Speciation

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SPECIATION defined as the creation of two or more new species from one ancestral species.

Allopatric speciation

most common type of speciation

involves geographical isolation

gene flow is interrupted when population is divided into geographically isolated subpopulations

isolation might occur because of great distance, etc.

Sympatric speciation

no geographical isolation

emergence of a reproductive barrier isolates a subset of the population

gene flow may be reduced by such factors: polyploidy, habit differentiation, and sexual selection

i.e.: Northern Spotted Owl and Mexican Spotted Owl

Terms

Geographical isolation defined as when the ancestral species are separated geographically and thus, over time, cannot interbreed anymore.

Hybrid zones

may be formed when allopatric populations come back into contact with one another

region in which members of different species meet and mate, and maybe produce offspring of mixed ancestry

has three possible consequences:

Reinforcement

cannot interbreed

most common

Fusion

can interbreed and produce offspring

can form new species

offspring cannot interbreed with parent species

Stability

can interbreed and produce offspring

can form new species

offspring can interbreed with either of the parent species

Macroevolution

evolutionary patterns on a larger scale

patterns:

Stasis

i.e. coelacanth

Mass extinction

i.e. mammoth

Adaptive Radiation

i.e. Pundamilia

Coevolution

i.e. blue butterfly