Biology subjects

Ravigne, V.

Publications and source records attributed to Ravigne, V..

7 recordsLinked to original sources

bioRxiv2025

Predictability of preference from acceptance: influence of visual and olfactory stimuli in the Mediterranean fruit fly

Oviposition behavior in phytophagous insects is influenced by different stimuli and plays a key role in pest dynamics and crop loss. This study used 3D-printed artificial fruits varying in colour (yellow, blue, white) and odour (cherry, orange, banana) to test how visual and olfactory cues affect oviposition acceptance (no-choice) and preference (choice). In no-choice assays, the nine artificial fruits displayed sufficiently different visual and olfactory cues to trigger different egg-laying outputs (by a factor 1:3 between the least attractive fruit, white fruit with banana scent and the most attractive fruit, yellow fruit with cherry scent). While cues acted independently in no-choice settings, significant interactions were observed in choice conditions, highlighting multimodal sensory integration. In choice assays, the number of eggs laid and female preference depended on both the characteristics of fruits and their context. However a strong correlation was found between acceptance and preference. The relationship found between acceptance and preference implied that when a fruit seemed preferred in no-choice assays, it was even more preferred in one-choice assays. We finally discussed the practical implications for behavior-based pest management strategies.

animal behavior and cognition↗

bioRxiv2024

Origin, divergence and migration routes of psyllids of the Cacopsylla pruni complex (Hemiptera: Psylloidea) inferred by Approximate Bayesian Computation methods

Population genetics is essential to decipher the evolutionary history of pests and insect vectors from both a theoretical point of view and to predict and mitigate the future of epidemics. We attempt to shed light on the evolutionary history and phylogeography of two cryptic psyllid species (namely A and B) of the Cacopsylla pruni complex, vectors of Candidatus phytoplasma prunorum. It is known to cause the European stone fruit yellows (ESFY), a disease affecting Prunus trees and causing significant crop losses each year. Analyses were conducted to decipher the origin, order and time of divergence, as well as the migration routes of the species complex in the Western Palearctic. We used mitochondrial and nuclear gene data to infer the population genetic diversity and structure of the complex, and to reconstruct a dated phylogenetic tree of the Psyllinae family in order to subsequently perform Approximate Bayesian Computation analyses. Both species have diverged in what is now France from a common ancestor, around 20.19 Mya, before expanding into Spain around 6.61 Mya for species A and Eastern Europe around 6.36 Mya for species B. Then species B seem to have passed into Corsica during the Messinian salinity crisis (5.96-5.33 Mya) from French or Italian B populations. No apparent admixture was found between both species after their divergence, which would indicate an absence of gene flow between them at the point when they recolonised common ecological niches. This strong genetic differentiation confirms previous work on reproductive barriers between the two species.

molecular biology↗

bioRxiv2022

Two bridgehead invasions of Xylella fastidiosa subsp. multiplex in France

Of American origin, a wide diversity of Xylella fastidiosa strains belonging to different subspecies have been reported in Europe since 2013 and its discovery in Italian olive groves. Strains from the subspecies multiplex (ST6 and ST7) were first identified in France in 2015 in urban and natural areas. To trace back the most probable scenario of introduction in France, the molecular evolution rate of this subspecies was estimated at 3.2165 x 10-7 substitutions per site per year, based on heterochronous genome sequences collected worldwide. This rate allowed the dating of the divergence between French and American strains in 1987 for ST6 and in 1971 for ST7. The development of a new VNTR-13 scheme allowed tracing the spread of the bacterium in France, hypothesizing an American origin. Our results suggest that both sequence types were initially introduced and spread in Provence-Alpes-Cote dAzur (PACA); then they were introduced in Corsica in two waves from the PACA bridgehead populations.

microbiology↗

bioRxiv2020

Joint species distributions reveal the combined effects of host plants, abiotic factors and species competition as drivers of community structure in fruit flies

AO_SCPLOWBSTRACTC_SCPLOWThe relative importance of ecological factors and species interactions for phytophagous insect species distributions has long been a controversial issue. Using field abundances of eight sympatric Tephritid fruit flies on 21 host plants, we inferred flies realized niches using joint species distribution modelling and network inference, on the community as a whole and separately on three groups of host plants. These inferences were then confronted to flies fundamental niches estimated through laboratory-measured fitnesses on host plants. Species abundances were mainly determined by host plants followed by climatic factors, with a minor role for competition between species sharing host plants. The relative importance of these factors mildly changed when we focused on particular host plant groups. Despite overlapping fundamental niches, specialists and generalists had almost distinct realized niches, with possible competitive exclusion of generalists by specialists on Cucurbitaceae, and different assembly rules: specialists were mainly influenced by their adaptation to host plants while generalist abundances varied regardless of their fundamental host use.

ecology↗

bioRxiv2019

How do invasion syndromes evolve? An experimental evolution approach using the ladybug Harmonia axyridis

Experiments comparing native to introduced populations or distinct introduced populations to each other show that phenotypic evolution is common and often involves a suit of interacting phenotypic traits. We define such sets of traits that evolve in concert and contribute to the success of invasive populations as an invasion syndrome. The invasive Harlequin ladybird Harmonia axyridis displays such an invasion syndrome with, for instance, females from invasive populations being larger and heavier than individuals from native populations, allocating more resources to reproduction, and spreading reproduction over a longer lifespan. Invasion syndromes could emerge due to selection acting jointly and directly on a multitude of traits, or due to selection on one or a few key traits that drive correlated indirect responses in other traits. Here, we investigated the degree to which the H. axyridis invasion syndrome would emerge in response to artificial selection on either female body mass or on age at first reproduction, two traits involved in their invasion syndrome. To further explore the interaction between environmental context and evolutionary change in molding the phenotypic response, we phenotyped the individuals from the selection experiments in two environments, one with abundant food resources and one with limited resources. The two artificial selection experiments show that the number of traits showing a correlated response depends upon the trait undergoing direct selection. Artificial selection on female body mass resulted in few correlated responses and hence poorly reproduced the invasion syndrome. In contrast, artificial selection on age at first reproduction resulted in more widespread phenotypic changes, which nevertheless corresponded only partly to the invasion syndrome. The artificial selection experiments also revealed a large impact of diet on the traits, with effects dependent on the trait considered and the selection regime. Overall, our results indicate that direct selection on multiple traits was likely necessary in the evolution of the H. axyridis invasion syndrome. Furthermore, they show the strength of using artificial selection to identify the traits that are correlated in different selective contexts, which represents a crucial first step in understanding the evolution of complex phenotypic patterns, including invasion syndromes.

evolutionary biology↗

bioRxiv2019

Evolution of trade-offs across environments following experimental evolution of the generalist Drosophila suzukii to different fruit media

The process of local adaptation involves differential changes in fitness over time across different environments. While experimental evolution studies have extensively tested for patterns of local adaptation at a single time point, there is relatively little research that examines fitness more than once during the time course of adaptation. We allowed replicate populations of the fruit pest Drosophila suzukii to evolve in one of eight different fruit media. After five generations, populations with the highest initial levels of maladaptation had mostly gone extinct, whereas experimental populations evolving on cherry, strawberry and cranberry media had survived. We measured the fitness of each surviving population in each of the three fruit media after five and after 26 generations of evolution. After five generations, adaptation to each medium was associated with increased fitness in the two other media. This was also true after 26 generations, except when populations that evolved on cranberry medium developed on cherry medium. These results suggest that, in the theoretical framework of a fitness landscape, the fitness optima of cherry and cranberry media are the furthest apart. Our results show that studying how fitness changes across several environments and across multiple generations provides insights into the dynamics of local adaptation that would not be evident if fitness were analyzed at a single point in time. By allowing a qualitative mapping of an experimental fitness landscape, our approach will improve our understanding of the ecological factors that drive the evolution of local adaptation in D. suzukii.

evolutionary biology↗

bioRxiv2017

Maintenance of Polymorphism in Spatially Heterogeneous Environments: An Experimental Test of Hard and Soft Selection

This preprint has been reviewed and recommended by Peer Community In Evolutionary Biology (http://dx.doi.org/10.24072/pci.evolbiol.100020). Predicting and managing contemporary adaption requires a proper understanding of the determinants of genetic variation. Spatial heterogeneity of the environment may stably maintain polymorphism when habitat contribution to the next generation can be considered independent of the degree of adaptation of local populations within habitats (i.e., under soft selection). In contrast, when habitats contribute proportionally to the mean fitness of the populations they host (hard selection), polymorphism is not expected to be maintained by selection. Although mathematically established decades ago, this prediction had never been properly explored. Here we provide an experimental test in which polymorphic populations of Escherichia coli growing in heterogeneous habitats were exposed to hard and soft selection regimes. As predicted by theory, polymorphism was longer preserved under soft selection. Complementary tests established that soft selection slowed down fixation processes and could even protect polymorphism on the long term by providing a systematic advantage to rare genotypes.

evolutionary biology↗