claire

Claire de Mazancourt

Centre for Biodiversity Theory and Modelling, Centre for Biodiversity Theory and Modelling, Moulis, France

vendredi 13 décembre 2019 - 11h30 Grand salle réunion du CEFE

First I will present a new view on coexistence in high dimensional systems, that we call diffuse cliques. In high dimensional systems, coexistence most likely occurs with a subtle correlation structure, and the search for a low-dimensional trade-off signature is bound to fail. Data from large biodiversity experiments support a diffuse clique structure.

I will then talk about the effect of biodiversity on ecosystem functioning (BEF). Using a simple model, I will show the effect of different types of experiments (community assembly, species removal, observation along a succession), and experiment duration on the BEF relationship. In particular, I show that the BEF relationship is expected to strengthen through time in assembly experiments, and weaken through time in species removal experiments.

Finally, I will talk about the effect of biodiversity on ecosystem stability. Stability research is marred with different communities using different concepts; in particular, empirical and theoretical research use different stability definitions, impeding their cross fertilization. Invariability can be a way forward, as it can be both measured experimentally and theoretically developed, and therefore lead to an operational stability theory.

Recent publications:

Montoya, D., B. Haegeman, S. Gaba, C. de Mazancourt, V. Bretagnolle, and M. Loreau. 2019. Trade-offs in the provisioning and stability of ecosystem services in agroecosystems. Ecological Applications 29(2): e01853. 10.1002/eap.1853.

Wang S., Loreau M., Arnoldi J.-F., Fang J., Rahman K. A., Tao S., de Mazancourt C. 2017. An Invariability-Area Relationship sheds new light on the spatial scaling of ecological stability. Nature Communications, 8:15211.

de Mazancourt, C.; Isbell, F.; Larocque, A.; Berendse, F.; De Luca, E.; Grace, J.; Haegeman, B.; Polley, H.; Roscher, C.; Schmid, B.; Tilman, D.; van Ruijven, J.; Weigelt, A.; Wilsey, B.; Loreau, M. 2013. Predicting ecosystem stability from community composition and biodiversity. Ecology Letters 16: 617-625.

 

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Benoit Moury

Benoit Moury

Pathologie Vegétale, INRA, Avignon, France

vendredi 6 décembre 2019 - 11h30 Grand salle réunion du CEFE

Plant breeders usually choose the plant resistance genes according to their immediate efficiency and spectrum of action against pathogens. To promote resistance durability, it would be also desirable to choose them according to their effects on pathogen evolution. In this perspective, one standing question is: which pathogen evolutionary trait (or combination of traits) should be targeted by plant resistance genes in order to minimize pathogen adaptation?

                  We explored this question on the pepper (Capsicum annuum; family Solanaceae) – Potato virus Y (PVY; genus Potyvirus, family Potyviridae) system using an experimental evolution approach. We chose six pepper genotypes possessing the same major-effect resistance gene but carrying different genetic backgrounds. At the individual plant level, these genotypes exert contrasted effects on PVY initial fitness (measured as PVY load within the plant at the beginning of experimental evolution) and on selection and genetic drift effects in PVY populations.

The PVY evolutionary trajectories were highly contrasted and dependent on the pepper genotype. Most lineages did not show any significant fitness change, others showed a significant fitness gain or went to extinction. Almost all PVY fitness gains were due to the fixation of one or two amino acid substitutions in PVY VPg, the protein linked to the viral RNA, which is a ligand of the product of the plant major resistance gene.

                  We analysed the effects of PVY initial fitness (Fi), effective population size (Ne) and selection coefficient (S) during plant infection on the change of PVY fitness during experimental evolution. The two significant factors were Ne and the interaction Ne × Fi. High and significant PVY fitness gains were observed mostly when Ne was high and Fi was low, which could be explained by low genetic drift and more opportunities for large-effect beneficial mutations. Extinctions of PVY lineages were observed only when Ne and Fi were low, which could be explained by the combination of high genetic drift and low probability of de novo mutations due to low Fi.

                  Our study shows that it is possible for plant breeders to combine a high resistance efficiency and high resistance durability, even with strong selection exerted on virus populations by a major-effect resistance gene, by using plant genotypes where viruses have a low Ne during infection.

Recent publications:

  1. Rousseau et al. (2019). Virus epidemics, plant-controlled population bottlenecks and the durability of plant resistance. Phil Tr Roy Soc B 374:20180263.
  2. Rousseau et al. (2018). Impact of genetic drift, selection and accumulation level on virus adaptation to its host plants. Mol Plant Pathol 19:2575-2589.
  3. Rousseau et al. (2017). Estimating virus effective population size and selection without neutral markers. PLoS Path 13:e1006702.
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Guillaume Martin and Alison Duncan: Cette adresse e-mail est protégée contre les robots spammeurs. Vous devez activer le JavaScript pour la visualiser./Cette adresse e-mail est protégée contre les robots spammeurs. Vous devez activer le JavaScript pour la visualiser.

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