Surya P Sharma
Projet
The genomics of adaptation to abiotic and biotic stressors in brook trout populationsBiodiversity is declining worldwide, but not all populations respond to environmental change in the same way. Some decline rapidly, while others persist for centuries despite being small and isolated. Understanding why some populations endure, and identifying those most vulnerable before decline becomes irreversible, is critical for effective conservation. My doctoral research investigates three interrelated dimensions of population resilience and vulnerability using brook trout (Salvelinus fontinalis), a freshwater fish widely distributed across Canada. (1) Whether genomic regions such as paralogs help small, isolated populations withstand the effects of having fewer individuals. Small, isolated populations are expected to experience reduced genetic diversity, more inbreeding, and an accumulation of harmful mutations that can erode their ability to adapt, increasing their risk of extinction. Yet some small populations persist for surprisingly long periods despite these disadvantages, for reasons that remain poorly understood. Brook trout and other salmonids retain large amounts of duplicated genetic material, or paralogs, originating from an ancient whole-genome duplication. I will investigate whether these duplicated regions help buffer the effects of harmful mutations and contribute to population persistence. (2) Whether local stream conditions improve our ability to identify populations vulnerable to future climate change. Identifying vulnerable populations early provides valuable time for conservation action, but predictions of climate vulnerability often rely on broad-scale climate data, such as air temperature, which may not reflect the conditions fish actually experience within individual streams. Stream temperatures can differ substantially over short distances due to groundwater, stream morphology, and water flow. I will compare predictions based on broad-scale climate data with those based on fine-scale, field-measured stream temperatures to determine whether local environmental information improves our ability to identify climate-vulnerable populations. (3) How size-selective fishing changes the genetic makeup of wild populations over time. Harvesting is one of the predominant causes of population decline in freshwater fishes. Size-selective harvesting removes larger individuals, potentially favouring changes in body size and other traits over generations. Using populations exposed to an ongoing, controlled harvesting program in Banff, Yoho, and Kootenay National Parks, I will compare genetic changes over time between harvested and unharvested populations to determine whether harvesting leaves measurable genetic signatures, and how quickly such changes occur. Together, this study will help identify vulnerable populations and support conservation before declines become irreversible. It will also improve predictions of climate vulnerability, giving conservation managers the information needed to act before declines begin. Finally, this work supports the goals of Québec's 2030 Nature Plan and Canada's 2030 Nature Strategy, and its approach can be applied to other freshwater fish and wildlife facing similar pressures.
