Responses to artificial and natural selection

(a) Response to artificial selection after one generation depends on h2. M is mean phenotype in parental generation; MS is the mean phenotype selected for mating; M′ is the mean phenotype of offspring after selection; selection differential is S = MS − M. (b) Three modes of artificial or natural selection produce different results after several generations(a) Response to artificial selection after one generation depends on h2. M is mean phenotype in parental generation; MS is the mean phenotype selected for mating; M′ is the mean phenotype of offspring after selection; selection differential is S = MS − M. (b) Three modes of artificial or natural selection produce different results after several generations

(a) h2 = 0.0 h2 = 0.2 h2 = 1.0 Parent M S M, M 5 Ms M 5 Ms Offspring M' Phenotypic value Consequence: Same population mean Slight change in Large change in population mean j population mean Conclusion: Selection response Selection response lectionresponse is zero. is small. is semaximal Directional Stabilizing Disruptive selection selection selection Parent Portion favored by Portions favored by natural selection IA natural selection After several Phenotypic value‘ generations Conclusion: Changed mean and Same mean but Same mean but reduced variance reduced variance increased variance