Population statistics
Since these statistics may be unfamiliar, the definition of each one is given below:
Effective number of founders (fe)
A breed may have, for example, 25 founders, but part of the genetic diversity originally present is inevitably lost over the generations.
Today, The effective number of founders (fe) is an estimate of how many founders, contributing equally, would be needed to produce the genetic diversity currently observed in the population.
This parameter therefore represents the proportion of the founders' genetic contribution that remains in the current population.
Founder genome equivalents (fg)
Today, The founder genome equivalents (fg) correspond to the number of founders with equal genetic contribution that would be needed to produce the same genetic diversity observed in the current population, assuming no random loss of founder alleles in the descendants, as can happen through genetic drift.
In other words, while fe considers the effective contribution of the founders, taking into account the losses over the generations, fg seeks to represent the amount of original genetic diversity that actually remains available in the population.
Effective number of ancestors (fa)
Today, The effective number of ancestors (fa) corresponds to the minimum number of ancestors (who may be founders or individuals from later generations) needed to explain the genetic diversity present in the current population.
When there have been no population bottlenecks, the fa is expected to be close to or equal to fe.
The difference between fe and fa may indicate the occurrence and intensity of population bottlenecks or of unequal genetic contributions among certain ancestors.
The greater the difference between these parameters, the more the genetic contribution may have been concentrated in certain ancestors over the population's history.
Mean kinship coefficient (MK)
Today, The mean kinship coefficient (MK) is an index representing the average degree of genetic relationship between a given animal and the other individuals in the population.
An animal that has many relatives or that descends from lines heavily represented in the population tends to show greater average genetic similarity to the other individuals and, consequently, a higher MK.
On the other hand, animals with less genetic relationship to the rest of the population tend to show lower MK values.
At the population level, individuals with lower MK may have greater genetic conservation value, because they may carry alleles that are less frequent or poorly represented in the population.
It is important to note that MK is not a fixed value. Every birth or death changes the genetic makeup of the population and, consequently, changes the mean kinship values of the remaining individuals.
Relationship between kinship and inbreeding
Today, An animal's inbreeding coefficient (F) is equivalent to the coefficient of kinship between its parents.
Thus, the greater the genetic similarity between the two parents, the greater the probability that the offspring will receive two copies of the same allele from a common ancestor.
This is one of the reasons why kinship analysis is fundamental in conservation and genetic improvement programs.
In short
ParameterWhat it representsfe | How much of the founders' genetic diversity actually remains in the population
fg | Amount of genetic diversity equivalent to the contribution of equally represented founders
fa | Minimum number of ancestors needed to explain the current genetic diversity
MK | Average degree of kinship between an individual and the population
F | Probability that an individual receives two copies of alleles originating from a common ancestor
These indicators are especially important when the goal is to evaluate genetic diversity, concentration of lines, effects of population bottlenecks, inbreeding and selection strategies within a breed.
Source: Institute of Canine Biology · How to Interpret Breed Analyses
