Speciation: what is it and how does it develop in biological evolution?

These are the characteristics of speciation, a phenomenon studied by biology.

From a Biological point of view, speciation is a process by which a certain species gives rise to another species or other species.

We must bear in mind that this process has been active for 3.8 billion years, and therefore, it is not surprising that scientists estimate that there are almost 8 million animal species on our planet. Until 2014, according to bibliographic sources, humans had only described 1,426,337 of all these animals, so as far as biodiversity is concerned we have only scratched the tip of the iceberg.

Any evolutionary biologist will surely affirm that speciation is a fascinating process, to say the least.And no wonder, for time acts as the engine of change under our very eyes. If you want to know more about this fascinating evolutionary mechanism, we encourage you to read on.

Speciation: life generates life

To understand this concept in its entirety, it is first necessary to delimit what a species is. In order not to enter fully into a basic biology lesson, we will limit ourselves to say that A species is a group of natural populations whose individuals can interbreed and produce fertile offspring..

No matter how great the phenotypic resemblance (i.e., morphological characteristics) between two living beings, if they cannot produce offspring or are all sterile, we must assume that they are different species. This is the case of the mule, for example, a hybrid between a mare and a donkey that is sterile.

If we take a more evolutionary approach to the concept, we will see that species are groups of organisms that are reproductively homogeneous but by no means watertight. Animals interact with the environment in a given time and space, and therefore undergo multiple modifications throughout their history.

Nowadays, more and more species are emerging from what used to be considered a single species.. For example, it turns out that the giant salamander Andrias davidianus Andrias davidianus is not just one species, but comprises at least three different ones. This discovery was made in 2019, does this mean that we have observed a speciation process in less than 100 years, between its description and differentiation?

Sad as it sounds, no, evolution does not go that fast in the vast majority of cases.. Every day we have more sophisticated genetic tools, which allow us to differentiate between animal groups at the molecular level beyond their physical appearance and ecology.

Thus, speciation is known as the process process by which a population of a particular species gives rise to one or more other different species, which will accumulateThese will accumulate genetic differences between them over time until they can be considered different. There are two meanings for this term:

• Phyletic evolution or anagenesis, when an entire species gradually changes over time (one ancestor, one descendant).
• Evolution by cladogenesis, where an ancestral lineage splits into several siblings that evolve independently (one ancestor, several descendants).

Now that we have described what a species is and why so many species have arisen in recent times, it is time to answer all the questions about speciation. The first one? Well, how it is produced, of course.

Mechanisms

Geographical isolation plays an essential role in many processes of speciation.The lack of physical contact between animals promotes overcrossing between separate populations that become more and more genetically isolated. However, it is not the only one. Below, we present the various mechanisms of this process.

1. Allopatric

Let us turn to the etymological root of the word to understand the process we are facing. "Alo" means "on the other side" and "pátrica" means homeland. If the homeland is on the other side, then we are talking about a species that separates geographically.

When a natural event occurs (e.g., a rise in sea level) that separates the same population permanently, the effects of independent mutations and natural selection on the resultant ones will give rise to variations that will end up differentiating them completely.

These effects are much more noticeable if one of the populations is in an environment with new demands compared to the previous habitat. For example, if on one side of the uncrossable river there are only birds available as prey and on the other side there are only mice, it is clear that the individuals of the population that are best adapted to hunting their prey will be selected.

It is important to note that the evolution of living beings is not a thinking mechanism: mutations are random, random, random and random.Mutations are random, some good and some bad. It is those that generate an evolutionary advantage that end up being fixed in the population, because the individuals that present them are more successful and give rise to offspring, allowing them to be inherited.

2. Peripatric

"Peri" means "around", and patric, "homeland". Thus, in this process of speciation we are faced with a population that differs from another population at the periphery of its area of distribution. These processes are often associated with dispersal and colonization. For example, if a central population of a species monopolizes all the resources of the environment, it is natural to think that certain individuals may occupy adjacent areas so as not to compete directly with their congeners.

Depending on the geographical distance and the new demands of this environment, the two populations may become sufficiently different genetically to no longer be considered the same species after many years.

3. Sympatric

"Sim" means union. In this case, we are dealing with populations that differentiate until they achieve evolutionary independence in the same geographical space. This is usually associated with the exploitation of different ecological niches within the same environment.which promotes the development of reproductive isolation mechanisms. Let's take an example:

If it turns out that within a population of bats the less fit ones are not able to hunt insects at night as their more prepared conspecifics take away all their food, it is theoretically possible that they will seek the exploitation of new niches. If they start living during the day and hunting at this time, they will naturally only interact with each other and reproduce during the day while the rest live at night.

This behavioral barrier, in the long run, would be a mechanism of evolutionary isolation.. Diurnal and nocturnal bats would only interact among those that share their habits, developing more and more independently of the environment they dominate.

4. Parapatric

"For", together. In this case, the following occurs speciation in populations that share a geographic area with a continuous distribution in space. It is a relatively intermediate point between the concepts mentioned above, since gene flow between populations is better than in the sympatric variant but greater than in the allopatric variant.

This is a relatively conflicting term, since the empirical evidence of this process can be somewhat ambiguous. Therefore, we will not dwell on it.

A question of space, or not?

As we have said before and as we have seen in these lines, geographic isolation is an essential promoter of differentiation between populations, but not the only one.:

• Ecological isolation: needs for different lighting, humidity and other variants within the same ecosystem.
• Ethological isolation: behavioral differences that act as a barrier to interaction.
• Sexual isolation: when variations occur in the reproductive organs or in the morphology of the gametes.
• Genetic isolation: chromosomal variations that produce sterility or lack of viability of hybrids.

Thus, not everything depends on a geographical barrier, not everything depends on a geographical barrier. The simple fact that a certain sector of the population of a species develops an arbitrary hostile behavior towards others of its species can theoretically already represent a barrier large enough to cause a decrease in gene flow, which promotes differentiation into different species.

Conclusions

As we have shown you, speciation is a fascinating process that has produced the immense biodiversity that can be found on planet Earth today. Divergence is a common process in the natural world, as the environment is changing and different adaptations are required in the face of new challenges.

In the face of change, survival takes precedence over any previous kinship relationship. Living beings have only one goal in life: to continue their genetic lineage, and they will do everything possible to reproduce before they die, even if this means isolating themselves from the rest of their relatives permanently.

Bibliographical references:

• Speciation, Universidad Complutense de Madrid. Retrieved August 18 from https://www.ucm.es/data/cont/media/www/pag-56185/26e-Gen%C3%A9tica%20Evolutiva.-Especiaci%C3%B3n.pdf.
• Evolución filética, todosobrelaevolución.org. Retrieved on August 18 from http://todosobrelaevolucion.org.mx/capsula.php?id=641
• Types of speciation, understandingevolution, Berkeley. Retrieved August 18 from https://evolution.berkeley.edu/evolibrary/article/side_0_0/speciationmodes_01_sp
• Turvey, S. T., Marr, M. M., Barnes, I., Brace, S., Tapley, B., Murphy, R. W., ... & Cunningham, A. A. (2019). Historical museum collections clarify the evolutionary history of cry](http://)ptic species radiation in the world's largest amphibians. Ecology and evolution, 9(18), 10070-10084.