Evaluating the fitness consequences of plasticity in tolerance to pesticides

In a rapidly changing world, phenotypic plasticity may be a critical
mechanism allowing populations to rapidly acclimate when faced with novel
anthropogenic stressors. Theory predicts that if exposure to anthropogenic
stress is heterogeneous, plasticity should be maintained as it allows
organisms to avoid unnecessary expression of costly traits (i.e.
phenotypic costs) when stressors are absent. Conversely, if exposure to
stressors becomes constant, costs or limits of plasticity may lead to
evolutionary trait canalization (i.e. genetic assimilation). While these
concepts are well-established in theory, few studies have examined whether
these factors explain patterns of plasticity in natural populations facing
anthropogenic stress. Using wild populations of wood frogs that vary in
plasticity in tolerance to pesticides, the goal of this study was to
evaluate the environmental conditions under which plasticity is expected
to be advantageous or detrimental. We found that when pesticides were
absent, more plastic populations exhibited lower pesticide tolerance and
were more fit than less plastic populations, likely avoiding the cost of
expressing high tolerance when it was not necessary. Contrary to our
predictions, when pesticides were present, more plastic populations were
as fit as less plastic populations, showing no signs of costs or limits of
plasticity. Amidst unprecedented global change, understanding the factors
shaping the evolution of plasticity will become increasingly important.