Sd. Pletcher et Jw. Curtsinger, The influence of environmentally induced heterogeneity on age-specific genetic variance for mortality rates, GENET RES, 75(3), 2000, pp. 321-329
Using parametric models that describe the increase in mortality rates with
age, we demonstrate that environmentally induced heterogeneity among geneti
cally identical individuals is sufficient to generate biased estimates of a
ge-specific genetic variance. Although the magnitude of the bias may change
with age, one general trend emerges: the true genetic variance at the olde
st ages is likely to be dramatically underestimated. Our results are robust
to different manifestations of heterogeneity and suggest that such a bias
is a general feature of these models. We note that age-dependent estimates
of genetic variance for characters that are correlated with mortality (eith
er genetically or environmentally) can be expected to be similarly affected
. The results are independent of sample size and suggest that the bias may
be more widespread in the literature than is currently appreciated. Our res
ults are discussed with reference to existing data on mortality variance in
Drosophila melanogaster.