Evolutionary feedback mediated through population density, illustrated with viruses in chemostats.

Area of Science:

• Evolutionary Ecology
• Microbial Ecology
• Population Dynamics

Background:

• Population density is a key factor influencing adaptation, with reciprocal effects on population size.
• Empirically linking population density and adaptation in real-time is challenging.
• Viral (bacteriophage) chemostats offer a model system to study these dynamics.

Purpose of the Study:

• To investigate the co-evolution of population density and adaptation in bacteriophage chemostats.
• To compare the effects of two distinct chemostat designs on viral evolution.
• To understand the ecological and evolutionary feedback loops between viruses and their hosts.

Main Methods:

• Modeling viral population dynamics in two chemostat designs.
• Experimental manipulation of host and virus in chemostats.
• Analysis of phenotypic and molecular data to track viral adaptation.

Main Results:

• A predator-prey chemostat design led to low viral density, with adaptation impacting host density but not viral density.
• A refuge-based chemostat design showed evolutionary succession: low density adaptation increased viral density, which then favored competitive ability.
• Experimental data supported the model predictions for both chemostat designs.

Conclusions:

• Chemostat design significantly alters viral evolutionary trajectories and population regulation.
• Viral adaptation can drive population density changes, and density, in turn, shapes adaptation.
• These experimental systems provide insights into natural population dynamics and evolution.