Impact of environmental variation and temporal autocorrelation on
underlying genetics
Research on the evolutionary effect of environmental variability and
autocorrelation is often framed in terms of increasing frequencies of novel and unfavourable environments [60]. Greater
environmental variability and lower temporal autocorrelation expose
individuals to environments that are novel and often unfavourable, and
their impact on the evolutionary response is mixed depending on other
factors at play. One direct consequence of higher variability and lower
autocorrelation is that individuals and populations spend less time in temporal refugia [31], which reduces fitness. On the other
hand, exposure to unfavourable environments driven by higher variability
and lower temporal autocorrelation can also lead to increased additive
genetic variance, thereby increasing the evolutionary potential of a
trait[26,61,61,62,62–67]. The hypotheses for why such an increase
in genetic variance could occur are reviewed in [60]. One is that
selection is ineffective in removing mutations that are maladaptive only
in rare environments[68]. Thus, exposure to novel environments will
increase genetic variation and therefore heritability[26,69].
Determining the magnitude and frequency of this phenomenon in natural
populations is an important focus for research, as the opposite effect
is also known to occur[65,66,70–75].
The effect of environmental novelty on heritability, selection, and
genetic variance depends also on the system-specific evolutionary
history and relationship between environmental and genetic effects in
producing phenotypes[60]. Contrary to above for example, some
studies show that both environmental novelty and harshness can decrease
additive genetic variance[65,66,70–75]. This decrease may occur if
an unfavourable condition prevents individuals from expressing the
underlying genetically determined benefits from a trait, for example due
to lack of nutrition[71]. In such cases, selection could favour the
regulation of gene expression such that alleles are not expressed in an
unfavourable environment, for example by decreasing the heritability of
traits underpinned by associated alleles[60]. In turn, depending on
the mechanisms at play, evolutionary tracking may be either facilitated
or hindered in environments with an increasing rate of change,
variation, and/or autocorrelation. Whether or not a population is likely
to successfully track a moving environmental optimum will in part
determine the ability of plasticity to help bridge this gap.