195,282 research outputs found

    Making the most of clade selection

    Get PDF
    Clade selection is unpopular with philosophers who otherwise accept multilevel selection theory. Clades cannot reproduce, and reproduction is widely thought necessary for evolution by natural selection, especially of complex adaptations. Using microbial evolutionary processes as heuristics, I argue contrariwise, that (1) clade growth (proliferation of contained species) substitutes for clade reproduction in the evolution of complex adaptation, (2) clade-level properties favoring persistence – species richness, dispersal, divergence, and possibly intraclade cooperation – are not collapsible into species-level traits, (3) such properties can be maintained by selection on clades, and (4) clade selection extends the explanatory power of the theory of evolution

    Microbial ecology of extreme environments: Antarctic dry valley yeasts and growth in substrate-limited habitats

    Get PDF
    The success of the Antarctic Dry Valley yeasts presumeably results from adaptations to multiple stresses, to low temperatures and substrate-limitation as well as prolonged resting periods enforced by low water availability. Previous investigations have suggested that the crucial stress is substrate limitation. Specific adaptations may be pinpointed by comparing the physiology of the Cryptococcus vishniacii complex, the yeasts of the Tyrol Valley, with their congeners from other habitats. Progress was made in methods of isolation and definition of ecological niches, in the design of experiments in competition for limited substrate, and in establishing the relationships of the Cryptococcus vishniacii complex with other yeasts. In the course of investigating relationships, a new method for 25SrRNA homology was developed. For the first time it appears that 25SrRNA homology may reflect parallel or convergent evolution

    Fossilized skin reveals coevolution with feathers and metabolism in feathered dinosaurs and early birds

    Get PDF
    Feathers are remarkable evolutionary innovations that are associated with complex adaptations of the skin in modern birds. Fossilised feathers in non-avian dinosaurs and basal birds provide insights into feather evolution, but how associated integumentary adaptations evolved is unclear. Here we report the discovery of fossil skin, preserved with remarkable nanoscale fidelity, in three non-avian maniraptoran dinosaurs and a basal bird from the Cretaceous Jehol biota (China). The skin comprises patches of desquamating epidermal corneocytes that preserve a cytoskeletal array of helically coiled α-keratin tonofibrils. This structure confirms that basal birds and non-avian dinosaurs shed small epidermal flakes as in modern mammals and birds, but structural differences imply that these Cretaceous taxa had lower body heat production than modern birds. Feathered epidermis acquired many, but not all, anatomically modern attributes close to the base of the Maniraptora by the Middle Jurassic

    Home birth midwifery in the United States: evolutionary origins and modern challenges

    Full text link
    Human childbirth is distinct in requiring-or at least strongly profiting from-the assistance of a knowledgeable attendant to support the mother during birth. With economic modernization, the role of that attendant is transformed, and increased access to obstetric interventions may bring biomedicine into conflict with anatomical, physiological, and behavioral adaptations for childbirth. This article provides an overview of the role of midwifery in human evolution and ways in which this evolutionary heritage is reflected in home birth in the contemporary United States. Opportunities remain for evolutionary scholars to apply their knowledge and skills to strengthen culturally consonant, evolutionarily grounded maternity care within a complex, multilevel, pluralistic medical system

    Evolution of Complex Features in Digital Organisms

    Get PDF
    This thesis examines how complex features evolve in digital organisms, and how capabilities that evolved earlier provide a scaffold for evolving new features. I wanted to see how the organisms used previous adaptations to succeed in new environments, and how significant are these previous adaptations. The system used is the Avida platform, which is software that implements Darwinian evolution on self-replicating digital organisms. First, the system is seeded with ancestors that can only replicate, which gave a baseline for the quality of the task at the end of evolution. Second, the system used ancestors from a simpler environment as seeds. I observed that the quality of the task improved, but not drastically except for one of the environments. Lastly, the organism gets transferred form the simplest environment to the most complex one. I observed that only when the transplant included a similar complex adaptation the improvement was remarkable

    Evolution combined with genomic study elucidates genetic bases of isobutanol tolerance in Escherichia coli

    Get PDF
    <p>Abstract</p> <p>Background</p> <p>Isobutanol is a promising next-generation biofuel with demonstrated high yield microbial production, but the toxicity of this molecule reduces fermentation volumetric productivity and final titer. Organic solvent tolerance is a complex, multigenic phenotype that has been recalcitrant to rational engineering approaches. We apply experimental evolution followed by genome resequencing and a gene expression study to elucidate genetic bases of adaptation to exogenous isobutanol stress.</p> <p>Results</p> <p>The adaptations acquired in our evolved lineages exhibit antagonistic pleiotropy between minimal and rich medium, and appear to be specific to the effects of longer chain alcohols. By examining genotypic adaptation in multiple independent lineages, we find evidence of parallel evolution in <it>marC</it>, <it>hfq</it>, <it>mdh</it>, <it>acrAB, gatYZABCD</it>, and <it>rph </it>genes. Many isobutanol tolerant lineages show reduced RpoS activity, perhaps related to mutations in <it>hfq </it>or <it>acrAB</it>. Consistent with the complex, multigenic nature of solvent tolerance, we observe adaptations in a diversity of cellular processes. Many adaptations appear to involve epistasis between different mutations, implying a rugged fitness landscape for isobutanol tolerance. We observe a trend of evolution targeting post-transcriptional regulation and high centrality nodes of biochemical networks. Collectively, the genotypic adaptations we observe suggest mechanisms of adaptation to isobutanol stress based on remodeling the cell envelope and surprisingly, stress response attenuation.</p> <p>Conclusions</p> <p>We have discovered a set of genotypic adaptations that confer increased tolerance to exogenous isobutanol stress. Our results are immediately useful to further efforts to engineer more isobutanol tolerant host strains of <it>E. coli </it>for isobutanol production. We suggest that <it>rpoS </it>and post-transcriptional regulators, such as <it>hfq</it>, RNA helicases, and sRNAs may be interesting mutagenesis targets for future global phenotype engineering.</p

    Mapping Information Flows That Support Adaptive Capacity in the Sterile Processing Department (SPD)

    Get PDF
    The Sterile Processing Department (SPD) is the part of the hospital that is responsible for decontaminating, assembling, and sterilizing surgical trays for use in the Operating Rooms (ORs). Errors in the SPD can lead to delayed surgeries or patient harm. The SPD is a complex system, with multiple interconnected subdepartments and roles. Complex systems require coordination between stakeholders. This study aims to discover how an organization can adapt to scale, and how information flows support these adaptations. In this study, observations, semi-structured interviews, and on-the-job interviews were conducted with members across the SPD and OR to elicit pressures, adaptations, and their corresponding information flows to understand the how coordination supports adaptive capacity in the SPD. A qualitative data analysis was conducted to find themes related to adaptations and coordination. Themes involving pressures include missing instruments and lack of proper staffing. Frequent adaptations include role evolution, prioritization, and anticipation. Coordination themes include unreliable artifacts and mistrust between the OR and the SPD. Maps of the adaptive workflows were created to visualize how pressures affect the textbook workflow, the responsive adaptations to overcome the pressures, and the information flow paths that support these adaptations. These findings can be used to provide insights to improve coordination and adaptive capacity of the SPD

    In ovo omnia: diversification by duplication in fish and other vertebrates

    Get PDF
    Gene and genome duplications are considered to be the main evolutionary mechanisms contributing to the unrivalled biodiversity of bony fish. New studies of vitellogenin yolk proteins, including a report in BMC Evolutionary Biology, reveal that the genes underlying key evolutionary innovations and adaptations have undergone complex patterns of duplication and functional evolution
    corecore