Data from: Body size, swimming speed, or thermal sensitivity? Predator-imposed selection on amphibian larvae

Background: Many animals rely on their escape performance during predator
encounters. Because of its dependence on body size and temperature, escape
velocity is fully characterized by three measures, absolute value,
size-corrected value, and its response to temperature (thermal
sensitivity). The primary target of the selection imposed by predators is
poorly understood. We examined predator (dragonfly larva)-imposed
selection on prey (newt larvae) body size and characteristics of escape
velocity using replicated and controlled predation experiments under
seminatural conditions. Specifically, because these species experience a
wide range of temperatures throughout their larval phases, we predict that
larvae achieving high swimming velocities across temperatures will have a
selective advantage over more thermally sensitive individuals. Results:
Nonzero selection differentials indicated that predators selected for prey
body size and both absolute and size-corrected maximum swimming velocity.
Comparison of selection differentials with control confirmed selection
only on body size, i.e., dragonfly larvae preferably preyed on small newt
larvae. Maximum swimming velocity and its thermal sensitivity showed low
group repeatability, which contributed to non-detectable selection on both
characteristics of escape performance. Conclusions: In the newt-dragonfly
larvae interaction, body size plays a more important role than maximum
values and thermal sensitivity of swimming velocity during predator
escape. This corroborates the general importance of body size in
predator–prey interactions. The absence of an appropriate control in
predation experiments may lead to potentially misleading conclusions about
the primary target of predator-imposed selection. Insights from predation
experiments contribute to our understanding of the link between
performance and fitness, and further improve mechanistic models of
predator–prey interactions and food web dynamics.