In: Biology
What role does neutral evolution/genetic drift play in speciation (in conjunction with barrier(s) to gene flow)?
Changes in allele frequency over time within a population is termed microevolution. Microevolution ultimately leads to new species or speciation. The factors that contribute to microevolution are mutation, natural selection, genetic drift & gene flow.
Genetic drift is a process which causes changes in allele frequency of a population changes over sampling error. Unlike natural selection which select beneficial alleles, genetic drift is neutral, ie, both harmful and /or beneficial alleles may increase in a population over the generations. The effects of genetic drifts are strong in case of a small population.
Eg : founder effect: When individuals of a population are separated by a barrier, a small group of individuals may be isolated. This small group does not represent the full genetic diversity of the population. Certain alleles may be missing. The missing allele cannot be reestablished as there is no gene flow from the original population due the barrier. With time this population becomes distinct from the original population leading to speciation