What are sources of variation within a species?
The possibility of continued evolution is critically dependent on renewed variation.
For a given population , there are three sources of variation :
- Immigration of genes.
Mutation rates are so low that mutation alone cannot account for the rapid evolution of population and species.
However, recombination by itself does not produce variation, and immigration cannot provide variation if entire species is homozygous. Ultimately the source of all variations must be mutation.
The creation of genetic variation by recombination can be a faster process than its creation by mutation.
However asexual organisms like bacteria , that seldom undergo sexual recombination do not have this source of variation.
Immigration of genes
Another source of variation is migration into a population from other populations with different gene frequencies. Migration means any form of the introduction of genes from one population to another.
The resulting mixed population will have an allele frequency that is somewhere intermediate between its original value and the frequency in the donor population.
Unlike mutation rate , migration rate can be large, so the change in frequency may be substantial.