Abstract

We have reviewed the available data on V_M , the amount of genetic variation in phenotypic traits produced each generation by mutation. We use these data to make several qualitative tests of the mutation-selection balance hypothesis for the maintenance of genetic variance (MSB). To compare V_M values, we use three dimensionless quantities: mutational heritability, the mutational coefficient of variation, CV_M ; and the ratio of the standing genetic variance to V_M , V_G /V_M . Since genetic coefficients of variation for life history traits are larger than those for morphological traits, we predict that under MSB, life history traits should also have larger CV_M . This is confirmed; life history traits have a median CV_M value more than six times higher than that for morphological traits. V_G /V_M approximates the persistence time of mutations under MSB in an infinite population. In order for MSB to hold, V_G /V_M must be small, substantially less than 1000, and life history traits should have smaller values than morphological traits. V_G /V_M averages about 50 generations for life history traits and 100 generations for morphological traits. These observations are all consistent with the predictions of a mutation-selection balance model.