One of the main processes of evolution - natural selection - is unfolding right before our eyes. Over the past half century, insects that are not afraid of pesticides, mice that are not sensitive to poison, and bacteria that are resistant to antibiotics have appeared on Earth. Who and how adapts to adverse conditions.
Hurricane survivors
In the summer of 2017, a group of scientists from Harvard University observed populations of small lizards, Anolis scriptus, living in the Turks and Caicos Islands in the West Indies. Four days after the end of the expedition, hurricanes Irma and Maria hit the archipelago. Six weeks later, the biologists returned there to re-collect the data.
It turned out that after the natural disaster, the lizards changed noticeably - the surviving toes were on average longer, the forelimbs were larger, the body was shorter, and the thigh bones were smaller. Scientists have suggested that these signs helped the reptiles survive the hurricane, and now they will gain a foothold in the next generations of Anolis scriptus living on the islands.
After hurricanes Irma and & quot; Maria & quot; in 2017, the appearance of the Anolis scriptus lizards, living on the islands in the West Indies, has changed - in surviving animals, the toes on the paws were on average longer, the forelimbs were larger, the body length was shorter / Rian Castillo / Anolis scriptus femelle.
Artificial evolution
Promotional video:
So, thanks to the raging elements, researchers for the first time observed natural selection in nature. Prior to this, the processes of adaptation of living organisms to changing environmental conditions and speciation were artificially simulated in laboratories.
Most often, bacteria became the object of study - they multiply rather quickly, and their genome is small in size, which allows for a relatively short time to study the processes that take thousands of years in more complex organisms. The most famous experiment, which began in 1988 and continues to this day, was staged by a group of scientists from the University of Michigan, led by evolutionary biologist Richard Lensky.
In February 1988, researchers created twelve populations of a single strain of Escherichia coli (E. coli) and placed them in an artificial environment where glucose was the only food source. In addition, citrate was present in the solution, but E. coli could not feed on it.
Twelve populations of E. coli bacteria that have been observed by scientists for 30 years. Photo: Brian Baer and Neerja Hajela.
For thirty years (more than 68 thousand generations of E. coli have changed) bacteria in all populations have grown and have learned to more efficiently absorb nutrients, including citrate. The mutations that allowed E. coli to adapt to their environment were different in all populations, but they occurred in the same genes - each bacterial community tried to find its own path in evolution.
Stronger teeth, bigger heads
Sometimes complex organisms adapt to environmental conditions not for millennia, but much faster. For example, the wall lizard Podarcis sicula, living on one of the islands in the Adriatic Sea, has changed the size, shape of the head and the structure of the digestive tract in just 36 years, although genetically they are still indistinguishable from relatives living elsewhere.
In 1971, researchers transported five pairs of adults of Podarcis sicula from Pod Kopiste Island to neighboring Pod Markaru. The conditions in the new place resembled the usual habitat, but there were practically no land-based predators, and after thirty years the reptiles that had spread throughout the island were outwardly different from their congeners on Pod Kopist.
The wall lizard (Podarcis siculus), when relocated to the island of Pod Markaru, changed in appearance: it became larger, its hind limbs were shortened, and an ileocecal valve Kurt W. Becker / Lucertola campestre a caccia appeared in the gastrointestinal tract.
The settler lizards increased in size, began to run slower (their hind limbs were shortened), their heads looked more massive, and their teeth were stronger, because on Pod Markaru they had to feed mainly on tough and fibrous plants, and not insects, as before. Due to changes in the diet of animals, a new structure has also appeared in the gastrointestinal tract - the ileocecal valve, which forms a kind of fermentation chambers in the intestine, in which microbes break down difficult-to-digest pieces of plant food.
Island life makes you smarter
In general, island animals, as a rule, are of more interest to scientists than their mainland cousins - on islands, evolution is faster. Large animals, once in isolation, become smaller, small ones, on the contrary, become huge, and sometimes in a very short time.
Life on the islands sometimes gives quite unexpected advantages. As an international group of scientists found out, after analyzing data on the brain size of eleven and a half thousand birds belonging to 1931 species, the brain of island birds is larger than that of continental relatives, and this is the result of evolution.
The New Caledonian Raven makes "currency" for the vending machine. Photo: Jelbert et al. / Scientific Reports 2018.
Living conditions on the islands are less predictable, and if the situation worsens, it is more difficult to move to another place than on the continent. Therefore, a large brain capable of more complex adaptive behavior is an evolutionary advantage. These findings support observations of the New Caledonian raven (Corvus moneduloides), which is able to use tools and recreate them from memory, and the woodpecker tree finch (Camarhynchus pallidus), which can use tools and even process them.
Mice that cannot be poisoned
Unfavorable living conditions force continental animals to evolve rapidly. This happened with ordinary house mice. Since the 1950s, they were poisoned with warfarin poison - some individuals resistant to this pesticide were found already in 1964, and by 2011 scientists described a population of house mice (Mus musculus domesticus), on which warfarin does not act at all.
Such a quick adaptation (60-70 years is nothing by the standards of evolution) was due to the incredibly fast reproduction of these rodents. As German researchers point out, resistance to poison is the result of a mutation in the vkorc1 gene, which is present in the genomes of all mammals and is responsible for the work of vitamin K.
The constant attempts of a person to destroy certain pests and parasites, as a rule, go sideways. It was the desire to defeat deadly infections that led to the emergence of antibiotic-resistant superbugs, and the desire to protect plants from insects led to the spread of pesticide-resistant animals. Over the past half century, more than two and a half cases of adaptation of insect pests to various poisons have been recorded.
Alfiya Enikeeva