INBREEDING DEPRESSION AND INFERRED DELETERIOUS-MUTATION PARAMETERS INDAPHNIA

DENG and LYNCH recently proposed a method for estimating deleterious g enomic mutation parameters from changes in the mean and genetic Varian ce of fitness traits upon inbreeding in outcrossing populations. Such observations are readily acquired in cyclical parthenogens. Selfing an d life-table experiments were performed for two such Daphnia populatio ns. We observed a significant inbreeding depression and an increase of genetic Variance for all traits analyzed. DENG and LYNCH'S original p rocedures were extended to estimate genomic mutation rate (U), mean do minance coefficient ((h) over bar), mean selection coefficient ((s) ov er bar), and scaled genomic mutational variance (V-m/V-e). On average, (U) over cap, (h) over bar (h) over cap, (s) over bar (s) over cap an d (V) over cap(m)/V-e (<^> indicates an estimate) are 0.74, 0.30, 0.14 and 4.6E-4, respectively. For the true values, the (U) over cap and ( h) over bar (h) over cap are lower bounds, and (s) over bar (s) over c ap and (V) over cap(m)/V-e upper bounds. The present (U) over cap, (h) over bar (h) over cap and (V) over cap(m)/V-e are in general concorda nce with earlier results. The discrepancy between the present s and th at from mutation-accumulation experiments in Drosophila (similar to 0. 04) is discussed. It is shown that different reproductive modes do not affect gene frequency at mutation-selection equilibrium if mutational effects on fitness are multiplicative and not completely recessive.