Temperature-associated population diversity in salmon confers benefits to mobile consumers

Abstract

Habitat heterogeneity can generate intraspecific diversity through local adaptation of populations. While it is becoming increasingly clear that population diversity can increase stability in species abundance, less is known about how population diversity can benefit consumers that can integrate across population diversity in their prey. Here we demonstrate cascading effects of thermal heterogeneity on trout-salmon interactions in streams where rainbow trout rely heavily on the seasonal availability of anadromous salmon eggs. Water temperature in an Alaskan stream varied spatially from 5 degrees C to 17.5 degrees C, and spawning sockeye salmon showed population differentiation associated with this thermal heterogeneity. Individuals that spawned early in cool regions of the 5 km long stream were genetically differentiated from those spawning in warmer regions later in the season. Sockeye salmon spawning generates a pulsed resource subsidy that supports the majority of seasonal growth in stream-dwelling rainbow trout. The spatial and temporal structuring of sockeye salmon spawn timing in our focal stream extended the duration of the pulsed subsidy compared to a thermally homogeneous stream with a single population of salmon. Further, rainbow trout adopted movement strategies that exploited the multiple pulses of egg subsidies in the thermally heterogeneous stream. Fish that moved to track the resource pulse grew at rates about 2.5 times higher than those that remained stationary or trout in the reference stream with a single seasonal pulse of eggs. Our results demonstrate that habitat heterogeneity can have important effects on the population diversity of dominant species, and in turn, influence their value to species that prey upon them. Therefore, habitat homogenization may have farther-reaching ecological effects than previously considered.

Effects of Temperature and Spatial Scale on Rio Grande Cutthroat Trout Growth and Abundance

“…In other salmonids, diverse life history attributes (particularly growth rates) and even genetic differentiation have been linked to fine‐scale (within‐stream) temperature heterogeneity (Ruff et al. ). Asynchronous population dynamics in response to temperature at fine scales may also be important for the persistence of RGCT populations, as many populations are already isolated within streams (Alves et al.…”

Meiotic maps of sockeye salmon derived from massively parallel DNA sequencing

“…This threat, occurring during an era empowered by the advent of conservation genomics [12], precipitates a need for genomic resources to enable studies of genetic diversity, adaptive variation, and genotype-by-environmental interactions in sockeye salmon. Additionally, sockeye salmon exhibit a variety of unique life histories [28,36], and additional genomic resources are necessary for determining the genetic basis for these diverse life history traits.…”

Variation in spawning phenology within salmon populations influences landscape‐level patterns of brown bear activity

“…While research has emphasized the magnitudes of among‐stream thermal variation that drive inter‐population variation in spawning phenology (Hodgson and Quinn , Ruff et al. , Lisi et al. ), these ranges in temperatures can also be expressed within single rivers (Webb and McLay ) and streams (Baldock et al.…”

“…Bears can potentially exploit migrating salmon in route to other spawning sites (e.g., streams draining lakes may be both spawning sites and migration corridors for salmon, Ruff et al. ), scavenge the carcasses of senescent salmon that persist after a run has subsided (Quinn and Buck ), and capitalize on multiple salmon species that spawn at different times at the same site (Levi et al. ).…”