Genetic Differentiation among Livestock Breeds-Values for Fst

Simple Summary The degree of relationship among livestock breeds can be quantified by the F-st statistic, which measures the extent of genetic differentiation between them. An F-st value of 0.1 has often been taken as indicating that two breeds are indeed genetically distinct, but this concept has not been evaluated critically. Here, F-st values have been collated for the six major livestock species: cattle, sheep, goats, pigs, horses, and chickens. These values are remarkably variable both within and between species, demonstrating that F-st > 0.1 is not a reliable criterion for breed distinctiveness. However, the large body of F-st data accumulated in the last 20-30 years represents an untapped database that could contribute to the development of interdisciplinary research involving livestock breeds. (1) Background: The F-st statistic is widely used to characterize between-breed relationships. F-st = 0.1 has frequently been taken as indicating genetic distinctiveness between breeds. This study investigates whether this is justified. (2) Methods: A database was created of 35,080 breed pairs and their corresponding F-st values, deduced from microsatellite and SNP studies covering cattle, sheep, goats, pigs, horses, and chickens. Overall, 6560 (19%) of breed pairs were between breeds located in the same country, 7395 (21%) between breeds of different countries within the same region, 20,563 (59%) between breeds located far apart, and 562 (1%) between a breed and the supposed wild ancestor of the species. (3) Results: General values for between-breed F-st were as follows, cattle: microsatellite 0.06-0.12, SNP 0.08-0.15; sheep: microsatellite 0.06-0.10, SNP 0.06-0.17; horses: microsatellite 0.04-0.11, SNP 0.08-0.12; goats: microsatellite 0.04-0.14, SNP 0.08-0.16; pigs: microsatellite 0.06-0.27, SNP 0.15-0.22; chickens: microsatellite 0.05-0.28, SNP 0.08-0.26. (4) Conclusions: (1) Large amounts of F-st data are available for a substantial proportion of the world's livestock breeds, (2) the value for between-breed F-st of 0.1 is not appropriate owing to its considerable variability, and (3) accumulated F-st data may have value for interdisciplinary research.