If an environmental change is severe enough that local conditions are no longer within a species’ ecological persistence limits, populations must evolve in order to locally persist. Most species do not live in isolation and interactions with other species may help or hinder their ability to persist in a variety of ways. Previous studies have focused on the demographic effects of ecological...
Random mutant data suggest that the genetic basis for changes in vital rates (survival, fecundity, birth and death rates) is typically very wide: most random mutations, everywhere in the genome, have an effect on these life history traits. However, most stochastic models of ER are only manageable with a narrow basis (one resistant genotype per ER
trajectory). I will present past and present...
Models of evolutionary rescue are predominantly applied in two fields:
conservation biology, ecology and epidemiology. We are presenting two models using branching processes that cover these two fields of application.
First, we study the probability of adaptation and evolutionary rescue in a spatially structured environment. A common assumption of spatial models is that emigrating...
Over the last decades, numerous studies have begun documenting the impacts of climate deregulation on species ranges. Among them, specialists, which thrive under specific environmental conditions, typically in narrow geographic ranges, are widely recognised as one of the most threatened categories. Many might rely on both their potential to adapt and on the existence of an environmental...
Bacterial plasmids and other extra-chromosomal DNA elements frequently carry genes that have important effects on the fitness of their hosts. Because plasmids often exist in the bacterial cell in multiple copies, different plasmid copies can carry distinct alleles, allowing for heterozygosity not possible for loci on haploid chromosomes. This plasmid-mediated heterozygosity may increase the...
A prime example of evolutionary rescue is the ability of cancer cells to survive treatment. Aneuploidy, the state of abnormal number of chromosomes in the cell, is hypothesized to increase fitness in the presence of anti-cancer drugs, e.g. due to incomplete pathways targeted by drugs. Aneuploidy is highly prevalent in tumours, and certain anti-cancer drugs attempt to combat cancer by...
(work with Paulo R. A. Campos, Universidade Federal de Pernambuco, Brazil)
By defining a discrete set of available mutation vectors, the mapping from trait vector to fitness provided by Fisher's Geometric Model (FGM) has been previously extended to a mapping from genotype to fitness. We examine evolutionary rescue across this genotypic landscape. We first
provide a simple derivation of...
Cancer cells evolve from a normal tissue due to the accumulation of pro-tumor mutations, called drivers, that coexist together with thousands of other somatic mutations that do not promote cancer growth, named passengers. However, the existence of drivers in normal tissues has been reported, suggesting that isolated drivers alone are not enough to trigger the development of malignant...
Evolution of drug resistance is contingent on sufficient mutational supply as well as successful establishment of the initially rare resistant cells that are subject to stochastic extinction. Importantly, the potential for resistance evolution strongly depends on the drug concentration that not only directly affects the strength of selection, but also impacts the required mutational targets,...
Rapid and widespread environmental change worldwide has raised concern about the ability of natural populations to rapidly adapt to novel conditions. Ancestral population phenotypes and population dynamics should predict successful evolutionary rescue (and adaptation) - but which specific phenotypic traits and demographic events matter? Might different founding traits and demographic events...
Most populations are heterogeneous, containing individuals in different stages that have different tolerances to environmental changes and different contributions to the evolutionary and demographic future of the population. Several theoretical studies have examined how this heterogeneity makes the probability of evolutionary rescue dependent on the life cycle in structured populations. These...
Maladaptive changes in the environment can provoke an adaptive response, but also induce plastic changes in organisms. Here we derive a general model of the effects of maladaptation on vitals rates—recruitment and adult mortality—in order to explore plasticity in generation time in threatened populations. We find that generation time can shift considerably during the process of evolutionary...
Classic studies on evolutionary rescue have considered single species dynamics, but no species exist in isolation in nature. By considering various interspecific interactions as well as coevolution, complex dynamics can emerge in evolutionary rescue. For example, rapid adaptive evolution of prey species can prevent predator extinction when there is a trade-off between defense and growth in the...
Uncertainty in the outcome of individual-level processes, such as death or reproduction, complicates the ability to predict population extinction; random chance may cause otherwise identical populations to experience different fates. Individual-level variability generates multiple population-level phenomena – such as demographic stochasticity, sex-ratio stochasticity, and phenotypic...
Many ecologically important organisms (including perennial grasses that shape prairies and savannahs, reef-building corals, and many invasive and pathogenic species) have life histories that include stage structure and both sexual and asexual reproduction (partial clonality) Yet how partial clonality affect a populations ability to respond by phenotypic evolution to rapid environmental change...
Modern agriculture faces the problem of meeting the rapidly increasing demand for food in a growing world population while minimising the environmental impacts. Weeds are a major threat to crop production, causing the highest yield losses among pests. Since the late 1960s, conventional agriculture has primarily relied on herbicides for controlling weeds. This overreliance on herbicides has led...
Populations of microbial pathogens or cancer cells possess enormous adaptive potential that allows them to emerge from homeostatic regulations for example by the immune system. From a reductionistic viewpoint, the fundamental processes in such populations are replication, mutation and death. Using traits to represent these processes, the emergence from homeostatic regulation can be understood...
Evolution is a heritable change in the characteristics of the population over time and adaptation is the evolutionary process by which a population survives in its environment. Stochastic fluctuations due to finite population size can alter the fate of the population and therefore, it is crucial to understand the dynamics of adaptation in a finite population. We explore the evolution of a...
In hematologic cancers, the initial response to therapy can be observed via temporal changes in tumor burden or approximate measures of tumor burden during treatment. Once the cancer cell population is small, further disease evolution is dominated by underlying stochastic disease kinetics. Many treatments evoke an initial response and tumor decline, but hidden (or difficult to detect) cancer...
The evolution of antimicrobial resistance in bacteria poses a major challenge for patient treatment worldwide. One option to reduce the risk of the undesired evolutionary rescue during treatment is to increase the genetic barrier to resistance, which can, for example, be achieved by increasing the number of drugs applied. With multiple drugs in combination, applying the different drugs at the...
Bacterial populations face bottlenecks during infection of host populations, caused by factors such as transmission of pathogens, host immune response, and antibiotic treatment. Bottlenecks can increase the influence of random effects during bacterial evolution and directly affect the diversity of resistance alleles. Despite the importance of bottlenecks in resistance evolution, their role in...
