Current address: School of Environmental Studies, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
Predation and facilitation determine chironomid emergence in a bromeliad-insect food web
Article first published online: 7 JAN 2010
© 2010 The Authors. Journal compilation © 2010 The Royal Entomological Society
Volume 35, Issue 1, pages 53–60, February 2010
How to Cite
STARZOMSKI, B. M., SUEN, D. and SRIVASTAVA, D. S. (2010), Predation and facilitation determine chironomid emergence in a bromeliad-insect food web. Ecological Entomology, 35: 53–60. doi: 10.1111/j.1365-2311.2009.01155.x
- Issue published online: 7 JAN 2010
- Article first published online: 7 JAN 2010
- Accepted 16 October 2009
- Mecistogaster modesta;
- processing chain
1. Ecological theory has focused on negative interactions, such as competition and predation, to explain species' effects on one another. This study demonstrates the importance of considering both positive and negative interactions in explaining how species influence abundances at the local scale.
2. Two experiments were conducted using the aquatic insect food web in Costa Rican bromeliad phytotelmata. Manipulations contrasted the strength of predation between trophic levels versus facilitation within a trophic level on the emergence of detritivore chironomids.
3. Predation had a strong negative effect on chironomids, reducing emergences by 81% overall. Most predation was as a result of the top predator, the odonate Mecistogaster modesta; the intermediate predator, a tanypodine chironomid, had little effect. In the absence of predators, shredder and scraper detritivores (tipulid and scirtid larvae) increased the emergence rate of chironomid larvae by 86%. The mechanism of facilitation was likely the processing, by tipulids and scirtids, of intact detritus into fine particles that the detritivore chironomids consume or use to build protective cases.
4. This study is among the first demonstrations of a processing chain in a multi-species context, and in bromeliad-insect food webs. Our finding that top-down effects are of similar magnitude to facilitative effects suggests that the relative importance of processing chains in nature will depend on food web context.