Genetic variation is maintained in populations over time through several mechanisms.
One of the most basic mechanisms is mutation. Even deleterious alleles that are highly selected against may never fully disappear as there is always the chance for mutation to occur. New mutations can crop up at any point and be passed on to the individual's offspring, adding more genetic variation to the gene pool. As discussed in a previous blog post, high mutation rates can even be selected for under certain conditions such as highly variable environments.
Another mechanism for maintaining genetic variation within a population is immigration. When new individuals from a different population immigrate to a new population and begin interbreeding, their genes are added to the gene pool. Their genes may be different due to novel mutations or adaptations to different environmental conditions in where they immigrated from.
While it is assumed selection eliminates genetic variation, some forms of selection actually help maintain it. Disruptive selection is when quantitative traits at extreme ends of the spectrum are selected for and intermediate traits are selected against, creating broader trait variation.
Comments
Post a Comment