Environmental, biological, and genetic factors influencing local adaptation of pink salmon (Oncorhynchus gorbuscha) in Auke Creek, Alaska

Thesis (Ph.D.) University of Alaska Fairbanks, 2016Pacific salmon form distinct, locally adapted populations because of the spatial and temporal precision with which they home to their natal streams. Local adaptation is recognized as an important component underlying the productivity and sustainability of salmonid populations, yet there remains uncertainty of the scale at which it occurs. This uncertainty was addressed by analysis of demographic, genetic, and experimental data collected from seasonally structured brood lines of Pink Salmon that spawn in Auke Creek, Alaska. An extensive background of research on this system has indicated that the timing of the adult and juvenile migrations is closely aligned with fitness and productivity in this stream; this background provided a framework for synthesizing the results of the analyses to address these questions: (1) What ecological factors influence productivity of the freshwater and marine life history stages; (2) Do these factors suggest a mechanism for evolution of migration time; (3) What are the consequences of disrupting fine-scale local adaptation of migration time? Freshwater productivity appeared to be influenced primarily by competition for spawning habitat, rather than variability in environmental conditions. Marine productivity, conversely, was associated with physical processes that influence survival of juveniles in the nearshore environment. Consistent with these findings, genetic evolution of earlier migration time, which was observed in both adults and juveniles over two generations, appeared to be driven by earlier vernal warming of the nearshore environment. Despite these environmental changes and resulting selection against late migrating fish, recruitment to Auke Creek has remained stable, thereby indicating that seasonal structure of migration time has supported sustained productivity in a changing climate. Experimental relaxation of natural barriers to gene flow that maintain the seasonal structure resulted in intermediate adult migration times in two generations of hybrid fish. These patterns were consistent with an additive genetic basis for migration time and suggest that ecological outbreeding depression is a post-zygotic mechanism that maintains adaptive variation of migration time in Auke Creek. Collectively, these results provide evidence that fine-scale local adaptation can enhance productivity of salmonid populations while providing resilience to climate change.Introduction -- Chapter 1 - Ecological factors influencing lifetime fitness of Pink Salmon (Oncorhynchus Gorbuscha) in an Alaskan stream -- Chapter 2 - Evolution of phenology in a salmonid population: a potential adaptive response to climate change -- Chapter 3 - Local adaptation of phenology revealed in out crosses between spawning segments of a salmonid population -- Conclusions -- Supplementary materials

A test of local adaptation in seasonally separate subpopulations of pink salmon (Oncorhynchus gorbuscha)

Thesis (M.S.) University of Alaska Fairbanks, 2012Differences in fitness related traits were observed between first generation (F₁) hybrid and control lines of temporally distinct subpopulations of pink salmon (Oncorhynchus gorbuscha). The lines were cultured in a common freshwater environment, released to sea together, and collected at their natal stream as adults. Early-and late-run pink salmon, which are partially genetically isolated by the time at which they return to Auke Creek in Southeast Alaska to spawn, were crossed to create F₁ and F₂ hybrid groups in the even- and odd-year brood lines. Marine survival of controls exceeded that of F₁ hybrids of the even-year brood line, whereas no difference in marine survival between those experimental groups was detected in the odd-year brood line. First generation hybrids expressed intermediate time of return relative to controls in both brood lines. Second generation hybrids exhibited similar embryonic development rates to controls in both brood lines. These results demonstrate that removal of a genetic barrier as fine as that which occurs within a brood line and location can disrupt local adaptation in a population of pink salmon, which may cause outbreeding depression in hybrids and may potentially reduce the overall biodiversity and productivity of the population.National Oceanic and Atmospheric Administration Office of Sea Grant, Department of Commerce, under grant no. NA060AR4170013 project no. R/31-13, and from the University of Alask

Evolution of phenology in a salmonid population: a potential adaptive response to climate change

Accumulating evidence has indicated that many fish populations are responding to climate change through shifts in migration time, but genetic data identifying the role of evolution in these shifts are rare. One of the first demonstrations of evolution of migration time was produced by monitoring allozyme alleles that were experimentally manipulated to genetically mark late-migrating pink salmon. Here, we extend that research by using observations of the marker alleles in fry to demonstrate that these changes in migration time were caused by directional selection against the late-migrating phenotype during the oceanic phase of the salmonid life cycle. The selective event, which appeared to be driven by early vernal warming of the nearshore marine environment and consequent decreased survival of late-migrating fry relative to early-migrating fry, decreased the late-migrating phenotype from more than 50% to approximately 10% of the total fry abundance in only one generation. These demographic changes have persisted over the subsequent thirteen generations and suggest that a larger trend toward earlier migration time in this population may reflect adaptation to warming sea-surface temperatures.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

A laboratory-calibrated model of coho salmon growth with utility for ecological analyses

We conducted a meta-analysis of laboratory- and hatchery-based growth data to estimate broadly applicable parameters of mass- and temperature-dependent growth of juvenile coho salmon (Oncorhynchus kisutch). Following studies of other salmonid species, we incorporated the Ratkowsky growth model into an allometric model and fit this model to growth observations from eight studies spanning ten different populations. To account for changes in growth patterns with food availability, we reparameterized the Ratkowsky model to scale several of its parameters relative to ration. The resulting model was robust across a wide range of ration allocations and experimental conditions, accounting for 99% of the variation in final body mass. We fit this model to growth data from coho salmon inhabiting tributaries and constructed ponds in the Klamath Basin by estimating habitat-specific indices of food availability. The model produced evidence that constructed ponds provided higher food availability than natural tributaries. Because of their simplicity (only mass and temperature are required as inputs) and robustness, ration-varying Ratkowsky models have utility as an ecological tool for capturing growth in freshwater fish populations.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Ecological factors influencing lifetime productivity of pink salmon (Oncorhynchus gorbuscha) in an Alaskan stream

Ecological factors underlying freshwater productivity and marine survival of pink salmon (Oncorhynchus gorbuscha) were evaluated by analyzing a 30-year time series of local environmental data and censuses of migrating adult and juvenile fish collected at Auke Creek, Alaska. Freshwater productivity was influenced primarily by spawning habitat limitation and less so by stream temperature and flow. Furthermore, a trend of declining freshwater productivity was detected over the time series, which may be related to observed declines in spawning substrate quality and in the duration of the adult migration. Marine survival was highly variable among brood years and was influenced by physical conditions in the nearshore marine environment; warm sea-surface temperatures during nearshore residency were associated with higher marine survival rates, whereas high stream flows late in the fry emigration period were associated with reduced marine survival. Simulations of adult recruitment, based on ecological factors in the freshwater and marine environments, indicated that the productivity of pink salmon in this stream is determined primarily by early marine survival.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author