Population differentiation and the correlation among traits at the population level

• Published in: The American naturalist Vol. 133; no. 6; pp. 888 - 900
• Main Author: Goodnight, C.J. (University of Illinois at Chicago, Chicago, IL)
• Format: Journal Article
• Language: English
• Published: Chicago, IL University of Chicago Press 01-06-1989
• Subjects: ANIMAL POPULATION; Animals; Biological and medical sciences; Coleoptera; DIFERENCIACION; DIFFERENCIATION; DIFFERENTIATION; Emigration; Evolution; Evolutionary genetics; Fundamental and applied biological sciences. Psychology; Genetic correlation; GENETICA; GENETICS; Genetics of eukaryotes. Biological and molecular evolution; GENETIQUE; Group selection; HEREDABILIDAD; HERITABILITE; HERITABILITY; Invertebrata; MIGRACION; MIGRATION; Phenotypic traits; POBLACION ANIMAL; POPULATION ANIMALE; Population characteristics; Population genetics; Population genetics, reproduction patterns; Population size; Tenebrionidae; TRIBOLIUM; TRIBOLIUM CASTANEUM; TRIBOLIUM CONFUSUM; Tribolium confusum; Genetic variability; Coleoptera; Arthropoda; Insecta; Population number; Tribolium castaneum; Invertebrata; Tenebrionidae; Population genetics; Natural selection
• ISSN: 0003-0147; 1537-5323
• DOI: 10.1086/284958

Population heritability is a measure of genetic differentiation among populations that is directly proportional to the response to group selection (Wade 1978; Wade and McCauley 1980). The experiment reported here extends this concept to a system in which multiple traits are measured and the possibility of phenotypic and genotypic correlations among traits considered. Correlations among traits have a major impact on evolution by individual selection (Lande 1979; Lande and Arnold 1983), and by the same reasoning, genetic correlations at the population level have a major impact on evolution by group selection. In this study, significant genetic variance for both population sizes and emigration rate was found in both species of flour beetle studied, Tribolium castaneum and T. confusum. These results are in strong agreement with the findings of other workers who have observed significant responses to group selection for population size in T. castaneum (Wade 1977) and emigration rate in T. confusum (Craig 1980, 1982). In addition, a genetic correlation between population size and emigration rate was found in T. confusum but not in T. castaneum. Thus, this experiment provides empirical evidence that correlations may occur between traits measured at the group level. These genetic correlations at the group level may be due, at least in part, to nonadditive genetic variance that is contributing to the differentiation of populations. This finding corroborates earlier experiments suggesting that at least a portion of the correlation between population size and emigration rate in T. confusum is due to ecological interactions among individuals. These ecological interactions, which contribute only to the environmental variation at the individual level, become heritable at the group level.