Biological invasions as fortuitous experiments in nature: ecology, evolution, and phenotypic plasticity of non-native brown trout (Salmo trutta) in Newfoundland, Canada

Westley, Peter A. H. (2012) Biological invasions as fortuitous experiments in nature: ecology, evolution, and phenotypic plasticity of non-native brown trout (Salmo trutta) in Newfoundland, Canada. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Biological invasions represent under-utilized research opportunities to gain insight into fundamental evolutionary and ecological questions. I focused on the invasion of brown trout to Newfoundland, Canada, as a case study and conducted meta-analyses of published literature, field sampling, laboratory, common-garden, and reciprocal transplant experiments to understand what can be learned by embracing the fortuitous research opportunities afford by this invasion. -- In the first chapter I conducted a meta-analysis of published rates of phenotypic change to assess the contribution of invasive versus native species in revealing the rate and form of phenotypic change in wild populations. I found that invasive species have disproportionately contributed to published rates of phenotypic change, but most of these estimated rates are based on extensive studies in a few species. Results in Chapter One suggest that invasive and native species both exhibit evidence of abrupt phenotypic change and suggest an important role of the environment in driving trait change in wild populations. -- In Chapter Two I examined the dynamics of the brown trout invasion in Newfoundland by assembling a presence-absence database to investigate the physical environmental correlates associated with population establishment at the watershed-scale. I found that relatively large and productive watersheds are more likely to be successfully established, but that all watersheds in Newfoundland are susceptible to invasion and population establishment. -- In Chapter Three, I quantified among-population differences in a suite of phenotypic traits (e.g. growth rates, body shape and size, colour patterns) and correlated this diversity with environmental features. On the whole, phenotypic variation was predictable given habitat use, suggesting either phenotypic plasticity or adaptive evolution in maintaining this association. -- In the final chapter, I assessed the contribution of genetics and environmental effects on the population differentiation detected in Chapter Three, along with the associated fitness consequences of these phenotypic differences. With a combination of common-garden and reciprocal transplant experiments, I quantified the role of plasticity in facilitating survival in novel environments and revealed patterns not predicted by theory. Specifically, results suggested that plasticity in functional morphology - while common - did not occur in the direction favoured by natural selection.

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