Speciation – All about the topic

All mammals descend from a common ancestor. Going even further back in evolutionary history, according to the synthetic theory of evolution, all living creatures descended from a common ancestor. How is that possible? In the course of evolution, species split into two or more species. This process is called speciation or speciation.

There are several ways in which speciation can occur. Usually lead isolation mechanisms lead to subpopulations evolving independently and splitting into two species.

speciation definition

The process of speciation is a fundamental theme of evolution. The splitting of species into several species is responsible for the huge biodiversity on our planet.

speciation, also speciation, describes the splitting of a species into two or more species. Isolation mechanisms ensure genetic barriers between populations of a species. If the isolated populations develop divergently, species splitting and thus speciation can occur.

Basic speciation terms

Before you get a detailed insight into the different forms of speciation and their mechanisms, you will get to know the most important terms on this topic here.

kind

Of the biological species concept refers to a group of organisms which, in shape, behavior and physiology, agree insofar as they can be distinguished from other groups of organisms. Individuals of a species are capable of producing potentially fertile offspring. There is gene exchange between populations of a species (gene flow). This is possible because their gene pools are very similar.

population

One population is a group of individuals of the same species or race living in a specific geographic area, interbreeding through generations and linked genetically.

subpopulation

Subpopulations are groups of individuals in a population who, because of their way of life, are in closer reproductive exchange. A population can consist of several subpopulations.

races

races are populations of the same species. They differ in a few or more characteristics that are heritable. Breeds of the same species can produce fertile offspring. Races arise from the isolation of individual populations. The exchange of genes between the populations is thus restricted and the gene pools of the populations develop independently of one another.

gene pool

Of the gene pool is all the genetic material of a sexually reproducing organism. It is influenced by factors such as mutation, recombination, gene drift, horizontal gene transfer through gene flow, reproductive isolation and selection.

gene flow

gene flow refers to the genetic exchange between two populations. Individuals introduce their genes into another population by migrating, thereby contributing to mixing and gene diversity.

isolation

Populations are isolated from each other when exchange of genetic material is not possible or does not occur.

Speciation concept

Various mechanisms can cause one species to split into two or more species. The basic concept of speciation is always the same.

Isolation mechanisms mean that subpopulations of a species are genetically isolated from one another. This means that gene flow between the subpopulations is no longer possible.

Now, evolutionary factors lead to the gene pools of the subpopulations developing divergently independently of one another. Random mutations play a role here, but changing environmental conditions and the resulting selection pressure also have a significant influence on changes in the gene pool. Mutation and selection are among the most important evolutionary factors in speciation.

mutations are permanent changes in the genetic material of an organism that can be inherited. They occur spontaneously or they can be caused by mutagens.

Of the selection pressure describes the effect of a specific selection factor on a population of a species. selection factors are environmental factors that affect the survival of a population in a given environment and favor certain traits of the species.

Mutations and selection pressure combine to ensure that populations develop divergently.

If the subpopulations have been genetically isolated from each other for a long enough time, this can lead to the gene pools being very different and successful reproduction between the individuals in the subpopulations being no longer possible. The subpopulations are now reproductively isolated and the original population has split into two species.

speciation processes

The described isolation between subpopulations can be based on different processes. Depending on the way in which subpopulations are isolated from one another and then split up into different species, a distinction is made between different speciation processes.

Basically, between allopatric speciation, sympatric speciation and parapatric speciation distinguished. There is also the process of adaptive radiation, which describes a splitting of a species into several species. In the following section, the individual forms of speciation are briefly explained.

allopatric speciation

One possible cause of isolation is the spatial separation of populations (geographical isolation). If a new species arises due to the spatial separation, one speaks of allopatric speciation (Species through geographic isolation). Allopatric speciation leads to the formation of new plant and animal species.

Geographical isolation is the basic requirement for allopatric speciation. There are several processes that can lead to geographic isolation. These include the founding principle, geological events and climatic events.

In the article on allopatric speciation you will get to know the individual isolation processes and can learn more about the process of allopatric speciation.

Process of allopatric speciation (example)

A population of snails lives in a certain area (1). Due to geological events, these are separated into two groups, which are geologically isolated from each other. From a population arise 2 subpopulations (2). Both populations live independently of each other.

Mutations that occur in one population are not transmitted to the other population because there is no gene flow between populations is possible (3).

The populations are subject to different selection pressures due to different environmental conditions. The gene pools of the populations evolve independently of each other. Mutations contribute to divergent development.

In this case the mutations are represented by different colors of the shells (4). After a longer period of time, there are two populations with different gene pools and different characteristics. Should the barrier between the populations be overcome at some point, the snails will no longer be able to mate with each other (5).

Figure 3: Schematic representation of the example

Sympatric Speciation

Sympatric speciation is opposed to allopatric speciation. It describes the emergence of new species within a common distribution area. In sympatric speciation, species are separated by different reproductive isolation mechanisms.

Certain isolation mechanisms can prevent gene flow between populations, even if they are in the same range.

The following reproductive isolation mechanisms can lead to subpopulations within a distribution area being genetically isolated from one another.

You can find more detailed information on sympatric speciation and the corresponding isolation mechanisms in a separate article.

Ethological isolation (behavioural isolation)

Ethological isolation is the isolation of species due to behaviors usually manifested as differential mating behavior. If, for example, the courtship song changes, the mating partners no longer react to the courtship call, which is now unfamiliar.

The Warbler (Winger Willow Warbler) and Willow Warbler (Chiffchaff) look almost similar, but are distinct species due to different sound patterns in their courtship songs. A bird species has calls or other courtship displays that differ from those of other bird species.

This type of isolation is linked to the behavior of individuals. Different behavior patterns can lead to isolation. This can include different behavior when looking for a partner.

Temporal isolation

Species that are closely related can be sexually active at different times. There is a different timing of egg maturation, which has to be fertilized at a certain point in time. The time when individuals mate differs from species to species and mating usually does not take place. The same principle applies to plants and their flowering times.

The Lesser Black-backed Gull’s mating and nesting period is three weeks later than that of the Herring Gull.

mechanical isolation

if body features are different between species, then mating between individuals of the different species is not possible. This prevents sexual reproduction.

The mating organs of males and females of a species in insects, spiders and centipedes fit together like a key and lock, so that copulation is only possible in pairs of the same species.

polyploidy

the polyploidization represents a type of genetic isolation. Genome mutation leads to polyploidization of plants. Here the complete set of chromosomes is multiplied. In the meiosis the reduction division fails. Thus, the germ cells are diploid (2n) rather than haploid (1n). Self-fertilization produces offspring with a tetraploid set of chromosomes (4n). Crossing with diploid plants of the parent species is possible, but results in triploid offspring (3n) that cannot produce offspring.

As a rule, polyploidy in mammals is fatal or leads to infertility.

ecological isolation

the ecological isolation refers to the occupation of different ecological niches in the same habitat. For example, food shortages in a habitat can lead to a subpopulation specializing in a different food source and thereby isolating itself from the original population.

The occupation of different biological niches can lead to the independent and divergent development of the gene pools of subpopulations. By changing the gene pools, it can lead to sympatric speciation come.

The ecological niche (also biological niche) includes all biotic and abiotic environmental factors that are relevant to the way of life of the corresponding species or population.

adaptive radiation

The adaptive…