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Nov 29, 2024
Congratulations to Marion Dellinger on earning her PhD!
On November 29, 2024, Marion successfully defended her PhD thesis in Reykjavik, at the University of Iceland. Supervised by David Benhaïm, she carried out an ambitious research project entitled : “Eco-evolutionary processes in personality and spatial cognition of Arctic charr morphs (Salvelinus alpinus)”.
This defense marks the culmination of several years of rigorous work, scientific exploration, and dedication to research. The event brought together jury members, colleagues, and family to celebrate this major milestone in Marion’s academic journey. Inside her PhD research Marion’s PhD project focussed on the co-evolution between boldness personality trait (the propensity to take risks) and spatial cognitive abilities (mental processes to navigate in space), and how these traits develop in response to environmental factors (developmental plasticity). Among others, she was particularly interested in the effect of structural complexity of the environment (but see also https://doi.org/10.1098/rspb.2023.2302). She compared five morphs of Arctic charr on a gradient of ecological and evolutionary divergence: an anadromous morph from Fljótaá River considered ancestral, two moderately diverged sympatric morphs from Lake Vatnshlíðarvatn, and two highly diverged sympatric morphs from Lake Þingvallavatn. All of them were reared in contrasting treatments: either in structurally enriched tanks with artificial plants and volcanic rocks, or in plain tanks with no additionnal features. Thanks to an Open Field Test with shelter, she compared the personality profiles between groups and found that mean boldness is predominantly genotype-dependent, and most likely highly heritable. Interestingly, the more diverged the population, the bolder. However, structural complexity did not influence mean boldness (to learn more: https://doi.org/10.1016/j.anbehav.2025.123077). In a second time, the same individuals screened for personality were also screened for spatial learning speed and orientation strategy, thanks to a specially-developped T-shaped maze (https://doi.org/10.1111/jfb.15936). It turned out that the more diverged the morph, the longer it needs for spatial learning, which suggests a syndrome between boldness and spatial learning at the global scale. This is the first empirical support for the coevolution between these two traits. Marion also inspected which genes could be involved in such a syndrome, by quantifying the expression of 18 genes of interest in different brain regions. The dopaminergic pathway notably seemed to be a good candidate. With this project, Marion highlights that spatial cognition, boldness personality trait, the syndrome they form, and their underlying neural mechanisms are dependent all at once on the morph, the treatment, the morph-by-treatment interaction, the spatial cognitive ability, and the scale (global or individual) considered. This implies extremely intricate eco-evo-devo interactions governing their formation, a reminder that nature is complex, full of surprises, maybe unpredictable and chaotic sometimes, and that this is what makes it beautiful. Curious to learn more? Her thesis is available here: https://hdl.handle.net/20.500.11815/5134 Embarking on a new scientific adventure With her PhD degree freshly earned, Marion continues to explore fish behavioural and evolutionary ecology at Stockholm University, Sweden. As a Postdoc fellow within the Department of Zoology, she is now studying the link between the evolution of brain size/architecture and behavioural and cognitive traits in the Trinidadian guppy. |
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