MARKER-BASED METHOD FOR INFERENCES ABOUT QUANTITATIVE INHERITANCE IN NATURAL-POPULATIONS

A marker-based method for studying quantitative genetic characters in natural populations is presented and evaluated. The method involves re gressing quantitative trait similarity on marker-estimated relatedness between individuals. A procedure is first given for estimating the na rrow sense heritability and additive genetic correlations among traits , incorporating shared environments. Estimation of the actual variance of relatedness is required for heritability, but not for genetic corr elations. The approach is then extended to include isolation by distan ce of environments, dominance, and shared levels of inbreeding. Invest igations of statistical properties show that good estimates do not req uire great marker polymorphism, but rather require significant variati on of actual relatedness; optimal allocation generally favors sampling many individuals at the expense of assaying fewer marker loci; when r elatedness declines with physical distance, it is optimal to restrict comparisons to within a certain distance; the power to estimate shared environments and inbreeding effects is reasonable, but estimates of d ominance variance may be difficult under certain patterns of relations hip; and any linkage of markers to quantitative trait loci does not ca use significant problems. This marker-based method makes possible stud ies with long-lived organisms or with organisms difficult to culture, and opens the possibility that quantitative trait expression in natura l environments can be analyzed in an unmanipulative way.