Sympatric speciation is an evolutionary process that occurs when brand new species evolve from one common ancestral species. The newly evolved species occupies the same geographical location that the common ancestor inhabited.
Sympatric speciation is one type of speciation that doesn’t occur very often. Other types of speciation include allopatric and parapatric speciation. Sympatric speciation refers to any type of speciation that doesn’t involve a large geographical area. Unlike the other two types, sympatric speciation occurs in one common geographical area. This type of evolution is thought to be a result of organisms living together in similar geographical areas and occupying similar niches. A niche is an organism's vector space of the area in which it can thrive and survive. Included in an organism’s niche are its food sources, its mates, and its home.
Biologists believe that when animals occupy similar niches they may evolve together and form a new species over time. When this occurs, it is known as sympatric speciation. Since the organisms occupy similar niches, it's easy for gene flow to occur between species. Over time, the two species will have similar genes and their offspring will be genetically similar as well. After many generations, an entirely new species will be born that is genetically different from the two parental species.