Selection and genetic (co)variance in bighorn sheep.
Genetic theory predicts that directional selection should deplete additive genetic variance for traits closely related to fitness, and may favor the maintenance of alleles with antagonistically pleiotropic effects on fitness-related traits. Trait heritability is therefore expected to decline with the degree of association with fitness, and some genetic correlations between selected traits are expected to be negative. Here we demonstrate a negative relationship between trait heritability and association with lifetime reproductive success in a wild population of bighorn sheep (Ovis canadensis) at Ram Mountain, Alberta, Canada. Lower heritability for fitness-related traits, however, was not wholly a consequence of declining genetic variance, because those traits showed high levels of residual variance. Genetic correlations estimated between pairs of traits with significant heritability were positive. Principal component analyses suggest that positive relationships between morphometric traits constitute the main axis of genetic variation. Trade-offs in the form of negative genetic or phenotypic correlations among the traits we have measured do not appear to constrain the potential for evolution in this population.
Coltman
David W
DW
Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada. david.coltman@ualberta.ca
O'Donoghue
Paul
P
Hogg
John T
JT
Festa-Bianchet
Marco
M
D000367:Age Factors; D000416:Alberta; D000704:Analysis of Variance; D000818:Animals; D001837:Body Weights and Measures; D005298:Fertility / Q000235:genetics*; D016013:Likelihood Functions; D010375:Pedigree; D010641:Phenotype; D025341:Principal Component Analysis; D019655:Quantitative Trait, Heritable; D012098:Reproduction / Q000235:genetics*; D012641:Selection, Genetic; D012756:Sheep / Q000235:genetics*