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Дисертації з теми "Modélisation de distribution d'espèces (SDM)":
Urvois, Teddy. "Structure génétique et modélisation de la distribution des populations de deux espèces invasives de Xylosandrus (Scolytinae - Xyleborini) : deux espèces proches aux histoires d’invasion différentes." Electronic Thesis or Diss., Orléans, 2022. https://theses.univ-orleans.fr/prive/accesESR/2022ORLE1031_va.pdf.
Xylosandrus compactus and X. crassiusculus are two ambrosia beetles originating from Southeastern Asia and invasive on several continents, whose atypical biology and ecology favour invasion. During this thesis, a multidisciplinary approach was used to (i) identify the origin of invasive populations and their invasion routes and (ii) determine the areas in which they could spread and establish. Invasion routes were traced using a mitochondrial marker and genomic markers, and the suitable areas for each species were identified using species distribution models (SDM).Despite their ecological and phylogenetic proximity, the two species have different invasion histories. Two lineages were identified in X. compactus, one originating from India or Vietnam, who invaded Africa, and the other from the Shanghai area, who independently invaded the American-Pacific and Europe. X. crassiusculus comprises two very diverging clusters, mostly allopatric and with different ecological niches. Cluster 1 independently invaded Pacific islands and Africa. Cluster 2 is responsible for the invasion in the Americas, Europe, Africa and Oceania, with several independent introductions from multiple sources (including bridgehead, where an invasion occurs from an area already invaded) followed by intra-continental dispersion. For both species, SDM showed suitable areas where the pests are not present yet and which could be invaded. We expect an impact of climate change on their future potential distributions. Conversely, the recent evolution of climate is not responsible for their recent invasion in Europe, which has already been suitable for decades
Schickele, Alexandre. "Modélisation des aires de répartition futures d'espèces marines d'intérêt commercial en Méditerranée dans un contexte de changement climatique." Thesis, Université Côte d'Azur, 2020. http://www.theses.fr/2020COAZ4069.
Environmental conditions are shaping the spatial distribution of marine species worldwide. However, climate change may alter their future distribution, impacting marine resources exploitation and ecosystems balance. In this context, this PhD identifies climate induced impacts in species and geographical areas, by focusing on some species, indigenous or non-indigenous, of commercial interest in the Mediterranean.Based on the ecological niche concept, that defines the potential distribution of a species according to the environmental conditions in which it is observed, we developed a contemporary and future distribution modelling procedure for marine species. This procedure includes an ensemble of statistical algorithms, future climate models and scenarios while accounting for common ecological niche modelling limitations. Applied to small pelagic fish and cephalopods, we projected major climate induced impacts in the Mediterranean Sea by 2100, including local extinctions in its south-eastern basin. Conversely, we projected a distributional range expansion of most of the studied species towards the North, Norwegian and Baltic seas. In the Gulf of Lion, the small pelagic fish distributional range shifts may indirectly impact their harvesting capacity as well as the productivity of low trophic levels. The combined effects of climate warming and the opening of the Suez Canal induced biological invasions, especially in the South-East Mediterranean. These non-indigenous Mediterranean species may be of commercial interest subject to future harvesting. After quantifying the invasive potential of several non-native Mediterranean marine species, according to their functional and ecological traits, we applied our modelling procedure to estimate their future distributional range expansion. We projected a major distributional range expansion of non-native species in the whole Mediterranean Sea by 2100, especially for warming exceeding 2°C.This work highlights the sensitivity of the Mediterranean Sea to climate change while proposing adaptation and conservation perspective of species and ecosystems facing the upcoming climate trends of the 21st century
Moua, Yi. "Correction de l’effet du biais d’échantillonnage dans la modélisation de la qualité des habitats écologiques : application au principal vecteur du paludisme en Guyane française." Thesis, Guyane, 2017. http://www.theses.fr/2017YANE0002/document.
Species distribution models are identified as relevant to map and characterize the habitat quality of Anopheles genusmosquitoes, transmitting malaria, and thus to both participate in the estimation of the transmission risk of this disease and inthe definition of targeted vector control actions. The malaria transmission depends on the presence and distribution of thevectors, which are themselves dependent on the environmental conditions that define the quality of the ecological habitats of the Anopheles. However, in some areas, Anopheles collection data remain scarce, making it difficult to model these habitats. In addition, the collection of these data is very often subjected to significant sampling biases, due, in particular, to unequal accessibility to the entire study area. This thesis provides a solution to the mapping of malaria vectors, considering two very few studied aspects in modeling: the low number of available presence sites and the existence of a sampling bias. An original method for correcting the effect of the sampling bias is proposed and then applied to presence data of Anopheles darlingi species - the main vector of malaria in South America - in French Guiana. Then, a distribution model of An. darlingi was built to obtain a map of habitat quality consistent with entomologists’ knowledge and providing high prediction performances. The proposed correction method was then compared to existing methods in an application context characterized by the scarcity of the species occurence data and the presence of a sampling bias. The results show that the developed method is adapted to cases where the number of sites of presence is low. This thesis contributes, on the one hand, to fill theoretical and applicability lacuna of current methods intended to correct the effect of the sampling bias and, on the other hand, to supplement the knowledge on both the spatial distribution and the bio-ecology of the main malaria vector in French Guiana
Guo, Chuanbo. "Modélisation des effets des changements climatiques et des activités anthropiques sur les assemblages des poissons des lacs en Chine." Toulouse 3, 2014. http://thesesups.ups-tlse.fr/2333/.
Knowledge of the spatial distribution of species and communities in ecosystems is an essential prerequisite for the understanding of ecosystem functioning and processes as well as conservation and spatial planning issues. During the last several decades, in the context of global change, climate change and anthropogenic activities have long been acknowledged as the two main determinants which drive the fish diversity and distributions patterns, and ultimately affect the aquatic ecosystem properties and structure. However, up until now, very few efforts aimed at the fish diversity and ecosystem in the lakes across China. Consequently in the present study, we contribute to highlight the effects of climate change and anthropogenic activities on fish diversity and distribution patterns as well as the ecosystem properties with the approach of several ecological modelling. Specifically, we first build the global perspective on the fish distribution and assemblage patterns for a total of 425 fish species (subspecies) in 135 lakes across China using a novel multi-species approach fitted by the Multivariate Regression Tree (MRT). Five fish assemblages were defined by the constrained clustering, 107 indicator species were thus identified. Species diversity showed significantly differences among each assemblage: fish species richness in plateau lakes was significantly lower than plain lakes; however the diversity of the whole assemblage in plateaus was higher than other regions. Altitude, minimum temperature of the coldest month, annual temperature range and precipitation during the driest month were found to be the most important determinants affecting fish assemblages and distribution patterns in Chinese lakes. Then, MRT model was used to predict both species richness and species distribution in order to improve the management and conservation of fish species in China. Our results showed that MRT is a reliable and ideal community-based predictive technique for multi-species prediction. At the species composition level, altitude was the main determinant for the prediction, followed by precipitation of the driest month, temperature annual range and annual mean temperature. While at the richness level, precipitation of driest month, maximum temperature of warmest month and lake area were the main drivers for the prediction of the fish species richness pattern. Thirdly, we examine the capacity and uncertainty of ensemble modelling in predicting fish species distribution and diversity. Potential impacts from two main kinds of uncertainty sources were thus considered: species characteristics (contained species prevalence, altitude range, temperature range and precipitation range) and model techniques (calibration technique and evaluation technique). Finally, our results highlight that predictions from single SDM were so variety and unreliable for all species while ensemble approaches could yield more accurate predictions; we also found that there was no significant influence on the model outcomes from the evaluation measures; we emphasized that species characteristics as species prevalence, altitude range size and precipitation range size would strongly affect the outcomes of SDMs, but temperature range size didn't show a significantly influence; our findings finally verified the hypothesis that species distributed with a smaller range size could be more accurately predicted than species with large range size to be plausible in aquatic ecosystems. Lastly, a case study focused on evaluating the lake ecosystem properties and foodweb structure as well as the effects in a typical shallow macrophytic lake (Bao'an Lake, distributed in the middle reaches of the Yangtze River basin), using the Ecopath model. Finally, the results showed that all the commercial fish suffered from high fishing pressure while forage resources such as attached algae, submerged plants and molluscs were not fully utilized. Moreover, we highlight that the Bao'an Lake ecosystem was a mature system according to Odum's theory. However when compared with some other lake ecosystems, the Bao'an Lake ecosystem, as well as some China lake ecosystems, showed extremely low values of CI (Connectance Index), FCI (Finn's Cycling Index) and SOI (System Omnivory Index), indicating that the ecosystem functions and food web structure of these Chinese lake tended to be simpler and linear than lake ecosystems in other countries. Consequently, this study indicated an urgent need for the adjustment and management of artificial fishery stocking in such type of lakes. Our present study have pictured the global perspective of lake fish diversity and distribution patterns in China, defined the main determinants, and examined the potential effects of climate change and anthropogenic activities on fish diversity and ecosystem properties. Our results will benefit the conservation and management of fish resources, biodiversity, as well as the lake ecosystems all over the world
Buisson, Laetitia. "Poissons des rivières françaises et changement climatique : impacts sur la distribution des espèces et incertitudes des projections." Thesis, Toulouse, INPT, 2009. http://www.theses.fr/2009INPT005A/document.
Climate change and its impact on biodiversity are receiving increasing attention from scientists and people managing natural ecosystems. Indeed, climate has a major influence on the biology and ecology of fauna and flora, from physiology to distribution. Climate change may thus have major consequences on species and assemblages. Among freshwater ecosystems, stream fish have no physiological ability to regulate their body temperature and they have to cope with streams' hydrological variability and strong anthropogenic pressures. Yet their response to current and future climate change has been poorly studied. The aim of this PhD thesis is to assess the potential impact of climate change on fish in French streams, mainly on species distribution and assemblages' structure. Data provided by the Office National de l'Eau et des Milieux Aquatiques combined with a modelling approach based on species' ecological niche (i.e., distribution models) have been used. Several sources of uncertainty have also been considered in an ensemble modeling framework in order to account for the variability between projected impacts and to provide reliable estimates of such impact. First, we have identified the main environmental factors that determine the spatial distribution of fish species within river networks. Overall, it appears that a combination of both climatic variables and variables describing the local habitat and its position within the river network is important to explain the current species distribution. Moreover, each fish species responded differently to the environmental factors. Second, we have highlighted that the choice of the statistical method used to model the fish ecological niche is crucial given that the current and future patterns of distribution predicted by different statistical methods vary significantly. The statistical method appears to be the main source of uncertainty, resulting in more variability in projections than the global circulation models and greenhouse gas emission scenarios. The variability between predictions from several statistical methods can be taken into account by a consensus approach. Consensual predictions based on the computation of the average of the whole predictions ensemble have achieved accurate predictions of the current species distribution and assemblages' composition. We have therefore selected this approach to assess the potential impacts of climate change on fish in French streams at the end of the 21st century with the highest degree of confidence. We have found that most fish species could be sensitive to the future climate modifications. Only a few cold-water species (i.e., brown trout, bullhead) could restrict their distribution to the most upstream parts of river networks. On the contrary, cool- and warm-water fish species could colonize many newly suitable habitats and expand strongly their distribution. These changes of species distribution could lead to a rearrangement of fish assemblages both at the taxonomic and functional levels. An increase in local diversity together with an increase in regional similarity (i.e., homogenization) are therefore expected. All these results bring new insights for the understanding of stream fish species distribution and expected consequences of climate change. This work thus provides biodiversity managers and conservationists with a basis to take efficient preservation measures. In addition, methodological developments considered in this PhD thesis are an important contribution to the improvements of projections by statistical models of species distribution and to the quantification of their uncertainty
Botella, Christophe. "Méthodes statistiques pour la modélisation de la distribution spatiale des espèces végétales à partir de grandes masses d’observations incertaines issues de programmes de sciences citoyennes." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS135.
Human botanical expertise is becoming too scarce to provide the field data needed to monitor plant biodiversity. The use of geolocated botanical observations from major citizen science projects, such as Pl@ntNet, opens interesting paths for a temporal monitoring of plant species distribution. Pl@ntNet provides automatically identified flora observations, a confidence score, and can thus be used for species distribution models (SDM). They enable to monitor the distribution of invasive or rare plants, as well as the effects of global changes on species, if we can (i) take into account identification uncertainty, (ii) correct for spatial sampling bias, and (iii) predict species abundances accurately at a fine spatial grain.First, we ask ourselves if we can estimate realistic distributions of invasive plant species on automatically identified occurrences of Pl@ntNet, and what is the effect of filtering with a confidence score threshold. Filtering improves predictions when the confidence level increases until the sample size is limiting. The predicted distributions are generally consistent with expert data, but also indicate urban areas of abundance due to ornamental cultivation and new areas of presence.Next, we studied the correction of spatial sampling bias in SDMs based on presences only. We first mathematically analyzed the bias when the occurrences of a target group of species (Target Group Background, TGB) are used as background points, and compared this bias with that of a spatially uniform selection of base points. We then show that the bias of TGB is due to the variation in the cumulative abundance of target group species in the environmental space, which is difficult to control. We can alternatively jointly model the global observation effort with the abundances of several species. We model the observation effort as a step spatial function defined on a mesh of geographical cells. The addition of massively observed species to the model then reduces the variance in the estimation of the observation effort and thus on the models of the other species.Finally, we propose a new type of SDM based on convolutional neural networks using environmental images as input variables. These models can capture complex spatial patterns of several environmental variables. We propose to share the architecture of the neural network between several species in order to extract common high-level predictors and regularize the model. Our results show that this model outperforms existing SDMs, that performance is improved by simultaneously predicting many species, and this is confirmed by two cooperative SDM evaluation campaigns conducted on independent data sets. This supports the hypothesis that there are common environmental models describing the distribution of many species.Our results support the use of Pl@ntnet occurrences for monitoring plant invasions. Joint modelling of multiple species and observation effort is a promising strategy that transforms the bias problem into a more controllable estimation variance problem. However, the effect of certain factors, such as the level of anthropization, on species abundance is difficult to separate from the effect on observation effort with occurrence data. This can be solved by additional protocolled data collection. The deep learning methods developed show good performance and could be used to deploy spatial species prediction services
Tisseuil, Clément. "Modéliser l'impact du changement climatique sur les écosystèmes aquatiques par approche de downscaling." Toulouse 3, 2009. http://thesesups.ups-tlse.fr/763/.
This thesis aimed at assessing the impact of global change on freshwater ecosystems during the 21st century in the Adour Garonne area (SW France). A downscaling approach was developed linking techniques from climate, hydro-chemical and ecological sciences. The main results suggest an increase of high flows in winter as well as more severe low flows in summer. Nitrogen concentrations and thermophile fish species distribution may also increase. Reducing green house gas emissions and modifying agricultural practices (e. G reducing nitrate fertilizers) could reduce the intensity of ecological disturbances. This study is an original contribution to the management of future hydrological and ecological resources
Sommeria-Klein, Guilhem. "From models to data : understanding biodiversity patterns from environmental DNA data." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30390/document.
Integrative patterns of biodiversity, such as the distribution of taxa abundances and the spatial turnover of taxonomic composition, have been under scrutiny from ecologists for a long time, as they offer insight into the general rules governing the assembly of organisms into ecological communities. Thank to recent progress in high-throughput DNA sequencing, these patterns can now be measured in a fast and standardized fashion through the sequencing of DNA sampled from the environment (e.g. soil or water), instead of relying on tedious fieldwork and rare naturalist expertise. They can also be measured for the whole tree of life, including the vast and previously unexplored diversity of microorganisms. Taking full advantage of this new type of data is challenging however: DNA-based surveys are indirect, and suffer as such from many potential biases; they also produce large and complex datasets compared to classical censuses. The first goal of this thesis is to investigate how statistical tools and models classically used in ecology or coming from other fields can be adapted to DNA-based data so as to better understand the assembly of ecological communities. The second goal is to apply these approaches to soil DNA data from the Amazonian forest, the Earth's most diverse land ecosystem. Two broad types of mechanisms are classically invoked to explain the assembly of ecological communities: 'neutral' processes, i.e. the random birth, death and dispersal of organisms, and 'niche' processes, i.e. the interaction of the organisms with their environment and with each other according to their phenotype. Disentangling the relative importance of these two types of mechanisms in shaping taxonomic composition is a key ecological question, with many implications from estimating global diversity to conservation issues. In the first chapter, this question is addressed across the tree of life by applying the classical analytic tools of community ecology to soil DNA samples collected from various forest plots in French Guiana. The second chapter focuses on the neutral aspect of community assembly.[...]