Determining whether this hypothesis is correct would require a large-scale prospective study in which statistical models assessed whether increased rates of autism in children of older fathers were statistically mediated by effects on variance in gene expression.
For example, it is important to determine what portion of phenotypic variance in adaptive traits is mediated by genetic variation captured in these inversions.
In contrast to selection mediated by early survival, variation in the linear selection gradients were less explained by variance in fertility than by time alone (3% versus 8% and 2% versus 11%), indicating that temporal linear trends in the selection gradients were not accounted for by changes in the variance in relative fertility alone.
Our conclusion that the increase in 2-DOG transport in response to palmitate was mediated by AMPK is also at variance with the study of [ 19] which showed that 2-DOG transport in primary adipocytes was decreased by AICAR.
Variation in selection mediated by early mortality was particularly well explained by variance in relative survival and by linear trends in time, with 20%and32%2% of variation explained for height and BMI, respectively (Table 2).
Variation in linear selection mediated by fertility was less explained by time and variance in relative fertility and reached 10%and14%4% for height and BMI, respectively.
We analyzed variance in relative fitness mediated by early survival and by adult fertility separately, as did other demographic studies involving lifetime fitness measurements [ 10 14, 25].
In both of these cases, more was explained by variance alone than by time alone (9% versus 2% and 17% versus 6%, respectively), indicating that temporal changes in selection mediated by survival were mainly due to changes in the variance in relative survival rather than other environmental effects on the selection gradient.
In an experimental study, using regression analyses, Palumbo et al. (2005) found that cognitive ability accounted for 12% of variance in performance, but this was completely mediated by the association between cognitive ability and job knowledge.
The fact that the change in fitness variance was more important in modifying selection mediated by survival, whereas other temporal trends were more influential in modifying selection mediated by fertility, may or may not be generalizable to other populations that undergo similar demographic trends.
