Environmental Stressors

Projet IPEV 136 SUBANTECO

Le réchauffement climatique et les invasions biologiques représentent des menaces croissantes pour la biodiversité et les habitats des régions subantarctiques. Les îles subantarctiques constituent des environnements sentinelles des changements pouvant être assimilés à des laboratoires à ciel ouvert pour l’étude des synergies entre changements climatiques et invasions biologiques sur la biodiversité polaire. Nos recherches sont centrées sur la faune et la flore terrestres et aquatiques, avec pour objectif d’accroître nos connaissances de l'écologie et de distribution des espèces subantarctiques (activités observatoires de la biodiversité, et approches expérimentales en conditions contrôlées). Ces connaissances sont ensuite employées pour prédire la manière dont la biodiversité polaire pourrait évoluer dans le futur, et suggérer des mesures d'atténuation des impacts des changements globaux. Nos recherches visent également à améliorer les connaissances des mécanismes écologiques et physiologiques qui régissent la distribution et les assemblages d'espèces, des échelles locales aux échelles régionales, dans les Îles Crozet et Kerguelen. Les plantes et les invertébrés constituent des modèles d’études privilégiés, en raison de leur sensibilité aux variations microclimatiques. Ces modèles biologiques constituent par ailleurs des espèces clés qui structurent les réseaux écologiques, et leur sensibilité aux changements globaux pourrait ainsi avoir des effets en cascade sur les interactions écologiques. En démêlant la complexité des processus dirigeant la redistribution de la biodiversité dans les îles subantarctiques, les données produites constitueront un socle de connaissances pour le développement de stratégies de conservation des Îles Crozet et Kerguelen, deux archipels protégés et classés au patrimoine mondial de l'UNESCO.

The recent invasion by the Spotted Wing Drosophila (SWD) is a major concern for the fruit sector worldwide. Temperature and thermal biology of this species are recognized as the main factors dictating the distribution, populations’ dynamics and seasonal phenology of SWD. However, major knowledge gaps remain regarding its thermal and trophic ecology, thus compromising the assessment and prediction of field population dynamics from year to year. In particular, there is a critical lack of knowledge about the thermotolerance and winter survival strategies of this invasive species, which are essential for anticipating spring population levels and dynamics. Small insects such as fruit flies certainly respond to environmental variations on much finer temporal and spatial scales than those generally considered so far in classical experimental studies and predictive models. The transfer of the macroclimate projections into the microclimates actually encountered by SWDs in nature requires the acquisition of novel ecologically relevant data with a level of resolution corresponding to the insect's scale. DroThermal is based on the idea that most of the findings from laboratory experiments are difficult to extrapolate to field situations. Current knowledge on the thermal and trophic ecology of SWD is mainly based on laboratory data that lack the appropriate resolution and ecological relevance and thus hamper the accurate assessment of the persistence of SWD populations in the wild, as well as the associated modelling efforts. Many critical variables are at play in nature but absent from classical experimental conditions: i) unlike the laboratory where conditions are constant and optimal, there is a high spatial and temporal variability of abiotic factors (e.g. temperature) in nature (subject of tasks 1 & 2). ii) there is a high diversity of host plants that varies with the seasons and thus a range of available trophic resources (including unknown winter hosts) that shape phenotypes such as thermotolerance (subject of task 3). iii) Symbionts and microbes associated with the host (e.g. Wolbachia) are much more diverse in nature than in the laboratory, and can affect host characteristics, including thermotolerance (subject of task 4). Consideration of these effects in a single integrative project will generate new knowledge on the thermal and seasonal ecology of SWD, allowing better modelling of population dynamics and seasonal phenology (subject of task 5). By considering different levels of variation across appropriate spatio-temporal scales, we plan to elucidate the thermal (and seasonal) responses and adaptations of SWD, and thus better predict population persistence and dynamics in the field. DroThermal also has the applied goal of generating data needed to develop innovative predictive models of population dynamics, which are useful for sustainable management programs against SWD. Our high-resolution integrative approach will provide a better understanding of the invasive success of this species in temperate regions and will provide new knowledge essential for the management of SWD, such as improving the timing and forecasting of control measures. More broadly, the project will provide an innovative new framework to understand the success of biological invasions that present significant eco-socio-economic issues.