Sympathetic speciation

Species genesis in the area of ​​origin

The emergence of a new species in the area of ​​origin is called sympatric speciation. This type of speciation requires direct reproductive isolation, for example by polyploidization of plant species, so that the plant will no longer have allele exchange with the rest of the population.

In rare cases it can also lead to a sympatric speciation without polyploidization. Two species of fish from a crater lake in Central Africa, in which there was definitely no geographical separation, developed from a source species. It is assumed that a strong selection pressure was responsible for the species splitting.

In the sympatric speciation by polyploidization one differentiates between two variants:

 Allopolyploidization: After a crossing of two different species that were barren usually occurs by doubling the chromosomes to a polyploid plant with an even number of chromosomes (as tetraploid = four sets of chromosomes). As a result, the plant is genetically isolated from the previous diploid species and fertile on the other hand.

 Autopolyploidization: The duplication of the chromosomes is done by the plant itself and not by species crossing. Reasons can e.g. Mistake during meiosis.

Schematic example of sympatric speciation

1. Two different flowers exist side by side.

2. Both flowers have propagated with each other. From this infertile flowers have arisen, which have propagated only through asexual reproduction.

3. By random allopolyploidization, the number of chromosomes has doubled and the plant can reproduce sexually. From now on it exists as a third species next to the two original flower species.

Summary

Sympatric speciation describes the emergence of species in the area of ​​origin.

This form of speciation can be observed especially in plant species. In mammals, polyploidization would usually lead to infertility or be lethal to the organism.