scholarly journals Treating symptomatic infections and the co-evolution of virulence and drug resistance

2020 ◽  
Author(s):  
Samuel Alizon
Keyword(s):  
Evolutionary Dynamics ◽  
Adaptive Dynamics ◽  
Drug Resistant ◽  
Treatment Rate ◽  
Virulence Evolution ◽  
Trade Offs ◽  
Virulent Strains ◽  
Host Mortality ◽  
Parameter Values

AbstractAntimicrobial therapeutic treatments are by definition applied after the onset of symptoms, which tend to correlate with infection severity. Using mathematical epidemiology models, I explore how this link affects the coevolutionary dynamics between the virulence of an infection, measured via host mortality rate, and its susceptibility to chemotherapy. I show that unless resistance pre-exists in the population, drug-resistant infections are initially more virulent than drug-sensitive ones. As the epidemic unfolds, virulence is more counter-selected in drug-sensitive than in drug-resistant infections. This difference decreases over time and, eventually, the exact shape of genetic trade-offs govern long-term evolutionary dynamics. Using adaptive dynamics, I show that two types of evolutionary stable strategies (ESS) may be reached in the context of this simple model and that, depending on the parameter values, an ESS may only be locally stable. In general, the more the treatment rate increases with virulence, the lower the ESS value. Overall, both on the short-term and long-term, having treatment rate depend on infection virulence tend to favour less virulent strains in drug-sensitive infections. These results highlight the importance of the feedbacks between epidemiology, public health policies and parasite evolution, and have implications for the monitoring of virulence evolution.

scholarly journals Functional and evolutionary trade-offs co-occur between two consolidated memory phases in Drosophila melanogaster

2012 ◽  
Vol 279 (1744) ◽  
pp. 4015-4023 ◽  
Author(s):  
Fabrice Lagasse ◽  
Celine Moreno ◽  
Thomas Preat ◽  
Frederic Mery
Keyword(s):  
Evolutionary Dynamics ◽  
Functional Relationship ◽  
Learning Task ◽  
Long Term Memory ◽  
Phenotypic Traits ◽  
Trade Offs ◽  
Memory Phase ◽  
Fitness Benefits ◽  
Benefits And Costs

Memory is a complex and dynamic process that is composed of different phases. Its evolution under natural selection probably depends on a balance between fitness benefits and costs. In Drosophila , two separate forms of consolidated memory phases can be generated experimentally: anaesthesia-resistant memory (ARM) and long-term memory (LTM). In recent years, several studies have focused on the differences between these long-lasting memory types and have found that, at the functional level, ARM and LTM are antagonistic. How this functional relationship will affect their evolutionary dynamics remains unknown. We selected for flies with either improved ARM or improved LTM over several generations, and found that flies selected specifically for improvement of one consolidated memory phase show reduced performance in the other memory phase. We also found that improved LTM was linked to decreased longevity in male flies but not in females. Conversely, males with improved ARM had increased longevity. We found no correlation between either improved ARM or LTM and other phenotypic traits. This is, to our knowledge, the first evidence of a symmetrical evolutionary trade-off between two memory phases for the same learning task. Such trade-offs may have an important impact on the evolution of cognitive capacities. On a neural level, these results support the hypothesis that mechanisms underlying these forms of consolidated memory are, to some degree, antagonistic.

scholarly journals Attracting pollinators vs escaping herbivores: eco-evolutionary dynamics of plants confronted with an ecological trade-off

2021 ◽  
Author(s):  
Youssef Yacine ◽  
Nicolas Loeuille
Keyword(s):  
Evolutionary Dynamics ◽  
Plant Traits ◽  
Adaptive Dynamics ◽  
Disruptive Selection ◽  
Stabilizing Selection ◽  
Ecological Communities ◽  
Trade Off ◽  
Trade Offs ◽  
Herbivore Community ◽  
Plant Animal Interactions

AbstractA large number of plant traits are subject to an ecological trade-off between attracting pollinators and escaping herbivores. The interplay of both plant-animal interactions determines their evolution. Within a plant-pollinator-herbivore community in which interaction strengths depend on trait-matching, eco-evolutionary dynamics are studied using the framework of adaptive dynamics. We characterize the type of selection acting on the plant phenotype and the consequences for multispecies coexistence. We find that pollination favors stabilizing selection and coexistence. In contrast, herbivory fosters runaway selection, which threatens plant-animal coexistence. These contrasting dynamics highlight the key role of ecological trade-offs in structuring ecological communities. In particular, we show that disruptive selection is possible when such trade-offs are strong. While the interplay of pollination and herbivory is known to maintain plant polymorphism in several cases, our work suggests that it might also have fueled the diversification process itself.

scholarly journals Understanding site choice and competition through the adaptive dynamics of microbial settling strategy in a chemostat

2020 ◽  
Author(s):  
Yuhua Cai ◽  
Stefan A. H. Geritz
Keyword(s):  
Evolutionary Dynamics ◽  
Adaptive Dynamics ◽  
Low Frequency ◽  
Long Term Evolution ◽  
Operating Conditions ◽  
Settling Rate ◽  
Nutrient Input ◽  
Occupied Site ◽  
Term Evolution

AbstractTo understand the choice and competition of sites in nature, we consider an ecological environment in a chemostat consisting of a polymorphic microbial population that can float in the fluid or settle down on the wall of the chemostat. For the transition of a microbe from its floating state to its settled state at a particular settling rate involving the choice and competition of sites on the wall, we consider three different mechanisms: (i) unimolecular-Bourgeois settling, i.e., floaters land freely on the wall, but in an occupied site, the owner keeps the site (Bourgeois behaviour); (ii) unimolecular-anti-Bourgeois settling, i.e., floaters land freely on the wall, but in an occupied site, the intruder gets the site (anti-Bourgeois behaviour); (iii) bimolecular settling, i.e., floaters land only on the vacant sites of the wall. Employing the framework of adaptive dynamics, we study the evolution of the settling rate with different settling mechanisms and investigate how physical operating conditions affect the evolutionary dynamics. Our results indicate that settling mechanisms and physical operating conditions have significant influences on the direction of evolution and the diversity of phenotypes. (1) For constant nutrient input, theoretical analysis shows that the population is always monomorphic during the long-term evolution. Notably, the direction of evolution depends on the settling mechanisms and physical operating conditions, which further determines the composition of the population. Moreover, we find two exciting transformations of types of Pairwise Invasibility Plots, which are the gradual transformation and the bang-bang transformation. (2) For periodic nutrient input, numerical analysis reveals that evolutionary coexistence is possible, and the population eventually maintains dimorphism. Remarkably, for all three settling mechanisms, the long-term evolution leads to one of the two coexisting species settle down totally on the wall if the input is low-frequency but float entirely in the fluid if the input becomes high-frequency.

scholarly journals EVOLUTIONARY DYNAMICS CAN BE CHAOTIC: A FIRST EXAMPLE

2010 ◽  
Vol 20 (11) ◽  
pp. 3473-3485 ◽  
Author(s):  
FABIO DERCOLE ◽  
SERGIO RINALDI
Keyword(s):  
Bifurcation Analysis ◽  
Food Chain ◽  
Evolutionary Dynamics ◽  
Adaptive Dynamics ◽  
Three Dimensional ◽  
Phenotypic Trait ◽  
Predator Species ◽  
Evolutionary Trajectories ◽  
Trait Space

We present in this paper the first example of chaotic evolutionary dynamics in biology. We consider a Lotka–Volterra tritrophic food chain composed of a resource, its consumer, and a predator species, each characterized by a single adaptive phenotypic trait, and we show that for suitable modeling and parameter choices the evolutionary trajectories approach a strange attractor in the three-dimensional trait space. The study is performed through the bifurcation analysis of the so-called canonical equation of Adaptive Dynamics, the most appropriate modeling approach to long-term evolutionary dynamics.

scholarly journals Predicting metabolic adaptation from networks of mutational paths

2017 ◽  
Author(s):  
Christos Josephides ◽  
Peter S. Swain
Keyword(s):  
Adaptive Evolution ◽  
Evolutionary Dynamics ◽  
Evolutionary Model ◽  
Metabolic Adaptation ◽  
Long Term Outcomes ◽  
Reliable Prediction ◽  
Graph Theoretic ◽  
Incomplete Observations ◽  
Trade Offs

Competition for substrates is a ubiquitous selection pressure faced by microbes, yet intracellular trade-offs can prevent cells from metabolizing every type of available substrate. Adaptive evolution is constrained by these trade-offs, but their consequences for the repeatability and predictability of evolution are unclear. Here we develop an eco-evolutionary model with a metabolic trade-off to generate networks of mutational paths in microbial communities and show that these networks have descriptive and predictive information about the evolving communities. We find that long-term outcomes, including community collapse, diversity, and cycling, have characteristic evolutionary dynamics that determine the entropy, or repeatability, of mutational paths. Although reliable prediction of evolutionary outcomes from environmental conditions is difficult, graph-theoretic properties of the mutational networks enable accurate prediction even from incomplete observations. In conclusion, we present a novel methodology for analyzing adaptive evolution and report that the dynamics of adaptation are a key variable for predictive success.

scholarly journals How to maintain a high virulence: evolution of a killer in hosts of various susceptibilities

2019 ◽  
Author(s):  
Aurélien Chateigner ◽  
Yannis Moreau ◽  
Davy Jiolle ◽  
Cindy Pontlevé ◽  
Carole Labrousse ◽  
...  
Keyword(s):  
Experimental Evolution ◽  
Transmission Probability ◽  
Evolutionary Potential ◽  
Virulence Evolution ◽  
Specific Host ◽  
Trade Offs ◽  
Virulent Strains ◽  
High Virulence ◽  
Infection Cycles ◽  
Highly Virulent

AbstractPathogens should evolve to avirulence. However, while baculoviruses can be transmitted through direct contact, their main route of infection goes through the death and liquefaction of their caterpillar hosts and highly virulent strains still seem to be advantaged through infection cycles. Furthermore, one of them,Autographa californicamultiple nucleopolyhedrovirus, is so generalist that it can infect more than 100 different hosts.To understand and characterize the evolutionary potential of this virus and how it is maintained while killing some of its hosts in less than a week, we performed an experimental evolution starting from an almost natural isolate of AcMNPV, known for its generalist infection capacity. We made it evolve on 4 hosts of different susceptibilities for 10 cycles and followed hosts survival each day. We finally evaluated whether the generalist capacity was maintained after evolving on one specific host species and tested an epidemiological model through simulations to understand how.Finally, on very highly susceptible hosts, transmission-virulence trade-offs seem to disappear and the virus can maximize transmission and virulence. When less adapted to its host, the pathogen’s virulence has not been modified along cycles but the yield was increased, apparently through an increased transmission probability and an increased latent period between exposition and infection.

scholarly journals Mathematical model for the evolutionary dynamics of innovation in city public transport systems

Memorias ◽  
2018 ◽  
pp. 36-50
Author(s):  
Hernán Darío Toro-Zapata ◽  
Gerard Olivar-Tost
Keyword(s):  
Mathematical Model ◽  
Transport System ◽  
Public Transport ◽  
Evolutionary Dynamics ◽  
Adaptive Dynamics ◽  
Transport Systems ◽  
State Variables ◽  
Long Term Study ◽  
Long Term Behavior

In this study, a mathematical model is formulated and studied from the perspective of adaptive dynamics (evolutionary processes), in order to describe the interaction dynamics between two city public transport systems: one of which is established and one of which is innovative. Each system is to be influenced by a characteristic attribute; in this case, the number of assumed passengers per unit it that can transport. The model considers the proportion of users in each transport system, as well as the proportion of the budget destined for their expansion among new users, to be state variables. Model analysis allows for the determination of the conditions under which an innovative transportation system can expand and establish itself in a market which is initially dominated by an established transport system. Through use of the adaptive dynamics framework, the expected long-term behavior of the characteristic attribute which defines transport systems is examined. This long-term study allows for the establishment of the conditions under which certain values of the characteristic attribute configure coexistence, divergence, or both kinds of scenarios. The latter case is reported as the occurrence of evolutionary ramifications, conditions that guarantee the viability of an innovative transport system. Consequently, this phenomenon is referred to as the origin of diversity.

How Molecular Epidemiology Can Affect Tuberculosis Control in the Middle East Countries: A Systematic Review and Meta-Analysis

2020 ◽  
Vol 20 ◽  
Author(s):  
Mohammad Asgharzadeh ◽  
Jalil Rashedi ◽  
Behroz Mahdavi Poor ◽  
Hossein Samadi kafil ◽  
Hossein Moharram Zadeh ◽  
...  
Keyword(s):  
Middle East ◽  
Molecular Epidemiology ◽  
Average Rate ◽  
Meta Analysis ◽  
Close Monitoring ◽  
Drug Resistant ◽  
Middle East Countries ◽  
Virulent Strains ◽  
Recent Transmission ◽  
Highly Virulent

: Nowadays, due to the incidence of specific strains of Mycobacterium tuberculosis and also increase the rate of drug resistant-TB mortality rate has elevated by this disease. Identification of common strains in the region as well as sources of transmission are essential to control the disease that this has been possible by using molecular epidemiology. In this survey, studies which have been carried out based on spoligotyping method in Muslim Middle East countries were considered to determine their role in control of TB. All studies conducted from 2005 to June 2016 were considered systematically in three electronic data bases and finally, 23 studies were selected. The average rate of clustering was 84% and the rate of recent transmission was variable from 21.7% to 92.4%. Incidence of Beijing strains was been rising in the considered countries. In Iran and Saudi Arabia which are immigration and labour-hosting countries, respectively, rapid transmittable strains and drug resistant Beijings were higher than other considered countries. Considering the incidence of highly virulent strains, due to the increase of immigration and people infected with HIV, tuberculosis, especially drug resistant form, the lack of close monitoring in the future will be induce trouble.

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