Effective population size and connectivity in fish

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 influence of life history from that of environment. I also plan to reconstruct ancestral population dynamics; I will compare historical changes in Ne and timing of ancestral population bottlenecks across salmonid and non-salmonid fish 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 will take place in northern and central Labrador (Torngat Mountains National Park and vicinity, and Mealy Mountains National Park and vicinity, respectively).