What is rapid evolution in Biology?

Evolution, from a contemporary point of view, is an issue that brings zoologists, geneticists and phylogeny specialists to their heads. It is clear that planet Earth is in a period of profound change and, therefore, the rates of genotypic variability and The phenotypic pattern of the species is no longer circumscribed to the traditionally postulated theoretical parameters, at least to some extent. spot.

For example, perhaps many do not know that, today, as these lines are being written, we are in the midst of the sixth mass extinction (or anthropocene extinction). The current extinction rate is between 100 and 1,000 times higher than what would be expected in a natural environment and, therefore, it is not we are surprised to learn that one in every 8 birds, one in every 4 mammals and one in every 3 amphibians are in danger of extinction. Plants are not far behind, as 70% of all of them are at risk.

With these preliminary data we want to demonstrate a reality: fast evolving processes that respond to environmental variations could be essential for the permanence of certain taxa over time in such a changing and unstable world. If you want to know all the secrets behind this little-explored concept, keep reading.

• Related article: "The theory of biological evolution: what it is and what it explains"

What is biological evolution?

Laying the foundations of evolutionary mechanisms is the first step to adequately explore the subject that concerns us here. In a simple way, evolution can be defined as the set of changes in genetic characters (included in the genome) and phenotypic (the expression of said genome) of the biological populations through the generations. There are two broad types of evolution: divergent and convergent.

Divergent evolution is one in which a species, over time, separates into two different. This type of adaptive process is included in the term "speciation", where the living beings of the same population acquire different traits before different challenges, whether due to physical, physiological or chromosomal barriers (among many others) until they become different species that cannot reproduce with each other Yeah.

On the other hand, a species can also appear where there was another, without the need for two populations to separate. Simply, the genetic changes of a specific taxon can become enough for us to say that one species has evolved into another.

In convergent evolution, two (or more) different species acquire similar traits because they have been subjected to similar evolutionary pressures.. For example, the bodies of a whale and a fish have comparable features with functions analogous (swimming and predating underwater), but their evolutionary history and ancestry are completely different.

Finally, it is necessary to note that the most powerful mechanism when describing the evolution of species is selection. natural, that "force" that promotes the permanence of the fittest and causes the least viable to end up disappearing from the "pool" genetic. Even so, this is not the only one: processes such as genetic drift cause the loss and variation of genes in populations, although these are random and do not respond to the biological fitness of beings alive.

• You may be interested in: "Charles Darwin: biography of this famous English naturalist"

What do we mean by "rapid evolution"?

Fitting rapid evolution into the current definition of evolution is extremely complex, since it is assumed that Genetic changes in animal species (not so much in viruses and bacteria) occur slowly, over thousands of years. years.

The term "rapid evolution" is used in scientific publications to describe the changes in allele frequencies (gene variations) within a specific population within a few generations. These changes within the same species can arise from the appearance of new genotypes (mutations), gene flow between populations or genetic mixtures between individuals and/or species.

Some authors postulate that rapid evolution must imply a change in the ecological trajectory of the populations that experience it, that is, In other words, it must be translated into a series of tangible observations that demonstrate that the living being has "varied", simplifying the language by maximum. Meanwhile, other researchers argue that this need not be the case: sometimes rapid evolution may occur to maintain the status quo of a population in the ecosystem in which it proliferates, without having to produce ethological changes or in its trophic chain, for example.

The race of populations against extinction

The potential for local adaptation by a population (and hence its potential for rapid evolution) depends on several factors. Among them, we find the following:

• The local selection force, that is, the environmental changes and challenges that the given population must face.
• The number of variable genes within the analyzed population.
• The population size, because the larger it is, the more it can deal with random processes such as genetic drift.

So, we see that an accelerated rate of evolution depends both on the environment and on the intrinsic characteristics of the analyzed species. For example, if we look at a taxon that has hardly changed in the last 1,000 years and that exhibits genetic variability extremely small, we find it hard to imagine that it could suddenly accumulate tangible genotypic changes in a few generations.

In addition to this, it should be noted that there are accelerated growth regions of DNA (ARs) in many animal species, that is, they suffer much faster mutation rates than expected. One might imagine that the higher the proportion of ARs, the more likely rapid evolution would be, but again, at this point we can only speculate.

Darwin's finches: a book example

Talking about rapid evolution today is, in many cases, being untrue, since even if it occurs in a shorter time window than normal evolutionary processes, it is still too wide an interval for one (or several) studies to cover it.

On the other hand, there are examples that demonstrate to a certain extent the ideas postulated here. A clear event that shows this is that of one of Darwin's finches (inhabitant of the Galapagos Islands) which, according to one study, decreased its average bill size in 22 years due to the introduction of another competing species.

It turns out that finches with larger beaks were introduced into their habitat and, therefore, displaced to the original large-beaked finches by being more effective at destroying hard seeds. So that, birds with smaller beaks that exploited a niche were increasingly prospering (the smallest seeds) where there were no competitors. For this reason, little by little the proportion of individuals in the original population with small peaks increased.

final considerations

Do not believe everything you see in certain media. Arguing the presence of a rapid evolutionary process is extremely complex, since it does not happen in one or two generations. There are many factors that must be taken into account and, therefore, we ask you the following questions: did the favored character in the population already exist before the supposed "rapid evolution"? Has it been fixed over time or is it a sporadic observation? Is the variation significant?

For example, some media argue that certain species have "learned" to metabolize the poison of a species introduced into their habitat in a few years. Fascinating, right? We dare to say that this is practically impossible. It is one thing for mutations to exist in a population that alter the composition of a toxin and the individuals who present it are favored, and another different that this character appears from the nothing in response to a given selective pressure. If rapid evolution were so simple and efficient, how come almost 150 species go extinct every 24 hours?

Summary

In these last lines we have not tried, far from it, to dismiss the concept of rapid evolution. What is necessary is a critical and analytical perspective. Evolution, in all cases, is a slow process that requires fixation of characters over time. We simply cannot know if a population trend is sporadic or definitive until many years later. of its documentation and, therefore, demonstrating rapid evolution in complex beings is a real headache. head.

Bibliographic references:

• Ferris, E., Abegglen, L. M., Schiffman, J. D., & Gregg, C. (2018). Accelerated evolution in distinctive species reveals candidate elements for clinically relevant traits, including mutation and cancer resistance. Cell reports, 22(10), 2742-2755.
• Maron, J. L., Vilà, M., Bommarco, R., Elmendorf, S., & Beardsley, P. (2004). Rapid evolution of an invasive plant. Ecological Monographs, 74(2), 261-280.
• Thomson, J. no. (1998). Rapid evolution as an ecological process. Trends in ecology & evolution, 13(8), 329-332.
• Yoshida, T., Jones, L. E., Ellner, S. P., Fusmann, G. F., & Hairston, N. g. (2003). Rapid evolution drives ecological dynamics in a predator–prey system. Nature, 424(6946), 303-306.