Dynamics Of Evolutionary Change Research Articles

The Odyssey of Mentoring: "A Paradigm Shift from Baby Boomer to Millennial and Beyond".

The role of a mentor has metamorphosed from the traditional Halsteadian model to a more "mosaic mentor" with innovative strategies specific to the mentee. The contemporary mentor continues to be faced with the challenges of a new breed of oral and maxillofacial surgeons. This article accompanies the reader on an "odyssey" of surgical mentorship beginning with historic origins, followed by a series of definitions of what a mentor is and is not, the dynamics of evolutionary change with respect to style of surgical mentoring, and evidence-based studies in the tools now applied to mentor our future oral and maxillofacial surgeons.

Evolutionary dynamics and structural consequences of de novo beneficial mutations and mutant lineages arising in a constant environment

BackgroundMicrobial evolution experiments can be used to study the tempo and dynamics of evolutionary change in asexual populations, founded from single clones and growing into large populations with multiple clonal lineages. High-throughput sequencing can be used to catalog de novo mutations as potential targets of selection, determine in which lineages they arise, and track the fates of those lineages. Here, we describe a long-term experimental evolution study to identify targets of selection and to determine when, where, and how often those targets are hit.ResultsWe experimentally evolved replicate Escherichia coli populations that originated from a mutator/nonsense suppressor ancestor under glucose limitation for between 300 and 500 generations. Whole-genome, whole-population sequencing enabled us to catalog 3346 de novo mutations that reached > 1% frequency. We sequenced the genomes of 96 clones from each population when allelic diversity was greatest in order to establish whether mutations were in the same or different lineages and to depict lineage dynamics. Operon-specific mutations that enhance glucose uptake were the first to rise to high frequency, followed by global regulatory mutations. Mutations related to energy conservation, membrane biogenesis, and mitigating the impact of nonsense mutations, both ancestral and derived, arose later. New alleles were confined to relatively few loci, with many instances of identical mutations arising independently in multiple lineages, among and within replicate populations. However, most never exceeded 10% in frequency and were at a lower frequency at the end of the experiment than at their maxima, indicating clonal interference. Many alleles mapped to key structures within the proteins that they mutated, providing insight into their functional consequences.ConclusionsOverall, we find that when mutational input is increased by an ancestral defect in DNA repair, the spectrum of high-frequency beneficial mutations in a simple, constant resource-limited environment is narrow, resulting in extreme parallelism where many adaptive mutations arise but few ever go to fixation.

Management and the representative firm revisited: the modern significance of Marshall's evolutionary economics

In an essay written in honour of Peter Swann, it is second nature to discuss some aspects of the economics of innovation, as that is the very challenging area of economic life where he has added so much to our understanding. I will attempt to do this by posing the problem of how innovation fits into the theory of value. Innovation research continues apace, but its broader systemic implications for how we understand the dynamics of capitalism are in danger of being overlooked. But two important economists, Schumpeter and Marshall, have seen the problem differently and built innovation into their theoretical schemes from the start. Marshall's theory of evolutionary change provides a natural focus for our discussion, and this is reflected in his treatment of management, in his use of the representative firm and in the variation-cum-selection dynamics of his open competitive process. We treat each of these topics and show how his evolutionary dynamics can be expressed in the Fisher/Price dynamics of evolutionary change. More generally, the key to economic development is the uneven nature of innovation and it is the uneven nature that gives economic transformation its evolutionary character. This, I suggest, is the proper legacy of Marshalls economics.

Strategies of Model Building in Population Genetics

In 1966, Richard Levins argued that there are different strategies in model building in population biology. In this paper, I reply to Orzack and Sober's (1993) critiques of Levins and argue that his views on modeling strategies apply also in the context of evolutionary genetics. In particular, I argue that there are different ways in which models are used to ask and answer questions about the dynamics of evolutionary change, prospectively and retrospectively, in classical versus molecular evolutionary genetics. Further, I argue that robustness analysis is a tool for, if not confirmation, then something near enough, in this discipline.

The German Variety of Capitalism: Forces and Dynamics of Evolutionary Change

This is the peer reviewed version of the following article: [Bathelt, H., & Gertler, M. S. (2005). The German variety of capitalism: Forces and dynamics of evolutionary change. Economic Geography, 81(1), 1-9.], which has been published in final form at: http://onlinelibrary.wiley.com/doi/10.1111/j.1944-8287.2005.tb00252.x/abstract. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

Plant genetic resource management: The next investments in quantitative and qualitative genetics

Substantial investments are being made in molecular genetic technology as a means to support plant breeding and improved crop and forestry productivity. We suggest that although these investments will bring some benefits, it is critical that this technology not replace or even limit the expansion of more traditional breeding activities. Biotechnology firms create a situation where investors require almost immediate returns. Globally, this may be at the expense of longer-term returns that will arise from investments in different types of pre-breeding, breeding, testing and selection efforts that are needed in many varieties or populations of lesser-developed species. National and international agencies, responsible for conserving and breeding crop and forest tree genetic resources, need to think about and undertake programs that consider the dynamics of evolutionary change in crops as the main focus, supported by molecular genetics. A better balance between investments in privately funded single-gene technologies, and the maintenance and development of multiple-gene sets in many more species than we consider today, will be of much more value to society in the long run.

Ancient origin of the tryptophan operon and the dynamics of evolutionary change.

The seven conserved enzymatic domains required for tryptophan (Trp) biosynthesis are encoded in seven genetic regions that are organized differently (whole-pathway operons, multiple partial-pathway operons, and dispersed genes) in prokaryotes. A comparative bioinformatics evaluation of the conservation and organization of the genes of Trp biosynthesis in prokaryotic operons should serve as an excellent model for assessing the feasibility of predicting the evolutionary histories of genes and operons associated with other biochemical pathways. These comparisons should provide a better understanding of possible explanations for differences in operon organization in different organisms at a genomics level. These analyses may also permit identification of some of the prevailing forces that dictated specific gene rearrangements during the course of evolution. Operons concerned with Trp biosynthesis in prokaryotes have been in a dynamic state of flux. Analysis of closely related organisms among the Bacteria at various phylogenetic nodes reveals many examples of operon scission, gene dispersal, gene fusion, gene scrambling, and gene loss from which the direction of evolutionary events can be deduced. Two milestone evolutionary events have been mapped to the 16S rRNA tree of Bacteria, one splitting the operon in two, and the other rejoining it by gene fusion. The Archaea, though less resolved due to a lesser genome representation, appear to exhibit more gene scrambling than the Bacteria. The trp operon appears to have been an ancient innovation; it was already present in the common ancestor of Bacteria and Archaea. Although the operon has been subjected, even in recent times, to dynamic changes in gene rearrangement, the ancestral gene order can be deduced with confidence. The evolutionary history of the genes of the pathway is discernible in rough outline as a vertical line of descent, with events of lateral gene transfer or paralogy enriching the analysis as interesting features that can be distinguished. As additional genomes are thoroughly analyzed, an increasingly refined resolution of the sequential evolutionary steps is clearly possible. These comparisons suggest that present-day trp operons that possess finely tuned regulatory features are under strong positive selection and are able to resist the disruptive evolutionary events that may be experienced by simpler, poorly regulated operons.

Why does differ?

Abstract The paper contends that man is most differentiated from other species in the nature of his sociality. In support of this thesis, the modes of social organization and the dynamics of evolutionary change in man and other animals are compared. The concluding section argues that man's material progress is due to his unique ability to employ modes of social organization which, by dealing effectively with the common property problem, permit the generation of ‘surplus’.