Sympatric population occupies one habitat, where organisms interbreed. Thus there is no physical barrier working to separate sub-populations. As long as random interbreeding between all members continue, sympatric speciation will not occur.
Speciation in sympatric population is rare and may occur by different means: e.g.
• Habitat selection- This includes separation and mate choice preference, ultimately leading to establishment of separate sub-populations (=demes). When gene flow between these demes completely stop, speciation is achieved. This is seen in many marine fauna.
(NEXT TO THE PHOTO)Instantaneous genetic isolation- This is very common in plants due to appearance of polyploidy, etc. due to abnormal meiosis. Chromosome doubling in accidentally generated flora immediately establishes a new species in same habitat.
