Sympatric Speciation

Date: 2015-10-07; view: 475.

Allopatric Speciation

There are two kind of speciation: Allopatric Speciation and Sympatric Speciation.

Speciation

As populations diverge, they form similar but related species. When are two populations new species? When populations no longer interbreed they are thought to be separate species. As natural selection adapts populations occupying different environments, they will diverge into races, subspecies, and finally separate species.

A species can be defined as one or more populations of interbreeding organisms that are reproductively isolated in nature from all other organisms. Genetic divergence results when adaptation, drift and mutation act on populations. Barriers to gene flow between populations isolate those populations, ultimately leading to the formation of new and separate species.

Populations begin to diverge when gene flow between them is restricted. Geographic isolation is often the first step in allopatric speciation. Other mechanisms may develop that further restrict reproduction between populations: these are the reproductive isolating mechanisms.

Sympatric speciation happens when members of a population develop some genetic difference that prevents them from reproducing with the parent type. This mechanism is best understood in plants, where failure to reduce chromosome number results in polyploid plants that reproduce successfully only with other polyploids. Reproduction with their parent population (the diploids) produces sterile offspring.