Evolutionary and Eco-Evolutionary Stability in Aposematic Prey Populations

The term aposematism or "warning colouration" (as first characterised by Alfred Russel Wallace in 1877) describes the process by which defended organisms (animals or plants) advertise their unprofitability to potential predators to gain selective advantage. The first part of the thesis explores the relationship between evolutionarily stable levels of signalling and defence within the context of a game-theoretical, prey-predator setup in which the prey population consists of a single type. While it is implicitly assumed that the prey population is large enough to be considered effectively infinite the evolution of prey traits is also explored for intermediate-sized populations within the context of genetic algorithm approach. In the later chapters considerable effort is devoted to extending the mentioned predator-prey description to systems in which the prey population consists of two types, including a model and a mimic. This modification leads us naturally into the celebrated adaptive mechanism named after Henry Walter Bates, Batesian mimicry. In Batesian mimicry complexes individuals from a palatable (mimic) species resemble individuals from an unpalatable (model) species to gain protection against predators. While there is ample empirical evidence to suggest that individuals from one species may gain selective advantage by resembling individuals from another, the mathematical modelling of Batesian mimicry is rather limited. We predict that models and mimics can co-exist along a continuum of solutions (representing the conspicuousness, noxiousness, and average mimicto-model proportion) that are both ecologically and locally evolutionarily stable. We establish a number of novel results that confirm both common sense intuition and a considerable body of related works

Evolutionarily stable levels of aposematic defence in prey populations

Our understanding of aposematism (the conspicuous signalling of a defence for the deterrence of predators) has advanced notably since its first observation in the late nineteenth century. Indeed, it extends the scope of a well-established game-theoretical model of this very same process both from the analytical standpoint (by considering regimes of varying background mortality and colony size) and from the practical standpoint (by assessing its efficacy and limitations in predicting the evolution of prey traits in finite simulated populations). The nature of the manuscript at hand is more mathematical and it’s aim is two-fold: first, to determine the relationship between evolutionarily stable levels of defence and signal strength under various regimes of background mortality and colony size. Second, to compare these predictions with simulations of finite prey populations that are subject to random local mutation. We compare the roles of absolute resident fitness, mutant fitness and stochasticity in the evolution of prey traits and discuss the importance of population size in the above

Aposematic signalling in prey-predator systems:determining evolutionarily stability when prey populations consist of a single species

Aposematism is the signalling of a defence for the deterrence of predators. We presently focus on aposematic organisms that exhibit chemical defences, which are usually signalled by some type of brightly coloured skin pigmentation (as is the case with poison frog species of the Dendrobatidae family), although our treatment is likely transferable to other forms of secondary defence. This setup is not only a natural one to consider but also opens up the possibility for rich mathematical modelling: the strength of aposematic traits (signalling and defence) can be unambiguously realised using variables that are continuously quantifiable, independent from one another and which together define a two-dimensional strategy space wherein the aposematic behaviour of any one organism can be represented by a single point. We presently develop an extensive mathematical model in which we explore the joint co-evolution of aposematic traits within the context of evolutionary stability. Even though empirical and model-based studies are conflicting regarding how aposematic traits are related to one another in nature, the majority of works allude to a positive correlation. We presently suggest that both positively and negatively correlated combinations of traits can achieve evolutionarily stable outcomes and further, that for a given level of signal strength there can be more than one optimal level of defence. Our findings are novel and pertinent to a sizeable body of physical evidence, which we discuss

Residual stresses in girth butt welded pipes

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Residual stresses in girth butt welded pipes Results and implications

SIGLEAvailable from British Library Document Supply Centre- DSC:9106.17(CUED/D-STRUCT/TR--109) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Residual stresses in girth butt welded pipes Theoretical analysis

SIGLEAvailable from British Library Document Supply Centre- DSC:9106.17(CUED/D-STRUCT/TR--107) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Evolutionarily stable levels of aposematic defence in prey populations

Our understanding of aposematism (the conspicuous signalling of a defence for the deterrence of predators) has advanced notably since its first observation in the late nineteenth century. Indeed, it extends the scope of a well-established game-theoretical model of this very same process both from the analytical standpoint (by considering regimes of varying background mortality and colony size) and from the practical standpoint (by assessing its efficacy and limitations in predicting the evolution of prey traits in finite simulated populations). The nature of the manuscript at hand is more mathematical and its aim is two-fold: first, to determine the relationship between evolutionarily stable levels of defence and signal strength under various regimes of background mortality and colony size. Second, to compare these predictions with simulations of finite prey populations that are subject to random local mutation. We compare the roles of absolute resident fitness, mutant fitness and stochasticity in the evolution of prey traits and discuss the importance of population size in the above

Residual stresses in girth butt welded pipes Experimental techniques

SIGLEAvailable from British Library Document Supply Centre- DSC:9106.17(CUED/D-Struct/TR--108) / BLDSC - British Library Document Supply CentreGBUnited Kingdo