Relyea, R. A., and E. E. Werner. 2000. Morphological plasticity of four larval anurans distributed along an environmental gradient. Copeia 2000:178-190.

We investigated morphological plasticity to the presence of predators in the tadpoles
of four ranid frog species distributed along a pond hydroperiod gradient in
southeast Michigan. We first reared all four species (Wood Frog, Rana sylvatica;
Leopard Frog R. pipiens; Green Frog, R. clamitans; and Bullfrog, R. catesbeiana)
under identical laboratory conditions in the presence and absence of caged larval
dragonflies (Anax spp.). We then reared wood frog and leopard frog in outdoor
mesocosms to examine the predator-induced responses during ontogeny. Finally, we
reared leopard frog with predators fed either leopard frog or wood frog larvae to
determine whether prey responses depended upon predators consuming conspecific
prey. All four ranids exhibited some degree of morphological change in the presence
of Anax; these differences were species specific and fairly robust to different experimental
conditions. The responses over ontogeny indicated that the changes were
direct responses to the predator’s presence and not an indirect result of the predator
slowing anuran growth or development. Finally, larval leopard frog responded similarly
to predators feeding on conspecifics and congenerics. Taken together, these
results suggest that morphological responses to predators may be relatively common
in larval anurans. Further, because many of the responses are known to be adaptive
antipredator strategies, predator-induced morphological plasticity has important
evolutionary and ecological implications.