Inbreeding and inbreeding depression Flashcards
(17 cards)
What is the pedigree inbreeding coefficient?
The pedigree inbreeding coefficient measures an individual’s probability of two alleles at any locus being identical by descent
What is the coefficient of relatedness?
The coefficient of relatedness measures the expected proportion of alleles shared by two individuals that are identical by descent
What is lifetime breeding success (LBS)?
LBS is defined as the total number of offspring produced over an individual’s lifetime
What is lifetime reproductive success (LRS)?
LRS is defined as the number of offspring produced by an individual that reached independence, capturing variation in offspring survival due to inbreeding depression
What is lifetime allelic fitness (LAF)?
LAF is defined as the total number of identical by descent copies contributed from a focal individual to the next generation
What is the difference between lifetime breeding success (LBS) and lifetime reproductive success (LRS)?
LBS is the total number of offspring produced over an individual’s lifetime, whereas LRS is the number of those offspring that reached independence, capturing variation in offspring survival due to inbreeding depression
What mechanisms is inbreeding depression regarded as a driving force in the evolution of?
Dispersal Mate choice (among related or unrelated mates) Sperm selection
Why would an individual choose to mate with a related mate?
Any kin-selected benefits depend critically on which sex mate-limited and which sex provides parental care.
In polygynous systems with female-only parental care, males are typically mate-limited whereas females are resource-limited. For a male under these conditions and from a kin selection perspective, mating with a related female is of equal value to mating with an unrelated female: the shared alleles in the related female are passed on to the next generation regardless of his choice (as she will mate anyway)
The only effect of his choice is whether his or her allele copies end up in the same offspring, or in different offspring, and this is irrelevant to the male if he does not provide parental care
What is the opportunity cost of inbreeding?
The opportunity cost of inbreeding is when any inbred offspring a female produces is at the expense of an outbred offspring
At what population sizes is inbreeding most likely to occur? How efficient is the process of inbreeding selection at different population sizes?
It is in small, viscous populations that inbreeding is most likely to occur, potentially generating selection for inbreeding avoidance or preference. However, in small populations selection is relatively inefficient, reducing the chances of such strategies evolving.
In contrast, in large populations, selection is efficient but inbreeding is likely to be rare, generating little selection to avoid inbreeding
In what generations do inbreeding and inbreeding depression occur? Do they occur in the same generation?
Inbreeding and inbreeding depression occur in different generations. Consequently, the costs for an individual that inbreeds cannot be assessed only from the reduction in the fitness of its offspring
How is fitness defined from a quantitative genetics perspective?
Fitness is best defined as the number of zygotes produced by a zygote - it is possible for inbreeding to reduce fitness if it causes gamete incompatibility or embryo inviability
However, inbreeding avoidance may also reduce the number of zygotes produced if costs, of dispersal, loss of breeding opportunities or energy costs of locating unrelated individuals exist
How do studies in wild animal populations quantify the costs of inbreeding? What are the issues with this?
The costs of inbreeding are generally quantified using inbreeding depression, measuring the effect of an individual’s coefficient of inbreeding depression on its own fitness and therefore measuring selection against being inbred
However, selection on inbreeding should be assess from the perspective of the individual who mates with a relative or not. This can be achieved by quantifying the relationship between an individual’s relatedness to its mate and its own fitness and thus estimating selection on the act of inbreeding
Are microsatellites a good choice for estimating individual inbreeding and pairwise relatedness?
Microsatellites do not prove to be very precise since microsatellite homozygosity is often only weakly correlated with identity by descent
What is identity by descent?
dentical by descent (IBD) is a term used in genetic genealogy to describe a matching segment of DNA shared by two or more people that has been inherited from a common ancestor without any intervening recombination.
Inbreeding causes offspring to have IBD chromosome segments, which are characterized by long runs of homozygosity at mapped SNPs
The length of IBD chromosome segments is strongly influenced by the number of generations separating the inbred individual from the common parental ancestor(s)
What is the difference between inbreeding and inbreeding depression?
Inbreeding is mating among relatives
Inbreeding depression is the reduction in fitness observed in inbred individuals
What are two different definitions of inbreeding?
- Inbreeding as non-random mating within a population: mating between individuals who are more closely related than the average randomly selected pair of individuals within a population
- Inbreeding as population subdivision: population subdivision causes mates to be more closely related than when mating is random among all individuals
