Biology subjects

Thierry, M.

Publications and source records attributed to Thierry, M..

6 recordsLinked to original sources

bioRxiv2025

Dominant species determines Drosophila-parasitoid food web dynamics and stability more strongly than complexity, warming or invasion

Ecological communities face major challenges of biodiversity loss, invasive species, and warming due to human action. Factors that determine the dynamics, stability and functioning of network of interacting species have been debated in ecology since its beginning as discipline. Community complexity and dominant (keystone) species have been proposed as the most relevant factors, however there is lack of knowledge on how these factors will interact with warming and invasion. To determine the effect of complexity, warming or invasion and their combinations on stability and functioning of a food web we performed a microcosm laboratory experiment using Drosophila-parasitoid food webs as a model. During five months, we recorded the dynamics of twelve different food webs (different combinations of flies and parasitoid species with two complexity levels) subjected to two temperature regimes (ambient and warming) and invasion or not by Drosophila suzukii in a factorial design. We did not observe any major effect of complexity or invasion. However, species composition had major effect, as webs with Drosophila simulans present were rapidly dominated by it, reducing diversity, increasing parasitism rate, reducing stability and bringing the community on the verge of collapse. Warming in turn increased diversity, overall fly population and temporal stability, while decreasing parasitism rate. Invasion of D. suzukii was not successful in any of the networks, possibly due to its low competitive ability. Our results imply that dominant species can have very strong effects on dynamics and stability, compared to food web complexity.

ecology↗

bioRxiv2021

Warming decreases host survival with multiple parasitoids, but parasitoid performance also decreases

Current global changes are reshaping ecological communities and modifying environmental conditions. We need to recognize the combined impact of these biotic and abiotic factors on species interactions, community dynamics, and ecosystem functioning. Specifically, the strength of predator-prey interactions often depends on the presence of other natural enemies: it weakens with competition and interference or strengthens with facilitation. Such effects of multiple predators on prey are likely to be affected by changes in the abiotic environment, altering top-down control, a key structuring force in natural and agricultural ecosystems. Here, we investigated how warming alters the effects of multiple predators on prey suppression using a dynamic model coupled with empirical laboratory experiments with Drosophila-parasitoid communities. While multiple parasitoids enhanced top-down control under warming, parasitoid performance generally declined when another parasitoid was present due to competitive interactions. This could reduce top-down control over multiple generations. Our study highlights the importance of accounting for interactive effects between abiotic and biotic factors to better predict community dynamics in a rapidly changing world and thus better preserve ecosystem functioning and services such as biological control.

ecology↗

bioRxiv2021

Multiple parasitoid species enhance top-down control, but parasitoid performance is context-dependent

O_LIEcological communities are composed of many species, forming complex networks of interactions. Current environmental changes are altering community composition. We thus need to identify which aspects of species interactions are primarily driven by community structure and which by species identity to predict changes in the functioning of communities. Yet, this partitioning of effects is challenging and thus rarely explored. C_LIO_LIHere we disentangled the influence of community structure and the identity of co-occurring species on the outcome of consumer-resource interactions using a host-parasitoid system. C_LIO_LIWe used four community modules that are common in host-parasitoid communities to represent community structure (i.e., host-parasitoid, exploitative competition, alternative host, and a combination of both exploitative competition and alternative host). We assembled nine different species combinations per community module in a laboratory experiment using a pool of three Drosophila hosts and three larval parasitoid species. To investigate the potential mechanisms at play, we compared host suppression and parasitoid performance across community modules and species assemblages. C_LIO_LIWe found that multiple parasitoid species enhanced host suppression due to sampling effect, weaker interspecific than intraspecific competition between parasitoids, and synergism. However, the effects of community structure on parasitoid performance were species-specific and dependent on the identity of co-occurring species. Consequently, multiple parasitoid species generally strengthen top down-control, but the performance of the parasitoids depends on the identity of either the co-occurring parasitoid species, the alternative host species, or both. C_LIO_LIOur results highlight the importance of preserving predator diversity for ecosystem functioning, but also show that other effects depend on community composition, and will therefore be likely altered by current environmental changes. C_LI

ecology↗

bioRxiv2021

Role of molecular polymorphism in defining tau filament structures in neurodegenerative diseases

Misfolding and aggregation of tau protein is implicated in many neurodegenerative diseases that are typified by the presence of large, filamentous tau inclusions. The aggregation of tau in human brain is disease-specific with characteristic filaments defining the neuropathology. An understanding of how identical tau isoforms aggregate into disparate filament morphologies in phenotypically distinct tau-related diseases remains elusive. Here, we determine the structure of a brain-derived twisted tau filament in progressive supranuclear palsy and compare it to a dissimilar tau fold found in corticobasal degeneration. While the tau filament core in both diseases is comprised of residues 274 to 380, molecular-level polymorphism exists. Potential origins of the molecular polymorphism, such as noncovalent cofactor binding, are identified and predicted to modulate tau filament structures in the brain.

biophysics↗

bioRxiv2020

Ecological differentiation and incipient speciation in the fungal pathogen causing rice blast

Many invasive fungal species coexist as multiple lineages on the same host, but the factors underlying the origin and maintenance of population structure remain largely unknown. Here, we analyzed genetic and phenotypic diversity in isolates of the rice blast fungus (Pyricularia oryzae) covering a broad geographical range. We showed that the four lineages of P. oryzae were found in areas with different prevailing environmental conditions and types of rice grown, indicating niche separation. Pathogenicity tests revealed that specialization to rice subspecies contributed to niche separation between lineages, and differences in repertoires of putative virulence effectors were consistent with differences in host range. Experimental crosses revealed that female sterility and early post-mating genetic incompatibilities acted as strong barriers to gene flow between these lineages. Our results demonstrate that the spread of a pathogen across heterogeneous habitats and divergent populations of a crop species can lead to niche separation and reproductive isolation between distinct invasive lineages.

evolutionary biology↗

bioRxiv2017

Coexistence of multiple endemic and pandemic lineages of the rice blast pathogen

The rice blast fungus Magnaporthe oryzae (syn. Pyricularia oryzae) is both a threat to global food security and a model for plant pathology. Molecular pathologists need an accurate understanding of the origins and line of descent of M. oryzae populations, to identify the genetic and functional bases of pathogen adaptation, and to guide the development of more effective control strategies. We used a whole-genome sequence analysis of samples from different times and places to infer details about the genetic makeup of M. oryzae from a global collection of isolates. Analyses of population structure identified six lineages within M. oryzae, including two pandemic on japonica and indica rice, respectively, and four lineages with more restricted distributions. Tip-dating calibration indicated that M. oryzae lineages separated about a millenium ago, long after the initial domestication of rice. The major lineage endemic to continental Southeast Asia displayed signatures of sexual recombination and evidence of DNA acquisition from multiple lineages. Tests for weak natural selection revealed that the pandemic spread of clonal lineages entailed an evolutionary cost, in terms of the accumulation of deleterious mutations. Our findings reveal the coexistence of multiple endemic and pandemic lineages with contrasting population and genetic characteristics within a widely distributed pathogen.\n\nImportanceThe rice blast fungus Magnaporthe oryzae (syn. Pyricularia oryzae) is a textbook example of a rapidly adapting pathogen, and is responsible for one of the most damaging diseases of rice. Improvements in our understanding of Magnaporthe oryzae diversity and evolution are required, to guide the development of more effective control strategies. We used genome sequencing data for samples from around the world to infer the evolutionary history of M. oryzae. We found that M. oryzae diversified about a thousand years ago ago, separating into six main lineages: two pandemic on japonica and indica rice, respectively, and four with more restricted distributions. We also found that a lineage endemic to continental Southeast Asia displayed signatures of sexual recombination and the acquisition of genetic material from multiple lineages. This work provides a population-level genomic framework for defining molecular markers for the control of rice blast and investigations of the molecular basis of differences in pathogenicity between M. oryzae lineages.

evolutionary biology↗