At speciations can be understood as processes that lead to the formation of new species. They occur due to differences arising in the genome of different populations of the same species that caused the reproductive isolation and, consequently, the appearance of two species many different. Reproductive isolation is the inability of individuals to exchange genes through mating.
We can divide speciation into three basic types, considering geographic aspects: allopatric speciation, sympatric speciation and parapatric speciation.
THE allopatric speciation, happens when two populations of a species are separated by a geographic barrier. This geographic barrier, which can be a mountain, a desert or a forest, for example, causes a spatial separation (allopatry). In this case, we say that a geographic isolation occurred.
When these populations separate, they may experience different pressures as they are in different areas. These pressures, over time, cause a genetic divergence and, consequently, a possible reproductive isolation. Many consider this type of speciation to be the main model of speciation.
The founder effect is a special kind of allopatric speciation. In this process, a small part of a large population migrates out of the original population environments. The small population is generally driven to extinction. However, when small populations are successful, they are driven to faster speciation, mainly due to genetic drift.
Evidence of allopatric speciation can be seen on islands, where a species ends up differing in appearance and ecology. The most classic example are the finches observed by Darwin in the Galapagos Islands, which differ mainly by the shape of the nozzle, which is adapted to the type of feeding of each of the 14 species.
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THE sympatric speciation it is the one that occurs without geographic separation. In this case, two populations of the same species live in the same area, but there is no cross between populations. It is common to observe that some genetic modification prevented this interbreeding, thus generating differences that will lead to speciation. It is one of the rarest speciations.
Sympatric speciation is believed to be responsible for the large number of cichlid fish species found in African Lake Victoria. According to some researchers, the lake was colonized by only one ancestral species.
There is still the parapatric speciation, which occurs when two populations of the same species differ and occupy contiguous but ecologically distinct areas. Because they are in contact areas, interbreeding is possible, which ends up generating hybrids. These areas are called the hybrid zone and end up becoming a barrier to gene flow between the species that are forming.
We can cite as an example of parapatric speciation the case of grass Antoxanthum. Part of this species differentiated itself thanks to the presence of metals in the soil, starting to flower at a different time, which made it impossible to cross with the original population.
by Vanessa dos Santos
Graduated in Biology
Would you like to reference this text in a school or academic work? Look:
SANTOS, Vanessa Sardinha dos. "Speciation"; Brazil School. Available in: https://brasilescola.uol.com.br/biologia/especiacao.htm. Accessed on June 27, 2021.
