Dispersion des espèces impliquées dans une association phorétique vecteur - pathogène nouvellement formée : le cas de Monochamus galloprovincialis, vecteur natif d’un nématode invasif en Europe (Bursaphelenchus xylophilus)

Biological invasions dramatically increased over the last decades due to the intensification of international trade. These invasions constitute a threat for ecosystems and many anthropic activities, therefore it is crucial to understand underlying processes in order to better predict and manage their impacts. In this PhD thesis, I explore the potential of dispersion of native and non-native species involved in a novel phoretic association. I focus on the case of the association between a pest for pine forests, the pinewood nematode (Bursaphelenchus xylophilus) introduced in Europe, and its endemic insect vector (Monochamus galloprovincialis). I first estimated gene flows of the insect vector alone in order to identify the barriers and corridors to dispersal of this species. Then I have simulated the spatial spread of the nematode-vector couple using a spread model, and accounting for the synergistic effect of this novel association. The results obtained during this PhD showed that the invasive nematode has an important potential to spread through this phoretic association. However, some environmental features such as elevation, areas with low temperatures, and the high pine densities constitute barriers to dispersal of the vector and so, potential obstacles to the spread of the invasive nematode. Beyond these results focused on the model of study, this thesis has led to the development of several methods that may be adapted to other cases of novel phoretic association and, by extension, may contribute to a better understanding of dispersal of species involved in those complex and poorly known systems.Les invasions biologiques se sont intensifiées au cours des dernières décennies en raison d’une accélération des échanges commerciaux. Ces invasions représentent une menace pour les écosystèmes et de nombreuses activités anthropiques, il est donc crucial de comprendre les mécanismes qui les sous-tendent afin de mieux prévoir et limiter leurs impacts. Dans cette thèse, j’aborde la question du potentiel dispersif d’espèces natives et non natives impliquées dans une association phorétique nouvellement formée. En particulier, je me focalise sur le cas de l’association entre un nématode invasif ravageur des pinèdes, le nématode du pin (Bursaphelenchus xylophilus) et son insecte vecteur endémique en Europe (Monochamus galloprovincialis). J’ai tout d’abord étudié les flux de gènes de l’insecte vecteur seul afin d’identifier les barrières à sa dispersion. J’ai ensuite simulé l’expansion spatiale du couple nématode-vecteur à l’aide d’un modèle de dispersion, en intégrant l’effet synergique de cette nouvelle association. Les résultats obtenus au cours de cette thèse montrent qu’il existe un important potentiel de dispersion du nématode invasif en Europe par le biais de cette association phorétique. En revanche, certains paramètres de l’environnement tels que les reliefs et les températures basses qui leur sont associées, ainsi que les fortes densités en pins constituent des barrières à la dispersion du vecteur et donc des obstacles potentiels à l’expansion du nématode invasif. Au-delà des apports relatifs au modèle d’étude, cette thèse a conduit au développement de plusieurs méthodes pouvant être adaptées à d’autres cas d’associations phorétiques nouvelles et, par extension, contribuer à la compréhension de la dispersion des espèces au sein de ces systèmes complexes et peu étudiés

Most diverse, most neglected: weevils (Coleoptera: Curculionoidea) are ubiquitous specialized brood-site pollinators of tropical flora

In tropical environments, and especially tropical rainforests, a major part of pollination services is provided by diverse insect lineages. Unbeknownst to most, beetles, and more specifically hyperdiverse weevils (Coleoptera: Curculionoidea), play a substantial role there as specialized mutualist brood pollinators. The latter contrasts with a common view where they are only regarded as plant antagonists. This study aims to provide a comprehensive understanding of what is known about plant-weevil brood-site mutualistic interactions, through a review of the known behavioral, morphological and physiological features found in these systems, and the identification of potential knowledge gaps. To date, plant-weevil associations have been described or indicated in no less than 600 instances. Representatives of major plant lineages are involved in these interactions, which have emerged independently at least a dozen times. Strikingly, these mutualistic interactions are associated with a range of convergent traits in plants and weevils. Plants engaged in weevil-mediated pollination are generally of typical cantharophilous type exhibiting large, white and fragrant flowers or inflorescences and they also show specific structures to host the larval stages of their specialist pollinators. Another characteristic feature is that flowers often perform thermogenesis and exhibit a range of strategies to separate sexual phases, either spatially or temporally. Conversely, lineages of brood-site weevil pollinators present numerous shared behavioral and physiological traits, and often form multispecific assemblages of closely related species on a single host; recent studies also revealed that they generally display a high degree of phylogenetic niche conservatism. This pollination mutualism occurs in all tropical regions, and the contrasts between the known and expected diversity of these systems suggests that a wide range of interactions remain to be described globally. Our early estimates of the species richness of the corresponding weevil clades and the marked pattern of phylogenetic niche conservatism of host use further suggest that weevil-based pollination far exceeds the diversity of other brood-site mutualistic systems, which are generally restricted to one or a few groups of plants. As such, weevil pollinators constitute a relevant model to explore the emergence and evolution of specialized brood-site pollination systems in the tropics

Family-Level Sampling of Mitochondrial Genomes in Coleoptera : Compositional Heterogeneity and Phylogenetics

Mitochondrial genomes are readily sequenced with recent technology and thus evolutionary lineages can be densely sampled. This permits better phylogenetic estimates and assessment of potential biases resulting from heterogeneity in nucleotide composition and rate of change. We gathered 245 mitochondrial sequences for the Coleoptera representing all 4 suborders, 15 superfamilies of Polyphaga, and altogether 97 families, including 159 newly sequenced full or partial mitogenomes. Compositional heterogeneity greatly affected 3rd codon positions, and to a lesser extent the 1st and 2nd positions, even after RY coding. Heterogeneity also affected the encoded protein sequence, in particular in the nad2, nad4, nad5, and nad6 genes. Credible tree topologies were obtained with the nhPhyML ("nonhomogeneous") algorithm implementing a model for branch-specific equilibrium frequencies. Likelihood searches using RAxML were improved by data partitioning by gene and codon position. Finally, the PhyloBayes software, which allows different substitution processes for amino acid replacement at various sites, produced a tree that best matched known higher level taxa and defined basal relationships in Coleoptera. After rooting with Neuropterida outgroups, suborder relationships were resolved as (Polyphaga (Myxophaga (Archostemata + Adephaga))). The infraorder relationships in Polyphaga were (Scirtiformia (Elateriformia ((Staphyliniformia + Scarabaeiformia) (Bostrichiformia (Cucujiformia))))). Polyphagan superfamilies were recovered as monophyla except Staphylinoidea (paraphyletic for Scarabaeiformia) and Cucujoidea, which can no longer be considered a valid taxon. The study shows that, although compositional heterogeneity is not universal, it cannot be eliminated for some mitochondrial genes, but dense taxon sampling and the use of appropriate Bayesian analyses can still produce robust phylogenetic trees.Peer reviewe

Substitution for Cu in the electron-doped infinite-layer superconductor Sr0.9La0.1CuO2, Ni reduces Tc much faster than Zn

We report on the effect of substitution for Cu on Tc of electron-doped infinite-layer superconductors Sr0.9La0.1Cu1-xRxO2, R = Zn and Ni. We found that Tc was nearly constant until x = 0.03 for R = Zn, while superconductivity was nearly suppressed for x = 0.02 with dTc/dx = 20 K/% for R = Ni. This behavior is very similar to that of conventional superconductors. These findings are discussed in terms of the superconducting gap symmetry in the cuprate superconductors including another electron-doped superconductor, (Nd,Ce)2CuO4-y.Comment: 5 pages and 2 EPS figures, [email protected] for material reques

Coherent ultrafast torsional motion and isomerization of a biomimetic dipolar photoswitch

Femtosecond fluorescence up-conversion, UV-Vis and IR transient absorption spectroscopy are used to study the photo-isomerization dynamics of a new type of zwitterionic photoswitch based on a N-alkylated indanylidene pyrroline Schiff base framework (ZW-NAIP). The system is biomimetic, as it mimics the photophysics of retinal, in coupling excited state charge translocation and isomerization. While the fluorescence lifetime is 140 fs, excited state absorption persists over 230 fs in the form of a vibrational wavepacket according to twisting of the isomerizing double bond. After a short "dark'' time window in the UV-visible spectra, which we associate with the passage through a conical intersection (CI), the wavepacket appears on the ground state potential energy surface, as evidenced by the transient mid-IR data. This allows for a precise timing of the photoreaction all the way from the initial Franck-Condon region, through the CI and into both ground state isomers, until incoherent vibrational relaxation dominates the dynamics. The photo-reaction dynamics remarkably follow those observed for retinal in rhodopsin, with the additional benefit that in ZW-NAIP the conformational change reverses the zwitterion dipole moment direction. Last, the pronounced low-frequency coherences make these molecules ideal systems for investigating wavepacket dynamics in the vicinity of a CI and for coherent control experiments

Dispersal of species involved in a novel vector-pathogen phoretic association : the case of Monochamus galloprovincialis, native vector of an invasive nematode in Europe (Bursaphelenchus xylophilus)

Les invasions biologiques se sont intensifiées au cours des dernières décennies en raison d’une accélération des échanges commerciaux. Ces invasions représentent une menace pour les écosystèmes et de nombreuses activités anthropiques, il est donc crucial de comprendre les mécanismes qui les sous-tendent afin de mieux prévoir et limiter leurs impacts. Dans cette thèse, j’aborde la question du potentiel dispersif d’espèces natives et non natives impliquées dans une association phorétique nouvellement formée. En particulier, je me focalise sur le cas de l’association entre un nématode invasif ravageur des pinèdes, le nématode du pin (Bursaphelenchus xylophilus) et son insecte vecteur endémique en Europe (Monochamus galloprovincialis). J’ai tout d’abord étudié les flux de gènes de l’insecte vecteur seul afin d’identifier les barrières à sa dispersion. J’ai ensuite simulé l’expansion spatiale du couple nématode-vecteur à l’aide d’un modèle de dispersion, en intégrant l’effet synergique de cette nouvelle association. Les résultats obtenus au cours de cette thèse montrent qu’il existe un important potentiel de dispersion du nématode invasif en Europe par le biais de cette association phorétique. En revanche, certains paramètres de l’environnement tels que les reliefs et les températures basses qui leur sont associées, ainsi que les fortes densités en pins constituent des barrières à la dispersion du vecteur et donc des obstacles potentiels à l’expansion du nématode invasif. Au-delà des apports relatifs au modèle d’étude, cette thèse a conduit au développement de plusieurs méthodes pouvant être adaptées à d’autres cas d’associations phorétiques nouvelles et, par extension, contribuer à la compréhension de la dispersion des espèces au sein de ces systèmes complexes et peu étudiés.Biological invasions dramatically increased over the last decades due to the intensification of international trade. These invasions constitute a threat for ecosystems and many anthropic activities, therefore it is crucial to understand underlying processes in order to better predict and manage their impacts. In this PhD thesis, I explore the potential of dispersion of native and non-native species involved in a novel phoretic association. I focus on the case of the association between a pest for pine forests, the pinewood nematode (Bursaphelenchus xylophilus) introduced in Europe, and its endemic insect vector (Monochamus galloprovincialis). I first estimated gene flows of the insect vector alone in order to identify the barriers and corridors to dispersal of this species. Then I have simulated the spatial spread of the nematode-vector couple using a spread model, and accounting for the synergistic effect of this novel association. The results obtained during this PhD showed that the invasive nematode has an important potential to spread through this phoretic association. However, some environmental features such as elevation, areas with low temperatures, and the high pine densities constitute barriers to dispersal of the vector and so, potential obstacles to the spread of the invasive nematode. Beyond these results focused on the model of study, this thesis has led to the development of several methods that may be adapted to other cases of novel phoretic association and, by extension, may contribute to a better understanding of dispersal of species involved in those complex and poorly known systems

The Smicronychini of southern Africa (Coleoptera, Curculionidae): Review of the tribe and description of 12 new species

International audienceThis study reviews the species of the tribe Smicronychini Seidlitz, 1891 found in southern Africa. In total, 18 species are recognized in this region, 12 of them being described as new (Sharpia madibai sp. nov., Afrosmicronyx cycnii sp. nov., A. louwi sp. nov., A. marshalli sp. nov., A. nebulosipennis sp. nov., Smicronyx pseudocoecus sp. nov., S. australis sp. nov., S. drakensbergensis sp. nov., S. gracilipes sp. nov., S. paucisquamis sp. nov., S. san sp. nov., S. similis sp. nov.). The following genera and species are newly reported from this area: Afrosmicronyx Hustache, 1935; Sharpia Tournier, 1873; Smicronyx pauperculus Wollaston, 1864; S. albosquamosus Wollaston, 1854 and S. namibicus Haran, 2018. New host plant taxa and plant associations for the tribe are reported among the families Gentianaceae Juss., Orobanchaceae Vent. and Convolvulaceae Juss. A key to species and images of the habitus of adults and male genitalia are provided