Evolution of a guild of cereal aphids and their natural enemies along a longitudinal gradient in Europe: influences of climate and landscape, ... - Observatoire Des Sciences De L'Environnement De Rennes (OSERen)

Titre complet : "Evolution of a guild of cereal aphids and their natural enemies along a longitudinal gradient in Europe: influences of climate and landscape, and consequences for BYDV epidemiology"

My thesis defense, which will take place on Tuesday December 3 at 2pm at Rennes Beaulieu, in the OSUR conference room

The Jury will be composed of :

· Jacques Brodeur (Rapp.), Université de Montréal, Montreal, Canada

· Sandrine Petit-Michaut (Rapp.), INRAE, Dijon, France

· Anne Le Ralec (Exam.), Agrocampus Ouest, Rennes, France

· Philippe Jeanneret (Exam.), Agroscope, Zurich, Switzerland

· Chun-Sen Ma (Dir.), School of life sciences, Baoding, China

· Cécile Le Lann (Co-supervisor), University of Rennes, Rennes, France

Also invited:

· Joan van Baaren (Dir.), University of Rennes, Rennes, France

· Gang Ma (Co-supervisor), Chinese Academy of Agricultural sciences, Beijing, China

It will also be available online via zoom at the following link:

https://univ-rennes1-fr.zoom.us/j/68198424612

Abstract:

"Environmental stressors act as filters, triggering varied individual responses that influence the population dynamics of each species, determining their relative abundances, their interactions within guilds and consequently the functioning of food webs and ecosystems. In the context of climate change, an increase in the intensity, duration and frequency of environmental stresses can alter this functioning. This is a crucial issue in the case of agricultural pathosystems, where the guild of insect pests vectors of viruses they transmit to crop plants may be favored, while their control by natural enemies may be limited. The aim of this thesis is to understand, in the context of climate change, the respective influences of biotic and abiotic environmental parameters on (1) the relative abundances of the three species making up the cereal aphid guild (Sitobion avenae, Rhopalosiphum padi, Metopolophium dirhodum), (2) the structure of the aphid-primary parasitoid-hyperparasitoid food web, and (3) the epidemiology of Barley Dwarf Yellowing Disease, a viral disease transmitted by the various species of the aphid guild.

Using an approach based on the substitution of spatial variations for temporal variations along a longitudinal gradient in Europe, over two seasons (autumn and spring) and two consecutive years, we have shown that the effects of climate better explain cereal aphid population dynamics than other abiotic (landscape) and biotic (interactions with natural enemies) factors, and that among these climatic factors, short-term extreme events (both heat waves and cold spells) have greater effects than long-term average climatic conditions (the extreme climate hypothesis). All levels of the aphid-parasitoid-hyperparasitoid food web are impacted by extreme events. The resulting changes in phenology (abandonment of sexual reproduction in aphids and increased incidence of summer diapause in parasitoids) have an impact on guild composition, biocontrol and the seasonal dynamics of BYDV viruses”.