A Meta-Analysis on Facultative Responses of Embryonic Amphibians to Predation Risk.

Natural selection is predicted to favor the evolution of life history plasticity in response to differences in mortality risk between life stages, such that the duration of the more dangerous stage is reduced. I report a meta-analysis of 29 published tests of this hypothesis involving 20 amphibian species, in which exposure of embryos to predation risk was experimentally manipulated. The results confirm that amphibians are sensitive to risk during the embryonic stage, but the predictions of theory were only weakly upheld. Amphibians hatch at a less advanced developmental stage (0.24 SD units) and smaller body size (0.10 SD units) when exposed to predator species that consume eggs, but the expected decline in age at hatching (0.16 SD units) was not significant. Predators that consume larvae did not significantly delay hatching (0.19 SD units) or influence any other response. [ABSTRACT FROM AUTHOR]