Evolutionary ecology in a rapidly changing world
The field of evolutionary ecology seeks to understand how organisms adapt to their environments and how, in the process, biodiversity is generated and maintained. Human activities are rapidly altering both the 'ecological theater' and the 'evolutionary play' that produce and support this biodiversity. Effective conservation in a changing world must therefore be based on solid understanding of how our actions modify the fit between organisms and their environment.
A major thrust of our research is to understand patterns of local adaptation and population structuring in fish, in particular the ecological processes and genetic mechanisms that underpin these patterns. How do human activities such as fishing, supplemental stocking, fish farming, habitat alteration and climate change influence the demography and evolutionary dynamics of wild populations? What are the long-term consequences of lost population and life history diversity for the resilience of species and the stability of aquatic resources? Can some of this biocomplexity be restored?
The field of evolutionary ecology seeks to understand how organisms adapt to their environments and how, in the process, biodiversity is generated and maintained. Human activities are rapidly altering both the 'ecological theater' and the 'evolutionary play' that produce and support this biodiversity. Effective conservation in a changing world must therefore be based on solid understanding of how our actions modify the fit between organisms and their environment.
A major thrust of our research is to understand patterns of local adaptation and population structuring in fish, in particular the ecological processes and genetic mechanisms that underpin these patterns. How do human activities such as fishing, supplemental stocking, fish farming, habitat alteration and climate change influence the demography and evolutionary dynamics of wild populations? What are the long-term consequences of lost population and life history diversity for the resilience of species and the stability of aquatic resources? Can some of this biocomplexity be restored?
ANTHROPOGENIC-MEDIATED EVOLUTIONARY CHANGE
Recent reviews and meta-analyses suggest that human-induced pressures ranging from global climate change to local pollution and exploitation are altering the course of natural selection and driving rapid phenotypic changes in a variety of species (e.g. Hendry et al. 2008). In many cases, these may be underpinned by genetic (i.e. evolutionary) changes, but the relative role of genes versus environment remains poorly understood in most. These issues are more than simply academic and increasingly assume applied importance. For example, some types of human-mediated evolution (e.g. fisheries-induced evolution, stocking practices that alter the genetics of wild populations) might compromise the long-term resilience or economic value of a population or stock, although these issues remain hotly debated.
We are particularly interested in genetic changes that occur in fish in captivity and the consequent genetic and ecological impacts on wild populations when these captive-reared fish escape or are released. For example, Atlantic salmon are used extensively in fish farming and fish often escape, sometimes in very large numbers. In Ireland, most farmed salmon are derived from a few Norwegian strains, which are likely to be genetically very different from local fish. To determine the impacts of potential escapes on wild populations, an experiment was undertaken in the late 1990s in a natural spawning tributary of the Burrishoole system, to compare the performance of wild, farmed (Norwegian MOWI strain) and hybrid progeny. Genetic markers were used to assign juveniles to family and group parentage. Results showed reduced survival for progeny of farmed salmon to the smolt stage, compared with native fish, and also a lower incidence of male parr maturation. However, farm salmon grew faster and competitively displaced natives downstream (McGinnity et al. 1997). Performance of hybrids was generally intermediate to that of either pure group. A follow-on study (McGinnity et al. 2003) examined full lifetime reproductive success (LRS) of wild natives, farm-origin fish, F1 and F2 hybrids, and BC1 backcrosses, and showed that relative LRS of farm fish was only 2% that of wild fish, with the hybrids and backcrosses being somewhere in between, indicating additive genetic variation for fitness-related traits. There were also interesting additive differences in sea age and fecundity among the groups.
These studies indicate that interactions between farmed and wild fish can substantially depress the fitness of wild fish and that repeated escapes could result in an unsustainable genetic load. Many gaps in understanding remain, however, such as how introgression affects marine survival, whether maladapted farm genes can be purged from the wild population without an unsustainable demographic cost, and which phenotypic characters are involved in disrupted local adaptation. These and other questions continue to be explored by our group using experimental, observational and genetic techniques.
Related to the above issues, intentional stocking of populations with salmon hatched and raised (for part of their lives) in hatchery facilities can have similar consequences for the genetic integrity of wild populations. This raises questions as to whether stocking programs do more harm than good in the long term. In the Burrishoole catchment, wild and sea-ranched Atlantic salmon (sea-ranched = artificially spawned and reared to the smolt stage at the Burrishoole experimental hatchery facility) spawn together in the wild. Long term monitoring has revealed that the escape of sea-ranched fish into the wild substantially reduces egg to smolt survival rates of naturally spawning fish, and moreover can disrupt the capacity of the wild population to adapt to higher winter water temperatures associated with climate change (McGinnity et al. 2009). Further light will be shed on these effects through pedigree-based analysis and additional experiments.
We are also collaborating with others to address issues such as fisheries-induced evolution (e.g. Ernande et al. In Prep) and disease-mediated selection in Atlantic salmon (e.g. de Eyto et al. 2011) and wild trout affected by aquaculture activities (e.g. Coughlan et al. 2008, O'Farrell et al. 2011).
References:
Hendry, A. P., Farrugia, T. J., & Kinnison, M. T. (2008). Human influences on rates of phenotypic change in wild animal populations. Molecular Ecology,17(1), 20-29.
McGinnity, P., Stone, C., Taggart, J. B., Cooke, D., Cotter, D., Hynes, R., ... & Ferguson, A. (1997). Genetic impact of escaped farmed Atlantic salmon (Salmo salar L.) on native populations: use of DNA profiling to assess freshwater performance of wild, farmed, and hybrid progeny in a natural river environment.ICES Journal of Marine Science: Journal du Conseil, 54(6), 998-1008.
McGinnity, P., Prodöhl, P., Ferguson, A., Hynes, R., ó Maoiléidigh, N., Baker, N., ... & Cross, T. (2003). Fitness reduction and potential extinction of wild populations of Atlantic salmon, Salmo salar, as a result of interactions with escaped farm salmon. Proceedings of the Royal Society of London. Series B: Biological Sciences, 270(1532), 2443-2450.
McGinnity, P., Jennings, E., Allott, N., Samuelsson, P., Rogan, G., Whelan, K., & Cross, T. (2009). Impact of naturally spawning captive-bred Atlantic salmon on wild populations: depressed recruitment and increased risk of climate-mediated extinction. Proceedings of the Royal Society B: Biological Sciences, 276(1673), 3601-3610.
Ernande et al. Recent trends in return-length and return-date of Irish Atlantic salmon (Salmo salar L.) reveal disruptive but not directional fisheries-induced evolutionary responses. In preperation.
de Eyto, E., McGinnity, P., Huisman, J., Coughlan, J., Consuegra, S., Farrell, K., ... & Stet, R. (2011). Varying disease‐mediated selection at different life‐history stages of Atlantic salmon in fresh water. Evolutionary Applications, 4(6), 749-762.
Coughlan, J., McGinnity, P., O'Farrell, B., Dillane, E., Diserud, O., de Eyto, E., Farrell, K, Whelan, K., Stet, R.J.M. & Cross, T. F. (2006). Temporal variation in an immune response gene (MHC I) in anadromous Salmo trutta in an Irish river before and during aquaculture activities. ICES Journal of Marine Science: Journal du Conseil, 63(7), 1248-1255.
O'Farrell, B., Benzie, J. A., McGinnity, P., Carlsson, J., de Eyto, E., Dillane, E., Graham, C, Coughlan, J. & Cross, T. (2011). MHC-mediated spatial distribution in brown trout (Salmo trutta) fry. Heredity, 108(4), 403-409.
Recent reviews and meta-analyses suggest that human-induced pressures ranging from global climate change to local pollution and exploitation are altering the course of natural selection and driving rapid phenotypic changes in a variety of species (e.g. Hendry et al. 2008). In many cases, these may be underpinned by genetic (i.e. evolutionary) changes, but the relative role of genes versus environment remains poorly understood in most. These issues are more than simply academic and increasingly assume applied importance. For example, some types of human-mediated evolution (e.g. fisheries-induced evolution, stocking practices that alter the genetics of wild populations) might compromise the long-term resilience or economic value of a population or stock, although these issues remain hotly debated.
We are particularly interested in genetic changes that occur in fish in captivity and the consequent genetic and ecological impacts on wild populations when these captive-reared fish escape or are released. For example, Atlantic salmon are used extensively in fish farming and fish often escape, sometimes in very large numbers. In Ireland, most farmed salmon are derived from a few Norwegian strains, which are likely to be genetically very different from local fish. To determine the impacts of potential escapes on wild populations, an experiment was undertaken in the late 1990s in a natural spawning tributary of the Burrishoole system, to compare the performance of wild, farmed (Norwegian MOWI strain) and hybrid progeny. Genetic markers were used to assign juveniles to family and group parentage. Results showed reduced survival for progeny of farmed salmon to the smolt stage, compared with native fish, and also a lower incidence of male parr maturation. However, farm salmon grew faster and competitively displaced natives downstream (McGinnity et al. 1997). Performance of hybrids was generally intermediate to that of either pure group. A follow-on study (McGinnity et al. 2003) examined full lifetime reproductive success (LRS) of wild natives, farm-origin fish, F1 and F2 hybrids, and BC1 backcrosses, and showed that relative LRS of farm fish was only 2% that of wild fish, with the hybrids and backcrosses being somewhere in between, indicating additive genetic variation for fitness-related traits. There were also interesting additive differences in sea age and fecundity among the groups.
These studies indicate that interactions between farmed and wild fish can substantially depress the fitness of wild fish and that repeated escapes could result in an unsustainable genetic load. Many gaps in understanding remain, however, such as how introgression affects marine survival, whether maladapted farm genes can be purged from the wild population without an unsustainable demographic cost, and which phenotypic characters are involved in disrupted local adaptation. These and other questions continue to be explored by our group using experimental, observational and genetic techniques.
Related to the above issues, intentional stocking of populations with salmon hatched and raised (for part of their lives) in hatchery facilities can have similar consequences for the genetic integrity of wild populations. This raises questions as to whether stocking programs do more harm than good in the long term. In the Burrishoole catchment, wild and sea-ranched Atlantic salmon (sea-ranched = artificially spawned and reared to the smolt stage at the Burrishoole experimental hatchery facility) spawn together in the wild. Long term monitoring has revealed that the escape of sea-ranched fish into the wild substantially reduces egg to smolt survival rates of naturally spawning fish, and moreover can disrupt the capacity of the wild population to adapt to higher winter water temperatures associated with climate change (McGinnity et al. 2009). Further light will be shed on these effects through pedigree-based analysis and additional experiments.
We are also collaborating with others to address issues such as fisheries-induced evolution (e.g. Ernande et al. In Prep) and disease-mediated selection in Atlantic salmon (e.g. de Eyto et al. 2011) and wild trout affected by aquaculture activities (e.g. Coughlan et al. 2008, O'Farrell et al. 2011).
References:
Hendry, A. P., Farrugia, T. J., & Kinnison, M. T. (2008). Human influences on rates of phenotypic change in wild animal populations. Molecular Ecology,17(1), 20-29.
McGinnity, P., Stone, C., Taggart, J. B., Cooke, D., Cotter, D., Hynes, R., ... & Ferguson, A. (1997). Genetic impact of escaped farmed Atlantic salmon (Salmo salar L.) on native populations: use of DNA profiling to assess freshwater performance of wild, farmed, and hybrid progeny in a natural river environment.ICES Journal of Marine Science: Journal du Conseil, 54(6), 998-1008.
McGinnity, P., Prodöhl, P., Ferguson, A., Hynes, R., ó Maoiléidigh, N., Baker, N., ... & Cross, T. (2003). Fitness reduction and potential extinction of wild populations of Atlantic salmon, Salmo salar, as a result of interactions with escaped farm salmon. Proceedings of the Royal Society of London. Series B: Biological Sciences, 270(1532), 2443-2450.
McGinnity, P., Jennings, E., Allott, N., Samuelsson, P., Rogan, G., Whelan, K., & Cross, T. (2009). Impact of naturally spawning captive-bred Atlantic salmon on wild populations: depressed recruitment and increased risk of climate-mediated extinction. Proceedings of the Royal Society B: Biological Sciences, 276(1673), 3601-3610.
Ernande et al. Recent trends in return-length and return-date of Irish Atlantic salmon (Salmo salar L.) reveal disruptive but not directional fisheries-induced evolutionary responses. In preperation.
de Eyto, E., McGinnity, P., Huisman, J., Coughlan, J., Consuegra, S., Farrell, K., ... & Stet, R. (2011). Varying disease‐mediated selection at different life‐history stages of Atlantic salmon in fresh water. Evolutionary Applications, 4(6), 749-762.
Coughlan, J., McGinnity, P., O'Farrell, B., Dillane, E., Diserud, O., de Eyto, E., Farrell, K, Whelan, K., Stet, R.J.M. & Cross, T. F. (2006). Temporal variation in an immune response gene (MHC I) in anadromous Salmo trutta in an Irish river before and during aquaculture activities. ICES Journal of Marine Science: Journal du Conseil, 63(7), 1248-1255.
O'Farrell, B., Benzie, J. A., McGinnity, P., Carlsson, J., de Eyto, E., Dillane, E., Graham, C, Coughlan, J. & Cross, T. (2011). MHC-mediated spatial distribution in brown trout (Salmo trutta) fry. Heredity, 108(4), 403-409.