Speciation

Speciation

The process by which new species form when populations become reproductively isolated and can no longer interbreed

Main causes of speciation

Geographic isolation, genetic mutations, natural selection, sexual selection, and changes in chromosome number (polyploidy)

Allopatric speciation

Speciation that occurs when populations are physically separated by a geographic barrier

Key features of allopatric speciation

Geographic barrier forms, gene flow stops, populations evolve independently, reproductive isolation develops over time

Examples of geographic barriers

Mountains, rivers, oceans, glaciers

Sympatric speciation

Speciation that occurs without geographic separation, within the same area

Causes of sympatric speciation

Polyploidy (common in plants), different mating behaviors, sexual selection, and niche specialization

Why sympatric speciation can occur in the same area

Reproductive isolation develops even though populations live together

Abrupt speciation

Speciation that happens suddenly, usually in one generation

Key features of abrupt speciation

Most common in plants, caused by polyploidy, new species is immediately reproductively isolated

Autopolyploidy

A form of abrupt speciation where an organism has extra chromosome sets from the same species

Key features of autopolyploidy

Chromosome number doubles within one species due to meiosis errors; organism cannot breed with original diploid parent

Allopolyploidy

A form of abrupt speciation where an organism has chromosome sets from two different species

Key features of allopolyploidy

Two species hybridize, chromosome doubling restores fertility, new species has a different chromosome number and cannot interbreed with either parent species