Speaker
Description
Evolutionary dynamics are sensitive to the type of ecological interactions that drive reproduction and death. In this talk I will discuss how spatial interactions may change the laws of evolution. First I will describe spatial invasion dynamics and derive a number of scaling laws that describe the growth of disadvantageous, neutral, and advantageous mutants in growing populations. Applications of these laws to bacterial growth and carcinogenesis will be discussed. I will then talk about spatial enemy-victim dynamics. The literature about mutant invasion and fixation typically assumes populations to exist in isolation from their ecosystem. Yet, populations are part of ecological communities, and enemy-victim (e.g. pathogen-host) interactions are particularly common. I will use spatially explicit, computational pathogen-host models (with wild-type and mutant hosts) to re-visit the established theory about mutant fixation, where the pathogen equally attacks both wild-type and mutant individuals. Mutant fitness is assumed to be unrelated to infection. I will show that pathogen presence substantially weakens selection, increasing the fixation probability of disadvantageous mutants and decreasing it for advantageous mutants. A mathematical approach of coarse-grained approximation can be used to shed light onto this finding, which has relevance for phage therapies and antibiotic resistance. These results imply that the deleterious mutant burden in natural populations might be higher than expected from traditional theory.
