Conserving the Evolutionary Legacy of Arctic-Yukon-Kuskokwim Salmon
Robin S. Waples
Abstract.—The legacy of Pacific salmon Oncorhynchus spp. can be described as the genetic resources that are the product of past evolutionary events and which represent the future evolutionary potential of the species. A key step in conserving this legacy is identifying conservation units—major chunks of biodiversity that collectively comprise the evolutionary legacy. A variety of methods exist for defining conservation units, but all should follow a two-step process. Step One is describing the (often hierarchical) structure of biodiversity within each species—that is, the evolutionary relationships among populations and metapopulations or larger conservation units. In theory, this is an objective, data-driven exercise. Step Two involves considering questions such as, “Which level in the hierarchy is best for identifying conservation units?” and “How much biodiversity do we need to conserve?” These questions do not have a single ‘correct’ answer; instead, they must be informed by societal values. In Step Two, therefore, it is important to articulate clear program goals to provide a context for addressing these difficult questions. But defining conservation units is only part of a coherent, long-term conservation strategy; evolution is dynamic, whereas simply conserving certain fixed types promotes stasis. Therefore, equally important is the conservation of evolutionary processes, which are the dynamic relationships between salmon and their ecosystems that help shape their evolutionary trajectories. Evolutionary processes include patterns of connectivity, dispersal, and gene flow; sexual selection and natural selection; and interactions with physical and biological features of the habitat. Conserving evolutionary processes requires consideration of the same two steps outlined above. Reflecting on the long-term goals of the Arctic-Yukon-Kuskokwim Sustainable Salmon Initiative will help to focus efforts to identify important units for conservation and vital evolutionary processes for Alaska salmon.