Everything about Frequency-dependent Selection totally explained
Frequency dependent selection is the term given to an evolutionary process where the
fitness of a
phenotype is dependent on its frequency relative to other phenotypes in a given
population. In
positive frequency dependent selection, the fitness of a phenotype increases as it becomes more common. In
negative frequency dependent selection, the fitness of a phenotype increases as it becomes less common. Negative frequency dependent selection is a particular mechanism of
balancing selection.
Negative frequency dependent selection
Negative frequency dependent selection is often the result of interactions between species (predation, parasitism,or competition) or between genotypes within species (usually competitive or symbiotic). The first explicit statement of frequency dependence appears to have been by E.B. Poulton in 1884 with reference to the way that predators could maintain color polymorphisms in their prey.
Another example of negative frequency dependent selection is in the case of
plant self-incompatibility alleles. When two plants share the same incompatibility allele, they're unable to mate. Thus, a plant with a new (and therefore, rare) allele has more success at mating, and its allele spreads quickly through the population.
Negative frequency dependent selection also operates in the interaction of many human pathogens, such as the
flu virus. Once a particular strain has been common in a human population, most individuals would have developed an immune response to that strain. But a rare, novel strain of the flu virus would be able to spread quickly to almost any individual. This advantage of genetic novelty causes continual evolution of viral strains, with new versions common each year. Another immune-related example of negative frequency dependent selection is the
major histocompatibility complex, which is involved in antibody creation (Takahata and Nei, 1990).
Positive frequency dependent selection
Where negative frequency dependent selection gives an advantage to rare phenotypes, positive frequency dependent selection gives an advantage to common phenotypes. This means that new alleles can have a difficult time invading a population, since they don't experience significant benefit until they become common. This has been proposed as a difficulty in the evolution of aposematic (or warning) coloration in toxic or distasteful organisms. The presumed advantage of the
aposematic coloration is that predators have learned to avoid potential prey with that color pattern. But when the pattern is rare, the predator population doesn't become 'educated' and the pattern has no benefit. Therefore the warning color is only advantageous once it has become common. Warning coloration, if it involves more than one species, may also be an example of
convergent evolution.
Further Information
Get more info on 'Frequency-dependent Selection'.
|
External Link Exchanges
Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:
<a href="http://frequency_dependent_selection.totallyexplained.com">Frequency dependent selection Totally Explained</a>
Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned. |
