The low rate of evolution of new species is one of the main factors in the extinction of entire “branches” of the tree of life: as the characters in Lewis Carroll’s tale Through the Looking Glass must run to stay in the same place, so species must continue to evolve if they don’t want to disappear
The reduction in the generation rate of new species is as important a cause of extinction as others, and perhaps even more. This conclusion is reached by a research conducted by Tiago B. Quental, of the University of Sao Paulo, Brazil, and Charles R. Marshall, of the University of California at Berkeley, who signed an article published in “Science Express”.
According to the main current evolutionary models, extinction is substantially controlled by random processes, which allow – in the face of an environmental change – the manifestation of mutations more or less favorable to adaptation to the environment. This perspective is contrasted by the so-called “Red Queen” hypothesis, named after the character in Lewis Carroll’s story Through the Looking Glass, in whose world you have to run as fast as possible to be able to stay in the same place.
Translated into ecological terms this means that animal and plant species do not disappear due to unfortunate events in a normally static and unchanging environment, but that only by constantly evolving can they survive in a context that is constantly changing.
Quental and Marshall studied the fossil record of numerous species of land mammals belonging to 19 clades – the “branches” of the evolutionary tree of life – currently extinct or suffering from rapid decline, comparing real rates of origin and extinction of species and genera with those predicted by current models of evolutionary processes.
The researchers found that mammal diversity declined during the Cenozoic due to the asymmetry between high extinction rates and low generation rates.
of new species and genera. Notably, this imbalance has developed much faster than models in which extinction are controlled by random processes predict.
The impoverishment of the various clades therefore appears to be linked to the inability of species and genera to keep up evolutionarily with changing environmental conditions: “In essence, our data suggest that biological systems can never be in equilibrium, but that the different groups are always expanding and contracting as a result of persistent and, geologically speaking, rather rapid change, “Marshall said.
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