Lenski's E. Coli: citrate eatng type not new species (Introduction)

by David Turell , Tuesday, September 08, 2015, 14:45 (3343 days ago) @ David Turell

A researcher on the E. coli discusses the citrate change, but is not convinced they have created a new species:- http://beacon-center.org/blog/2013/03/25/beacon-researchers-at-work-the-origin-of-a-spe... increases diversity and complexity, and, importantly, it allows organisms to explore new evolutionary paths. There is little in biology that isn't touched by speciation, and it is little wonder that Darwin himself referred to it as “that mystery of mysteries.”-"Despite all the fantastic work done since Darwin's day, speciation is still mysterious. Speciation is complex, multifaceted, tricky to study, and, most importantly, hard to “catch in the act.” It would help if we had a model system in which we could study speciation in fine detail as it occurs, examine and manipulate the processes involved, and to do so over a humanly reasonable time scale.-***-"Is Cit+ a new species? That is a trickier question than you might think. Speciation is a process and not a sudden, instantaneous event, and there is no single, universally accepted species definition. (This reflects how nature really doesn't conform to the human need for sharply-drawn categories.) The most widely accepted, however, is Ernst Mayr's Biological Species Concept (BSC), which equates speciation with the evolution of reproductive isolation. This means that a group of organisms is a new species when its members can mate, mingle genes, and produce fertile offspring with each other, but not with members of its parent species.-"Unfortunately, the BSC is hard to apply to asexual bacteria.-***-"Despite these findings, I am not quite comfortable calling Cit+ a new species just yet. If Cit+ really is evolving to become well-adapted to the citrate niche, it might become better at growing on citrate, and worse at growing on glucose. This pattern could mean that some of the same mutations that are making Cit+ better at eating citrate are also making it worse at eating glucose."-Comment: As he points out, many mutations result in a loss of information.