Answer:
Because genetic drift (Founder effect) is acting on this population. Not all the Hardy weinberg criteria are accomplished. There are no random matings and populations are finite-sized.
Explanation:
This is a special case of genetic drift: the founder effect.
The “Founder effect” phenomenon refers to cases where a new population originates from a few founder individuals, coming from a bigger ancestral population, that established in a new environment. This small population might or might not be genetically representative of the original one. This subgroup carries with them some genetic information that they share with their original population. Over time, some genes can be lost, or they can increase in frequency. Some rare alleles might be exceeded or might be completely lost. On Consequence, when the small population grows, it will have a genetically different composition from the original one. In these situations, genetic variability is reduced and enhances the possibility of developing a peculiar allelic composition. In some cases, the founder effect is part of the process of speciation.
The criteria for maintaining a Hardy-Weinberg equilibrium are:
- Random matings
- No superposed generations
- No mutations
- No migration
- Infinite population size
- No natural selection
Genetic drift involved the un-accomplishment of random matings and infinite population sizes.
Genetic drift involves:
- limited population sizes
- individuals reproduce by endogamy/exogamy, and matings occur by phenotype.
