, in order to understand the evolutionary mechanisms between host and parasite. First of all, the biologists have painted the back of the approximately two-Millimeter-long lice white or black, and put it on a black and white pigeons.
So, they observed that pigeons detect the parasites, especially on contrast to your own spring dress. Black lice on white pigeons, and white lice on the black pigeons were quickly wiped away. Lice with the same color as the springs overlooked the pigeons, however, often.
Then, the researchers put natural colored Lice on 32 black, 32 gray, 32 white pigeons. The lice multiply undisturbed in the Plumage apart from the natural Pecking of pigeons as a defense.
Pigeon lice (below) were based on white pigeons, four years within the lighter, so that they were not recognized by the host Photo: Bush et. al. / Evo Letters
After four years had changed the descendants of the first bird lice solid. Those white doves were to become significantly brighter, and those black pigeons, in contrast, is darker, so you were for the pigeons now more difficult than at the beginning. The lice on the gray pigeons were used as a control group, there were hardly any changes.
The researchers were able to observe the “Survival of the Fittest” in real time: aphids, which were not camouflaged well enough, and survived long enough to reproduce. The best camouflaged parasites had a selective advantage in the course of the experiment, always more pronounced.
the “blink of An eye”
The adaptive Radiation had been clearly at work, conclude the biologists – and within just four years, or about 60 lice generations. “Compared to the time scale of Evolution, is not even a blink of an eye,” says biologist Dale Clayton of the University of Utah in communication from the University. The range of colors, which developed during the experiment, evolutionarily, would have been so large as those of lice in the wild to around 300 bird species.
The attempt is reminiscent of the change in butterflies at the beginning of the industrial Revolution in the 19th century. Century. In the course of a few decades, the number of black-dyed birch spinner in the North of England rapidly, while butterflies of the same type have been with white-colored wings rare.
biologists to write the of the increased air pollution from Factory chimneys: The Russ sat down in the trees, making black butterflies suddenly were better camouflaged and thus an advantage in the evolutionary race got.
The evolutionary biologist from Utah are now planning another Experiment in which you want to investigate, whether besides the color, the Size of the lice in an evolutionary control. May the lice could develop to various sizes, large and small, lice can no longer mate with each other – this would be a step in the development of a new subspecies.
(editing Tamedia)
Created: 24.03.2019, 18:40 PM
