Effective population size and connectivity in fish

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A fundamental concept in evolutionary biology is that of effective population size (Ne). Ne reflects the size of an "ideal" population experiencing the same rate of random genetic change per generation as the actual population under study (census size N). The concept is central to conservation genetics because of its links to inbreeding depression, population persistence and evolutionary potential. Effective sizes are typically much smaller than census sizes. Fluctuating population size over time, unequal sex ratio and variance in life time reproductive success contribute to the low Ne/N ratios commonly observed in nature. Such low ratios suggest that populations may be subject to the loss of genetic diversity even when census sizes are still relatively large. Knowledge of the mechanisms that affect Ne, its relationship with N and with gene flow (m) and their interaction is thus critical for understanding the mechanisms that affect biodiversity. My long term research goals are to understand the processes that affect Ne and m, and their relationship with N, and to identify the conditions under which Ne can be used to predict population persistence. I intend to compare patterns of Ne and m across sympatric populations of fish species to disentangle the influences of life history and environment. I also plan to reconstruct ancestral population dynamics; I will compare historical changes in Ne and timing of ancestral population bottlenecks across species and will relate this information to geo-morphological processes and past climatic changes (Quaternary). The goal is to determine how similar current and historic patterns of Ne and m are for populations of coexisting species and to examine the roles played by life histories and ecologies vs. geomorphology and climate in producing these patterns. Fieldwork takes place in two contrasting temperate systems: A northern "Salmonid" system, and a Patagonian system. Both are found in post-glacial landscapes. The northern salmonid system includes Atlantic salmon, brook trout, and Arctic char in Newfoundland and Labrador. The Patagonian system comprises two widely distributed native Patagonian fishes. In both cases, species are found in a variety of ecological settings.