Filling the Gaps in an Eco-Phenotypic Framework of Salmonid Population Resilience

Populations of resident and anadromous salmonids are expected to face increasing threats from chronic and stochastic disturbance arising from human activities that generate changes to climate, landscapes and marine systems. While there is a general recognition that the traits and ecological contexts of species and populations will differentially influence their resilience in the face of such disturbance, our understanding of how ecology and phenotypic variation interact to determine resilience is far from complete. Two notable perspectives have arisen on the role of trait diversity in resilience. One perspective emphasizes the importance of standing diversity, as a potential bet-hedging, or “portfolio” resource that buffers populations or species against uncertain effects of disturbance. A somewhat newer, but complementary perspective, emphasizes phenotypic lability and the dynamic potential for the traits of populations to adaptively keep pace (or not) with environmental change.  Both of these perspectives, but particularly the latter, are rooted in an implicit eco-phenotypic framework that has, for the most part not been explicitly stated and explored. Here I describe the elements of such a functional “eco-phenotypic” framework. This framework builds off current theory and insights from the growing study of eco-evolutionary dynamics, community genetics and niche evolution, to consider how genetic and other contributions to phenotypic diversity influence population, community and ecosystem processes and how resulting feedbacks on trait variation might further stabilize or destabilize population dynamics.  Although not yet fully predictive, this framework is heuristically useful for highlighting some major gaps in our understanding of how resilience arises and is maintained in wild salmonid populations. I will explore some of these gaps with respect to recent studies of salmonids and other taxa, and draw connections to a range of practical questions. What is the capacity for standing diversity and ongoing trait change to keep pace with changing environmental conditions?  To what degree is such diversity likely to be evolutionary or phenotypically plastic and what is the relative value of each to resilience?  When is local adaptation or gene flow beneficial versus detrimental to population persistence? Why are some species so amazingly resilient in some contexts (e.g., invasion) and yet prone to decline in others?