Impact of the rate of environmental change on underlying genetics
When the rate of environmental change is too slow, selection is weak and
can be ineffective in part due to lag load [50–52]. As the
rate of environmental change increases, selection strengthens, and the
population can track the moving optimum with a consistent phenotypic
lag[53]. In this range of environmental change, in some contexts
additive genetic variance and heritability can also increase[50,54].
In this case, up to a certain intermediate rate of environmental change,
genetic variation and evolutionary potential may be expected to increase
simply from an increase in standing variation available to selection.
However, phenotypic lag can become too large for the rate of selection
to follow if the environment, and thus the optimal trait, changes too
quickly[50,53,55]. Here, the gap between the mean trait in the
population and the optimal trait increases, which can lead to decreased
fitness and eventually extinction[56]. As such, the mean time to
extinction in a natural population decreases as the rate of
environmental change increases beyond the optimal rate[50].
Studies that directly assess the role of environmental variability and
temporal autocorrelation on genetic variation and heritability are
limited. However, increasing environmental variability, similar to the
rate of change, elicits a maximal response to selection at an
intermediate magnitude that optimizes selection and ultimately evolutionary tracking [57,58]. In contrast, the ability of
populations to evolutionarily track a shifting adaptive peak increases
with greater temporal autocorrelation because that implies increased
predictability of future environments[41,56]. Moreover, positively
autocorrelated environmental fluctuations can increase additive genetic
variance[59]. Thus, evolutionary potential may be higher in
temporally autocorrelated environments.