No question, the city is an extreme environment. The air is bad, it's loud and almost always something. At night it looks much better: As a city never really comes to rest. Only you can do this automatically to a hostile place?
The evolutionary biologist Menno Schilthuizen represents exactly the opposite Hypothesis: The city is the new engine of Evolution. As more and more researchers believe that we will be able to see in the big cities, just a stunning development – the emergence of new types quickly.
Schilthuizen has a number of striking examples of the adaptation of animals and plants to the city. He explores the Evolution currently at the biodiversity centre Naturalis in the Dutch city of Leiden on the example of the schnirkel screw, so omnipresent animal, that one finds it in Europe on virtually every corner, and in the meantime also in Overseas. to investigate
the Cepaea nemoralis, had Schilthuizen even have to leave his property. The soft animals ate him, again and again, the ornamental plants in his yard. So, he consoles them carefully from the Branches and noticed its strange colour. "The houses of the schnirkel snow cover in my garden are pale yellow with a few dark stripes on it. Usually they are reddish to dark brown."
the strange color Schilthuizen develops his own hypothesis. He believes that the schnirkel snail in the city is wearing a brighter house in the back than in rural regions, because it is in the cities hotter. "The buildings and streets in the city to absorb the heat of the sun, the to many people and your machines to control your heat. This leads to the fact that the average temperature in medium-sized cities, two to three degrees higher than in the surrounding regions of the case," he writes.
In megacities such as New York or Tokyo may be the difference in temperature to the surrounding area more than ten degrees. Schnirkel snow cover like heat and drought, they will remain for weeks in a kind of paralysis. "Add to that a few more degrees of heat, it can be deadly for you. So more snails survive with a light house, because it absorbs less heat."
Plage for commuters
An example for a whole new kind of mosquito on the London underground. The annoying insect has apparently developed rapidly after the opening of the London Underground in 1863. It genetically from his above-ground Culex-Relatives differs. So that two respective copies, not more plants together – in biology, the classical proof that a new type is created. However, the differences lie not only in the genetics: The above-ground Relatives live bird blood and keep the winter sleep. The track mosquito, every Season is up and kicking.
No wonder, then, finally, you will be in the subway tunnels, wagon way, supplied with fresh commuter blood and do not need to fly around to find a lunch deal For this reason, the mosquitoes of the individual lines develop independently of each other. So, the mosquitoes, the Bakerloo and the Victoria lines differ markedly in their genetic characteristics. "As they left their Tunnel, you would have to change at Oxford Circus to mate with the inhabitants of other lines," says Katharine Byrne of the University of London, who has studied the mosquitoes.
The city as a habitat not only differences, but also global similarities. "A big city is a big city, no matter whether you are located in Australia, Europe or Asia," says canadian Ecologist Marc Johnson. He was one of the first researchers who discovered the urban Evolution, and is today one of the leading representatives of the subject area.
Vivid green strip
it was him, according to the study, as almost all his colleagues: "I wanted to follow in Darwin's footsteps on the Galapagos Islands, or else where in the Wilderness do research. The green strip next to a main traffic artery appeared to us to be biologists at the time, as good as dead." But then he got a job at the University of Toronto and discovered that exciting research were questions directly on his doorstep – in the Form of a highly unspectacular Plant that has actually disheveled, every child: white clover.
"white clover grows in places where temperate climate prevails," says Johnson. Only the white clover in the cities in the world, a Commonality that distinguishes it from the white clover on the Land: "The plants contain much less hydrogen cyanide, which protects the enemies before eating." Exactly the help the clover but, with the climatic conditions of the city. To prove it, had the pick of the Ecologist in more than 190 cities of clover seedlings. So, it turned out that the Plant adapts itself everywhere in the same way to the urban climate. Two cities on different continents can be seen around similar as a city and the rural Region.
animals and genetically plants, and in their behavior to their environment adjust, is the essence of Evolution. However, cities seem to have a kind of turbo effect. Charles Darwin himself was convinced that the change in inheritable characteristics of Eons must be: "We see nothing of these slow progressive changes, until the Hand of time pointing to a past world period," he wrote.
For 20 years, the evidence that species change much more quickly, in less than two generations repeatedly. Recently, an American group of researchers from the University of Washington evaluated more than 1600 individual studies. The scientists came to the conclusion that the urbanisation of the environment increases the speed of Evolution – and in some cases even doubled.
That is on in the city so quickly, according to Schilthuizen of the tremendous evolutionary pressure that life gives. To add to the heat in the urban environment factors such as noise, traffic and pollution with chemicals. To new biological contexts must adapt to the urban life: "The people in the cities have exotic plants and Pets, bring seeds and larvae from foreign countries," says the evolutionary biologist. Who doesn't get in this wild situation and adapts to it, it dies out quickly.
Schilthuizen compares the city therefore, like a pressure cooker. It's just that he's not thinking of food will now be cooked faster. But in Evolution.
Created: 06.01.2019, 16:57 PM