Abstract

Effective population size (Ne) is a key parameter in conservation biology, as it influences the degree of genetic drift and adaptive potential of a population. Although Ne is widely reported in individual studies, it is not well integrated into monitoring programs, and there is still much to learn about how it is impacted by human-induced stressors. My thesis attempted to bridge these gaps through (1) an experiment assessing how Ne changes within populations exposed to size- selective harvest, and (2) a quantitative review summarizing Ne estimates across and within taxa in wild populations. I showed experimentally that in populations of brook trout (Salvelinus fontinalis) exposed to size-selective harvest, change in Ne is buffered through density-dependent genetic compensation. Therefore, in the short-term, Ne can be resilient to harvest even with substantial decreases in population size. My review also showed that Ne varies between taxonomic groups in wild populations, and that a high human footprint is associated with lower Ne, especially in amphibians and mammals. There were two broad conclusions from this work. Firstly, many wild populations fall below key conservation thresholds (Ne of 50 or 500), and I discuss the caveats of using conservation thresholds based on broad generalizations across taxa that vary in life history traits and adaptations. Secondly, I emphasize the importance of integrating genetic and demographic factors in monitoring and risk assessments. Overall, these conclusions can help guide the integration of Ne into research, monitoring, and policy.