Isolation by distance

Not to be confused with identity by descent, another concept in population genetics referred to as "IBD".
The patterns of isolation by distance as shown among human genetic data representing 346 microsatellite loci taken from 1484 individuals in 78 human populations. The horizontal axis of both charts is geographic distance as measured along likely routes of human migration. The upper graph illustrates that as populations are further from East Africa (represented by the city of Addis Ababa), they have declining genetic diversity as measured in average number of microsatellite repeats at each of the loci. The bottom chart measures the genetic distance between all pairs of populations according to the Fst statistic. Populations separated by greater distance are more dissimilar than those that are geographically close.

Isolation by distance (IBD) is a term used to refer to the accrual of local genetic variation under geographically limited dispersal.[1] The IBD model is useful for determining the distribution of gene frequencies over a geographic region.[2] Both dispersal variance and migration probabilities are variables in this model and both contribute to local genetic differentiation.[3] Isolation by distance is usually the simplest model for the cause of genetic isolation between populations. Evolutionary biologists and population geneticists have been exploring varying theories and models for explaining population structure. Yoichi Ishida compares two important theories of isolation by distance and clarifies the relationship between the two.[3] According to Ishida, Sewall Wright's isolation by distance theory is termed ecological isolation by distance while Gustave Malécot's theory is called genetic isolation by distance. Isolation by distance is distantly related to speciation. Multiple types of isolating barriers, namely prezygotic isolating barriers, including isolation by distance, are considered the key factor in keeping populations apart, limiting gene flow.[4]

  1. ^ Slatkin, Montgomery (1993). "Isolation by Distance in Equilibrium and Non-Equilibrium Populations". Evolution. 47 (1): 264–279. doi:10.2307/2410134. JSTOR 2410134. PMID 28568097.
  2. ^ Rohlf, F. James; Schnell, Gary D. (1971). "An Investigation of the Isolation-By-Distance Model". The American Naturalist. 105 (944): 295–324. doi:10.1086/282727. S2CID 84513946.
  3. ^ a b Ishida, Yoichi (2009). "Sewall Wright and Gustave Malecot on Isolation by Distance". Philosophy of Science. 76 (5): 784–796. doi:10.1086/605802. S2CID 6169432.
  4. ^ Coyne, JA; Orr, HA (2004). Speciation. Massachusetts: Sinauer Associates, Inc.