Evolution in changing seas: The loss of plasticity under predator invasion and warming oceans

The impact of invasive predators during the early stages of invasion is
often variable in space and time. Such variation is expected to initially
favor plasticity in prey defenses but fixed defenses as invaders become
established. Coincident with the range expansion of an invasive predatory
crab in the Gulf of Maine we document rapid changes in shell thickness – a
key defense against shell crushing predators – of an intertidal snail.
Field experiments, conducted 20 years apart, revealed that temporal shifts
in shell thickness were driven by the evolution of increased trait means
and erosion of thickness plasticity. The virtual elimination of the
trade-off in tissue mass that often accompanies thicker shells is
consistent with the evolution of fixed defenses under increasingly certain
predation risk.