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FRIBIO2-FRIPRO forskerprosjekt, biologi

Size-dependent anthropogenic perturbations -from genes to ecosystems and back.

Alternative title: Menneskeskapte endringer i ville populasjoner -fra gener til økosystemer og tilbake igjen.

Awarded: NOK 8.4 mill.

Worldwide, many fish stocks are in a state of serious decline or collapse due to chronic overexploitation. This incurs severe economic costs with ramifications to ecosystem function and services. For instance, it was shown in the eastern Scotian Shelf ecosystem off Nova Scotia (Canada) that collapse and failure to recover in Atlantic cod (Gadus morhua) induced a trophic cascade in which forage fish density increased, resulting in reduced zooplankton densities and increased algal concentrations. We argue that many of these problems arise because of an opposition between fisheries-induced selection, that targets fast-growing and large-sized individuals through the use of minimum-size limits, and natural selection that favours the same large individuals. Instead, fisheries should act in concert with natural selection by selectively harvesting small-sized individuals through the use of maximum size limits. We predict that such a reverse-fishing regime should increase both the productivity and resilience of exploited stocks, and alleviate fishing-induced trophic cascades by preserving large-sized individuals that have disproportionately large predatory effects. EvoSize is testing this general hypothesis using an artificial selection against or for a large body size on medaka (Orizias latipes) in the laboratory. We are measuring the effects of this bidirectional selection mimicking classical vs. reversed fishing regimes on medaka genetic makeup, productivity and resilience under both laboratory-controlled and natural conditions. We have been performing several experiments using the selected medaka lines. We have shown that size selection impacts behaviour and life history, and that these effects depend upon fish sex and availability of feed. Size selection therefore indirectly affects the rest of the food chain and ecosystem. In addition, we have shown that the endocrinological mechanisms affecting growth and reproduction (life history) are affected. We are currently preparing a paper in which we describe how various phenotypic traits are affected by the combination of size selection and environmental changes (temperature and light). We believe that our results provide important insight towards restoring marine ecosystems to their historical state, when top predators were larger and more numerous than today.

Scientific outcomes: 1. Evolutionary biology: interaction between natural and anthropogenic selection in shaping fish genotypes and phenotypes. 2. Ecology: interactions between fishing-induced POLS and cascading trophic interactions. 3. Physiology: discovery of several previously unknown endocrine mechanisms and their temporal dynamics. 4. Developmental biology: the description of all the cell types of the teleost pituitary gland. Scientific impacts: 1. Aquaculture genomics: a strategy of integrating scRNA-seq and an RNA-seq time series. 2. Climate change: POLS/mechanistic trends affected by increased temperature. 3. Interdisciplinary science: a consistent narrative based on different perspectives on a single phenomenon. Societal impact: Our scientific results will form a solid basis for the formulation of more sustainable fishing regimes, which consider the complex effects of anthropogenic disturbance.

Adaptive evolution is driven by both selective forces and trait genetic architectures (evolvability), which deflect the movements of the phenotype on the adaptive landscape. Additionally, selection itself may alter trait evolvability and simultaneously reshape the natural selection that acts back on phenotypes through eco-evolutionary feedback loops. We argue that integrating this suite of gene-to-ecosystem processes into a coherent framework will foster significant progress in biology. However, to date, this framework remains largely theoretical. EvoSize provides an experimental framework to explore eco-evolutionary feedback loops in the context of anthropogenic size truncation that results from worldwide overharvesting, habitat fragmentation or climate warming. We will impose bidirectional size-selection on medaka in the laboratory, thus rapidly generating high growth and low growth lines. In the selected medaka lines, we will map individual variation in life-history (somatic growth and maturation) and behaviour (food intake and risk-taking foraging) onto gene-expression profiles, while estimating key evolvability parameters (additive genetic variances and covariances) for both phenotype and gene expression. In parallel, we will measure the cascading effects of body-size evolution into pond food webs, and examine how these effects alter the natural selective forces that act back on medaka phenotypes. To our knowledge, this is the first project to fully investigate an eco-evolutionary feedback loop from genes to ecosystem and back. Because body size is so important in ecological processes, results from EvoSize will have a wide scope. Fundamentally, EvoSize will bring a significant breakthrough in our understanding of how evolutionary and ecological dynamics interact. From an applied perspective, EvoSize will provide knowledge to improve the resilience of human-perturbed ecosystems, and help modellers understand how anthropogenic impacts affect natural populations.

Publications from Cristin

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Funding scheme:

FRIBIO2-FRIPRO forskerprosjekt, biologi

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