Genetic variation reveals influence of landscape connectivity on population dynamics and resiliency of western trout in disturbance-prone habitats

Salmonid fishes have evolved and persisted in dynamic ecosystems (Waples and others 2008) where disturbance events vary in frequency, magnitude, timing, and duration (Gresswell 1999; Dale and others 2001), as well as the specific nature of associated effects (e.g., changes in thermal or flow regimes, geomorphology, or water chemistry; Reeves and others 1995; Benda and others 2004; Bisson and others 2005). In the western United States, one of the major drivers of disturbance in stream ecosystems is fire (Reeves and others 1995; Rieman and Clayton 1997; Gresswell 1999). Although there is a growing consensus that fish populations can ultimately benefit from the productive and heterogeneous habitats created by fire (Reeves and others 1995; Benda and others 2003; Minshall 2003; Rieman and others 2003), to persist they obviously have to withstand the immediate and shorter-term effects of fire, which can reduce or even extirpate local populations (Rieman and Clayton 1997; Brown and others 2001; Burton 2005; Sestrich 2005). Movement among interconnected stream habitats is thought to be an important strategy enabling persistence during and following fire, and there is mounting concern that the extensive isolation of salmonid populations in fragmented habitats is reducing their resiliency to fire (Gresswell 1999; Dunham and others 2003; Rieman and others 2003).