Linkage disequilibrium causing selection at a neutral locus in pooled Tribolium populations

Abstract

The role of linkage disequilibrium with respect to the changes in allele frequencies at a marker locus in newly started polymorphic populations is demonstrated using the marker locus black in Tribolium. The experiments, jointly taken, indicate that the black locus is selectively neutral, or nearly so, under the current experimental conditions. A number of possible mechanisms for selection at the neutral marker locus, i.e. a single linked or non-linked locus and a number of linked and/or non-linked loci through which selection acts, are discussed. On the basis of the experiments some of these models can be excluded, leaving three models for further evaluation: (A) a single linked fitness locus, (B) a number of linked fitness loci and (C) a number of both linked and non-linked fitness loci. The first of these models allows estimation of parameters (recombination fraction and selection coefficients). Models B and C are described in terms of heterozygosity of chromosome pairs. It is argued that in view of the history of a laboratory mutant stock, model C fits best to the experimental results.