In these experiments, selection is relaxed by propagating populations at as small an effective population size as is feasible.
Recent experiments with P. fluorescens-Φ2 manipulated the frequency of fluctuations in resource supply by propagating populations in environments that alternated between high and low resource supply at different rates.
An ideal design would be to propagate populations within the laboratory for at least two generations, which was only realized in 5/23 studies compiled in Table 2.
The nematode worm C. elegans had already been established as a useful model organism for studies of aging since it has a relatively short life span and can easily propagate populations of synchronized individuals.
We cannot manipulate the types of mutation that occur, but instead propagate populations in both stressful and permissive environments and assume that the extent of detrimental mutation clearance and beneficial mutation incorporation differs between them.
The MA method involves propagating multiple populations through repeated bottlenecks of a single, randomly chosen individual, thereby greatly reducing the effectiveness of selection.
Evolution experiments propagating bacterial populations in glucose- or phosphate-limited chemostats have been extensively developed to understand the dynamics of adaptive processes [ 19, 24- 26, 28].
However, in spite of the ability to undertake sexual reproduction, the frequency with which this occurs also varies greatly between species, from being an absolute pre-requisite for plant infection, as in Ustilago maydis, to being almost absent from clonally propagating asexual populations of M. oryzae.
Immigration randomly generates (P - 1) chromosomes to propagate the population (a mass immigration).
Two treatments matched the PP and ERA passages, except that each day the evolving virus lineage experienced a bottleneck size of N = 1, where a single plaque was isolated at random and used to propagate the population following described methods [ 29].
