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MARINFORSKHAV-Marine ressurser og miljø - havmiljø

The role of gene flow in the evolution of Antarctic icefishes

Alternative title: Rollen til genstrøm i utviklingen av antarktiske isfisker

Awarded: NOK 11.5 mill.

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Project Period:

2023 - 2027


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In the freezing waters of Antarctica, a unique group of fishes has evolved over the course of the last ten million years. The so-called icefishes are equipped with antifreeze proteins, which allow them to survive at subzero temperatures that are deadly for most other groups of fishes. Thus, it is hypothesized that the roughly 100 species of icefishes that live in Antarctic waters today derived from a single ancestor that evolved this antifreeze protection at a time when the water temperatures dropped and freezing conditions became widespread. This would have led to the extinction of most other fish groups, and allowed the icefishes to diversify into the ecological niches that were once occupied by other species. Antarctic icefishes thus form a marine example of the evolutionary process known as "adaptive radiation", which is assumed to be responsible for a great share of the planet's biodiversity. However, the mechanisms driving this species diversification, and the way in which the Antarctic environment contributed to it remain poorly known. In this project, both the drivers of the diversification and the contribution of the Antarctic environment will be investigated through an extensive analysis of the history of Antarctic icefishes. This analysis will be achieved using a vast dataset of genetic information from all 100 icefish species, extracted from small tissue samples that were taken during past expeditions to Antarctica. This large dataset will reveal the complete family tree of the group of fishes, and will show whether or not the different species have hybridized in the past. A particular focus will also be placed on species that are distributed all around Antarctica or on the shelves of different sub-Antarctic islands, to test whether the glaciation history and ongoing changes in ocean currents due to climate change have left signatures in the genes of these species.

This project will generate a massive genomic dataset to establish the adaptive radiation of Antarctic icefishes as a model system for explosive diversification, on par with the famous radiations of cichlid fishes, Darwin’s finches, and Heliconius butterflies. Through comparison with non-marine adaptive radiations, findings gained for Antarctic icefishes will allow the identification of drivers of diversification that act universally and explain species richness in adaptive radiation regardless of lifestyle and habitat. As interspecific gene flow has been implicated as one such potential driver, a particular focus will be placed on the estimation of past gene flow levels across the radiation, in relation to a range of species-specific parameters including genetic diversity, selection, and rates of diversification and morphological evolution. Besides insights about the drivers of diversification, the investigation of past gene flow in Antarctic icefishes will generate knowledge about the stability of Antarctic icesheets, which is critical for predictions of sea level rises in a future impacted by climate change. If the genomes of icefish populations should contain evidence for past genetic exchange between the Weddell and Ross seas, this would support the hypothesis that the West Antarctic Ice Shelf collapsed in the Pleistocene, implying that it is more fragile than previously assumed. Finally, this project will analyze whether gene flow between isolated shelf habitats occurs through passive larval dispersal with ocean currents or through actively swimming adult individuals. As climate change is known to alter the speed and other parameters of oceanic currents, this mode of gene flow in Antarctic icefishes determines their resilience to climate change-induced effects in oceanic currents, and as such, bears immense importance to the future of Antarctic ecosystems.

Funding scheme:

MARINFORSKHAV-Marine ressurser og miljø - havmiljø