Sources of variation in small rodent trophic niche: new insights from DNA metabarcoding and stable isotope analysis

† Contribution to Special Section “Stable Isotopes in Mammals.”

Abstract

Intraspecific competition for food is expected to increase the trophic niche width of consumers, defined here as their diet diversity, but this process has been little studied in herbivores. Population densities of small rodents fluctuate greatly, providing a good study model to evaluate effects of competition on trophic niche. We studied resource use in five arctic small rodent populations of four species combining DNA metabarcoding of stomach contents and stable isotope analysis (SIA). Our results suggest that for small rodents, the most pronounced effect of competition on trophic niche is due to increased use of secondary habitats and to habitat-specific diets, rather than an expansion of trophic niche in primary habitat. DNA metabarcoding and SIA provided complementary information about the composition and temporal variation of herbivore diets. Combing these two approaches requires caution, as the underlying processes causing observed patterns may differ between methodologies due to different spatiotemporal scales.

Keywords:

• animals
• carbon-13
• competition
• diet diversity
• DNA metabarcoding
• habitat use
• herbivore
• isotope ecology
• nitrogen-15
• trophic niche width
• tundra food web

Acknowledgements

We thank F. Bilodeau, S. Hamel, J.-A. Henden, M.-A. Giroux, S.T. Killengreen, J.-F. Therrien and numerous field assistants for sample collection and/or processing; E. Bolduc, S. Kaino, C. Miquel, D. Rioux, and A. Valentini for help with laboratory analyses; L. Zinger and E. Coissac for help with bioinformatics analyses as well as O. Huitu and V. T. Ravolainen for good comments on this manuscript. We also thank the staff at various museums that provided access to plant specimens used for construction of the taxonomic reference libraries, in particular L. J. Gillespie, J. M. Saarela, J. Doubt, M. Lomonosova, D. Shaulo, J. E. Eriksen and S. Ickert-Bond.

Funding

This study was funded by the Research Council of Norway (projects ‘Ecosystem Finnmark’, ‘EcoFinn’, ‘Arctic Predators’, ‘BarFrost’ and a Leiv Eiriksson mobility grant to EMS); Oskar Huttunen foundation (PhD Scolarship for EMS) and University of Tromsø (mobility grant for EMS). Field work on Bylot Island was supported by the Natural Sciences and Engineering Research Council of Canada; International Polar Year program of Indian and Northern Affairs Canada; the Network of Centers of Excellence of Canada ArcticNet; Canada Research Chairs Program; Fonds Québécois de la Recherche sur la Nature et les Technologies and Northern Scientific Training Program (INAC) as well as the Canadian Foundation for Innovation.

Conflict of interest

L.G. is one of the co-inventors of a patent concerning g−h primers and the subsequent use of the P6 loop of the chloroplast trnL (UAA) intron for plant identification using degraded template DNA. These patents only restrict commercial applications and have no impact on the use of this locus by academic researchers.

Supplemental material

Supplemental data for this article can be accessed 10.1080/10256016.2014.915824.

Notes

† Contribution to Special Section “Stable Isotopes in Mammals.”