251 research outputs found
Phytophthora global impacts
No full textData and code to reproduce the analysis in Barwell et al. Evolutionary trait-based approaches for predicting future global impacts of plant pathogens in the genus Phytophthor
What makes species more vulnerable to environmental change? Passerines as a case study
No full textEnvironmental change presents the greatest challenges to biodiversity conservation. From climate changes to land cover conversion and pollution effects, global biodiversity faces many threats. Though conservation actions have been put into place to halt the loss of biodiversity, recent studies suggest that conservation actions have largely failed to do this. Hence, understanding the links between species responses, environmental pressures and the role of species characteristics in conferring resilience to these environmental pressures would be fundamental to develop adequate conservation measures.
This thesis focuses on a range of approaches to investigate the impacts of well-known environmental pressures on the passerine community in the UK to try to uncover mechanisms underpinning species responses to environmental change. Furthermore, considering that bird species are currently been used as biodiversity indicators, it would be of great use to identify new venues to measure and monitor species responses to environmental change that would help improve the current set of indicators.
Examining multiple pressures within the same analytical framework was valuable for demonstrating that land cover and pollution drivers are of equivalent importance to climate in structuring bird communities at a broad scale in the UK. Both community and niche studies revealed that winter conditions and pollution were key in structuring passerine communities together with pollution at this broad scale. In terms of colonisation and extinction processes the spatial structure of the species occupancy appeared to have a dominant role in driving the observed dynamics as well as again, climate change in terms of warming winter temperatures.
Throughout this thesis, the above mentioned ecological responses were linked to species ecological traits with the aim of gaining a greater understanding of the mechanisms underpinning species’ differential responses to environmental change and identifying those trait groups that may be most vulnerable or most valuable as indicators. A significant group of characteristics that consistently appeared to be linked to species resilience to observed environmental pressures (particularly climate change) was phenological traits. Species with earlier laying dates and/or longer laying periods were associated with increasing population trends, larger colonisation rates and smaller extinction rates.
Also analysis of species niches in relation to environmental pressures not only revealed the dynamic nature of niche parameters, confirming niche evolution and niche tracking in some species but also confirmed their relationship with both species characteristics and current conservation categories.
Finally this study reiterated the fact that relationships between species characteristics and environmental pressures involve complex interactions that significantly affect and transform species responses to environmental pressures. For example the interaction between migratory behaviour and phenological traits (i.e. earlier laying dates and longer laying periods) meant that migrant species were less likely to have declining populations or that warming winter temperatures were associated with increased colonisation for migrants or species with more annual broods were less likely to show extinction in cells with temperature increase.
All these results not only confirm the suitability of birds and particularly passerine species as indicators of environmental use and their potential and importance as part of indices and monitoring programmes but also highlights the importance of updating the next generation of indicators with measurements that can take into account important species characteristics associated with resilience to environmental pressures (i.e. phenological traits)
Understanding the epidemiology of Bluetongue virus in South India using statistical models
No full textBluetongue is an economically important midge-borne disease affecting domestic and wild ruminants worldwide. The disease, caused by the bluetongue virus (BTV), is highly endemic in South India, occurring with varying severity every year since 1963, causing high morbidity and mortality, resulting in huge economic losses to subsistence farmers, impacting the GDP of the country and affecting food security. The bluetongue epidemiological system in South India is characterized by an unusually wide diversity of susceptible ruminant hosts, many potential Culicoides vector species and numerous pathogen serotypes and strains. These factors (intrinsic and extrinsic) contribute to disease impacts that vary widely over geographical space.
Chapter 2 deals with identification of remote sensed variables in discriminating between presence and absence of bluetongue outbreaks and development of a risk map using non-linear discriminant analysis (NLDA) approach.
Chapter 3 deals with understanding the role of extrinsic factors such as monsoon conditions in driving seasonality in BTV outbreaks over two decades in Andhra Pradesh, India using a Bayesian Poisson regression model framework, accounting for temporal autocorrelation.
In chapter 4, the mean annual numbers of outbreaks in each district in South Indian states were examined in relation to land-cover, host availability and climate predictors using a Bayesian generalised linear mixed model with Poisson errors and a conditional autoregressive error structure to account for spatial autocorrelation.
In chapter 5, the annual number of outbreaks in each district in South India was examined in relation to climate predictors (temperature and precipitation) at different lags using a Bayesian generalized linear mixed model with Poisson errors.
In chapter 6, a range of suitable predictors was considered for identifying their relationships with bluetongue outbreaks using Bayesian Network Modelling (BNM), and the important variables were used to develop a Bayesian geostatistical model accounting for spatial autocorrelation.
The analysis resulted in the development of spatial risk maps at district and village levels, district level yearly predictions and monthly state level predictions, which can contribute to the development of an early warning system for the disease in South India. </p
Bionomía y modelos de abundancia estacional de las especies del género Culicoides (Diptera; Ceratopogonidae) en España, con especial interés en los vectores del virus de la Lengua Azul
No full text[spa] . Introducción:
Las hembras de varias especies de insectos del género Culicoides (Diptera;
Ceratopogonidae) transmiten arbovirus que afectan a rumiantes domésticos y salvajes
tales como el virus de la Lengua Azul, de la Peste Equina Africana, el virus de
Schmallenberg y el virus de la enfermedad hemorrágica epizoótica. La llegada y
expansión de enfermedades de origen tropical o subtropical transmitidas por insectos
vectores causan importantes problemas tanto médico-veterinarios como económicos,
por lo tanto, el conocimiento de la biología y ecología de esos vectores es crucial para
comprender la transmisión de arbovirosis y otros patógenos. Gracias a esos
conocimientos podemos actuar en el momento preciso poniendo en marcha las
medidas necesarias para su control y así evitar una posible epidemia o minimizar sus
efectos.
. Contenido de la investigación:
El presente trabajo tiene dos objetivos fundamentales:
1.Estudiar la dinámica poblacional y fenología de especies de Culicoides vectores del
virus de la Lengua Azul en España, donde se analizará la distribución y
estacionalidad de hembras paras y nulíparas; se determinarán los factores ambientales
implicados en la fenología de estas especies gracias a Modelos Bayesianos
Generalizados Lineales Mixtos (GLMM) y se estudiaran los factores ambientales
incluyendo el efecto indirecto de la abundancia poblacional de Culicoides sobre el
periodo de actividad de hembras nulíparas y paras gracias a los Análisis de
Trayectorias (Path analysis models).
2.Estudiar la bionomía de Culicoides asociados a granjas en las Islas Baleares, donde se
determinarán los valores bionómicos básicos de diferentes especies en condiciones de
laboratorio comparando distintos métodos con la finalidad de establecer una futura
colonia en cautividad; además, se compararán resultados bionómicos de individuos a
distintas temperaturas utilizando dos poblaciones diferentes.
. Conclusión
El análisis de la variación estacional latitudinal de la PF demostró que C. imicola no
está presente en las provincias del norte mientras que las especies del complejo
Obsoletus son las mayoritarias en dichas provincias. Además, se han encontrado
provincias en las que hubo periodos del año donde no se capturaron individuos de
ninguna especie vector, lo cual se debe tener en cuenta a la hora de calcular el Periodo
Estacionalmente Libre de Vectores. C. newsteadi y C. pulicaris mostraron la población
más elevada en Toledo, posiblemente debido a su preferencia a las zonas de interior.
Culicoides imicola mostró que su periodo estacional fue más largo en zonas poco
elevadas y más corto en zonas con una elevada acumulación de días con temperaturas
sobre los 10ºC y precipitaciones altas durante el invierno. Para las especies del
complejo Obsoletus, el periodo de actividad de las hembras adultas también fue más
prolongado en zonas poco elevadas con mayor número de horas de sol y temperaturas
más cálidas en primavera y otoño, así como en zonas con altas precipitaciones en
otoño y gran abundancia de ganado bovino. Las hembras de C. newsteadi se
relacionaron con inviernos cálidos, otoños cálidos con altas precipitaciones y áreas
agroforestales con vegetación esclerófila y poca pendiente en el terreno. C. pulicaris
mostró períodos de adultos más largos en sitios con un elevado número de días con
temperaturas mayores a 10ºC durante el invierno.
Las especies C. paolae y C. circumscriptus parecieron ser las más adecuadas para la
cría en condiciones de laboratorio debido a sus tasas elevadas de oviposición, ciclo de
vida corto, elevada supervivencia de la fase adulta y elevado porcentaje de hembras en
la progenie. Temperaturas bajas mostraron una mayor tasa de supervivencia de
adultos, un tiempo de oviposición más largo y periodos más largos de las fases
inmaduras; mientras que las temperaturas elevadas aumentaron el número de huevos,
el porcentaje de pupado, la emergencia de adultos y la velocidad de crecimiento de las
larvas.[cat] . Introducció:
Les femelles de diverses espècies d'insectes del gènere Culicoides (Diptera;
Ceratopogonidae) transmeten arbovirus que afecten a remugants domèstics i
salvatges com ara el virus de la Llengua Blava, el de la Pesta Equina Africana, el
virus de Schmallenberg i el virus de la malaltia hemorràgica epizoòtica. L'arribada i
expansió de malalties d'origen tropical o subtropical transmeses per insectes vectors
causen importants problemes tant mèdic-veterinaris com econòmics, per tant, el
coneixement de la biologia i ecologia d'aquests vectors és crucial per comprendre la
transmissió d’arbovirosis i altres patògens. Gràcies a aquests coneixements podem
actuar en el moment precís posant en marxa les mesures necessàries per al seu
control i així evitar una possible epidèmia o minimitzar-ne els seus efectes.
. Contingut de la investigació:
El present treball té dos objectius fonamentals:
1. Estudiar la dinàmica poblacional i fenologia d'espècies de Culicoides vectors del
virus de la Llengua Blava a Espanya, on s'analitzarà la distribució i estacionalitat de
femelles pares i nul·lípares; es determinaran els factors ambientals implicats en la
fenologia d'aquestes espècies gràcies a Models Bayesians Generalitzats Lineals
Mixtes (GLMM) i s'estudiaran els factors ambientals incloent l'efecte indirecte de
l'abundància poblacional de Culicoides sobre el període d'activitat de femelles
nul·lípares i pares gràcies al Anàlisis de Trajectòries (Path analysis models).
2. Estudiar la bionomia de Culicoides associats a granges a les Illes Balears, on es
determinaran els valors bionòmics bàsics de diferents espècies en condicions de
laboratori comparant diferents mètodes, amb la finalitat d'establir una futura colònia
en captivitat; a més, es compararan resultats bionòmics d'individus a diferents
temperatures emprant dues poblacions diferents.
. Conclusió:
L'anàlisi de la variació estacional latitudinal de la PF va demostrar que a les províncies
del nord d’Espanya C. imicola no esta present mentre que les espècies del complex
Obsoletus son les espècies majoritàries a aquestes províncies. A més, s’han trobat
províncies on hi va haver períodes de l'any on no es va capturar cap individu de les
espècies vectors de Llengua Blava, la qual cosa s'ha de tenir en compte a l'hora de
calcular el Període Estacionalment Lliure de Vectors. C. newsteadi i C. pulicaris foren
igualment presents a totes les províncies analitzades mostrant la població més elevada
a Toledo, possiblement a causa de la preferència d’aquestes espècies per a les zones
d'interior.
Culicoides imicola va mostrar que el seu període estacional va ser més llarg en zones
poc elevades y més curt a zones amb major acumulació de dies amb temperatures
sobre els 10ºC i precipitacions elevades durant l'hivern. Per a les espècies del complex
Obsoletus, el període d'activitat de les femelles adultes també va ser més perllongat en
zones poc elevades amb major nombre d’hores de sol i temperatures mitjanes més
càlides a la primavera i a la tardor; així com en zones amb altes precipitacions a la
tardor i gran abundància de bestiar boví. Les femelles de C. newsteadi foren
relacionats amb hiverns càlids, tardors càlides amb altes precipitacions i àrees
agroforestals amb vegetació escleròfil·la i poca pendent en el terreny. D'altra banda, C.
pulicaris va mostrar períodes més llargs dels adults en llocs amb alta acumulació de
dies sobre els 10ºC durant l'hivern.
Les espècies C. paolae i C. circumscriptus van semblar ser les més adequades per a la
cria en condicions de laboratori degut a les seves elevades taxes d‘oviposició, cicle de
vida curt, elevada supervivència de la fase adulta i elevat percentatge de femelles en la
progènie. Les temperatures baixes van augmentar la taxa supervivència dels adults i
el temps de oviposició, a més d’un augment dels períodes de les fases juvenils; mentre
que temperatures elevades van augmentar el nombre d'ous, el percentatge de pupat,
l'emergència d'adults i la velocitat del creixement larvari.[eng] . Introduction:
Females of several biting midges species from genus Culicoides (Diptera;
Ceratopogonidae) transmit arboviruses affecting wild and domestic ruminants such
as Bluetongue, African Horse sickness, Schmallenberg virus and Epizootic
Haemorrhagic disease viruses. The arrival and expansion of tropical or subtropical
diseases transmitted by insect vectors cause important medical-veterinary and
economic impacts; therefore, the knowledge of the biology and ecology of these
vectors is crucial to understand the transmission of arbovirosis and other pathogens.
Then, we can implement the necessary measures at the correct timing for its control,
avoiding possible outbreaks or minimize its effects.
. Research content:
This work has two main objectives:
1. A study of the population dynamics and phenology of Culicoides Bluetongue virus
vector species in Spain; an analysis of the distribution and seasonality of parous and
nulliparous females; the environmental factors involved in the phenology of these
species determined with Mixed Linear Generalized Bayesian Models (GLMM) and a
study of environmental factors including the indirect effect of Culicoides population
abundance on the period of activity of parous and nulliparous females through Path
Analysis models.
2. A study of the bionomics of Culicoides associated with farms in the Balearic Islands.
The basic bionomic values of different species in laboratory conditions were
determined by comparing different methods to establish a future colony in the
laboratory; in addition, we compared bionomic results at different temperatures using
two different populations
. Conclusion
The analysis of the latitudinal seasonal variation of PF in Spain has demonstrated
that Northern provinces showed absence of C. imicola during the whole year while
the Obsoletus species were more present in Northern areas. In fact, depending on the
province and the species, there were periods of the year were no individuals of any
vector species were collected, which should be taken into account in order to
calculate the Seasonally Vector-Free Period. C. newsteadi and C. pulicaris were equally
present in all analysed provinces showing the highest population in Toledo, probably
related to their inland preferences.
For C. imicola, the length of the female adult season was longest in sites at low
elevation and shortest with more accumulated degree days over 10ºC and higher
rainfall during winter. For Obsoletus complex species, female adult seasons were also
longest in sites at low elevation, with long spring and autumn daylight hours and
warmer spring and autumn average temperatures as well as in sites with high
precipitation in autumn and high abundance of cattle. Culicoides newsteadi showed
early appearance and long adult seasons in sites with warm winters and autumns and
high precipitation in autumn, and in sites with higher coverage of agro-forestry with
schlerophyllous vegetation and gently sloping land. Meanwhile, C. pulicaris showed
longer adult periods in sites with high number of accumulated degree days over 10ºC
during winter.
Culicoides paolae and C. circumscriptus seemed to be the most suitable for laboratory
rearing due to their high oviposition rates, short life-cycle, long adult lifespan and
female biased sex ratio. Low temperatures increased the adult lifespan, time to
oviposit and life-cycle development whereas high temperatures increased the number
of eggs, percentages of pupation and adult emergence as well as the larvae growth
rate
Mapping and understanding the distributions of potential vector mosquitoes in the UK: New methods and applications
No full textA number of emerging vector-borne diseases have the potential to be transmitted in the UK by native mosquitoes. Human infection by some of these diseases requires the presence of communities of multiple vector mosquito species. Mitigating the risk posed by these diseases requires an understanding of the spatial distributions of the UK mosquito fauna. Little empirical data is available from which to determine the distributions of mosquito species in the UK. Identifying areas at risk from mosquito-borne disease therefore requires statistical modelling to investigate and predict mosquito distributions. This thesis investigates the distributions of potential vector mosquitoes in the UK at landscape to national scales. A number of new methodological approaches for species distri- bution modelling are developed. These methods are then used to map and understand the distributions of mosquito communities with the potential to transmit diseases to humans. Chapter 2 reports the establishment of substantial populations of the West Nile virus (WNV) vector mosquito Culex modestus in wetlands in southern England. This represents a drastic shift in the species’ known range and an increase in the risk of WNV transmission where Cx. modestus is present. Chapter 3 develops and applies a new species interaction distribution model which identifies fish and ditch shrimp of the genus Palaemonetes as predators which may restrict the distribution of the potential WNV vector community in these wetlands. Chapter 4 develops a number of methods to make robust predictions of the probability of presence of a species from presence-only data, by eliciting and applying estimates of the species’ prevalence. Chapter 5 introduces a new Bayesian species distribution modelling approach which outperforms existing methods and has number of useful features for dealing with poor- quality data. Chapter 6 applies methods developed in the previous two chapters to produce the first high-resolution distribution maps of potential vector mosquitoes in the UK. These maps identify several wetland areas where vector communities exist which could maintain WNV transmission in birds and transmit it to humans. This thesis makes significant contributions to our understanding of the distributions of UK mosquito species. It also provides methods for species distribution modelling which could be widely applied in ecology and epidemiology
Identity in Britain : a cradle-to-grave atlas /
No full textSixty million people live in Britain. Imagine sixty million. Imagine a map of sixty million. What would that map look like and what story would it tell us about identity in Britain today? Bethan Thomas and Danny Dorling have brought together this outstanding atlas to provide us with a unique visual picture of identity and geography combined. Identity in Britain explores our changing identities as we progress from infancy to old age and tells the story of the myriad geographies of life in Britain. Features and benefits include: over 280 full colour, detailed maps analysis of the contemporary neighbourhood geographies of people in Britain at various life stages clear introduction and how-to-use guide making the atlas highly accessible for a wide range of users locational reference maps to aid interpretation of the maps on each page Accompanying web resources, including locational cartograms Unlike conventional atlases of human geography, it allows us to see a range of data on a single map; further it allows us to easily see what social mixing does not occur as well as what does. Never before have we had such a vivid geographical picture of identity in Britain today. The atlas is essential reading for those interested in contemporary human identity and the social geography of early twenty first century Britain. It is also an invaluable resource for researchers working in a wide range of statutory and voluntary organisations, policy makers, journalists, politicians, students and academics.Title from publisher's bibliographic system (viewed on 06 Apr 2023).Sixty million people live in Britain. Imagine sixty million. Imagine a map of sixty million. What would that map look like and what story would it tell us about identity in Britain today? Bethan Thomas and Danny Dorling have brought together this outstanding atlas to provide us with a unique visual picture of identity and geography combined. Identity in Britain explores our changing identities as we progress from infancy to old age and tells the story of the myriad geographies of life in Britain. Features and benefits include: over 280 full colour, detailed maps analysis of the contemporary neighbourhood geographies of people in Britain at various life stages clear introduction and how-to-use guide making the atlas highly accessible for a wide range of users locational reference maps to aid interpretation of the maps on each page Accompanying web resources, including locational cartograms Unlike conventional atlases of human geography, it allows us to see a range of data on a single map; further it allows us to easily see what social mixing does not occur as well as what does. Never before have we had such a vivid geographical picture of identity in Britain today. The atlas is essential reading for those interested in contemporary human identity and the social geography of early twenty first century Britain. It is also an invaluable resource for researchers working in a wide range of statutory and voluntary organisations, policy makers, journalists, politicians, students and academics
Fast and flexible Bayesian species distribution modelling using Gaussian processes
No full text1. Species distribution modelling (SDM) is widely used in ecology, and predictions of species distributions inform both policy and ecological debates. Therefore, methods with high predictive accuracy and those that enable biological interpretation are preferable. Gaussian processes (GPs) are a highly flexible approach to statistical modelling and have recently been proposed for SDM. GP models fit smooth, but potentially complex response functions that can account for high-dimensional interactions between predictors. We propose fitting GP SDMs using deterministic numerical approximations, rather than Markov chain Monte Carlo methods in order to make GPs more computationally efficient and easy to use.
2. We introduce GP models and their application to SDM, illustrate how ecological knowledge can be incorporated into GP SDMs via Bayesian priors and formulate a simple GP SDM that can be fitted efficiently. This model can be fitted either by learning the hyperparameters or by using a fixed approximation to them. Using a subset of the North American Breeding Bird Survey data set, we compare the out-of-sample predictive accuracy of these models with several commonly used SDM approaches for both presence/absence and presence-only data.
3. Predictive accuracy of GP SDMs fitted by Laplace approximation was greater than boosted regression trees, generalized additive models (GAMs) and logistic regression when trained on presence/absence data and greater than all of these models plus MaxEnt when trained on presence-only data. GP SDMs fitted using a fixed approximation to hyperparameters were no less accurate than those with MAP estimation and on average 70 times faster, equivalent in speed to GAMs.
4. As well as having strong predictive power for this data set, GP SDMs offer a convenient method for incorporating prior knowledge of the species' ecology. By fitting these methods using efficient numerical approximations, they may easily be applied to large data sets and automatically for many species. An r package, GRaF, is provided to enable SDM users to fit GP models
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