Inducible defences in tadpoles: it's a complex world out there
A famous example of phenotypic plasticity is the case of inducible defences in tadpoles. But there are many predators in a pond and one type of defence does not fit all. In the presence of dragonfly larvae (a sit and wait predator), tadpoles grow deeper tail fins while they grow more muscle in the presence of sticklebacks, a predator which strike repeatedly. These morphological changes are increasing tadpoles survival in the face of these predators by distracting attacks from the vulnerable body towards the tail in the case of dragonly larvae and by increasing swimming speed and probably allowing to reach refugia in the case of sticklebacks.
However, in the real world, things are more complex as predator or no predator, and conflicting demands may arise from being faced to different predators (antagonist responses) or to different kind of stressors with limited energetic resources (e.g. detoxification vs predator avoidance). Using an experimental approach, we investigated the effects of natural stressors such as multiple predators, competitors but also anthropogenic stressors such as low pH and pesticides. In population of Rana arvalis adapted to low pH, inducible defences are not affected by exposure to acidity. In turn, the expression of these defences are inhibited in tadpoles from "neutral" populations. Exposure to pesticide did not affect the expression of inducible defences but their costs in terms of decreased growth rate and longer time to metamorphosis.
While plasticity is thought as one of the major mechanism of response to global change, one can thus wonder how plasticity is affected by global changes.