Double Séminaire Ecobio - Marion Lestienne et Valentin Cabon (Ecobio)

Marion : Development of the high diversity beech forest in the eastern Carpathians / Valentin : Behavioural thermoregulation in a fast changing environment: do arthropods adjust their thermal ...

Double Séminaire Ecobio - Marion Lestienne et Valentin Cabon (Ecobio)
Vendredi 13 janvier 2023, 13h00
Observatoire des Sciences de l'Univers (OSUR) Campus de Beaulieu, Bâtiment 15, salle Bernard Auvray - Université de Rennes, 35042 Rennes CEDEX

Séminaire de Marion : Over the past decades, a surge in the number of large and uncontrolled wildfires has occurred on all terrestrial ecosystems and global warming may amplify this trend. These alterations of fire regimes will affect fire-prone ecosystems but also areas that have not historically experienced high fire frequencies such as European beech forests which are hotspots of plant diversity. To anticipate possible changes in the on-going global warming, we will focus on how these forests have colonized Europe and what are the main factors explaining their high biodiversity with a multi proxies approach (pollen and charcoals analysis). Our results showed that low diversity spruce woods were dominant during the Neolithic (Mid Holocene / Neolithic). The establishment of Fagus sylvatica was facilitated by fire disturbances occuring at the late Neolithic, but the expansion of high diversity beech forests coincided with major gaps in fire events during the Bronze Age (Late Holocene). Later, the increase of human activities has also impacted the diversity (Roman period / Late Holocene). Séminaire de Valentin : Most ectotherms behaviourally thermoregulate to maintain their body temperature close to their physiological optimum by selecting preferred temperatures (Tpref) and avoiding deleterious ones. Yet, intraspecific Tpref variations across geographical clines remain overlooked compared to other thermal traits like thermal tolerances. In cities, the urban heat islands (UHI) provide an excellent opportunity to design combined field-laboratory thermal experiments. In our study, we intended to determine if Tpref differ across populations of a common wolf spider collected in contrasting thermal zones. We measured spiders’ Tpref using an experimental set up enabling to individually track the positions along a thermal laboratory gradient. We showed that endogenous factors such as body size or sex primarily drive median Tpref and Tpref range. To a lesser extent, the Tpref range was also linked to the UHI intensity, yet only in juveniles. The absence of relationship in adult spiders suggests that adjustments of temperature preferences to contrasting thermal conditions could be exposed to thermal inertia.