Sylvain Clerc PhD thesis

Abstract

The icehouse period during the lower Palaeozoic led to the development of a large continental ice-sheet over the Gondwana. This ice-sheet fluctuated in size and repeatedly recovered the north-Gondwana platform. The resulting glacial record includes major erosional surfaces of regional extent, with subglacial landforms and morphologies, including glacial valleys, and specific glaciogenic sedimentary record. Among these valleys, tunnel valleys refer to Quaternary analogues, associated with the development of ice-sheets over Europe and North-America. Tunnel valley defines elongated, linear to slightly sinuous depressions, measuring few kilometers in width and several kilometres in length. They start and terminate abruptly, are generally a few hundred of meters deep, and display frequent overdeepening along the floor. They are expected to be formed subglacially by pressurized meltwaters.Ordovician tunnel valleys are described from North Africa to the Middle East. Ordovician glacial deposits are considered as a major target for hydrocarbon exploration in these regions, with tunnel valleys forming lithological heterogeneities with excellent reservoir properties. In Europe, Quaternary tunnel valleys are targeted for groundwater resources as they form reliable aquifers. A major interest therefore exists for these valleys, as well as a need for better understanding of the nature and the stratigraphy of the infill, their origin and the parameters controlling their distribution. The recherché project presented in this thesis is based on an extensive fieldwork that focused on three main issues, regarding tunnel valleys: (1) the subglacial environment, (2) the processes and depositional environments associated with their infill and (3) the parameters controlling their distribution.

The subglacial environment is complex, and despite improving investigation techniques, it is hardly accessible for direct observations and remains poorly understood. This environment is generally associated with coarse-grained, poorly sorted facies, and is considered to be subordinate to proglacial environments. The study carried out in Killiney Bay, Ireland, demonstrated that a wide range of facies could be deposited but also preserved in a subglacial environment, because subglacial accommodation space can be provided by the subglacial topography. The different facies display specific characteristics that record the close interaction between the substrate the overflowing ice-sheet, through coupling/uncoupling phases. Subglacial deposits display specific stratigraphic and sedimentological characteristics, as well as typical deformation structures related to fluid overpressures between the ice and the substrate.

Today, the different scenarios for tunnel valley infill are associated with the ice-sheet decay during the deglaciation and the subsequent ice-front retreat. The greater part of sediments is deposited in proglacial environments, either in glaciomarine or glaciofluvial settings. However, based on the diagnostic criterion defined in the quaternary record, subglacial facies were identified in Alnif tunnel valley infill and these facies represent nearly 50 % of the whole valley infill. A subordinate amount of these subglacial facies, restricted to the basal infill, are deposited under a fully grounded ice-sheet. The rest of the sediments is deposited under a lightly grounded ice-sheet, which is locally and temporary grounded on the substrate. By analogy with recent observations in Antarctica, this subglacial environment is at the transition between the fully grounded ice-sheet located above the coupling line, and the proglacial environment, where the ice-sheet is floating in the sea, seaward from the grounding line. Beneath the lightly grounded ice sheet, the sedimentary record will differ according to the amount of accommodation space. Glaciturbidites, associated with expanding flow from a subglacial conduit will be deposited in large accommodation space setting. Conversely, subglacial braided canal network, which develop through lateral migration and overdeepening will characterise low accommodation space setting.

Different examples of tunnel valley are described in the Anti-Atlas, allowing their morphology and the preglacial architecture to be compared in different locations. The results demonstrate the combined influence of lithological and hydrological parameters on tunnel valley shape and distribution. Tunnel valley density is higher where the preglacial substrate is characterised by low diffusivity, where no valley is formed where the preglacial strata are composed of high diffusivity sediments. Low diffusivity sediments have low capacity for groundwater transfer and channels will form at the ice-bed interface to efficiently drain meltwaters towards the margin. These channels will develop to form tunnel valleys. Conversely, above high-diffusivity sediments, meltwaters are fully drained as groundwater. In addition, the preglacial sedimentary architecture has a strong influence on tunnel valley shape. Low-diffusivity units, along the first 200 m of preglacial sediments, form permeability barriers which unable groundwater to flow vertically through the sediment, and therefore stop the tunnel valley overdeepening. These parameters explain the difference in shape, from shallow and narrow valleys to deep and large tunnel valleys. Finally, both the lithological and hydrological parameters are influenced by the regional structural configuration, which controls the evolution of preglacial depositional environments, and thus lithological heterogeneity distribution, but also (2) influences the subglacial drainage configuration.

Émilie Arnoux PhD thesis

Phenotypic and genetic variability in forest thrush, Turdus lherminieri, at different scales

Funding: région Bourgogne, Office national de la chasse et de la faune sauvage

Supervisor: Bruno Faivre ; co-supervisors: Stéphane Garnier and Cyril Eraud

Beginning in november 2009

 

Abstract
Understanding the mechanisms underlying population structure is a crucial issue in evolutionary biology and ecology. Identifying the processes driving biodiversity is also of prime interest to draw up guidelines for population management and conservation planning. Level of differentiation depends on a subtle balance between gene flow, genetic drift and natural selection and insight into the relative contribution of these factors can be provided by spatial and temporal patterns of intra-specific phenotypic and genetic variations. Differentiation has mainly been studied in insular systems because i) islands give ideal framework to study divergence in species ii) islands enclosed endemic fauna and flora. These endemic species are characterised by small population sizes and small distribution areas. They are consequently more fragilized by strong environmental changes. The Forest thrush Turdus lherminieri is an endemic and understorey bird present in four islands of Lesser Antilles: Montserrat, Guadeloupe, Dominica and Saint-Lucia. Four subspecies have been described on each island on the basis of feathers coloration but no study has really quantified the divergence between these subspecies. In addition, bird numbers have decline since 15 years and now Forest thrushes are protected on three islands but are always hunted in Guadeloupe. Aims proposed in this study are i) to study the spatial structure in Forest thrush in order to deduce potential causes of this structure ii) to describe the temporal evolution of genetic diversity, iii) to determine if parasites can exert contrasted selection pressures which follow gentic and morphological pattern in Forest thrushes populations. In this study, we have identified three clades and subspecies on each island which are differentiated morphologically and genetically. At fine scale i.e Guadeloupe only, we have revealed an uncommon level of differentiation. In last, the parasites’ structure seems to follow the morphological and genetic structure observed in Forest thrushes. To conclude, three management units can be defined: a first in Saint-Lucia, a second in Dominica and a third including Montserrat and Guadeloupe.

 

Keywords

speciation, insularity, endemism, forest thrush,  conservation

 

Coraline Bichet PhD thesis

Avian malaria evolutionary ecology: hosts immunity and evolution of virulence

Funding: French research minister grant

Supervisor: Gabriele Sorci

Beginned in october 2009

Defended 18 december 2012

 

Abstract

Host-parasite interactions are one of the main topics in evolutionary sciences. This complex coevolution depends on several trade-offs and can be influenced by environmental factors. Here, we propose to study host-parasite interactions with a multi-level approach, using experimental and natural population studies, focusing on avian malaria parasites. First, we studied the effect of host characteristics, and more precisely the immune system. The immune system confers benefits in terms of protection against the parasite, but can also generated immunopathological costs. Life history traits, like age or social status, appear to modify parasitemia but not prevalence. In a second part, we evaluated the effect of environmental factors on host-parasite interactions. We found that temperature and heavy metal contamination had an effect on population prevalence, but not on host parasitemia. We also showed the direct parasite influence on host population genetic structure, and more precisely on MHC genes.

 

Keywords

avian malaria, domestic canaries, house sparrow, major histocompatibility complex, immune system, life history traits, environment, mate choice.

Romain Gueirreiro’s PhD profile

Oxidative stress, senescence and adaptive trade-offs through age in birds

Research funding: ministry grant

PhD supervisor: Bruno Faivre

Starting date: october 2008

 

Abstract

The study of mechanisms involved in senescence and of the adaptive trade-offs between different functions through age are of a crucial interest from a fundamental and functional point of view. My research couples descriptive and experimental approaches to try to determine how different components of redox balance, an indication of oxidative stress, are modified by age. I am also interested in the influence of environmental conditions (particularly at early stage) on these components. Some of these components (particularly antioxidant defences) have multiple biological functions and are thus involved in trade-offs between physiological functions. I will consider the influence of age on such adaptive trade-offs. The aim of this subject is to explore certain mechanisms of senescence from an evolutionary point of view. This is particularly interesting in birds, the mechanisms for whose longevity are still very unclear. This work aim to highlight some fine and still much neglected mechanisms that affect oxidative stress and its roles in senescence, and the adaptive nature of some physiological trade-offs linked to oxidative stress.

This PhD project aims to examine, in birds, (i) the modification through age of different components of oxidative stress, and their possible links with senescence and longevity and (ii) their possible relation along life, in terms of trade-offs, with certain life history trade-offs directly involved in micro-evolutionary processes. It combines descriptive and experimental approaches on cohorts of different ages, and longitudinal monitoring of cohorts through time. Experimental control of environmental conditions and of individual’s investment in certain functions (like reproduction for example) will be easily attainable. The main species studied will be the Zebra Finch (Taeniopygia guttata), a small passerine with a maximum longevity reaching 5 years. Access to all possible age classes during this work will be possible on reconstructed cohorts but also on monitored individuals (longitudinal approach). We plan to evaluate oxidative stress, using 3 crucial parts methods: (i) antioxidant defences, (ii) the control of free radical production and (iii) the balance between antioxidant defences and production of free radicals.

To summarise, the aim of this project is to combine the study of oxidative stress, senescence and longevity, and attempt to isolate key stages in an individuals’ life and to assess possible trade-offs of key resources (antioxidant components) between anti-oxidative defences and other important biological functions during life.

 

Keywords

senescence, oxidative stress, redox balance, trade-offs, life history traits, longitudinal approach

 

PhD Committee

- Thierry Boulinier, chargé de recherche CNRS, CEFE (Centre d’écologie fonctionnelle et évolutive), UMR 5175, Montpellier, France

- Gabriele Sorci, directeur de recherche CNRS, université de Bourgogne, laboratoire Biogéosciences, UMR 5561, Dijon, France

Mathieu Martinez' PhD thesis

Astronomical calibration of the Valanginian and Hauterivian stages: palaeoclimatic and palaeoceanographic implications

Funding: Ministry of higher education and research + ANR Astronomical time scale for the Cenozoïc and Mesozoïc era (leaded by J. Laskar, Observatoire de Paris)

Supervisors: Jean-François Deconinck and Pierre Pellenard

Begined: october 2009

Submitted 3 june 2013

 

Summary

The Geological Time Scale shows numerous uncertainties on the Valanginian-Hauterivian interval (Early Cretaceous) that impacts on the palaeoceanographic reconstructions. Notably, the chronological reliationships between the positive excursion in ?13C in the middle Valanginian (the "Weissert Event"), the Faraoni oceanic anoxic event (latest Hauterivian) and the Paraná-Etendeka traps are badly understood. This works presents the results of an orbital calibration of the Valanginian Stage and part of the Hauterivian Stage, based on the record of the eccentricity cycle on palaeoclimate proxies measured at a high resolution, in the alternating series of the Vocontian Basin (SE France) and the Subbetic Domain (SE Spain).

A total of 3,000 gamma-ray spectrometry measurements, performed every 20 cm on five Valanginian reference sections in the Vocontian Basin, allowed the identification of the various orbital parameters. A duration of 5.08 myr is proposed for the Valanginian Stage, based on the identification of the 405-kyr eccentricity cycle. This duration combined with available radiometric ages, shows that the Weissert Event is prior to the onset of the Paraná-Etendeka activity. In addition, a stronger expression of the obliquity cycle in the Upper Valanginian (Nicklesi and Furcillata subzones) may reflect the development of low-extension polar ice.

A multi-proxy approach on the Hauterivian-Barremian transition in the Río Argos section (Subbetic Domain) shows cyclic fluctuations in detrital supplies and continental weathering conditions linked to the marl-limestone alternations. Marl interbeds were deposited in a humid climate marked by a strong continental weathering, while limestone beds were deposited under semi-arid conditions. An orbital calibration based on magnetic susceptibility, CaCO3 contents and clay minerals allowed the Ohmi and Hugii zones to be assessed at 0.78 and 0.54 myr, respectively. The Faraoni event has a duration comprised between 100 and 150 kyr. By correlation with other sections in the Western Tethys, Río Argos appears to be the best GSSP candidate for the Hauterivian-Barremian boundary.

 

Keywords

Valanginian, Hauterivian, Milankovitch cycles, cyclostratigraphy, gamma-ray spectrometry, magnetic susceptibility, palaeoclimatology, palaeoceanography

 

PhD committee

 

François Baudin (Pr., université Paris VI)

 

Fabrice Monna (Pr., université de Bourgogne)

Mathieu Moiroud PhD thesis

Thumbnail imageEvolution of the oceanic deep circulation during the Cretaceous – Insight from the neodymium isotopes

Funding: research grants from Burgundy Regional Council and CEA-Saclay

Supervisor: Jean-François Deconinck (HDR), university of Burgundy

Co-supervisors: Emmanuelle Pucéat (university of Burgundy) and Yannick Donnadieu (laboratoire des sciences du climat et de l'environnement, CEA Saclay)

Start date: 15 novembre 2010

defended the 2 july 2014

 

Abstract

The Cretaceous is depicted as the warmest period of the last 300 Ma. The Late Cretaceous is characterized by a long-term cooling, the cessation of oceanic anoxic events with deposits rich in organic matter, and major changes in the configuration of the continents. Though the oceanic circulation modes are essential to understand the role of oceans in climate evolution, the oceanic circulation and location of source zones of deep-waters in the basins remain unclear for the Cretaceous.

The neodymium (Nd) isotopes are used to track oceanic circulation and exchanges between water masses, in both past and modern oceans. The Nd isotope composition (eNd) in the ocean derives more or less directly from that of adjacent continental landmasses. In deep-waters, the isotopic signature is related to the composition of the continents surrounding the area of water sinking and current transport, thus every oceanic basin acquires a singular eNd. Unequivocal interpretations of the Cretaceous seawater eNd values stem from the insufficient spatial and temporal cover of the available data. In particular, data from continental margins remain very scarce, yet they are essential to identify the neritic regions of deep-water production by comparing their eNd with basinal bottom waters.

This PhD thesis firstly intents to collect the Nd signature of continental margins and in regions without data for the Cretaceous, with special attention given to the potential source zones of deep-water production. Fossil fish teeth, oxide coatings on foraminifera tests and detrital fraction from Late Cretaceous sediments are analyzed for their eNd. The results of this work are compared to a compilation of eNd values available in the literature for the Cretaceous and the Paleogene, in order to propose hypotheses for the location of the potential deep-water source zones and their evolution throughout the Cretaceous.

These hypotheses are then confronted to a coupled ocean-atmosphere circulation model. The results show that the eNd values seem to follow the long-term temperature variations during the Late Cretaceous and the Paleocene. However the numerical simulations suggest that deep oceanic circulation is not significantly altered by global climate. Instead, the tectonic evolution may be the primary cause of fluctuations in the continental eNd exported to the oceans, as well as the changes in oceanic circulation and climate, through modifications of the basinal configurations and the eroded landmasses.

 

Keywords

Cretaceous, neodymium isotopes, rare earth elements, oceanic circulation, climate model

 

PhD thesis committee members

Emmanuelle Vennin (HDR), laboratoire Biogéosciences, university of Burgundy

Frédéric Fluteau (HDR), Institut de physique du globe de Paris, Laboratoire de paléomagnétisme, Paris

Alexis Ndongo PhD thesis

canyon Sedimentological and tectonic setting of paleoproterozic Franceville basin (Gabon) : fluid pressure structures, bitumen and uranium deposits

Funding: Areva and Gabon government

Supervisors: Michel Guiraud, laboratoire Biogéosciences; Jean-Louis Feybesse, Areva NC Géoscience Groupe Technique  

Beginning of the thesis: november 2010

 

Abstract

série francevillienne Metallogenic deposits within paleproterozoic basins depend on generation and migration of fluids. The aim of this study is to provide a better understanding of tectonic, sedimentological and diagenetic setting of the uranium deposits in the Franceville basin and to characterize hydraulic fracturing impact on fluid migration processes in sandstone reservoirs.

Tectonic study define the N180-170° transfer faults, associated with Archean tectonic and the N110-120° longitudinal normal faults. These two fault directions split the Franceville basin into small sub-basins. The longitudinal normal faults are associated with footwall anticlines and hanging wall synclines. The uranium deposits of Franceville basin are located in footwall anticlines of longitudinal normal faults.

carte géologique Franceville Sedimentological analysis allows to describe four depositional environments: Fluvial (lower FA), deltaic (middle FA), tidal (upper FA), and open marine environments (FB). Facies distribution in the FA-FB transition promotes the establishment of permeability barriers. These latter are responsible of the increase in fluid pressure and of the formation of fluid pressure structures (dykes, stylolites, quartz veins), in footwall anticlines of longitudinal normal faults. Increase in fluid pressure allows the migration of uranium-fluids, and hydrocarbon from the deep basin to the footwall anticline. Hydraulic fracturing processes lead the precipitation of uranium mineralization, associated with bitumen, in microfractures.

 

affleurement stratigraphique Keywords

Franceville basin, paleoproterozoic, transfer faults, longitudinal normal faults, footwall anticlines, permeability barriers, fluid pressure structures, hydraulic fracturing, bitumen, uranium mineralization

 

PhD commitee

Michel Mbina, université des sciences du Gabon

Michel Guiraud, laboratoire Biogéosciences

Roger Soliva, université de Montpellier 2

Emmanuelle Vennin, laboratoire Biogéosciences

Fanny Vogelweith PhD thesis

Host plant effect on immunity of pests: influence of grapevine on ability of European grapevine moth to defend against bio-aggressors

Doctoral funding

Supervisors: Jérôme Moreau and Yannick Moret (Biogéosciences, Dijon), Denis Thiéry (UMR INRA 1065 santé végétale, ISVV, INRA Bordeaux)

Beginning : october 2010


Summary

In tritrophic interactions involving phytophagous insects, host plants and natural enemies, trophic levels are highly dependent on each other. Host plant may strongly affect directly phytophagous insect and indirectly natural enemies growing on these phytophagous insects. When a natural enemy attacks a phytophagous insect, the host immune system constitutes the last chance for the host to survive to an infection. A great variation of insect immune system is generally found in populations for susceptibility to pathogens, suggesting that variable selection pressures may have shaped and driven adaptation of immune traits. This project aims to determine the influence of both host plant and natural enemies on the larval immune system of grapevine moth pests, Lobesia botrana and Eupoecilia ambiguella.

During these three years, we have demonstrated a strong influence of grape variety on immune effectors of grapevine moth larvae. In addition, the grape variety modulates a trade-off between the constitutive and induced immune pathways. The variable presence of microbes on the surface of grape berries does not explain the trade-off in immune function. Beyond the grape variety effect, we also demonstrated a strong influence of parasitoids on the immune parameters of the grapevine moth larvae. In France, the most immunocompetent populations of grapevine moth are also the most parasitized. This positive correlation between successful parasitism and larval immune parameters seems not explained by a plastic response of the larval immune system to parasitoids presence, but rather by a local selection of larval immune system in response to parasitism pressure suffered by larvae for several years.

The different experiments realized in my thesis confirm the complexity of the tri-trophic interactions between host plant, phytophagous insects and natural enemies. The integration of phytophagous insect immune system seems essential in understanding the interactions linking these three protagonists.

 

Keywords

immune trade-off, insect immune system, grape varieties, grapevine moth, local immune selection, phenotypic plasticity, successful parasitism, tritrophic interactions

 

Committee members

Thierry Rigaud (Biogéosciences, Dijon)

Emmanuel Desouhant (LBBE, Lyon)

 

 

David Beaune PhD thesis

bonobo The ecological role of the bonobo. Seed dispersal service in Congo forests

 

Cédric Cuccia PhD thesis

Climate change impact on Pinot noir phénology over Burgundy

Funding: bureau interprofessionnel des vins de Bourgogne et région Bourgogne

Supervisors: Yves Richard (dir. Thèse, CRC), Thierry Castel (co-dir., CRC) et Benjamin Bois (co-dir., CRC)

Beginned: october 2008

Defended the 14 may 2013

 

Abstract

The viticulture is an important economic and cultural sector in Burgundy. The current climate change raises a number of issues including its impact on crops. In this thesis, the idea is to develop a methodology to address the problem: what are the potential impacts of changes in temperature on the phenology of Pinot noir in Burgundy for years 2031-2048?

The evolution of temperatures in Burgundy since 1961 is characterized by a positive temperature shift at the end of the 1980s followed by a period where the temperature increases of about 1.5 °C.

One of the interests of this thesis is to develop, following a strategy developed during the thesis, a spatial database conducted over the period 1989-2009 to estimate the ability of the WRF model to reproduce the climate Burgundy by disaggregating large scale data. The model reproduces satisfactorily the seasonal and spatial variability in global climate despite bias (cold on the Tx and hot on the Tn).

To regionalize the climate change, WRF was used to disaggregate data from the scenario SRES/A2 on the periods 1970-1987 and 2031-2048. After being evaluated and inter-compared three phenological models, using average temperatures data to simulate the dates of occurrence of phenological stages of Pinot Noir, have been applied to these decompositions.

The impact of warming temperatures on the horizon 2031-2048 (SRES/A2), estimated at 1.35 ° C on average, is characterized by an earlier flowering and veraison of about 7 and 15 days respectively. The interstadial duration is also reduced of about 5 days.

 

Keywords

climate change, temperature, pinot noir, Burgundy, phenology, regional climate model

 

Jury

Hervé Quenol, université de Rennes 2 – rapporteur
Cornelis Van Leeuwen, Bordeaux sciences agro – rapporteur
Iñaki Garcia de Cortazar-Atauri, INRA Avignon – examinateur
Daniel Joly, université de Franche-Comté – examinateur
Malika Madelin, Université Paris 7 – examinatrice
Christine Monamy, BIVB – invitée
Denis Thévenin, Météo-France – invité
Yves Richard, université de Bourgogne – directeur de thèse
Benjamin Bois, université de Bourgogne – co directeur
Thierry Castel, AgroSup Dijon – co directeur

Paul-Arthur Monerie's PhD thesis

The climate change effect on the african monsoon region: evolution of the precipitations and atmospheric fields in the CMIP3 and CMIP5 simulations under the A1B and rcp4.5 scenario. (1960-1999, 2031-2070)

Defended 18 june 2013

 

Abstract

The fourth IPCC report in 2007 established the synthesis of previously published work on the effects of climate change on global and regional scales. It shows in particular that no consensus can be found with regard to the future of rainfall — and atmospheric dynamics- associated with region — African monsoon. This dissertation revisits this issue in the light of new data and using an approach avoiding over-representation of the number of simulations available for one type of model and taking into account the diversity of models and their evolution in time: twenty general circulation models (GCMs) participating in the exercises CMIP3 (twelve GCMs) and CMIP5 (eight GCMs) under the A1B emissions scenario and rcp4.5, respectively. Outputs are analyzed on two 40-year periods, — ‘Present’ (1960-1999) and ‘Future’ (2031-2070) — and discussed in terms of likelihood, through an approach allowing us to both quantify differences ‘future’ minus ‘present’, measure robustness and statistical significances and associate a probability measuring the model consensus as a function of scales and variables.

Analyzes conducted on CMIP3 and CMIP5 show that consensus on the effect of climate change in West Africa can be achieved if we do not consider the Sahel as a whole and homogeneous entity but at lower scales. The results show contrasted responses over the central and western Sahel, with for the future, (i) an increase in precipitation in the central region explained primarily by a greater convergence of flow in the lower layers and a most northerly monsoon penetration over the continent, (ii) a rainfall decrease in the western Sahel explained by increased Walker-type circulation, African easterly jet and mid-level subsidence. Moreover, we can expect a change in the mean annual cycle of the monsoon season with a delayed withdrawal linked to additional inputs of moisture from the Atlantic due to increasing thermal and moisture contrasts between ocean and continent but also to a stronger contribution of moisture fluxes in September and October from the Mediterranean into the Sahel.

 

Keywords

Climate Change, African Monsoon, Sahel, General Circulation Models, CMIP3, CMIP5, A1B and rcp45 emission scenarios

 

Jury

Bernard Fontaine : Directeur
Pascal Roucou : Co-directeur
Thierry Lebel : Rapporteur
Benjamin Sultan : Rapporteur
Paolo Ruti : Examinateur
Serge Janicot : Examinateur

Lucile Dianne's PhD thesis

Characterization of the role of the acanthocephalan parasite Pomphorhynchus laevis non-infective larval stage in the behavioural manipulation of its amphipod intermediate host

Funding: CNRS / région Bourgogne

Directeurs : Thierry Rigaud and Marie-Jeanne Perrot-Minnot

Beginned in october 2009

Defended the 6 december 2012

 

Abstract

In trophically-transmitted parasites, exploitation strategies of the intermediate host have been selected, in a way increasing parasites transmission probabilities to their definitive host. Particularly, numerous parasites are able to alter their intermediate host behaviour, a phenomenon called ‘behavioural manipulation’. This manipulation only occurs when the parasite developmental stage (or larval stage) is infective for the definitive host. Before reaching this stage, the development of parasite larvae is not sufficiently advanced to allow establishment in the definitive host (this stage is thus called ‘non-infective’). Early transmission of a non-infective stage therefore implies parasite death. Parasites able to reinforce their intermediate host anti-predatory defences when non-infective (i.e. protecting them from predation), before manipulating their intermediate host behaviour when infective (i.e. exposing them to predation by definitive hosts), should have been selected. In this thesis, I showed that, when non-infective, the acanthocephalan parasite Pomphorhynchus laevis strengthens its amphipod intermediate host anti-predatory defences, which diminishes its host predation risk. This protective-like strategy negatively affects the amphipod food intake, although it has no effect on host energetic reserves. Similarly, the male amphipod reproductive behaviour is not affected by infection with a non-infective stage of the parasite. The origins of such parasitic strategy are discussed, and ecological perspectives to this host behavioural change are suggested.

 

Jury

Loïc Bollache, Professeur, Université de Bourgogne    Président
Jacob Koella, Professeur, Université de Neuchâtel (Suisse)    Examinateur
Yannick Outreman, Professeur, Agrocampus Ouest, Rennes    Rapporteur
Marie-Jeanne Perrot-Minnot, Maître de conférences, Université de Bourgogne    Directeur
Thierry Rigaud, Directeur de recherches CNRS, Dijon    Directeur
Ana Rivero, Chargée de recherches CNRS, Montpellier    Examinateur
Frédéric Thomas, Directeur de recherches CNRS, Montpellier    Rapporteur

Matthias Galipaud' PhD thesis

Mating strategies and resulting patterns in mate guarding crustaceans: an empirical and theoretical approach

Finding: ministry of research

Supervisors : Loïc Bollache and F.-X. Dechaume-Moncharmont

Beginned in october 2009

Defended the 13 december 2012

 

Abstract

In several species, reproductive partners associate for a long time before or after reproduction. Pairs are therefore easily observable in natural population which provides useful information about pairing strategies used by individuals. However, several constraints induced by competition for access to mates for example may affect pairing strategies. Consequently, it is generally not sufficient to infer paring strategies from pairing patterns only. In species with precopulatory mate guarding strategies, males grab females several days before copulation. Males and females have often been reported to be assorted by size. During this PhD, we first focused our investigations on the causes of such size assortment between mates. Using a theoretical approach, we showed that size-assortative pairing could result from a male mate choice strategy based on female maturity. This emphasizes the possibility for a given pairing pattern to come from several pairing strategies and highlights the importance of considering the whole pairing process in mate choice studies. We then studied male mate choice strategies in Gammarus pulex, a precopulatory mate guarding amphipod crustacean. Previous studies on the subject showed that males were capable of discriminating females before entering in precopulatory mate guarding, after which they were considered to be resolute in their choice, remaining with the chosen female until reproduction. However, we showed that males sometimes switched partners while guarding a female. This switching behaviour yet seemed not always optimal, as males did not always switch when a female of better quality than there current female was available for pairing. This reveals possible constraints on the evolution of decision making in mate choice in such mating systems.

Female mating strategies may also have an important effect on pairing patterns. Precopulatory mate guarding is often considered to be beneficial for males and costly for females. Consequently, a sexual conflict is supposed to exist over the duration of precopulatory mate guarding, males preferring long lasting guarding whereas females preferring short lasting guarding. However, only few studies have examined potential benefits associated with precopulatory mate guarding for females, therefore potentially over-estimating the strength of a sexual conflict over guarding duration. We showed that G. pulex females potentially benefited from being pairing for a long time because they had higher mating rates. This result call into question the existence of a strong sexual conflict over precopulatory mate guarding in this species.

 

Jury

Loïc Bollache, Professeur, Université de Bourgogne                 Directeur
Frank Cézilly, Professeur, Université de Bourgogne                 Examinateur
François-Xavier Dechaume-Moncharmont, Maître de conférences,
Université de Bourgogne                                 Directeur
Tim W. Fawcett, Research associate, University of Bristol                 Examinateur
Jacques Labonne, Chargé de recherche, INRA, Saint-Pée sur Nivelle         Examinateur
François Rousset, Directeur de recherche, CNRS, Université Montpellier II     Rapporteur
Michael Taborsky, Professor, University of BERN                     Rapporteur

Caroline Zanchi's PhD thesis

Evolutionary ecology of transgenerational immune priming in an insect

Funding: ANR trans-immunity

Supervisors : Yannick Moret and Jérôme Moreau

Beginning: october 2009

Defended the 17 december 2012

 

The Typescript is downloadable [ at this address ].


Abstract

Trans-generational immune priming (TGIP) is defined as the plastic enhancement of offspring's immunocompetence following an immune challenge of the females of the parental generation. In vertebrates, this phenomenon is well described, and is achieved by the maternal transfer of antibodies. In invertebrates however, it has only recently been described. Since invertebrates do not possess antibodies, the mechanism of this transmission remains unknown.

If the offspring is exposed to the maternal infection, an elevated immunocompetence can help it cope better with it. Nonetheless, apart from this benefit, several cues indicate that the TGIP bears some fitness costs for individuals. The evolution of TGIP will be favoured when its benefits outweigh its fitness costs. Thus, studying its costs and benefits can lead us to a better understanding of the selection pressures that lead to its evolution in invertebrates.

During my thesis, I associated the occurrence of TGIP in an insect, the mealworm beetle Tenebrio molitor, to several fitness costs for the females transmitting it as well as for the offspring receiving it.


Jury

Benjamin Gourbal, université de Perpignan – examinateur

Yanis Michalakis, CNRS, université de Montpellier II – rapporteur

Jérôme Moreau, université de Bourgogne – co-directeur

Yannick Moret, CNRS, université de Bourgogne – directeur

Thierry Rigaud, CNRS, université de Bourgogne – examinateur

Paul Schmid-Hempel, ETH Zürich – rapporteur