<p>(A) Ascospore and (B) conidia experimental sites. Dispersal kernels (DK) parameter value... more <p>(A) Ascospore and (B) conidia experimental sites. Dispersal kernels (DK) parameter values are given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0103225#pone-0103225-t001" target="_blank">Table 1</a>. Density of resistant lesions (DRL) is expressed in a “log (1+ of the value)” scale. Smallest dots represents sites where DRL = 0 and gaps (B) represents missing data due to plants mortality.</p
<p>Density of lesions (i.e., DL, A & C) and density of resistant lesions (i.e., DRL, B ... more <p>Density of lesions (i.e., DL, A & C) and density of resistant lesions (i.e., DRL, B & D) as a function of geographical distances from the central source. Top: ascospores site (A & B); Bottom: conidia site (C & D). The different axis of the experimental design are represented separately using different symbols. DL and DRL are plotted in “log (1+the value)” scale but values are indicated in natural scales.</p
<p>Estimated directional functions (solid lines, A&C for the density and B&D for th... more <p>Estimated directional functions (solid lines, A&C for the density and B&D for the mean distance) are compared to their equivalent uniform functions (dotted lines) for both the ascospores (A&B) and conidia (C&D) experimental site. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0103225#pone-0103225-t001" target="_blank">Table 1</a> for details on values and statistical support. Directional angles are given in degrees.</p
This data file contains all the flow cytometry data used to estimate cell concentrations, fitness... more This data file contains all the flow cytometry data used to estimate cell concentrations, fitness measures etc
Predicting and managing contemporary adaption requires a proper understanding of the determinants... more 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 demonstrated experimentally. 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 preserved longer under soft selection. Complementary tests established that soft selection slowed fixation processes and could even protect polymorphism in the long term by providing a systematic advantage to rare genotypes
Sexual reproduction and dispersal are often coupled in organisms mixing sexual and asexual reprod... more Sexual reproduction and dispersal are often coupled in organisms mixing sexual and asexual reproduction, such as fungi. The aim of this study is to evaluate the impact of mate limitation on the spreading speed of fungal plant parasites. Starting from a simple model with two coupled partial differential equations, we take advantage of the fact that we are interested in the dynamics over large spatial and temporal scales to reduce the model to a single equation. We obtain a simple expression for speed of spread, accounting for both sexual and asexual reproduction. Taking Black Sigatoka disease of banana plants as a case study, the model prediction is in close agreement with the actual spreading speed (100 km per year), whereas a similar model without mate limitation predicts a wave speed one order of magnitude greater. We discuss the implications of these results to control parasites in which sexual reproduction and dispersal are intrinsically coupled.
Efficient strategies for limiting the impact of pathogens on crops require a good understanding o... more Efficient strategies for limiting the impact of pathogens on crops require a good understanding of the factors underlying the evolution of compatibility range for the pathogens and host plants, i.e., the set of host genotypes that a particular pathogen genotype can infect and the set of pathogen genotypes that can infect a particular host genotype. Until now, little is known about the evolutionary and ecological factors driving compatibility ranges in systems implicating crop plants. We studied the evolution of host and pathogen compatibility ranges for rice blast disease, which is caused by the ascomycete Magnaporthe oryzae. We challenged 61 rice varieties from three rice subspecies with 31 strains of M. oryzae collected worldwide from all major known genetic groups. We determined the compatibility range of each plant variety and pathogen genotype and the severity of each plant−pathogen interaction. Compatibility ranges differed between rice subspecies, with the most resistant subs...
Adaptation to divergent environments can result in ecological specialization. The detection of tr... more Adaptation to divergent environments can result in ecological specialization. The detection of trade-offs across environments (i.e., negative correlations in performance between different environments) is the hallmark of specialization. Although such trade-offs are predicted by theory, experimental evidence that trade-offs can readily evolve in the laboratory remains scarce. Here, we investigated the evolution of adaptation to distinct environments, including potential fitness trade-offs by maintaining populations of the generalist fruit pest, Drosophila suzukii, for 26 generations on media made with different fruits. We measured the performance and preference of each evolved population on the different fruits using reciprocal transplant experiments after five generations and at the end of our experiment. After five generations, experimental populations on most fruits had gone extinct, but they had adapted to three test fruit media, without exhibiting trade-offs. By generation 26 on...
Cassava mosaic disease (CMD) in Madagascar is caused by a complex of at least six African cassava... more Cassava mosaic disease (CMD) in Madagascar is caused by a complex of at least six African cassava mosaic geminivirus (CMG) species. This provides a rare opportunity for a comparative study of the evolutionary and epidemiological dynamics of distinct pathogenic crop-infecting viral species that coexist within the same environment. The genetic and spatial structure of CMG populations in Madagascar was studied and Bayesian phylogeographic modelling was applied to infer the origins of Madagascan CMG populations within the epidemiological context of related populations situated on mainland Africa and other south western Indian Ocean (SWIO) islands. The isolation and analysis of 279 DNA-A and 117 DNA-B sequences revealed the presence in Madagascar of four prevalent CMG species (South African cassava mosaic virus, SACMV; African cassava mosaic virus, ACMV; East African cassava mosaic Kenya virus, EACMKV; and East African cassava mosaic Cameroon virus, EACMCV), and of numerous CMG recombina...
In a cross-infection experiment, we investigated how seasonal changes can affect adaptation patte... more In a cross-infection experiment, we investigated how seasonal changes can affect adaptation patterns in a Zymoseptoria tritici population. The fitness of isolates sampled on wheat leaves at the beginning and at the end of a field epidemic was assessed under environmental conditions (temperature and host stage) to which the local pathogen population was successively exposed. Isolates of the final population were more aggressive, and showed greater sporulation intensity under winter conditions and a shorter latency period (earlier sporulation) under spring conditions, than isolates of the initial population. These differences, complemented by lower between-genotype variability in the final population, exhibited an adaptation pattern with three striking features: (i) the pathogen responded synchronously to temperature and host stage conditions; (ii) the adaptation concerned two key fitness traits; (iii) adaptation to one trait (greater sporulation intensity) was expressed under winter conditions while, subsequently, adaptation to the other trait (shorter latency period) was expressed under spring conditions. This can be interpreted as the result of short-term selection, driven by abiotic and biotic factors. This case study cannot yet be generalized but suggests that seasonality may play an important role in shaping the variability of fitness traits. These results further raise the question of possible counterselection during the interepidemic period. While we did not find any trade-off between clonal multiplication on leaves during the epidemic period and clonal spore production on debris, we suggest that final populations could be counterselected by an Allee effect, mitigating the potential impact of seasonal selection on long-term dynamics.
<p>(A) Ascospore and (B) conidia experimental sites. Dispersal kernels (DK) parameter value... more <p>(A) Ascospore and (B) conidia experimental sites. Dispersal kernels (DK) parameter values are given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0103225#pone-0103225-t001" target="_blank">Table 1</a>. Density of resistant lesions (DRL) is expressed in a “log (1+ of the value)” scale. Smallest dots represents sites where DRL = 0 and gaps (B) represents missing data due to plants mortality.</p
<p>Density of lesions (i.e., DL, A & C) and density of resistant lesions (i.e., DRL, B ... more <p>Density of lesions (i.e., DL, A & C) and density of resistant lesions (i.e., DRL, B & D) as a function of geographical distances from the central source. Top: ascospores site (A & B); Bottom: conidia site (C & D). The different axis of the experimental design are represented separately using different symbols. DL and DRL are plotted in “log (1+the value)” scale but values are indicated in natural scales.</p
<p>Estimated directional functions (solid lines, A&C for the density and B&D for th... more <p>Estimated directional functions (solid lines, A&C for the density and B&D for the mean distance) are compared to their equivalent uniform functions (dotted lines) for both the ascospores (A&B) and conidia (C&D) experimental site. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0103225#pone-0103225-t001" target="_blank">Table 1</a> for details on values and statistical support. Directional angles are given in degrees.</p
This data file contains all the flow cytometry data used to estimate cell concentrations, fitness... more This data file contains all the flow cytometry data used to estimate cell concentrations, fitness measures etc
Predicting and managing contemporary adaption requires a proper understanding of the determinants... more 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 demonstrated experimentally. 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 preserved longer under soft selection. Complementary tests established that soft selection slowed fixation processes and could even protect polymorphism in the long term by providing a systematic advantage to rare genotypes
Sexual reproduction and dispersal are often coupled in organisms mixing sexual and asexual reprod... more Sexual reproduction and dispersal are often coupled in organisms mixing sexual and asexual reproduction, such as fungi. The aim of this study is to evaluate the impact of mate limitation on the spreading speed of fungal plant parasites. Starting from a simple model with two coupled partial differential equations, we take advantage of the fact that we are interested in the dynamics over large spatial and temporal scales to reduce the model to a single equation. We obtain a simple expression for speed of spread, accounting for both sexual and asexual reproduction. Taking Black Sigatoka disease of banana plants as a case study, the model prediction is in close agreement with the actual spreading speed (100 km per year), whereas a similar model without mate limitation predicts a wave speed one order of magnitude greater. We discuss the implications of these results to control parasites in which sexual reproduction and dispersal are intrinsically coupled.
Efficient strategies for limiting the impact of pathogens on crops require a good understanding o... more Efficient strategies for limiting the impact of pathogens on crops require a good understanding of the factors underlying the evolution of compatibility range for the pathogens and host plants, i.e., the set of host genotypes that a particular pathogen genotype can infect and the set of pathogen genotypes that can infect a particular host genotype. Until now, little is known about the evolutionary and ecological factors driving compatibility ranges in systems implicating crop plants. We studied the evolution of host and pathogen compatibility ranges for rice blast disease, which is caused by the ascomycete Magnaporthe oryzae. We challenged 61 rice varieties from three rice subspecies with 31 strains of M. oryzae collected worldwide from all major known genetic groups. We determined the compatibility range of each plant variety and pathogen genotype and the severity of each plant−pathogen interaction. Compatibility ranges differed between rice subspecies, with the most resistant subs...
Adaptation to divergent environments can result in ecological specialization. The detection of tr... more Adaptation to divergent environments can result in ecological specialization. The detection of trade-offs across environments (i.e., negative correlations in performance between different environments) is the hallmark of specialization. Although such trade-offs are predicted by theory, experimental evidence that trade-offs can readily evolve in the laboratory remains scarce. Here, we investigated the evolution of adaptation to distinct environments, including potential fitness trade-offs by maintaining populations of the generalist fruit pest, Drosophila suzukii, for 26 generations on media made with different fruits. We measured the performance and preference of each evolved population on the different fruits using reciprocal transplant experiments after five generations and at the end of our experiment. After five generations, experimental populations on most fruits had gone extinct, but they had adapted to three test fruit media, without exhibiting trade-offs. By generation 26 on...
Cassava mosaic disease (CMD) in Madagascar is caused by a complex of at least six African cassava... more Cassava mosaic disease (CMD) in Madagascar is caused by a complex of at least six African cassava mosaic geminivirus (CMG) species. This provides a rare opportunity for a comparative study of the evolutionary and epidemiological dynamics of distinct pathogenic crop-infecting viral species that coexist within the same environment. The genetic and spatial structure of CMG populations in Madagascar was studied and Bayesian phylogeographic modelling was applied to infer the origins of Madagascan CMG populations within the epidemiological context of related populations situated on mainland Africa and other south western Indian Ocean (SWIO) islands. The isolation and analysis of 279 DNA-A and 117 DNA-B sequences revealed the presence in Madagascar of four prevalent CMG species (South African cassava mosaic virus, SACMV; African cassava mosaic virus, ACMV; East African cassava mosaic Kenya virus, EACMKV; and East African cassava mosaic Cameroon virus, EACMCV), and of numerous CMG recombina...
In a cross-infection experiment, we investigated how seasonal changes can affect adaptation patte... more In a cross-infection experiment, we investigated how seasonal changes can affect adaptation patterns in a Zymoseptoria tritici population. The fitness of isolates sampled on wheat leaves at the beginning and at the end of a field epidemic was assessed under environmental conditions (temperature and host stage) to which the local pathogen population was successively exposed. Isolates of the final population were more aggressive, and showed greater sporulation intensity under winter conditions and a shorter latency period (earlier sporulation) under spring conditions, than isolates of the initial population. These differences, complemented by lower between-genotype variability in the final population, exhibited an adaptation pattern with three striking features: (i) the pathogen responded synchronously to temperature and host stage conditions; (ii) the adaptation concerned two key fitness traits; (iii) adaptation to one trait (greater sporulation intensity) was expressed under winter conditions while, subsequently, adaptation to the other trait (shorter latency period) was expressed under spring conditions. This can be interpreted as the result of short-term selection, driven by abiotic and biotic factors. This case study cannot yet be generalized but suggests that seasonality may play an important role in shaping the variability of fitness traits. These results further raise the question of possible counterselection during the interepidemic period. While we did not find any trade-off between clonal multiplication on leaves during the epidemic period and clonal spore production on debris, we suggest that final populations could be counterselected by an Allee effect, mitigating the potential impact of seasonal selection on long-term dynamics.
Uploads
Papers by Virginie Ravigne