Seth Bybee

College of Life Sciences, Brigham Young University, Provo, Utah, USA

vendredi 20 décembre 2019 - 11h30 Grand salle réunion du CEFE

Odonata (dragonflies and damselflies) are an excellent insect model for evolutionary studies. They occupy an ancient phylogenetic position, are among the best flyers of any animal group, have an excellent fossil record, exhibit an extensive phenotypic and at the same time a unique ecological diversity. The link between color and diversity is a question that remains to be explored broadly within insects. Using dragonflies, it is possible to examine color across the order and explore how this may have driven their diversification. The evolution of the genes that support odonate color vision (opsins) are explored in a phylogenetic context using ancestral reconstruction and tests of selection. An update of odonate phylogenetics, including the need for and challenges of combining fossils with extant taxa in a single phylogeny are presented.

Recent publications:

Toussaint, E., S.M. Bybee, R.J. Erickson^G, F.L. Condamine. 2019. Forest Giants on Different Evolutionary Branches: Ecomorphological Convergence in Helicopter Damselflies. Evolution.73(5): 1045-1054. doi.org/10.1111/evo.13695

Suvorov, A., N.O. Jensen^U, M.S. Fujimoto^G, P. Bodily, H.M. Cahill Wightman^G, C.R. Sharkey^P, T.H. Ogden, M.J. Clement, S.M. Bybee. 2017. Opsins have evolved under the permanent heterozygote model: insights from phylotranscriptomics of Odonata. Molecular Ecology. 26(5): 1306-1322. doi: 10.1111/mec.13884

Martin, G.K.F. Stanger-Hall, M.A. Branham. L.F.L Da Silveira, S.E. Lower, D.W. Hall, X.Y. Li, A.R. Lemmon, E.M. Lemmon, S.M. Bybee. 2019. Higher-level phylogeny and reclassification of Lampyridae (Coleoptera: Elateroidea). Journal of Insect Systematics and Diversity. Accepted

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Mercredi 11 décembre 2019 – 14h00

Grande salle de réunion du CEFE | 1e étage, aile C

Kevin McGraw*, Russell Ligon, and Richard Simpson  

School of Life Sciences, Arizona State University, Tempe, AZ, USA

In many animals, signaling traits like bold coloration or body/ornament size are static and convey fixed attributes of an individual’s quality (e.g. development/growth, health history) to signal receivers. However, several other types of animal signals are dynamically expressed, like behaviors and songs, and reveal real-time information about the individuals producing the trait. In recent work in my lab, we have investigated signals that blur the line between these two categories of signals and show, for conspicuous coloration exhibited in two different groups of animals (chameleons and hummingbirds), how animal coloration can convey dynamic information in both mating and competitive social contexts. I will discuss these field and lab studies in hope of inspiring additional thought and work on how animal signals can exhibit both static and dynamic features. These instances require finely tuned investigations to parse the mechanistic, functional, and evolutionary underpinnings of the signals, especially when considering the complex interaction (i.e. emergent properties or composite traits) that can occur between the color itself and the behavior used to display/emphasize it.

(Seminar in English)
 

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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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Ecologie et Biodiversité

Soutiendra publiquement ses travaux de thèse intitulés :

De l’abondance des cerfs aux propriétés du sol : Une étude de cas dans les forêts d’Haïda Gwaii

jeudi 19 décembre 2019 à 13h 15
  Amphithéâtre de la délégation

L’augmentation récente et spectaculaire de l'abondance des cerfs en Amérique du Nord et en Europe occidentale a entraîné de profonds changements dans la structure des forêts tempérées. Si ces changements sont aujourd'hui bien caractérisés, les effets de cette forte abondance sur le sol restent cependant mal compris. Les cerfs peuvent interagir avec le sol par le rejet de fèces et d’urine, le piétinement et la réduction de la quantité et de la qualité de la litière par le broutage préférentiel des plantes appétantes. Ces interactions multiples rendent difficile la prédiction de l’effet net des cerfs sur les organismes et les processus du sol. En conséquent, les études actuelles dans les forêts tempérées ont révélé des résultats idiosyncratiques. Pour résoudre cette problématique, nous avons étudié la réponse des sols à la colonisation et à l'élimination du cerf de Sitka dans les forêts d’Haïda Gwaii. Nous avons constaté que les cerfs ralentissaient la décomposition en réduisant la qualité de la litière. La structure de la communauté microbienne et sa capacité à décomposer le carbone était impactée par la compaction du sol dû au piétinement. Nous avons également constaté que les effets des cerfs à court et moyen termes n’avaient que peu ou pas d'effet sur le sol, remettant en question les conclusions des études actuelles basées sur de plus court terme.

Mots clefs : Herbivores ongulés, Décomposition, Communautés procaryotes du sol, Cycle de l’Azote.

Abstract: The past century witnessed a dramatic increase in deer abundance in North America and Western Europe that triggered profound changes in the structure of temperate forests. If these changes are today well characterised, the effects of abundant deer belowground in these forests remain unclear. Deer can interfere with the soil through waste deposition, trampling, and reduction of litter quantity and quality by preferential browsing of palatable plants. The multiplicity of these pathways makes it difficult to predict the net effect deer will have on soil communities and processes. As a result, current studies in temperate forests have found inconsistent results within, and across, systems. In an attempt to resolve these inconsistencies, we studied the soil response to the colonisation and removal of Sitka black-tailed deer in the forests of Haida Gwaii. We found that deer slowed-down litter decomposition by reducing litter quality. They also modified microbial community structure and ability in decomposing carbon via soil trampling. Most of these effects became only apparent in the long term, hence questioning the results obtained through short term studies.

Keywords: Ungulate herbivores, Decomposition, Soil prokaryotic communities, Nitrogen cycle

Membres du jury

Sébastien BAROT                  Directeur de Recherche, IRD                                Rapporteur

Feth-el-Zahar HAICHAR          Maître de conférences, Université Lyon 1              Rapporteur

Cindy PRESCOTT                  Professeur, University of British Columbia             Examinateur

Thibaud DECAËNS                Professeur, Université de Montpellier                    Examinateur

Jean-Louis MARTIN               Directeur de Recherche, CNRS                            Directeur de thèse

Sue GRAYSTON                   Professeur, University of British Columbia              Directeur de thèse

Ecologie et Biodiversité

Soutiendra publiquement ses travaux de thèse intitulés :

Diversité vs uniformité : combiner les approches écologiques et évolutives pour concevoir des systèmes de culture durables

jeudi 12 décembre 2019 à 14 h
Montpellier SupAgro Campus de La Gaillarde - Bât.9 Amphi 206 2 Place Pierre Viala 34060 Montpellier

Mots clefs : biodiversité, agriculture, mélanges variétaux, complémentarité de niche, sélection de parentèle.       

Membres du jury

Soutiendra publiquement ses travaux de thèse intitulés :

The evolution of supergenes:

insights from mimicry polymorphism in a butterfly

Le jeudi 5 décembre 2019 à 13h
CEFE, Grande Salle de Reunion

(Soutenance en Français)

            Over a century after the first description of a polymorphism controlled by a supergene, these genetic architectures still puzzle biologists. Supergenes are groups of tightly linked loci facilitating the co-segregation of alternative combinations of alleles underlying complex adaptive strategies. Recombination suppression at supergenes is determined by polymorphic chromosomal rearrangements, which allows the coexistence of highly distinct morphs without the formation of poorly adapted recombinant phenotype. The existence of supergene raises theoretical and empirical questions. Why do these architectures evolve? How is recombination suppressed? How can alternative combinations of alleles be formed? How and why is polymorphism maintained?

The purpose of this thesis is to provide answers to these questions by studying Heliconius numata, a neotropical butterfly displaying a striking diversity of wing color patterns. In this thesis, I show that this polymorphism is encoded by more than ten loci controlling different features of wing patterns. Recombination between these loci is suppressed by three chromosomal inversions in tandem that form a supergene. In addition to the variants controlling wing coloration, I show that these inversions capture many recessive deleterious mutations, which associate with a high mortality in larvae homozygous for the inversions. In addition, inversions at this supergene are known to underlie morphs with a better protection from predators relative to morphs with ancestral arrangements. The antagonistic effects of inversions -low larval survival but good adult protection- maintains them at intermediate frequencies, and therefore explains the polymorphism observed in this taxon. Then, I show that the first derived inversion of the supergene arose in another species, and was introgressed into H. numata c.a. 2.3 million years ago. This resulted in the cluster of two differentiated, non-recombining haplotypes controlling various aspects of wing patterns, and therefore explains how the supergene of H. numata was formed. Finally, I show via a population genetics model that this scenario of supergene formation involving gene flows between species is able to explain the formation of supergenes in many cases. This thesis sheds new light on the conditions for the evolution of supergenes. In a broader context, it highlights mechanisms that play an important role in the evolution of new genomic architecture and in the adaptation of species

Mots clefs : Supergene, inversion, chromosomal rearrangement, polymorphism, balancing selection, introgression

Membre du jury composé de

Tatiana GIRAUD                                 Directrice de recherche, ESE - Orsay
Vincent CASTRIC                               Directeur de recherche, EEP - Lille
Marianne ELIAS                                 Directeur de recherche, ISYEB - Paris
Anna-Sophie FISTON-LAVIER             Maître de conférence, ISEM - Montpellier
Pierrick LABBÉ                                  Professeur, ISEM - Montpellier
Mathieu JORON                                 Directeur de recherche, CEFE - Montpellier