There are a number of ways to measure fitness in biological systems. One method is to partition fitness into components that are standardized across taxa. These components, however, can vary from one taxon to another. Another method is to subdivide fitness across arbitrary taxa. For instance, in insects, survival differences can be broken down into the larval, first, and second instars. However, this approach has its drawbacks.

Normalized fitness is not useful for predicting the outcome of selection

For example, if a genotype dd was not selected, then the overall survival rate of dd individuals would be one thousand percent, and dd individuals would die fewer times and produce more offspring. Similarly, if a genotype dd was selected, the reproductive rate would be one hundred percent, and so on. In this case, normalized fitness would not be useful for predicting the outcome of selection.

Inclusive fitness is the ability of an allele in one individual to promote the survival and reproduction of other individuals that share that allele

While many people think of inclusive fitness as an attribute of individuals who have many overlapping alleles, the concept goes beyond that. It includes an individual’s fitness when the individual has a gene copy that is identical to their own. This includes half of an individual’s fitness if the other person is a sibling or a quarter if the two share a common ancestor. However, it is impossible to quantify the fitness of all individuals who share a certain gene allele. In addition, the contribution of distantly related individuals is very small.

Relative fitness is a measure of prevalence

Relative fitness is a measure of the abundance of a particular genotype. The mean relative fitness is one. Increasing frequencies of a particular genotype are regarded as more advantageous than decreasing ones. Hence, … Read More