Periodic Reporting for period 1 - MATA (Mitochondrial Adaptations associated with Thermophily in Ants)
Période du rapport: 2021-07-01 au 2023-06-30
Insects represent more than half of the world's biodiversity and are considered the most successful group of multicellular organisms on the planet. They contribute significantly to vital ecological services such as pollination, pest control, and maintenance of wildlife species. As opposed to homeotherm organisms which include mammals and birds, insects lack the ability to efficiently regulate their temperatures at the metabolic level. They nevertheless colonized most biomes on the planet, ranging from warm deserts to subarctic tundra, displaying a striking ability to readily adapt to novels and sometimes extreme conditions. In link with climate change, understanding these adaptations might prove pivotal in our ability to predict current and future climate warming will have on insect communities. This can give us the tools to better predict and mitigate some dire socioeconomic issues related to insects and climate change, such as its impact on worldwide food safety that relies on polenisators, the increased spread of new insect-borne diseases to temperate ecosystems, and overall the chronic resurgence of insect pests of economic/societal significance. Representing 14 000 described species, ants are one of the largest families of insects, with respect to species diversity and total number of individuals. They provide an unprecedented amount of ecosystem services by their sheer biomass and are an important part of nutrient cycling, soil turnover, and food web control. Associated with their global distribution, ants have evolved to tolerate highly variable thermal conditions. They thus represent a good model system to undertake the exploration of mechanisms underlying thermal adaptation in insects. The objective of MATA was thus to explore the physiological adaptations of insect life to temperatures using ants as models, with a focus on mitochondrial metabolism.
From the beginning to the end of MATA, we have sampled 13 ants species distributed from the Mediterranean region to northern Scandinavia, and studied several aspects of their temperature tolerance. First, we explored how their heat-tolerance and acclimation potential (i.e. how well they can acclimate to warmer temperatures) related to their current distribution (Willot et al., 2022), in order to understand the link between heat-tolerance and habitat colonisation in insects. Doing so, we discovered a phenomenon of "metabolic compensation", meaning that the metabolism of northern species is specifically optimized to work faster at cooler temperatures, giving them and edge over competitors in temperate climates (Willot et al., 2023, BioRxv). However, we also point out that this comes at a costs - these species suffer greater risks of heat-induce damages and lose metabolic performance sooner at warm temperatures, meaning they can easily be outcompeted and displaced north as the climates warms up. Finally, we also explored insect mitochondrial resilience to low temperatures, and how cold episodes such as temperate winter might affect the energetic metabolism of invading tropical insects using several species of Drosophila flies as models (Jørgensen et al., 2023). We show that the sensitivity of mitochondrial metabolism to temperature is tightly correlated with the onset of cold-induced coma, meaning that in warm-adapted species, mitochondrial failure underpins poor cold-tolerance. These results have been published or are currently under review in peer-reviewed journals. They have been disseminated through oral presentations in 5 international congresses dedicated to insect sciences and cold-blooded animals' physiology spawning from 2021 to 2023. They have further been used as support for the dissemination of insect physiology science in 2 editions of the Sciences is Wonderful event to school and high-school pupils, and have been included in blogs aimed at distributing accessible sciences to the public.
The results of MATA have provided further knowledge and tools of the broad mechanisms of thermal adaptation in insect life, with a focus on energetic and mitochondrial metabolism. They have been very positively received by peers, and find their place in our integrated understanding of the impact of climate change on insects. Brick by brick, such work thus helps build the necessary knowledge to adapt society - to a degree- to global warming. MATA's outputs are themselves relevant witin its specialized spheres, pushing forth our comprehension of insect and social insect thermal adaptation to both high and low temperatures, and how this relates to key traits of their physiology. These physiological results are of interest for people batteling insect-borne deases and pests in a warming climate, and also for industries using insects as tool in agriculture to make enlighted decisions on the methods used with regard to climate and biocontrol.