Adaptive and non-adaptive plasticity in changing environments:
implications for sexual species with different life history strategies
Abstract
Populations adapt to novel environmental conditions by genetic changes
or phenotypic plasticity. Plastic responses are generally faster and can
buffer fitness losses under variable conditions. Plasticity is typically
modelled as random noise and linear reaction norms that assume simple
one-to-one genotype-phenotype maps and no limits to the phenotypic
response. Most studies on plasticity have focused on its effect on
population viability. However, it is not clear, whether the advantage of
plasticity depends solely on environmental fluctuations or also on the
genetic and demographic properties (life histories) of populations. Here
we present an individual-based model and study the relative importance
of adaptive and non-adaptive plasticity for populations of sexual
species with different life histories experiencing directional
stochastic climate change. Environmental fluctuations were simulated
using differentially autocorrelated climatic stochasticity or noise
color, and scenarios of directional climate change. Non-adaptive
plasticity was simulated as a random environmental effect on trait
development, while adaptive plasticity as a linear, logistic, or
sinusoidal reaction norm. The last two imposed limits to the plastic
response and emphasized flexible interactions of the genotype with the
environment. Interestingly, this assumption led to (i) smaller
phenotypic than genotypic variance in the population and the coexistence
of polymorphisms, (ii) many-to-one genotype-phenotype map, and (iii) the
maintenance of higher genetic variation – compared to linear reaction
norms and genetic determinism – even when the population was exposed to
a constant environment for several generations. Limits to plasticity led
to genetic accommodation, when costs were negligible, and to the
appearance of cryptic variation when limits were exceeded. We found that
adaptive plasticity promoted population persistence under red noise
stochasticity and was particularly important for life histories with low
fecundity. Populations producing more offspring could cope with
environmental fluctuations solely by genetic changes or random
plasticity, unless environmental change was too fast.