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FROM INDIVIDUAL ATTRIBUTES TO POPULATION DYNAMICS AND WHOLE COMMUNITY STABILITY IN AQUATIC SYSTEMS

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Title: FROM INDIVIDUAL ATTRIBUTES TO POPULATION DYNAMICS AND WHOLE COMMUNITY STABILITY IN AQUATIC SYSTEMS
Author: Caskenette, Amanda
Department: Department of Integrative Biology
Program: Integrative Biology
Advisor: McCann, Kevin
Abstract: The way ecologists study the world creates boundaries between individual, population, and community scales. All scales interact, however, and changes in function or stability at one scale resonates at all other scales. Starting from the individual scale, this thesis crosses these artificial boundaries and determines the effect of individual behaviour, size, and life-stage on population density, energy flow in food webs, and food web stability. Chapter 1 uses a novel approach to test the behavioural mechanism behind how changes in resource and habitat use respond to changes in resource availability and accessibility for lake trout (Salvelinus namaycush) across Ontario. These results ultimately reveal how these aquatic ecosystems respond to environmental variation and alter the flow of carbon through the ecosystem. Chapter 2 explores how changes in resource use as an individual grows influence the relationship between body size and population density. The commonly seen relationship between mean body-size and density at the global scale often breaks down as the scale of observation decreases, and we suggest that this is due to the increased importance of variation in body size. Using data on lake trout body-size and density across communities, we ask if variation in body-size influences population density. Lastly, Chapter 3 explores how ontogenetic changes in resource use may distribute energy in a way that stabilizes communities with life-history intra-guild predation. There are three main conclusions in this thesis. First, by using a behavioural approach to measure habitat use, we find support for a behavioural mechanism for how lake trout respond to changes in resource availability and accessibility (Chapter 1). Second, variability in body size mediated by the available resource spectrum may cause the break-down of the broad scale body size – density relationship at the population level (Chapter 2). Finally, maturation and reproduction can redistribute energy away from strong interactions to weak interactions in populations with ontogenetic diet shifts, in turn stabilizing the community (Chapter 3).
URI: http://hdl.handle.net/10214/8722
Date: 2015-01
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