Mutator alleles, which elevate an individual’s mutation rate from 10 to 10,000-fold, have been found at high frequencies in many natural and ex- perimental populations. Mutators are continually produced from nonmu- tators, ...

Background: On rugged fitness landscapes where sign epistasis is common, adaptation can often involve either individually beneficial “uphill” mutations or more complex mutational trajectories involving fitness valleys or ...

As deleterious variants continually arise in a population, they tend to be purged via purifying selection, leading to distortions in the shapes of genealogies relative to neutral expectations. In recent years, a mounting ...

In the era of high-throughput genome sequencing, it has become possible to measure the genetic changes that drive evolution. These direct observations enable us to test both qualitative and quantitative hypotheses about ...

The outcomes of evolution are determined by which mutations occur and fix. In rapidly adapting microbial populations, this process is particularly hard to predict because lineages with different beneficial mutations often ...

Positive selection distorts the structure of genealogies and hence alters patterns of genetic variation within a population. Most analyses of these distortions focus on the signatures of hitchhiking due to hard or soft ...

The fate of a newly arising beneficial mutation depends on many factors, such as the population size and the availability and fitness effects of other mutations that accumulate in the population. It has proven difficult ...

In rapidly adapting asexual populations, including many microbial pathogens and viruses, numerous mutant lineages often compete simultaneously for dominance within the population. These complex evolutionary dynamics determine ...

Advances in DNA sequencing are creating new opportunities for studying the process of evolution. These measurements can be particularly useful for rapidly evolving microbial organisms, whose small size and fast generation ...

Sex and recombination are pervasive throughout nature despite their substantial costs1. Understanding the evolutionary forces that maintain these phenomena is a central challenge in biology2,3. One longstanding hypothesis ...