Biology subjects

Godefroid, M.

Publications and source records attributed to Godefroid, M..

9 recordsLinked to original sources

bioRxiv2025

Predicting the cross-continental spread of the cassava brown streak disease epidemic in sub-Saharan Africa

Cassava brown streak disease (CBSD) is a major threat to smallholder farmers in sub-Saharan Africa (SSA), where cassava is a staple crop. Caused by cassava brown streak ipomoviruses (CBSIs), CBSD has spread extensively since its detection in Uganda in 2004, raising concerns about ongoing spread through Southern and Central Africa and potential expansion to West Africa, home to the worlds largest cassava producer, Nigeria. Building on a stochastic epidemiological model that predicts CBSD spread at the scale of Uganda, we incorporate extensive field surveillance records to extend the model to all thirty-two major cassava-producing countries in SSA. We then deploy the model to address key strategic questions such as estimating the present day CBSD distribution and predicting rates of ongoing spread towards West Africa. We also evaluate the risk of direct introductions resulting from long range movement of infected planting material, which could trigger outbreaks beyond predicted localised dispersal limits. Our model predicts the likely arrival of CBSD in Nigeria via cross-continental spread within 25 years, and if directly introduced anywhere in West Africa, spreading to most West African nations within 10 years. The risks of ongoing and future CBSD spread highlighted in this study underscore the need for proactive phytosanitation measures, including clean seed programs, vector control, and quarantine policies to curb CBSD spread. Moreover, the model described in this study not only provides estimates for arrival times across SSA, but also lays the foundations for a continental-scale quantitative framework wherein both surveillance and management options can be explored and optimised.

ecology↗

bioRxiv2023

Asexual lineages of a cosmopolitan pest aphid are associated with different climatic niches

Asexual lineages often exhibit broader distributions and can thrive in extreme habitats compared to their sexual counterparts. Two hypotheses have been proposed to explain this phenomenon. The general-purpose genotype model posits that selection favours a few versatile asexual genotypes with wide environmental tolerance, enabling their long-term persistence across diverse conditions. Conversely, the frozen niche variation model suggests that selection favours specialised genotypes with minimal niche overlap among them and their sexual relatives, potentially leading to competition-driven exclusion of both sexual and asexual relatives. To investigate these hypotheses, we examined ecological niche differentiation among six globally distributed obligate asexual lineages of the cosmopolitan aphid pest, Brachycaudus helichrysi. We initially investigated the presence of different endosymbionts across clones, as endosymbionts play a major role in aphid niche differentiation. Subsequently, we conducted multivariate analyses to explore climatic niche divergence among clones. We provide evidence for climatic niche specialisation in asexual lineages, which is not related to variations in endosymbiont associations. Therefore, despite their apparent global distribution, B. helichrysi clones exhibit characteristics of specialised genotypes, which aligns with the frozen niche variation hypothesis. This study represents the first comprehensive evidence of climatic adaptation in aphid superclones, providing novel insights into their global distribution.

ecology↗

bioRxiv2022

Ecological models predict narrow potential distribution for Trioza erytreae, vector of the citrus greening disease

The African citrus psyllid, Trioza erytreae (Hemiptera: Triozidae), is a vector of citrus greening disease (Huanglonbing - HLB) caused by the bacterium Candidatus liberibacter. Native from Africa, T. erytreae was detected in northwestern Spain in 2014, and since then it has established along Atlantic coastal areas of the Iberian Peninsula. Given the severe bio-economic impact of HLB, an accurate assessment of the risk of potential spread of African citrus psyllid to citrus-growing regions of the Mediterranean area and the rest of the world, is urgently needed to design effective control strategies and anticipate economic losses. Therefore, I calibrated species distribution models to understand the bioclimatic characteristics that shape the distribution of T. erytreae and to assess the climatic suitability of the worlds major citrus-growing regions for this species under current and future climate conditions. The models identify mild summer and winter temperatures and high levels of precipitation as optimal conditions for long-term psyllid establishment. It is noteworthy that the models trained without the available occurrences in continental Europe, predict only the Atlantic coastal regions of the Iberian Peninsula as highly climatically suitable in Europe, which corresponds perfectly with the area currently invaded by the psyllid. This striking predictive accuracy lends great credibility to the model predictions. Most economically important citrus production areas in the world are predicted to be of low or moderate climatic suitability for T. erytreae. This research is crucial for assessing the global risk of HLB and is particularly timely for Europe where the African citrus psyllid has recently been detected.

ecology↗

bioRxiv2022

Global predictions for the risk of establishment of Pierce's disease of grapevines

The vector-borne bacterium Xylella fastidiosa is responsible for Pierces disease (PD), a lethal grapevine illness that originated in the Americas. The international plant trade is expanding the geographic range of this pathogen, posing a new threat to viticulture worldwide. To assess the potential incidence of PD, we have built a dynamic epidemiological model based on the response of 36-grapevine varieties to the pathogen in inoculation assays and on the vectors distribution when this information is available. Key temperature-driven epidemiological processes, such as PD symptom development and recovery, are mechanistically modelled. Integrating into the model highresolution spatiotemporal climatic data from 1981 onward and different infectivity (R0) scenarios, we show how the main wine-producing areas thrive mostly in non-risk, transient, or epidemic-risk zones with potentially low growth rates in PD incidence. Epidemic-risk zones with moderate to high growth rates are currently marginal outside the United States. However, a global expansion of epidemic-risk zones coupled with small increments in the disease growth rate is projected for 2050. Our study globally downscales the risk of PD establishment while highlighting the importance of considering climate variability, vector distribution and an invasive criterion in obtaining accurate risk maps to guide policy decision-making in plant health.

plant biology↗

bioRxiv2021

Investigating densities of Symbiodiniaceae in two species of Antipatharians (black corals) from Madagascar

Here, we report the first methodological approach to investigate the presence and estimate the density of Symbiodiniaceae cells in corals of the order Antipatharia subclass Hexacorallia, known as black corals. Antipatharians are understudied ecosystem engineers of shallow (<30 m depth), mesophotic (30-150 m) and deep-sea (>200 m) reefs. They provide habitat to a vast number of marine fauna, enhancing and supporting coral reefs biodiversity globally. Nonetheless, little biological and ecological information exists on antipatharians, including the extent at which global change disturbances are threatening these corals. The assumption that they were exempted from threats related to climate change was challenged by findings of high density of dinoflagellates within three antipatharian colonies. Further methodical studies were necessary to investigate the regularity of these findings. An integrated design combining microscopy and molecular techniques was used to investigate the presence and estimate density of Symbiodiniaceae cells within two antipatharians species -Cupressopathes abies and Stichopathes maldivensis -from shallow and mesophotic reefs of SW Madagascar. Symbiodiniaceae-like cells were found within the two species from both shallow and mesophotic reefs, although the overall cell density was very low (0-4 cell mm-3). These findings suggest that high abundance of Symbiodiniaceae is not characteristic of antipatharians, which has relevant implications considering disruptions associated to climate change affecting other corals. However, the high densities of dinoflagellates found in antipatharian colonies exposed to higher light irradiance in other studies should be further examined.

molecular biology↗

bioRxiv2020

The risk of Xylella fastidiosa outbreaks will decrease in the Mediterranean olive-producing regions

The bacterium Xylella fastidiosa (Xf) is a worldwide distributed invasive insect-borne plant pathogen, which causes lethal diseases to many economically-important crops including olives, citrus, almonds and grapes as well as numerous forest, ornamental, and uncultivated plants. The Mediterranean basin is the top supplier of olive oil with 93% of the world production and is consequently highly concerned about the recent invasion of Xf in Europe. Recently, bioeconomic models estimated putative losses induced by the spread of Xf across the European olive-producing area ranging from 1.9 to 5.2 billion euros over 50 years; however, such models did not take into account the insect vectors, which constitute a key driver of Xf spread. In the present study, we used bioclimatic species distribution models to predict the current and future climate suitability of the Mediterranean area for the main efficient or putative transmitters of Xf to olive (i.e. Philaenus spumarius, Neophilaenus campestris and Aphrophora alni). An important part of the total extent of the Mediterranean olive-producing area, mainly situated in southern Spain, Turkey and Greece, is predicted as currently poorly suitable for these vector species. Moreover, models forecast that nearly the totality of the Mediterranean olive-producing regions will likely become climatically little suitable for these vectors by 2050 due to climate change. In Europe, Xf outbreaks have occurred so far only in localities predicted as climatically suitable for these main vector species (e.g. the Apulia region of Italy) while the areas predicted as poorly suitable are still apparently Xf-free, which suggests that climate tolerances of vectors might play a main role in shaping Xf outbreaks patterns. This pattern highlights the crucial necessity of accounting for vectors when assessing risk of Xf outbreaks, and when considering vector-borne diseases in general. The risk maps presented here will have important practical application for the optimization of current and future strategies to control Xf in the Mediterranean region.

ecology↗

bioRxiv2018

Climate change and the potential distribution of Xylella fastidiosa in Europe

The bacterium Xylella fastidiosa (Xf) is a plant endophyte native to the Americas that causes worldwide concern. Xf has been recently detected in several regions outside its natural range including Europe. In that context, accurate estimates of its response to climate change are required to design cost-efficient and environment-friendly control strategies. In the present study, we collected data documenting the native and invaded ranges of the three main subspecies of Xf: fastidiosa, pauca and multiplex, as well as two strains of Xf subsp. multiplex recently detected in southern France (ST6 and ST7). We fitted bioclimatic species distribution models (SDMs) to forecast their potential geographic range and impact in Europe under current and future climate conditions. According to model predictions, the geographical range of Xf as presently reported in Europe is small compared to the large extent of suitable areas. The European regions most threatened by Xf encompass the Mediterranean coastal areas of Spain, Greece, Italy and France, the Atlantic coastal areas of France, Portugal and Spain as well as the south-western regions of Spain and lowlands in southern Italy. Potential distribution of the different subspecies / strains are contrasted but all are predicted to increase by 2050, which could threaten several of the most economically important wine-, olive- and fruit-producing regions of Europe, warranting the design of control strategies. Bioclimatic models also predict that the subspecies multiplex might represent a threat to most of Europe under current and future climate conditions. These results may serve as a basis for future design of a spatially informed European-scale integrated management strategy, including early detection surveys in plants and insect vectors, quarantine measures as well as agricultural practices.

ecology↗

bioRxiv2018

Using insects to detect, monitor and predict the distribution of Xylella fastidiosa: a case study in Corsica

We sampled ca 2500 specimens of Philaenus spumarius throughout Corsica without a priori on the presence of symptoms on plants. We screened 448 specimens for the presence of Xylella fastidiosa (Xf) using qPCR and a custom nested PCR. qPCR appeared versatile and under-estimated the prevalence of Xf. Nested PCR showed that Xf was present in all populations. Molecular results were validated by prediction on the distribution of Xf made from tests conducted on plants, which shows the pertinence of using vectors in risk assessment studies. Xf was detected in tenerals and adults. Thus, P. spumarius could acquire Xf from its host plant, mostly Cistus monspeliensis in Corsica, which may act as reservoir for the next season. This contrasts with other observations and suggests that management strategies may have to be adapted on a case-by-case basis. At least two genetic entities and several variants of Xf not yet identified on plants were present in the insects, which suggests ancient introductions of Xf and a probable underestimation of the current diversity of the strains present in Corsica. Interestingly 6% of the specimens carried two subspecies. Studies are wanted to better characterize the strains present in Corsica and know how the disease was introduced, spread and why no sign of a potential epidemic was detected earlier. This study shows that, when sensitive enough methods are implemented, insects can be used to predict and better assess the exact distribution of Xf. Insects are indeed easy to collect, Xf multiply only in their foregut and does not become circulative, which facilitates its detection.\n\nKey messageO_LIInsect vectors can be used to detect, monitor and predict the distribution of Xylella fastidiosa\nC_LIO_LIThe widely used qPCR approach is not sensitive enough to detect low bacterial load\nC_LIO_LIDifferent strains/subspecies of Xf are widely distributed in Corsica which suggests old introduction(s)\nC_LIO_LIStrategies to manage Xf may need to be set up on a case-by-case basis\nC_LIO_LIThere is an urgent need to take stock of the situation in Europe to avoid unnecessary economic pressure on certain geographical areas and agricultural sectors.\nC_LI

ecology↗

bioRxiv2016

Buchnera has changed flatmate but the repeated replacement of co-obligate symbionts is not associated with the ecological expansions of their aphid hosts

Symbiotic associations with bacteria have facilitated important evolutionary transitions in insects and resulted in long-term obligate interactions. Recent evidence suggests that these associations are not always evolutionarily stable and that symbiont replacement and/or supplementation of an obligate symbiosis by an additional bacterium has occurred during the history of many insect groups. Yet, the factors favoring one symbiont over another in this evolutionary dynamic are not well understood; progress has been hindered by our incomplete understanding of the distribution of symbionts across phylogenetic and ecological contexts. While many aphids are engaged into an obligate symbiosis with a single Gammaproteobacterium, Buchnera aphidicola, in species of the Lachninae subfamily, this relationship has evolved into a \"menage a trois\", in which Buchnera is complemented by a cosymbiont, usually Serratia symbiotica. Using deep sequencing of 16S rRNA bacterial genes from 128 species of Cinara (the most diverse Lachninae genus), we reveal a highly dynamic dual symbiotic system in this aphid lineage. Most species host both Serratia and Buchnera but, in several clades, endosymbionts related to Sodalis, Erwinia or an unnamed member of the Enterobacteriaceae have replaced Serratia. Endosymbiont genome sequences from four aphid species+confirm that these coresident symbionts fulfill essential metabolic functions not ensured by Buchnera. We further demonstrate through comparative phylogenetic analyses that co-symbiont replacement is not associated with the adaptation of aphids to new ecological conditions. We propose that symbiont succession was driven by factors intrinsic to the phenomenon of endosymbiosis, such as rapid genome deterioration or competitive interactions between bacteria with similar metabolic capabilities.

evolutionary biology↗