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Links between evolution/epigenetics and population dynamics
A fundamental aim in ecology is to understand how organisms respond to changing environmental conditions. Empirical studies typically focus on direct effects on phenotypes through movement along reaction norms and corresponding effects on demographic rates and population dynamics, or on evolutionary/epigenetic changes in the shape of reaction norms. Yet, it is becoming increasingly clear that feedback between reaction norm shapes and population dynamics may substantially influence biological outcomes. Including such feedback mechanisms between these two processes provides great promise in advancing understanding of evolutionary and ecological dynamics, but is inherently challenging, and choice of suitable model systems are crucial for success. I am currently approaching these problems using Daphnia (D. magna) as a model organism, where I aim to quantify variation in both life history traits and population dynamics caused by exogenous (i.e. environment) and endogenous variables (i.e. acclimation, epigenetic effects, genetic variation). Daphnia are small crustaceans which commonly dominate the grazing communities in lakes and ponds, and they have several biological characteristics that make them favourable for such studies, such as clonal reproduction, short generation time, and a long history as model organisms in freshwater labs throughout the world.
Daphnia are famous for their high degree of phenotypic plasticitiy, with the presence of predators inducing production of a helmet-shaped carapace (right below)
Plants and other sessile organisms are commonly observed to vary in their population density over small spatial scales within single populations. For mobile organisms, such variation is commonly assumed to be minimized due to the ability to disperse away from patches of high density. Yet, even for such organisms (e.g. insects, fish), density has been shown to vary over surprisingly small spatial scales. This may have important consequences for mean levels of and within-population variation in competition intensity, population dynamics, and perhaps even evolutionary processes. Much of my recent research has focused on the issue of how the spatial distribution of individuals and resources within populations translates into population-level effects, using Atlantic salmon as a model organism.
Maternal effects can be defined as phenotypic variation in the offspring generation caused by genetically or environmentally induced phenotypic variation (i.e. maternal traits) in the maternal generation. One of my long-term scientific interests has been to understand the evolutionary dynamics of and empirically test theories underlying the spatiotemporal variation in maternal traits (in particular, breeding time and egg size). This has been accomplished through a series of small and large scale experiments (using salmonids) combined with comparative studies of fish. These studies have provided evidence for a causal effect of these traits on the fitness of juveniles. Furthermore, the effect of such traits on juvenile performance depends on environmental quality, suggesting a scope for local adaptations to occur among populations, but also for adaptive variation to occur within populations.
Divergence of wild and cultured fish
Billions of cultured fish are released intentionally or accidentally into nature each year, and biologists have for a long time been concerned about the effects such releases can have on wild fish populations. We have quantified experimentally and through meta-analyses to what degree and why cultured fish differ from wild ones. These studies have identified genetic divergence to occur in fitness related quantitative traits as well as in gene expression patterns between wild and cultured fish, and a high potential for interbreeding between wild and cultured fish. The results of this work indicate that inappropriate management using cultured fish and invasions of escaped farmed fish has the potential to negatively impact the productivity and genetic integrity of wild populations, and thus their long-term viability.
Robertsen, G., Skoglund, H., Einum, S. (2013) Offspring size effects vary over fine spatio-temporal scales in Atlantic salmon (Salmo salar). Canadian Journal of Fisheries and Aquatic Sciences, 70: 5-12.
Foldvik, A., Teichert, M. A. K., Einum, S., Finstad, A. G., Ugedal, O. & Forseth, T. (2012). Spatial distribution correspondence of a juvenile Atlantic salmon Salmo salar cohort from age 0+ to 1+ years. Journal of Fish Biology, 81: 1059-1069.
Sundt-Hansen, L., Einum, S., Neregård, L., Bjornsson, B., Johnsson, J., Fleming, I., Devlin, R., Hindar, K. (2012). Growth hormone reduces growth in free-living Atlantic salmon fry. Functional Ecology, 26: 904-911.
Einum, S, Forseth, T. & Finstad, A. G. (2012). Individual variation in response to intraspecific competition: problems with interference from growth variation measures. Methods in Ecology and Evolution, 3: 438-444.
Einum, S, Finstad, A. G., Robertsen, G., Nislow, K. H., McKelvey, S. & Armstrong, J. D. (2012). Natal movement in juvenile Atlantic salmon: a body size-dependent strategy? Population Ecology, 54: 285-294.
Skoglund, H., Einum, S., Forseth, T. & Barlaup, B. (2011) The penalty for arriving late in emerging salmonid juveniles: differences between species correspond to their interspecific competitive ability. Functional Ecology, 26: 104-111.
Einum, S, Nislow, K. H., McKelvey, S. & Armstrong, J. D. (2011). The spatial scale of competition from recruits on an older cohort in Atlantic salmon. Oecologia, 167: 1017-1025.
Skoglund, H., Einum, S., Forseth, T. & Barlaup, B. (2011) Phenotypic plasticity in physiological status at emergence from nests as a response to temperature in Atlantic salmon (Salmo salar). Canadian Journal of Fisheries and Aquatic Sciences, 68: 1470-1479.
Einum, S. & Kvingedal, E. (2011) Relative importance of size-based competitive ability and degree of niche overlap in inter-cohort competition of Atlantic salmon juveniles. Canadian Journal of Fisheries and Aquatic Sciences, 68: 969-976.
Kvingedal, E. & Einum, S. (2011) Prior residency advantage for Atlantic salmon in the wild: effects of habitat quality. Behavioural Ecology and Sociobiology, 65: 1295-1303.
Robertsen, G., Kvingedal, E. & Einum, S. (2011) Is there genetic variation in the response to competition intensity in juvenile brown trout, Salmo trutta? Journal of Fish Biology, 78: 635-646.
Skoglund, H. Einum, S. & Robertsen, G. (2011) Competitive interactions shape offspring performance in relation to seasonal timing of emergence in Atlantic salmon. Journal of Animal Ecology, 80: 365-374 .
Martinussen, P. A., Robertsen, G. & Einum, S. (2011) Density-dependent diet composition of juvenile Atlantic salmon (Salmo salar). Ecology of Freshwater Fish, 20:384-392.
Einum, S, Robertsen, G., Nislow, K. H., McKelvey, S. & Armstrong, J. D. (2011). The spatial scale of density-dependent growth and implications for dispersal from nests in juvenile Atlantic salmon. Oecologia, 165: 959-969.
Kvingedal, E. & Einum, S. (2011) Intra- and intercohort spatial density dependence in juvenile brown trout (Salmo trutta). Canadian Journal of Fisheries and Aquatic Sciences, 68: 115-121.
Teichert, M. A. K., Foldvik, A., Forseth, T., Ugedal, O., Einum, S., Finstad, A. G., Hedger, R. D. & Bellier, E. (2011) Effects of spawning distribution on juvenile Atlantic salmon density and growth. Canadian Journal of Fisheries and Aquatic Sciences, 68: 43-50.
Finstad, A. G., Einum, S., Sættem, L. M. & Hellen, B. A. (2010) Spatial distribution of Atlantic salmon breeders: among- and within-river variation and predicted consequences for offspring habitat availability. Canadian Journal of Fisheries and Aquatic Sciences, 67: 1993-2001.
Foldvik, A., Finstad, A. G. & Einum, S. (2010). Relating juvenile spatial distribution to breeding patterns in anadromous salmonid populations. Journal of Animal Ecology, 79, 501-509.
Sundt-Hansen, L., Neregård, L., Einum, S., Höjesjö, J., Björnsson, B. Th., Hindar, K., Økland, F. & Johnsson, J. (2009). Growth enhanced brown trout show increased movement activity in the wild. Functional Ecology, 23, 551-558.
Yeates, S. E., Einum, S., Fleming, I. A., Megens, H.-J., Stet, R. J. M., Hindar, K., Holt, W. V., Van Look, K. J. W., & Gage, M. J. G. (2009). Atlantic salmon eggs favour sperm in competition that have similar Major Histocompatibility alleles. Proceedings of the Royal Society of London, Ser. B, 276, 559-566.
Finstad, A. G., Einum, S., Ugedal, O. & Forseth, T. (2009). Spatial distribution of limited resources and local density regulation in juvenile Atlantic salmon. Journal of Animal Ecology, 78, 226-235.
Neregård, L., Sundt-Hansen, L., Hindar, K., Einum, S., Johnsson, J. I., Devlin, R. H., Fleming, I. A. & Björnsson, B. Th. (2008). Wild Atlantic salmon (Salmo salar L.) strains have greater growth potential than a domesticated strain selected for fast growth. Journal of Fish Biology, 73, 79-95.
Einum, S., Robertsen, G. & Fleming, I.A. (2008). Adaptive landscapes and density-dependent selection in declining salmonid populations: going beyond numerical responses to human disturbance. Evolutionary Applications, 1, 239-251.
Roberge, C., Normandeau, E., Einum, S. & Guderley, H. (2008). Genetic consequences of interbreeding between farmed and wild Atlantic salmon: insights from the transcriptome. Molecular Ecology, 17, 314-324.
Einum, S., Nislow, K. H., McKelvey, S. & Armstrong, J. D. (2008). Nest distribution shaping within-stream variation in Atlantic salmon juvenile abundance and competition over small spatial scales. Journal of Animal Ecology, 77, 167-172.
Einum, S., Nislow, K. H., Reynolds, J. D. & Sutherland, W. J. (2008). Predicting population responses to breeding habitat restoration in Atlantic salmon. Journal of Applied Ecology, 45, 930-938.
Finstad, A. G., Einum, S., Forseth, T. & Ugedal, O. (2007). Shelter availability affects size-dependent and mean growth of juvenile Atlantic salmon. Freshwater Biology, 52: 1710-1718
Einum, S. & Fleming, I. A. (2007). Of chickens and eggs: diverging propagule size of iteroparous and semelparous organisms. Evolution, 61: 232-238. (open access pdf)
Garcia de Leaniz, C., Fleming, I. A., Einum, S., Verspoor, E., Jordan, W. C., Consuegra, S., Aubin-Horth, N., Lajus, D., Letcher, B. H., Youngson, A. F., Webb, J. H., Vøllestad, L. A. Villanueva, B., Ferguson, A. & Quinn, T. P. (2007). A critical review of adaptive genetic variation in Atlantic salmon: implications for conservation. Biological Reviews, 82: 173-211.
Ward, D. M., Nislow, K. H., Armstrong, J. D., Einum, S. & Folt, C. L. (2007). Is the shape of the density-growth relationship for stream salmonids evidence for exploitative rather than interference competition? Journal of Animal Ecology, 76: 135-138.
Sundt-Hansen, L., Sundström, L.F., Einum, S., Hindar, K., Fleming, I. A. & Devlin, R. H. (2007). Genetically enhanced growth causes increased mortality in hypoxic environments. Biology Letters, 3: 165-168.
Roberge, C, Einum, S., Guderley, H. & Bernatchez, L. (2006). Rapid parallell evolutionary changes of gene transcription profiles in farmed Atlantic salmon. Molecular Ecology, 15: 9-20.
Einum, S., Sundt-Hansen, L. & Nislow, K. H. (2006). The partitioning of density-dependent dispersal, growth and survival throughout ontogeny in a highly fecund organism. Oikos, 113: 489-496.
Weir, L.K., Hutchings, J.A., Fleming, I.A. & Einum, S. (2005) Spawning behaviour and success of mature male Atlantic salmon (Salmo salar) parr of farmed and wild origin. Canadian Journal of Fisheries and Aquatic Sciences, 62, 1153-1160.
Einum, S. (2005) Salmonid population dynamics: stability under weak density dependence? Oikos, 110, 630-633.
Weir, L.K., Hutchings, J.A., Fleming, I.A. & Einum, S. (2004) Dominance relationships and behavioural correlates of individual spawning success in farmed and wild male Atlantic salmon, Salmo salar. Journal of Animal Ecology, 73, 1069-1079.
Einum, S. & Fleming, I.A. (2004) Environmental unpredictability and offspring size: diversified vs. conservative bet-hedging. Evolutionary Ecology Research, 6:443-455.
Nislow, K.H., Einum, S. & Folt, C.L. (2004) Testing predictions of the critical period for survival concept using experiments with stocked Atlantic salmon. Journal of Fish Biology, 65 (Suppl. A), 188-200.
Einum, S. (2003). Atlantic salmon growth in strongly food-limited environments: effects of egg size and paternal phenotype? Environmental Biology of Fishes, 67, 263-268.
Garant, D., Fleming, I. A., Einum, S. & Bernatchez, L. (2003). Alternative male life-history tactics as potential vehicles for speeding introgression of farm salmon traits into wild populations. Ecology Letters, 6, 541-549.
Fleming, I.A., Einum, S., Jonsson, B. & Jonsson, N. (2003). Comment on “Rapid Evolution of Egg Size in Captive Salmon”. Science, 302, 59b.
Einum, S., Thorstad, E. B. & Næsje, T. F. (2002). Growth rate correlations across life-stages in female Atlantic salmon from the River Alta, Norway. Journal of Fish Biology, 60, 780-784.
Einum, S. & Fleming, I. A. (2002). Does within-population variation in fish egg size reflect maternal influences on optimal values? American Naturalist, 160, 756-765.
Armstrong, J. D., Einum, S., Fleming, I. A. & Rycroft, P. (2001). A method for tracking the behaviour of mature and immature parr around nests during spawning. Journal of Fish Biology, 59, 1023-1032.
Einum, S. & Fleming, I.A. (2000). Selection against late emergence and small offspring in Atlantic salmon (Salmo salar). Evolution, 54, 628-639.
Einum, S. & Fleming, I.A. (2000). Highly fecund mothers sacrifice offspring survival to maximize fitness. Nature, 405, 565-567. (Nature News)
Einum, S. & Fleming, I.A. (1999). Maternal effects of egg size in brown trout (Salmo trutta): norms of reaction to environmental quality. Proceedings of the Royal Society of London, Ser. B, 266, 2095-2100.
Einum, S. & Fleming, I. A. (1997). Genetic divergence and interactions in the wild among native, farmed and hybrid Atlantic salmon. Journal of Fish Biology, 50, 634-651.
Fleming, I. A. & Einum, S. (1997). Experimental tests of genetic divergence of farmed from wild Atlantic salmon due to domestication. ICES Journal of Marine Sciences, 54, 1051-1063.
Aas, Ø., Einum, S., Klemetsen, A. & Skurdal, J. (2011). Atlantic Salmon Ecology. Wiley-Blackwell, 467 pp.
Fleming, I.A. & Einum, S. (2011). Reproductive ecology: a tale of two sexes. In: Atlantic Salmon Ecology, pp. 33-65 (eds. Ø. Aas, S. Einum, A. Klemetsen & J. Skurdal). Wiley-Blackwell.
Einum, S. & Nislow, K.H. (2011). Variation in population size through time and space: theory and recent empirical advances from Atlantic salmon. In: Atlantic Salmon Ecology, pp. 277-298 (eds. Ø. Aas, S. Einum, A. Klemetsen & J. Skurdal). Wiley-Blackwell.
Aas, Ø, Policansky, D., Einum, S., Klemetsen, A. & Skurdal, J. (2011). Salmon ecological research and conservation. In: Atlantic Salmon Ecology, pp. 445-456 (eds. Ø. Aas, S. Einum, A. Klemetsen & J. Skurdal). Wiley-Blackwell.
Garcia de Leaniz, C., Fleming, I.A., Einum, S., Verspoor, E., Consuegra, S., Jordan, W.C., Aubin-Horth, N., Lajus, D.L., Villanueva, B., Ferguson, A., Youngson, A.F. & Quinn, T.P. (2007). Local Adaptation. In: The Atlantic salmon. Genetics, conservation and management, pp. 195-235 (eds. E. Verspoor, L. Stradmeyer and J.L. Nielsen). Blackwell Publishing, Oxford, UK.
Einum, S., Kinnison, M. T. & Hendry, A. P. (2004). Evolution of egg size and number. In "Evolution illuminated: salmon and their relatives", A.P. Hendry and S. Stearns (eds.), Oxford University Press.
Økland, F., Fleming, I.A., Thorstad, E.B., Finstad, B., Einum, S. & McKinley, R.S. (2000). EMG telemetry to record the intensity of swimming- and breeding-related behaviour in Atlantic salmon. In: Advances in Fish Telemetry, pp.51-58 (eds. A. Moore & I. Russell). The Centre for Environment, Fisheries and Aquatic Science, Lowestoft, UK.