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PubMed1994

Collective phenomena in spatially extended evolutionary games.

A class of spatially extended evolutionary games with simple local rules is introduced. The emergent properties are studied through two complementary approaches. One is based on a heuristic local analysis, the other on exact global techniques. The local analysis provides criteria to group the games into classes with distinct behavior. The results facilitate numerical simulations and reveal that even simple games allow for complex spatio-temporal phenomena. The global analysis demonstrates that certain games perform an uphill march in a fitness landscape determined by the payoff parameters and the topology of the underlying lattice structure. For generic game parameters, the landscape is rugged owing to competing interactions and generates dynamical phenomena well known from frustrated systems: trapping in local maxima for noiseless dynamics and very long relaxation times for stochastic dynamics. Although the model is a mere caricature of evolutionary processes, some of its emergent properties are reminiscent of those observed in nature. It is argued that similar dynamical phenomena will be present in more elaborate approaches.

Animals↗
PubMed2001

The influence of predator--prey population dynamics on the long-term evolution of food web structure.

We develop a set of equations to describe the population dynamics of many interacting species in food webs. Predator-prey interactions are nonlinear, and are based on ratio-dependent functional responses. The equations account for competition for resources between members of the same species, and between members of different species. Predators divide their total hunting/foraging effort between the available prey species according to an evolutionarily stable strategy (ESS). The ESS foraging behaviour does not correspond to the predictions of optimal foraging theory. We use the population dynamics equations in simulations of the Webworld model of evolving ecosystems. New species are added to an existing food web due to speciation events, whilst species become extinct due to coevolution and competition. We study the dynamics of species-diversity in Webworld on a macro-evolutionary time-scale. Coevolutionary interactions are strong enough to cause continuous overturn of species, in contrast to our previous Webworld simulations with simpler population dynamics. Although there are significant fluctuations in species diversity because of speciation and extinction, very large-scale extinction avalanches appear to be absent from the dynamics, and we find no evidence for self-organized criticality.

Animals↗
PubMed2006

Extracellular matrix proteome of chickpea (Cicer arietinum L.) illustrates pathway abundance, novel protein functions and evolutionary perspect.

The extracellular matrix (ECM) or cell wall is a dynamic system and serves as the first line mediator in cell signaling to perceive and transmit extra- and intercellular signals in many pathways. Although ECM is a conserved compartment ubiquitously present throughout evolution, a compositional variation does exist among different organisms. ECM proteins account for 10% of the ECM mass, however, comprise several hundreds of different molecules with diverse functions. To understand the function of ECM proteins, we have developed the cell wall proteome of a crop legume, chickpea (Cicer arietinum). This comprehensive overview of the proteome would provide a basis for future comparative proteomic efforts for this important crop. Proteomic analyses revealed new ECM proteins of unknown functions vis-à-vis the presence of many known cell wall proteins. In addition, we report here evidence for the presence of unexpected proteins with known biochemical activities, which have never been associated with ECM.

Cell Wall↗
PubMed2000

Directionality theory and the evolution of body size.

Directionality theory, a dynamic theory of evolution that integrates population genetics with demography, is based on the concept of evolutionary entropy, a measure of the variability in the age of reproducing individuals in a population. The main tenets of the theory are three principles relating the response to the ecological constraints a population experiences, with trends in entropy as the population evolves under mutation and natural selection. (i) Stationary size or fluctuations around a stationary size (bounded growth): a unidirectional increase in entropy; (ii) prolonged episodes of exponential growth (unbounded growth), large population size: a unidirectional decrease in entropy; and (iii) prolonged episodes of exponential growth (unbounded growth), small population size: random, non-directional change in entropy. We invoke these principles, together with an allometric relationship between entropy, and the morphometric variable body size, to provide evolutionary explanations of three empirical patterns pertaining to trends in body size, namely (i) Cope's rule, the tendency towards size increase within phyletic lineages; (ii) the island rule, which pertains to changes in body size that occur as species migrate from mainland populations to colonize island habitats; and (iii) Bergmann's rule, the tendency towards size increase with increasing latitude. The observation that these ecotypic patterns can be explained in terms of the directionality principles for entropy underscores the significance of evolutionary entropy as a unifying concept in forging a link between micro-evolution, the dynamics of gene frequency change, and macro-evolution, dynamic changes in morphometric variables.

Animals↗
PubMed2002

Markers of disease evolution: the case of tuberculosis.

Abrupt changes in environmental conditions--broadly understood to include demographic and social dynamics--can seriously impact the local or global disease dynamics of a population. These changes in the evolutionary landscape, which may occur over relatively short time-scales, are very likely to play a critical role in disease evolution. The potential impact of demographic, social and epidemiological shifts on the evolution of tuberculosis epidemics in the United States over the past century and a half is the main subject of this article. Evidence is provided to support the hypothesis that the observed substantial decreases in the incidence of active tuberculosis are the result of abrupt reductions in the rates of disease progression.

Disease Outbreaks↗
PubMed1997

Stochastic processes in postural center-of-pressure profiles.

The stochastic processes of postural center-of-pressure profiles were examined in 3- and 5-year-old children, young adult students (mean 20 years), and an elderly age group (mean 67 years). Subjects stood still in an upright bipedal stance on a force platform under vision and nonvision conditions. The time evolutionary properties of the center-of-pressure dynamic were examined using basic stochastic process models. The amount of motion of the center of pressure decreased with increments of age from 3 to 5 years to young adult but increased again in the elderly age group. The availability of vision decreased the amount of motion of the center of pressure in all groups except the 3-year-old group, where there was less motion of the center of pressure with no vision. The stochastic properties of the center-of-pressure dynamic were assessed using both a two-process, random-walk model of Collins and De Luca and an Ornstein-Uhlenbeck model that is linear and has displacement governed only by a single stiffness term in the random walk. The two-process open- and closed-loop model accounted for about 96% and the Ornstein-Uhlenbeck model 92% of the variance of the diffusion term. Diffusion parameters in both models showed that the data were correlated and that they varied with age in a fashion consistent with developmental accounts of the changing regulation of the degrees of freedom in action. The findings suggest that it is premature to consider the trajectory of the center-of-pressure as a two-process, open- and closed-loop random-walk model given that: (a) the linear Ornstein-Uhlenbeck dynamic equation with only two parameters accommodates almost as much of the variance of the random walk; and (b) the linkage of a discontinuity in the diffusion process with the transition of open- to closed-loop processes is poorly founded. It appears that the nature of the stochastic properties of the random walk of the center-of-pressure trajectory in quiet, upright standing remains to be elucidated.

Adult↗
PubMed2006

Continuing education in nursing: a concept analysis.

The importance of continuing education for nurses has been increasingly emphasized in the nursing literature since the beginning of the profession. The concept of continuing education is often used as a substitute for associated terms such as continuing professional development and lifelong learning, thus highlighting a need for its clarification. The purpose of this article is to explain and describe continuing education, in order to encourage a broader understanding of the concept among nurses. The concept analysis is directed by Rodgers' [Rodgers, B.L., 1989. Concept analysis and the development of nursing knowledge: the evolutionary cycle. Journal of Advanced Nursing 14, 330-335] 'evolutionary approach' which is viewed as an ongoing dynamic process, and one that identifies the shared meaning of concepts. Examining everyday discourse used in the nursing literature identified the critical attributes, antecedents and consequence of continuing education in nursing. As a result, the emerging attributes of the concept are synthesised into a conceptual model. The article concludes with an exploration of the application of the concept of continuing education within nursing and its implications for professional development.

Concept Formation↗
PubMed2005

Game-theoretical approaches to studying the evolution of biochemical systems.

Evolutionary optimization has been successfully used to increase our understanding of key properties of biochemical systems. Traditional optimization is, however, often insufficient for gaining deeper insights into the evolution of such systems because usually there is a mutual relationship between the properties optimized by evolution and the properties of the environment. Thus, by evolving towards optimal properties, organisms change their environment, which in turn alters the optimum. Evolutionary game theory provides an appropriate framework for analyzing evolution in such 'dynamic fitness landscapes'. We therefore argue that it is a promising approach to studying the evolution of biochemical systems. Indeed, recent studies have applied evolutionary game theory to key issues in the evolution of energy metabolism.

Evolution, Molecular↗
PubMed2002

Bionformation: untangling the networks of life.

The growth of numerous subdisciplines at the interface between biology and computer science paves the way for reconsidering the special relationship between information and life. In this sense, the term 'bioinformation' appears as an integrative notion that is useful to promote a new understanding of the heterogeneous networkings that characterize life. Two conceptual avenues are explored here: representation and symmetry. It is argued that the special organization of the living cell, based on the overlapping of both sequential and 'amorphous' architectures, endlessly strives to fill in the occurring 'functional voids' or symmetry breakings; and it endlessly produces physiological networkings and evolutionary novelties as a byproduct. Characterizing the special dynamics inherent in the living cell may be a precondition for understanding the information-production processes on which other emergent informational entities are based, particularly, nervous systems and societies.

Animals↗
PubMed1999

On delayed impulsive Hopfield neural networks(1).

Many evolutionary processes, particularly some biological systems, exhibit impulsive dynamical behaviors, which can be well described by impulsive Hopfield neural networks. This paper formulates and studies a model of delayed impulsive Hopfield neural networks. Several fundamental issues such as global exponential stability, existence and uniqueness of the equilibrium of such networks are established. A numerical example is given for illustration and interpretation of the theoretical results.

Journal Article↗
PubMed2001

Chromosomal distribution of reverse transcriptase-containing retroelements in two Triticeae species.

A large portion of plant and particularly cereal genomes consist of repetitive DNA families, many of which are likely to be or to have evolved from retroelements. Molecular evidence suggests that repeated DNA sequences, although perhaps originating as innocuous or 'selfish' elements, can have dramatic effects on genome organization and function. Knowledge of chromosomal distribution of retroelements is important for understanding plant chromosome structure/functional organization, and could shed light on the dynamics of retroelements and their role in the evolutionary process. In the present study we aim to find a possible correlation between physical location of the regions with species-specific sequences and the distribution of conserved RT domains of the Ty1-copia, Ty3-gypsy and LINE groups of retroelements on the chromosomes of two diploid species that belong to the different branches of the tribe Triticeae, namely Aegilops speltoides Tausch (2n=2x=14) and Hordeum spontaneum L (2n=2x=14). All three groups of retroelements were found in large quantities in the genomes of the tested species. They are cluster-distributed, and the important role of these elements in the formation of terminal heterochromatin is shown. We found that there was a predominance of Ty1-copia and LINE elements in the chromosome regions with preferential content of species-specific sequences.

Chromosomes↗
PubMed2006

Phylogeography and systematics of zebra mussels and related species.

The genus Dreissena includes two widespread and aggressive aquatic invaders, the zebra mussel, Dreissena polymorpha, and the quagga mussel, Dreissena bugensis. This genus evolved in the Ponto-Caspian Sea basin, characterized by dynamic instability over multiple timescales and a unique evolutionary environment that may predispose to invasiveness. The objectives of this study were to gain insights into the demographic history of Dreissena species in their endemic range, to reconstruct intraspecific phylogeographic relationships among populations, and to clarify systematics of the genus, using DNA sequences from the mitochondrial cytochrome oxidase I (COI) gene. We found four deeply diverged clades within this genus, with a basal split that approximately coincided with the Cretaceous-Tertiary boundary. Divergence events within the four base clades were much more recent, corresponding to geographically disjunct sets of populations, which might represent species complexes. Across all taxa, populations of Dreissena shared a common pattern of genetic signatures indicating historical population bottlenecks and expansions. Haplotype diversity was relatively low in Ponto-Caspian drainages relative to more stable tectonic lakes in Greece, Macedonia, and Turkey. The phylogeographic and demographic patterns in the endemic range of Dreissena might have resulted from vicariance events, habitat instability, and the high fecundity and passive dispersal of these organisms.

Animal Migration↗
PubMed2000

Closure in the emergence and evolution of life. Multiple discourses or one?

Evolutionary theory formulated in terms of complex systems dynamics shows interesting convergences with the approaches of developmental systems theory and biosemiotics, especially when applied to the problem of the origin of life. Although starting from difference conceptual assumptions, all three approaches agree on the importance of closure in the form of semipermeable chemical and informational boundaries and a more circumscribed role for DNA.

Communication↗
PubMed2025

Extensive Introgression Failed to Erode Species Boundaries Among Multiple Sympatric Closely Related Species of Roscoea.

How species boundaries are maintained among sympatric closely related species experiencing gene flow is a puzzling question in evolutionary biology. Although introgression is commonly documented, the dynamics and gene function of introgression have rarely been explored to probe why frequent introgression does not necessarily destroy species boundaries in sympatry. In this study, we employ whole-genome resequencing data to examine introgression among five closely related species of Roscoea that coexist in a 'sky island' with seventeen distinct morphological traits. Our findings reveal that introgression has led to the phylogenomic discordance between nuclear and chloroplast genomes among these morphologically distinct species. Additionally, introgression is predominantly asymmetrical in both intensity and gene function, particularly concerning recombination. Notably, the majority of gene functions associated with introgressed loci are unrelated to reproductive processes. Our results suggest that closely related species with incomplete allele assortment can coexist despite theoretical predictions, highlighting the semipermeable nature of species boundaries as reproductive isolation develops. This provides a critical conceptual framework for understanding the interplay between introgression and species persistence. Our finding offers insights into how related sympatric species boundaries can be maintained in the face of frequent asymmetrical gene introgression.

Sympatry↗
PubMed1990

[Rehabilitation of the rheumatoid hand].

Treatment of patients suffering from rheumatoid arthritis is complicated and it consists mainly of applying general measures, medical therapy, physical therapy and rehabilitation, and, if necessary, surgical - orthopedic measures. The treatment is conducted as team work and it lasts for years. The chronic and evolutionary character of the disease requires a rather dynamic effort against the onset of joint deformation as well as the constant follow up of the evolution of the disease, and the local condition of the joints. Within the examined group of a hundred patients with classical and definitive rheumatoid arthritis, formed deformations of hand joints were registered in 72% of patients by means of clinical examination. Preventive measures against joint deformation make an integral part of rheumatoid arthritis patient treatment. Their application starts from the moment when the diagnosis is made and lasts as long as the disease does.

Adult↗
PubMed2003

Spatial models of prebiotic evolution: soup before pizza?

The problem of information integration and resistance to the invasion of parasitic mutants in prebiotic replicator systems is a notorious issue of research on the origin of life. Almost all theoretical studies published so far have demonstrated that some kind of spatial structure is indispensable for the persistence and/or the parasite resistance of any feasible replicator system. Based on a detailed critical survey of spatial models on prebiotic information integration, we suggest a possible scenario for replicator system evolution leading to the emergence of the first protocells capable of independent life. We show that even the spatial versions of the hypercycle model are vulnerable to selfish parasites in heterogeneous habitats. Contrary, the metabolic system remains persistent and coexistent with its parasites both on heterogeneous surfaces and in chaotically mixing flowing media. Persistent metabolic parasites can be converted to metabolic cooperators, or they can gradually obtain replicase activity. Our simulations show that, once replicase activity emerged, a gradual and simultaneous evolutionary improvement of replicase functionality (speed and fidelity) and template efficiency is possible only on a surface that constrains the mobility of macromolecule replicators. Based on the results of the models reviewed, we suggest that open chaotic flows ('soup') and surface dynamics ('pizza') both played key roles in the sequence of evolutionary events ultimately concluding in the appearance of the first living cell on Earth.

Animals↗
PubMed1999

Zoite migration during infection: parasite adaptation to host defences.

The apicomplexan parasite Eimeria tenella has evolved a number of strategies for migration into different compartments of the intestinal tissue during its life cycle. These migration events are associated intricately with pathogenesis and are currently of great interest to coccidiologists. Using evidence from in vivo studies and recent work on the dynamics of gut cell turnover, Peter Daszak suggests that E. tenella zoite migration might be viewed as parasite evolutionary adaptation to evade the host innate immune responses (resistance) and deal with the complex, dynamic nature of gut epithelial tissue.

Adaptation, Physiological↗
PubMed2006

Co-evolution of transcription factors and their targets depends on mode of regulation.

BACKGROUND: Differences in the transcription regulation network are at the root of much of the phenotypic variation observed among organisms. These differences may be achieved either by changing the repertoire of regulators and/or their targets, or by rewiring the network. Following these changes and studying their logic is crucial for understanding the evolution of regulatory networks. RESULTS: We use the well characterized transcription regulatory network of Escherichia coli K12 and follow the evolutionary changes in the repertoire of regulators and their targets across a large number of fully sequenced gamma-proteobacteria. By focusing on close relatives of E. coli K12, we study the dynamics of the evolution of transcription regulation across a relatively short evolutionary timescale. We show significant differences in the evolution of repressors and activators. Repressors are only lost from a genome once their targets have themselves been lost, or once the network has significantly rewired. In contrast, activators are often lost even when their targets remain in the genome. As a result, E. coli K12 repressors that regulate many targets are rarely absent from organisms that are closely related to E. coli K12, while activators with a similar number of targets are often absent in these organisms. CONCLUSION: We demonstrate that the mode of regulation exerted by transcription factors has a strong effect on their evolution. Repressors co-evolve tightly with their target genes. In contrast, activators can be lost independently of their targets. In fact, loss of an activator can lead to efficient shutdown of an unnecessary pathway.

Escherichia coli↗