Inbreeding avoidance
However, inbreeding also gives opportunity for genetic purging of deleterious alleles that otherwise would continue to exist in population and could potentially increase in frequency over time.
Inbreeding avoidance occurs in nature by at least four mechanisms: kin recognition, dispersal, extra-pair/extra-group copulations, and delayed maturation/reproductive suppression.
There have been numerous documented examples of instances in which individuals are shown to find closely related conspecifics unattractive.
[12][14][16] For example, in a study by Krackow et al., male wild house mice were set up in an arena with four separate openings leading to cages with bedding from conspecifics.
For example, in one study, Mateo and Johnston had golden hamsters reared with only non-kin then later had them differentiate between odors of related and non-related individuals without any postnatal encounters with kin.
[21] One idea is that the MHC genes code for a specific pheromone profile for each individual, which are used to discriminate between kin and non-kin conspecifics.
Experiments were performed with the dioecious plant Silene latifolia to test whether post-pollination selection favors less related pollen donors and reduces inbreeding.
[27] Birds tend to adopt monogamous mating systems in which the males remain in their natal groups to defend familiar territories with high resource quality.
Australian marsupial juvenile males have a greater tendency to disperse from their natal groups, while the females remain philopatric.
Delayed maturation scenarios can involve the removal of the original, opposite-sex parent, as is the case in female lions that exhibit estrus earlier following the replacement of their fathers with new males.
[33] Social cues from the surrounding environment often dictate when reproductive activity is suppressed and involves interactions between same-sex adults.
Inbreeding avoidance between philopatric offspring and their parents/siblings severely restricts breeding opportunities of subordinates living in their social groups.
A study by O'Riain et al. (2000) examined meerkats social groups and factors affecting reproductive suppression in subordinate females.
Reproductive activity only resumed upon another sexually mature female obtaining dominance, and immigration of an unrelated male.
[33] In various species, females benefit by mating with multiple males, thus producing more offspring of higher genetic diversity and potentially quality.
Females that are pair bonded to a male of poor genetic quality, as can be the case in inbreeding, are more likely to engage in extra-pair copulations in order to improve their reproductive success and the survivability of their offspring.
For females, extra-pair copulations ensure egg fertilization, and provide enhanced genetic variety with compatible sperm that avoid expression of damaging recessive genes that come with inbreeding.
[36] Through extra-pair mating, females are able to maximize the genetic variability of their offspring, providing protection against environmental changes that may otherwise target more homozygous populations that inbreeding often produces.
When paternal care is absent or has little influence on offspring survivability, it is generally favorable for females to engage in extra-pair mating to increase reproductive success and avoid inbreeding.
[38][39] Although the first option, individual behavioral observation, is preferred and most widely used, there is still debate over whether it can provide definitive evidence for inbreeding avoidance.
A majority of the literature on inbreeding avoidance was published at least 15 years ago, allowing for growth and development of the study through contemporary experimental methods and technology.
[12] Studying inbreeding avoidance in carnivores has garnered increased interest due to ongoing work to explain their social behaviors.
