Among‐individual diet variation within a lake trout ecotype: Lack of stability of niche use. Issue 3 (19th January 2021)

• Record Type: Journal Article
• Authors: Chavarie, Louise; Howland, Kimberly L.; Harris, Les N.; Gallagher, Colin P.; Hansen, Michael J.; Tonn, William M.; Muir, Andrew M.; Krueger, Charles C.
• Is Part Of: Ecology and evolution. Volume 11:Issue 3(2021)
• Page Start: 1457
• Page End: 1475
• Publication Date: 2021-01-19
• Subjects: Arctic -- fatty acids -- generalist -- genetic -- morphology -- resource use -- Salvelinus namaycush -- specialist; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.7158
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: In a polyphenic species, differences in resource use are expected among ecotypes, and homogeneity in resource use is expected within an ecotype. Yet, using a broad resource spectrum has been identified as a strategy for fishes living in unproductive northern environments, where food is patchily distributed and ephemeral. We investigated whether specialization of trophic resources by individuals occurred within the generalist piscivore ecotype of lake trout from Great Bear Lake, Canada, reflective of a form of diversity. Four distinct dietary patterns of resource use within this lake trout ecotype were detected from fatty acid composition, with some variation linked to spatial patterns within Great Bear Lake. Feeding habits of different groups within the ecotype were not associated with detectable morphological or genetic differentiation, suggesting that behavioral plasticity caused the trophic differences. A low level of genetic differentiation was detected between exceptionally large‐sized individuals and other piscivore individuals. We demonstrated that individual trophic specialization can occur within an ecotype inhabiting a geologically young system (8, 000–10, 000 yr BP), a lake that sustains high levels of phenotypic diversity of lake trout overall. The characterization of niche use among individuals, as done in this study, is necessary to understand the role that individual variation can play at the beginning of differentiation processes. Abstract : A common assumption in polyphenism is that partitioning and variability of resource use will occur predominantly among ecotypes rather than within ecotypes. In contrast, homogeneity of resource use is anticipated to occur within ecotypes, be spatially and temporally stable, and provide the selection opportunity for specialization. However, this study provided evidence that variation occurred within an ecotype due to diet specialization among individuals, possibly a precursor to further population diversification via fine‐scale ecological selection.