Ecological opportunities and intraspecific competition alter trophic niche specialization in an opportunistic stream predator

• Published in: The Journal of animal ecology 2014-09, Vol.83 (5), p.1025-1034
• Main Authors: Evangelista, Charlotte, Boiche, Anatole, Lecerf, Antoine, Cucherousset, Julien
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal ecology; Animal populations; Animal, plant and microbial ecology; Animals; Biological and medical sciences; competition; Ecological and Environmental Phenomena; Ecosystem; Forest canopy; Forests; France; Fresh water ecosystems; Freshwater ecology; Fundamental and applied biological sciences. Psychology; General aspects; individual performances; inter‐individual variability; Invertebrates - physiology; Isotopes; Population density; Population ecology; Predation; Predators; Predatory Behavior; Riparian ecology; riparian land‐use; Rivers; stable isotope analyses; Streams; Synecology; trophic subsidies; Trout; Trout - growth & development; Trout - physiology
• ISSN: 0021-8790; 1365-2656
• DOI: 10.1111/1365-2656.12208

1. Many generalist populations are composed of specialized individuals that use a narrow part of the population's niche. Ecological theories predict that individual specialization and population trophic niche are determined by biotic interactions and resource diversity emerging from environmental variations (i.e. ecological opportunities). However, due to the paucity of empirical and experimental demonstrations, the genuine importance of each of these drivers in determining trophic niche attributes is not fully appreciated. 2. The present study aimed at determining the population level and individual responses of brown trout (Salmo trutta) to variations in ecological opportunities (terrestrial prey inputs) and autochthonous prey communities among 10 stream reaches along a riparian condition gradient using individual longitudinal monitoring and stable isotope analyses. 3. Our results suggested that trophic niche diversity varied along the environmental gradient, while individual trophic specialization was indirectly driven by ecological opportunities through strengthened intraspecific competition. Individual diet was repeatable over the study period, and the growth rate of juvenile brown trout increased with their specialization for aquatic predatory invertebrates. 4. Our findings highlight the dual influences of intraspecific competition and ecological opportunities on individual trophic specialization and population trophic niche.