Molecular Ecology by Joanna R. Freeland

Author:Joanna R. Freeland [Freeland, Joanna R.]
Language: eng
Format: epub, pdf
ISBN: 9781119426172
Publisher: Wiley
Published: 2019-12-04T00:00:00+00:00

Inbreeding

Inbreeding occurs when individuals mate with their relatives. Inbreeding does not alter the allele frequencies within a population, but it does increase homozygosity throughout the genome, thereby decreasing levels of individual genetic diversity. Inbreeding will therefore reduce a population's diversity when measured as Ho, although it will not directly affect He. However, as we will see in Chapter 8, inbreeding is a potential concern because it can reduce fitness levels, and if this happens inbreeding will lead to a depletion of all measures of genetic diversity through increased mortality rates.

Historically, the only way to estimate inbreeding was from detailed pedigree records, a method that is impractical for most, if not all, wild populations. Fortunately, the advent of molecular markers has provided alternative methods. Key to these methods is the identification of alleles that are identical by descent, in other words alleles that are copies of an allele that existed in a relatively recent ancestor. Individuals that have two alleles that are identical by descent are autozygous and must, by definition, be homozygous at the locus in question. This contrasts with allozygous individuals, which have two alleles that are not identical by descent (Figure 5.9). Note that allozygous individuals can be either homozygous or heterozygous at the locus in question, because an allozygous individual may have two copies of the same allele that did not originate in a recent common ancestor. For this reason, estimates of inbreeding are not necessarily the same as measures of observed homozygosity.

Table 5.5 Some examples that illustrate differences in clonal richness between conspecific populations, and provide possible explanations for these differences.

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