Individuals in food webs: the relationships between trophic position, omnivory and among-individual diet variation

Abstract

Among-individual diet variation is common in natural populations and may occur at any trophic level within a food web. Yet, little is known about its variation among trophic levels and how such variation could affect phenotypic divergence within populations. In this study we investigate the relationships between trophic position (the population's range and average) and among-individual diet variation. We test for diet variation among individuals and across size classes of Eurasian perch (Perca fluviatilis), a widespread predatory freshwater fish that undergoes ontogenetic niche shifts. Second, we investigate among-individual diet variation within fish and invertebrate populations in two different lake communities using stable isotopes. Third, we test potential evolutionary implications of population trophic position by assessing the relationship between the proportion of piscivorous perch (populations of higher trophic position) and the degree of phenotypic divergence between littoral and pelagic perch sub-populations. We show that among-individual diet variation is highest at intermediate trophic positions, and that this high degree of among-individual variation likely causes an increase in the range of trophic positions among individuals. We also found that phenotypic divergence was negatively related to trophic position in a population. This study thus shows that trophic position is related to and may be important for among-individual diet variation as well as to phenotypic divergence within populations.

Keywords

Trophic position; Evolution; Communities; Populations; Eco-evolutionary feedback

Published in

Oecologia
2015, Volume: 178, number: 1, pages: 103-114
Publisher: SPRINGER

SLU Authors

• Olsson, Jens

  • Department of Aquatic Resources (SLU Aqua), Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Ecology


Publication identifier

DOI: https://doi.org/10.1007/s00442-014-3203-4

Permanent link to this page (URI)

https://res.slu.se/id/publ/73035