Charlotte Grossiord

Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, USA

le lundi 21 novembre 2016 - 11h Grande Salle CEFE (1919 Rte de Mende, 1e étage, aille C)

Moisture loss through temperature-driven increases in evapotranspiration and sparse precipitation are expected to affect the functioning of forest ecosystems. Understanding the consequences of these climatic changes and subsequently suggesting climate-smart management options are emerging as grand challenges for global change scientists. To persist and thrive under projected climate, plants will need to undergo rapid adjustments in their physiology and morphology. However, although the capacity of woody species to tune their traits to changing environmental conditions is widely recognized, climate–vegetation models rarely consider changes in individual species traits. In addition to natural tree-level acclimation processes, stand-level human interventions promoting sustainability, resilience and species conservation can help forests tackle the climate challenge. Among other approaches, promoting species diversity has been suggested to improve ecosystem resistance to climate change. However, it remains unclear whether higher tree diversity also leads to improved resistance of forest ecosystems to the more extreme conditions expected in the future. I will first present recent results showing how trees can acclimate both physiologically and structurally to atmospheric warming and precipitation reduction. Then I will present results on the relationship between tree species diversity and forest drought resistance across a large gradient of climatic conditions.

Selected publications:

Grossiord C, Sevanto S, Adams HD, Collins AD, Dickman LT, McBranch N, Michaletz ST, Stockton EA, Vigil M and McDowell NG, 2016. Precipitation, not air temperature, drives functional responses of trees in semi‐arid ecosystems. Journal of Ecology. DOI: 10.1111/1365-2745.12662

Grossiord C, Granier A, Ratcliffe S, Bouriaud O, Bruelheide H, Chećko E, Forrester DI, Dawud SM, Finér L, Pollastrini M and Scherer-Lorenzen M, 2014. Tree diversity does not always improve resistance of forest ecosystems to drought. PNAS, 111(41), pp.14812-14815.

Edze Westra     

University of Exeter, UK 

Le vendredi 25 novembre 2016 - 11h30 Grande Salle CEFE (1919 Rte de Mende, 1e étage, aille C)

(Seminar in English)

Bacteria have a range of sophisticated immune mechanisms to protect against virus infections, but it is unclear why all these different mechanisms evolved in the first place. Under laboratory conditions, bacteria typically evolve de novo virus resistance using either surface modification or CRISPR-Cas adaptive immune systems. In this talk I will discuss ecological factors that can tip the balance in the evolution of these two immune mechanisms and examine their distinct co-evolutionary implications.

Recent publications:

van Houte S, Buckling A, Westra ER. Evolutionary Ecology of Prokaryotic Immune Mechanisms. 2016 Microbiol Mol Biol Rev. 80(3):745-63.

van Houte S, Ekroth AK, Broniewski JM, Chabas H, Ashby B, Bondy-Denomy J, Gandon S, Boots M, Paterson S, Buckling A, Westra ER. 2016 The diversity-generating benefits of a prokaryotic adaptive immune system. Nature 532(7599):385-8.

Westra ER, van Houte S, Oyesiku-Blakemore S, Makin B, Broniewski JM, Best A, Bondy-Denomy J, Davidson A, Boots M, Buckling A. 2015 Parasite Exposure Drives Selective Evolution of Constitutive versus Inducible Defense. Curr Biol. 25(8):1043-9.

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Avis de Soutenance

Eva LIEVENS

Soutiendra publiquement ses travaux de thèse intitulés

Biotic challenges for extremophiles: reproductive interference and parasite specialization in Artemia

Soutenance prévue le lundi 12 décembre 2016 à 15h

Lieu : L'amphi des plantes de l'IRD

Composition du jury proposé

Mme Ellen Decaestecker, Associate Professor, KU Leuven – Leuven Rapporteur

Mme Meghan Duffy, Associate Professor, University of Michigan – USA Rapporteur

Mme Alison Duncan, CR, ISEM – Montpellier Examinateur

M. Thierry Rigaud, DR, Université de Bourgogne – Dijon Examinateur

M. Yannis Michalakis, DR, MIVEGEC – Montpellier Co-directeur de thèse

M. Thomas Lenormand, DR, CEFE – Montpellier Directeur de thèse

Résumé:

The challenges posed by biotic factors – interactions with competitors, parasites, etc. – play a large role in the evolution of populations, but are generally difficult to study. In this work, we used the Artemia system in the hypersaline salterns of Aigues-Mortes, France, to study the character and evolution of several interspecific interactions. The system is eminently suited to such studies: it is simple, containing two Artemia species, three highly prevalent parasites (one helminth and two microsporidians), and various microbiota; and many of its interactions are newly-established, because one of the Artemia species is invasive. We studied two types of interactions. First, the presence and evolution of reproductive interference between the native and invasive Artemia species. We found that the invasive Artemia species, which is sexual, undergoes severe interference in sex allocation when in the presence of the native, asexual Artemia, but no interference in mate guarding. Second, the evolution of parasite specialization in two microsporidian parasites infecting the Artemia species. Using field data, experimental infections, and experimental evolution, we investigated the state, causes, and consequences of specialization in the microsporidians. Results consistently indicated that the microsporidians are specialized for one host species, despite being able to complete their life cycle in either host. This specialization appears to be imposed by the precise toolkits needed to exploit each host species; in the non-specialized hosts, these triggered suboptimal exploitation, maladaptive virulence, and immunopathology. Overall, these studies suggest that the biotic factors acting on Artemia impose strong selection pressures, to which they cannot always respond easily. The importance of biotic factors in a system which is otherwise dominated by extreme abiotic conditions underlines the importance of species interactions in shaping evolution.

Mots-clés: reproductive interference, sex allocation, mate guarding, parasite specialization, parasite seasonality, virulence, trade-offs, maladaptation, interspecific interactions

Jenny Tung  

Departments of Evolutionary Anthropology and Biology, Duke University, USA,

Le vendredi 18 novembre 2016 - 11h30 Grande Salle CEFE (1919 Rte de Mende, 1e étage, aille C)

(Seminar in English)

In social species, including our own, interactions with other members of the same species powerfully shape the environment that animals face each day. These interactions mediate the evolutionary costs and benefits of group living. Here, I will present our recent research on the impact of social interactions at the molecular and organismal levels. Using a 45-year data set from wild baboons in Kenya, we demonstrate that social adversity in early life combines with ecological pressures to profoundly shape individual survival and lifetime reproductive success. Meanwhile, in captive rhesus macaques, we show that social status causally alters immune function, including the response to infection. Together, these results demonstrate that close ties between social adversity and survival have a long evolutionary history in the primate lineage, and that changes at the level of gene regulation contribute to this relationship.

Recent publications:

Snyder-Mackler et al. (in press, Science). Social status alters immune regulation and response to infection in macaques.

Tung et al. 2016. Cumulative early adversity predicts longevity in wild baboons. Nature Communications 7: 11181.

Lea et al. 2015. Developmental constraints in a wild primate. American Naturalist 185: 809-821.

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Avis de Soutenance

Françoise AMELINEAU

  Soutiendra publiquement ses travaux de thèse intitulés

Sensibilité d’un oiseau marin arctique aux changements environnementaux

Soutenance prévue le jeudi 08 décembre 2016 à 14h00
Lieu :   Amphithéâtre de la délégation CNRS

Composition du jury proposé

Avis de Soutenance

Charlotte FRANCESIAZ

Soutiendra publiquement ses travaux de thèse intitulés

Sélection d’habitat et dynamique spatio-temporelle des colonies chez deux espèces de laridés, la mouette rieuse et le goéland railleur

Soutenance prévue le vendredi 2 décembre 2016 à 14h30

Lieu : L'Amphi de la Délégation du CNRS

Composition du jury proposé

 M. Aurélien Besnard  CEFE-CNRS  Co-directeur de thèse

 M. Claude Miaud CEFE-CNRS  Directeur de thèse

 M. Christophe Barbaud Centre d'étude biologique de Chizé Rapporteur

 Mme Anne-Caroline Prévot CESCO-MNHN Rapporteur

 M. Thierry Boulinier CEFE-CNRS  Examinateur

 M. Arnaud Béchet Tour du Valat Examinateur

 M. Jean-Dominique   CEFE-CNRS   Lebreton Invité

Résumé:

La dynamique des populations vise à étudier les processus qui déterminent les fluctuations spatio-temporelles des effectifs d’organismes vivants. Ma thèse vise à caractériser les relations entre trois niveaux d’organisation des populations d’oiseaux coloniaux, l’individu, la colonie et la métacolonie, et à étudier l’influence de l’environnement physique et social sur cette organisation. A cette fin, je me suis concentrée sur deux espèces de laridés coloniaux aux dynamiques de populations contrastées: la mouette rieuse, Chroicocephalus ridibundus, et le goéland railleur, Chroicocephalus genei. J’ai décrit, dans un premier temps, la dynamique spatio-temporelle des colonies de goélands railleurs en France, dont la répartition tend à s’étendre le long de la côte Méditerranéenne. Malgré cette expansion, les individus nés en France restent fidèles à leur région natale, mais leur âge et leur sexe modulent leur recrutement et leur comportement de dispersion. J’ai affiné ce premier travail en montrant que la condition corporelle des poussins, paramètre majeur du recrutement, est modulée par la taille des colonies, sa date d’installation et la stratégie d’alimentation des parents. Mes travaux ont de plus permis de montrer l’existence de groupes sociaux chez le goéland railleur, dont la stabilité est modulée par le succès de reproduction de la colonie. Ainsi, le degré de relations entre les individus d’une colonie est modulé par les caractéristiques intrinsèques de la colonie et son contexte environnemental. J’ai en particulier montré, chez la mouette rieuse, que la persistance des colonies dépend du succès de reproduction local, mais que la colonisation de nouveaux sites dépend plutôt du succès de reproduction dans les colonies avoisinantes. Mes travaux montrent ainsi que l’ensemble des niveaux d’organisation des populations d’oiseaux coloniaux, de l’individu à la méta-colonie, doivent être étudiés à travers de nouvelles approches intégratives qui représentent des challenges conceptuels, méthodologiques et techniques à l’interface entre dynamique des populations et étude des réseaux sociaux.

Mots-clés: colonialité, dispersion, dynamique des populations, Chroicocephalus ridibundus, Chroicocephalus genei, ressources alimentaires, sélection multiniveaux