identical by descent
Alleles that are identical copies of the same allele from a common ancestor.

inbreeding
The mating between related individuals that results in an increase of homozygosity in the progeny because they possess alleles that are identical by descent.

inbreeding coefficient
A measure of the level of inbreeding in a population that determines the probability that an individual possesses two alleles at a locus that are identical by decent. It can also be used to describe the proportion of loci in an individual that are homozygous.

inbreeding depression
The reduction in fitness of progeny from matings between related individuals compared to progeny from unrelated individuals.

inbreeding effect
Inbreeding eventually will occur in panmictic small populations due to the individuals becoming increasingly related through time.

inbreeding effective number (NeI)
The size of the ideal panmictic population that loses heterozygosity at the same rate as the observed population.

introduction
The placement, or escape, of a species or individual into a novel habitat. Often introductions are used in conservation to aid genetic rescue of isolated populations.

introgression
The incorporation of genes from one population to another through hybridization that results in fertile offspring that further hybridize and backcross to parental populations.

intron
A portion of a gene that produces a nonfunctional RNA strand that is cleaved prior to translation; a noncoding region between the exons.

invasive species
An introduced alien species that is likely to cause harm to the natural ecosystem, the economy, or human health.

island model of migration
A model of migration in which a population is subdivided into a series of demes, of size N, that randomly exchange migrants at a given rate, m.

isolation by distance
The case where genetic differentiation is greater the further individuals (or populations) are from each other because gene flow decreases as geographic distance increases. Originally individuals used in the case where individuals are distributed continuously across large landscapes (e.g., coniferous tree species across boreal forests) and are not subdivided by sharp barriers to gene flow.

ISSR
Intersimple sequence repeat markers that use similar PCR methods as PINE fragments, but have primers based on simple sequence repeats of microsatellites.

IUCN
World Conservation Union (formerly International Union for Conservation of Nature).