Speciation: What It Is And How It Develops In Biological Evolution
From a biological point of view, speciation is a process by which a certain species gives rise to another or other species.
We must keep in mind that this process has been active for 3.8 billion years, and therefore, it is not a surprise 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 when it comes to biodiversity we have only scratched the tip of the iceberg.
Any evolutionary biologist will confidently affirm that speciation is a fascinating process to say the least, and it is no wonder, since time acts as an engine of change under our own eyes. If you want to know more about this fascinating evolutionary mechanism, we encourage you to continue reading.
To understand this concept in its entirety, it is necessary to first define what a species is. In order not to go completely into a basic biology lesson, we will limit ourselves to saying that A species is a group of natural populations whose individuals can interbreed with each other and produce fertile offspring
No matter how great the phenotypic similarity (that is, the morphological characteristics) between two living beings, if they cannot give rise to descendants or they 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 give the concept a more evolutionary prism, we will see that species are groups of reproductively homogeneous organisms but in no case watertight. Animals interact with the environment in a given time and space, which is why they undergo multiple modifications throughout their history.
Nowadays, more and more species are emerging from what was previously considered a single species For example, it turns out that the giant salamander Andrias davidianus It is not just one species, but includes 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?
As sad as it sounds, no, evolution does not go so fast in the vast majority of cases Every day we have more sophisticated genetic instruments, which allow us to differentiate between animal groups at a molecular level beyond their physical appearance and ecology.
Thus, it is known as speciation. process by which a population of a specific species gives rise to another or different ones, which will accumulate genetic differences between them over time until they can be considered different. There are two meanings for this term:
Once we have described what a species is and why so many have emerged in recent times, it is time to answer all the doubts regarding speciation. The first of them? Well, how it is produced, of course.
Mechanisms
Geographic isolation plays an essential role in many speciation processes, since the lack of physical contact between animals promotes overcrossing between separate populations that are increasingly genetically isolated. Still, he is not the only one. Below, we present the various mechanisms of this process.
1. Allopatric
Let’s turn to the etymological root of the word to understand the process we are facing. “Alo” means “to the other side” and “patrica”, homeland. If the homeland is on the other side, then we will be talking about a species that is geographically separated.
When a natural event occurs (for example, a rise in sea level) that permanently separates the same population, the effects of independent mutations and natural selection on the resulting ones will give rise to variations that will end up differentiating them completely.
These effects are much more notable 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 impossible-to-cross river there are only birds available as prey and on the other side there are mice, it is clear that the individuals from 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, some good and some bad. They are those that generate an evolutionary advantage that end up becoming established in the population, since the individuals that present them are more successful and give rise to offspring, allowing them to be inherited.
2. Peripatric
“Peri” means “around”, and patrica, “homeland”. Thus, in this speciation process we are faced with a population that differs from another at the periphery of its range These processes are associated, in many cases, with dispersal and colonization. For example, if a central population of a species monopolizes all the resources in the environment, it is natural to think that certain individuals may occupy adjacent areas so as not to compete directly with their conspecifics.
Depending on the geographical distance and the new demands of this environment, the two populations can become genetically differentiated enough to not 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 It 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 least fit are not able to hunt insects at night because their more prepared congeners take away all their food, theoretically it is possible that they seek to exploit new niches. If they begin to live by day and hunt at this time, naturally, they will only interact with each other and reproduce during the day while the rest live at night.
This behavioral barrier, in the long run, would represent an evolutionary isolation mechanism Daytime and nocturnal bats would only interact among those that share their habits, developing increasingly independently of the environment they dominate.
“Stop,” together. In this case, it occurs a speciation in populations that share a geographic area with continuous distribution in space It represents a relatively intermediate point between the concepts mentioned above, since the gene flow between populations is better than in the sympatric variant but greater than in the allopatric variant.
We are facing a relatively conflictive term, since the empirical evidence of this process can be somewhat ambiguous. Therefore, we are not going to dwell on it any longer.
A question of space, isn’t it?
As we have said previously and we have been able to see in these lines, Geographic isolation is an essential promoter of differentiation between populations, but not the only one:
So that, not everything depends on a geographical barrier The simple fact that a certain sector of the population of a species develops 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 through which the immense biodiversity that can be found on planet Earth today has been produced. Divergence is a common process in the natural world, since the environment is changing and different adaptations are required to face new challenges.
In the face of changes, 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.
