Why is evolution going faster on the islands?

Why is evolution going faster on the islands?
Why is evolution going faster on the islands?
Anonim

Why is evolution going faster on the islands? This question is answered by biologist Alexander Markov.

Island

Everyone knows that the flora and fauna of the islands is often very, very different from that on the continent. And the example of the hobbits, degraded on the wonderful island of Flores to an almost bestial state, is quite indicative. (Recall that the Floresian man, the so-called hobbit, came to the Indonesian island of Flores about 95 thousand years ago and lived there up to 12 thousand years ago, degrading in the conditions of a warm and fertile island to the level of Australopithecus with a brain volume of only 400 square meters. cm).

“Ever since the time of Darwin, who studied the Galapagos finches, remote islands have been considered a kind of“evolutionary laboratories”in which species undergo rapid and sometimes very sophisticated evolutionary changes,” writes Alexander Markov in his book The Birth of Complexity. Evolutionary biology today: unexpected discoveries and new questions."

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Thus, large animals, once on such an isolated island with depleted vegetation, often shrink, small ones, on the contrary, become giants. Moreover, in a very short time. At least this is the case with many species.

In 2006, Virginia Millien of McGill University, Canada, conducted a study comparing data from 86 island and 84 inland mammalian populations. For each of them, the rate of evolutionary changes in one or more dimensional traits was calculated over a certain time period.

Millienne concluded that morphological evolution on the islands is indeed progressing faster. However, this is noticeable only at intervals of less than 45 thousand years. With an increase in the time period, the differences between populations on the mainland and islands become statistically insignificant.

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Such differences cannot be explained by the fact that some animals are found more often on the islands than on the mainland, and vice versa. “It turned out that the rate of evolution is not 'phylogenetically conservative,'” Markov writes. "For example, species that evolved more slowly on a continent will not necessarily continue to behave similarly on an isolated island."

According to the author, mammals that find themselves in the conditions of an isolated island very quickly adapt to them, and this sometimes leads to serious changes in the size and proportions of the animal's body. Due to the high "speed" of these transformations, scientists fail to detect transitional forms between island endemics and their continental ancestors. However, after the changes have taken place, the rate of evolution of island animals usually slows down - in this regard, it was not possible to identify differences between the rates of evolution over an interval of more than 45 thousand years.

The so-called fragmentation of natural habitats (through the fault of humans as well) can lead to the fact that animals find themselves in conditions similar to those of an isolated island. In this case, one should also expect rapid changes in the “island” scenario. This has happened, for example, with 25 mammalian species in Denmark, whose bodies have evolved dramatically over the past 200 years.

“The rate of evolution can increase threefold or more in just a couple of decades. It turns out that under the conditions of the growing anthropogenic load on natural ecosystems, many animals familiar to us can begin to change in the most unexpected and rapid way,”sums up Markov.

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