Trophic assimilation efficiency markedly increases at higher trophic levels in four-level host–parasitoid food chain

Sanders, D., Moser, A., Newton, J. and van Veen, F. V. F. (2016) Trophic assimilation efficiency markedly increases at higher trophic levels in four-level host–parasitoid food chain. Proceedings of the Royal Society of London Series B: Biological Sciences, 283, 1826. (doi: 10.1098/rspb.2015.3043) (PMID:26962141)

Abstract

Trophic assimilation efficiency (conversion of resource biomass into consumer biomass) is thought to be a limiting factor for food chain length in natural communities. In host–parasitoid systems, which account for the majority of terrestrial consumer interactions, a high trophic assimilation efficiency may be expected at higher trophic levels because of the close match of resource composition of host tissue and the consumer's resource requirements, which would allow for longer food chains. We measured efficiency of biomass transfer along an aphid-primary–secondary–tertiary parasitoid food chain and used stable isotope analysis to confirm trophic levels. We show high efficiency in biomass transfer along the food chain. From the third to the fourth trophic level, the proportion of host biomass transferred was 45%, 65% and 73%, respectively, for three secondary parasitoid species. For two parasitoid species that can act at the fourth and fifth trophic levels, we show markedly increased trophic assimilation efficiencies at the higher trophic level, which increased from 45 to 63% and 73 to 93%, respectively. In common with other food chains, δ15N increased with trophic level, with trophic discrimination factors (Δ15N) 1.34 and 1.49‰ from primary parasitoids to endoparasitic and ectoparasitic secondary parasitoids, respectively, and 0.78‰ from secondary to tertiary parasitoids. Owing to the extraordinarily high efficiency of hyperparasitoids, cryptic higher trophic levels may exist in host–parasitoid communities, which could alter our understanding of the dynamics and drivers of community structure of these important systems.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Newton, Dr Jason
• Authors: Sanders, D., Moser, A., Newton, J., and van Veen, F. V. F.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Proceedings of the Royal Society of London Series B: Biological Sciences
• Publisher: The Royal Society
• ISSN: 0962-8452
• ISSN (Online): 1471-2954
• Copyright Holders: Copyright © 2016 The Authors
• First Published: First published in Proceedings of the Royal Society of London Series B: Biological Sciences 283:1826
• Publisher Policy: Reproduced under a Creative Commons License