Density dependence in animal populations: effects of biological predictors and methodological biases
The importance of density in the regulation of animal populations is well established, but the mechanisms by which it operates are still equivocal. More specifically, the extent to which density influences individual fitness remains uncertain, and the variability in responses to density across gradi...
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| Format: | Thesis |
| Language: | English |
| Published: |
2020
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| Online Access: | https://spectrum.library.concordia.ca/id/eprint/987272/ https://spectrum.library.concordia.ca/id/eprint/987272/1/Matte_PhD_F2020.pdf |
| Summary: | The importance of density in the regulation of animal populations is well established, but the mechanisms by which it operates are still equivocal. More specifically, the extent to which density influences individual fitness remains uncertain, and the variability in responses to density across gradients of environmental conditions, and between distinct populations, species, taxonomic classes, and experimental designs has received limited empirical investigation. Using a combination of field experiments with salmonids and meta-analyses at a broader scale, my thesis investigates the relationship between density, somatic growth, and survival, and the extent by which these relationships can be related to biological predictors and methodological biases. In chapter 1, the mechanisms of density dependence are investigated by manipulating the density (range: 0.3 - 7 fish/m^2) of young-of-the-year brook trout (Salvelinus fontinalis) in three genetically distinct populations (θST = 0.13-0.30) during three consecutive summers in sections of streams in Cape Race, Newfoundland. I found that populations exhibited population-specific patterns of density dependence that were consistent across years, which were partially related to environmental conditions. In chapter 2, the mechanisms of competition that cause density dependence in these populations were investigated. To do so, I quantified the consumption and depletion of invertebrate prey communities across brook trout densities in the same experiment as chapter 1. My results demonstrated that strong density dependence can occur without prey depletion or reductions in consumption, suggesting that alternative mechanisms can be important. In chapter 3, a meta-analysis was conducted to quantify the relative importance of biological predictors and methodological biases on the patterns of density dependence in salmonids. This meta-analysis demonstrated that methodological biases (experimental design, density gradient) were better predictors of the shape and strength of density ... |
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