A central goal of evolutionary biology is to explain the origin of complex organs — the ribosomal machinery that translates the genetic code, the immune system that accurately distinguishes self from non-self, eyes that can resolve precise images, and so on. Although we understand in broad outline how such extraordinary systems can evolve by natural selection, we know very little about the actu...

26 27 Evolutionary innovations that enable organisms to colonize new ecological niches are rare 28 compared to gradual evolutionary changes in existing traits. We discovered that key mutations in 29 the gltA gene, which encodes citrate synthase (CS), occurred both before and after Escherichia 30 coli gained the ability to grow aerobically on citrate (Cit + phenotype) during the Lenski long-31 t...

The positive replies to our original paper (West et al., 1999) leave us in the pleasurable position of being able to keep our ®nal comments short. Kondrashov (1999) demonstrates what Seger (1999) called `physics envy'. The idea that the Mutational Deterministic hypothesis can be easily validated or rejected, once the minimum rate of deleterious mutations per genome per generation (U) is known, ...

Examples of ecological specialization abound in nature but the evolutionary and genetic causes of tradeoffs across environments are typically unknown. Natural selection itself may favor traits that improve fitness in one environment but reduce fitness elsewhere. Furthermore, an absence of selection on unused traits renders them susceptible to mutational erosion by genetic drift. Experimental ev...

Evolutionary adaptation to a constant environment is often accompanied by specialization and a reduction of fitness in other environments. We assayed the ability of the Lenski Escherichia coli populations to grow on a range of carbon sources after 50,000 generations of adaptation on glucose. Using direct measurements of growth rates, we demonstrated that declines in performance were much less w...

New mutations leading to structural variation (SV) in genomes-in the form of mobile element insertions, large deletions, gene duplications, and other chromosomal rearrangements-can play a key role in microbial evolution. Yet, SV is considerably more difficult to predict from short-read genome resequencing data than single-nucleotide substitutions and indels (SN), so it is not yet routinely iden...

The subject of bacterial resistance to antibiotics has not only inundated the commercial market, but also provided powerful evolutionary insight into larger studies of evolution. Genetic resistance using bacterial models is highly regarded for their rapid proliferation, easy maintenance, and simple manipulation of variables. Despite their widespread use, these studies have yet to signify the pr...

References 1. Buss, L.W. (1987). The Evolution of Individuality (Princeton, New Jersey: Princeton University Press). 2. Bonner, J.T. (1967). The Cellular Slime Molds, Second Edition (Princeton, New Jersey: Princeton University Press). 3. Buss, L.W. (1982). Somatic cell parasitism and the evolution of somatic tissue compatibility. Proc. Natl. Acad. Sci. USA 79, 5337–5341. 4. Kessin, R.H. (2001)....