Increasing conspecific density weakens the ability of intermediate predators to develop induced morphological defences to top predators
Article first published online: 30 SEP 2013
© 2013 John Wiley & Sons Ltd
Volume 59, Issue 1, pages 87–99, January 2014
How to Cite
Davenport, J. M. and Chalcraft, D. R. (2014), Increasing conspecific density weakens the ability of intermediate predators to develop induced morphological defences to top predators. Freshwater Biology, 59: 87–99. doi: 10.1111/fwb.12248
- Issue published online: 10 DEC 2013
- Article first published online: 30 SEP 2013
- Manuscript Accepted: 29 AUG 2013
- National Science Foundation. Grant Number: DEB-0716558
- North Carolina Herpetological Society
- induced defences;
- intraguild predation;
- larval development;
- phenotypic plasticity
Intraguild predation is common in nature, but it is unclear how species that both compete and eat each other can persist together. One possibility is that intermediate predators possess inducible morphological defences that protect them from top predators while not compromising their ability to compete with top predators.
The ability of intermediate predators to develop morphological defences may be compromised in environments with a high density of conspecifics because of reduced resource availability and predation risk due to the saturating functional response of top predators. Furthermore, since morphological defences take time to develop, the type and extent of morphological defences may vary during development.
We conducted an experiment to measure the phenotypic responses of an intermediate predator (larvae of the salamander Ambystoma opacum) to the presence of a caged top predator (larvae of the dragonfly Anax spp.) throughout ontological development in environments that differed in the density of conspecifics present. We also assessed how intermediate predators, reared in the different environments, differed in their vulnerability to top predators and ability to deplete their food resources.
We found that Anax induced morphological defences in A. opacum, but the extent of morphological change declined with the density of conspecifics. Moreover, some morphological traits disappeared, while others appeared just prior to A. opacum metamorphosis. The change in A. opacum phenotype in response to Anax made A. opacum less vulnerable to predation by Anax but had no significant effect on the foraging ability of A. opacum.
Our study demonstrates that top predators can induce phenotypes in intermediate predators that reduce their vulnerability to top predators while not compromising their ability to feed on a common prey. An increase in intermediate predator density, however, could diminish the ability of intermediate predators to develop the full suite of morphological defences. The inability to develop the full suite of morphological defences may reduce the probability of persistence with top predators.