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PubMed2006

Evolutionary selective trends of insect/mosquito antimicrobial defensin peptides containing cysteine-stabilized alpha/beta motifs.

Insect defensins containing cysteine-stabilized alpha/beta motifs (Cs-alpha/beta defensin) are cationic, inducible antibacterial peptides involved in humoral defence against pathogens. To examine trends in molecular evolution of these antimicrobial peptides, sequences similar to the well-characterized Cs-alpha/beta defensin peptide of Anopheles gambiae, using six cysteine residues as landmarks, were retrieved from genomic and protein databases. These sequences were derived from different orders of insects. Genes of insect Cs-alpha/beta defensin appear to constitute a multigene family in which the copy number varies between insect species. Phylogenetic analysis of these sequences revealed two main lineages, one group comprising mainly lepidopteran insects and a second, comprising Hemiptera, Coleoptera, Diptera and Hymenoptera insects. Moreover, the topology of the phylogram indicated dipteran Cs-alpha/beta defensins are diverse, suggesting diversity in immune mechanisms in this order of insects. Overall evolutionary analysis indicated marked diversification and expansion of mature defensin isoforms within the species of mosquitoes relative to non-mosquito defensins, implying the presence of finely tuned immune responses to counter pathogens. The observed higher synonymous substitution rate relative to the nonsynonymous rate in almost all the regions of Cs-alpha/beta defensin of mosquitoes suggests that these peptides are predominately under purifying selection. The maximum-likelihood models of codon substitution indicated selective pressure at different amino acid sites in mosquito mature Cs-alpha/beta defensins is differ and are undergoing adaptive evolution in comparison to non-mosquito Cs-alpha/beta defensins, for which such selection was inconspicuous; this suggests the acquisition of selective advantage of the Cs-alpha/beta defensins in the former group. Finally, this study represents the most detailed report on the evolutionary strategies of Cs-alpha/beta defensins of mosquitoes in particular and insects in general, and indicates that insect Cs-alpha/beta defensins have evolved by duplication followed by divergence, to produce a diverse set of paralogues.

Amino Acid Motifs↗
PubMed2006

March 27, 1827 and what happened later--the impact of psychiatry on evolutionary theory.

In the interaction between Psychiatry and evolutionary theory the force of the impact has not always been in one direction. The Brownes, father and son, had an influence on the development of Darwin's theory at different points in the nineteenth century. The crystallization by Miskolczy in 1933 of the concept that schizophrenia is a disorder that is specific to Homo sapiens is another example. In 1964 the formulation of the central paradox of psychosis by Huxley, Mayr and co-authors and the subsequent critique by Kuttner et al. of the solution Huxley et al. had offered opened up evolutionary approaches to aetiology. Here it is argued that a resolution of this paradox requires identification of the speciation event for modern H. sapiens and elucidation of its neuroanatomical and physiological consequences. It necessitates a saltational account of species transitions and the recognition of species-specific genetic variation. Pursuit of these objectives leads to the hypothesis that speciation events occur selectively on the heterogametic chromosome (the Y in mammals) and are followed by a phase of sexual selection to establish a new specific mate recognition system. In H. sapiens the core component of this system is the capacity for language; the nuclear symptoms of schizophrenia are necessary clues to its neural structure.

Animals↗
PubMed2006

The normalcy of neurosis: evolutionary origins of obsessive-compulsive disorder and related behaviors.

One of the most curious questions plaguing subscribers of evolutionary theory is how natural selection's fine-tuned editing function could allow disease to persist. For evolutionary psychiatrists, the existence of psychopathology is thus perplexing. To illustrate a potential answer to one instance of this broad question, we examine the correlates of obsessive-compulsive disorder (OCD) within our normal repertoire of thought and action. The evidence presents a picture of OCD as a dysregulation of normal behaviors and mental states throughout the course of human development. We speculate that such correspondence may be more than a coincidence and that OCD is a consequence of a dysregulation of the neural circuits that are crucially involved in threat detection and harm avoidance. These neural systems are also likely to underlie aspects of religious experience and ritual as well as the wonders of romantic and early parental love.

Animals↗
PubMed2005

The evolutionary origin of genetic instability in cancer development.

The standard model of carcinogenesis is currently being questioned. The main controversy concerns genetic instability and has links to fundamental questions in evolutionary biology. This paper aims to clarify the underlying conflict between the linear configuration of the standard model and the non-linear dynamics of Darwinian evolution. It addresses the problem of applying the concept of clonal selection to genetically unstable cells and presents an alternative perspective based on the principles of molecular evolution. This model explains genetic instability in terms of competition between genetic strategies and draws lines to basic aspects of evolutionary biology.

Animals↗
PubMed2026

Evolutionary and resistance dynamics in oligometastatic and oligoprogressive cancer treated with stereotactic radiotherapy and systemic therapies: A systematic review and focused meta-analysis.

BACKGROUND: Oligometastatic and oligoprogressive disease treated with stereotactic ablative radiotherapy (SABR) represents a clinically heterogeneous entity. Increasing evidence suggests that anatomical definitions alone may not adequately capture underlying biological diversity. This systematic review aimed to synthesize translational evidence exploring evolutionary dynamics, resistance mechanisms, and biomarker-driven stratification in patients treated with SABR. METHODS: A systematic literature review was performed including prospective and retrospective studies evaluating translational biomarkers in oligometastatic or oligoprogressive settings treated with SABR. Studies assessing genomic, transcriptomic, circulating or immune-related biomarkers were included. Data were summarized qualitatively according to predefined translational domains: (i) evolutionary dynamics under systemic therapy pressure, (ii) baseline biological stratification, (iii) longitudinal circulating biomarkers, and (iv) systemic immune remodeling. Exploratory quantitative visual syntheses were performed using reported hazard ratios when conceptually comparable endpoints were available. RESULTS: 19 studies comprising 1527 patients were included. Across tumor types and treatment contexts, translational analyses consistently indicated that anatomically defined oligometastatic states encompass biologically distinct subgroups with different risks of systemic progression. Studies evaluating oligoprogression under ongoing systemic therapy suggested a distinction between spatially constrained resistance and systemic molecular escape, supported by circulating tumor DNA and tissue- or plasma-based molecular profiling (including genomic and transcriptomic analyses). Baseline biological features, including adverse genomic signatures and circulating biomarkers, were associated with inferior progression outcomes despite metastasis-directed therapy. Longitudinal biomarkers provided early signals of treatment response and systemic control. Immune remodeling after SABR showed context-dependent effects, both systemic immune activation and treatment-related immunosuppression reported across studies.

Humans↗
PubMed2006

Two different evolutionary origins of stem cell systems and their molecular basis.

We propose two major evolutionary origins of stem cell systems in the animal kingdom. Adult pluripotent stem cell systems are found in many invertebrates and probably evolved as components of asexual reproduction. Lineage-specific stem cell systems probably evolved later and include neural and hematopoietic stem cell types. We propose that these two types of stem cell systems evolved independently. The vasa-like genes regulate reproductive stem cells, but not lineage-specific stem cells, which may be regulated by gcm genes. Here, we review the evidence for the molecular basis for the evolutionary origin of these two different stem cell systems.

Animals↗
PubMed2006

Organisms as natural purposes: the contemporary evolutionary perspective.

Kant's conception of organisms as natural purposes raises a challenge to the adequacy of mechanistic explanation in biology. Certain features of organisms appear to be inexplicable by appeal to mechanical law alone. Some biological phenomena, it seems, can only be accounted for teleologically. Contemporary evolutionary biology has by and large ignored this challenge. It is widely held that Darwin's theory of natural selection gives us an adequate, wholly mechanical account of the nature of organisms. In contemporary biology, the category of the organism plays virtually no explanatory role. Contemporary evolutionary biology is a science of sub-organismal entities-replicators. I argue that recent advances in developmental biology demonstrate the inadequacy of sub-organismal mechanism. The category of the organism, construed as a 'natural purpose' should play an ineliminable role in explaining ontogenetic development and adaptive evolution. According to Kant the natural purposiveness of organisms cannot be demonstrated to be an objective principle in nature, nor can purposiveness figure in genuine explain. I attempt to argue, by appeal to recent work on self-organization, that the purposiveness of organisms is a natural phenomenon, and, by appeal to the apparatus of invariance explanation, that biological purposiveness provides genuine, ineliminable biological explanations.

Biological Evolution↗
PubMed2004

Characterizing the evolutionary dynamics of language.

In a recent article Mitchener and Nowak present a model of the evolutionary dynamics of language. The model exhibits regular and chaotic oscillations in changes to the proportions of grammars spoken in a population over the course of evolution. These oscillations are within the purview of evolutionary game theory, but they suggest the lack of an evolutionarily stable strategy. Implications for self-organization across scales of adaptation are discussed.

Adaptation, Psychological↗
PubMed2005

An evolutionary framework for common diseases: the ancestral-susceptibility model.

Unlike rare mendelian diseases, which are due to new mutations (i.e. derived alleles), several alleles that increase the risk to common diseases are ancestral. Moreover, population genetics studies suggest that some derived alleles that protect against common diseases became advantageous recently. These observations can be explained within an evolutionary framework in which ancestral alleles reflect ancient adaptations to the lifestyle of ancient human populations, whereas the derived alleles were deleterious. However, with the shift in environment and lifestyle, the ancestral alleles now increase the risk of common diseases in modern populations. In this article, we develop an explicit evolutionary model and use population genetics simulations to investigate the expected haplotype structure and type of disease-association signals of ancestral risk alleles.

Alleles↗
PubMed2005

The evolutionary dynamics of endogenous retroviruses.

Endogenous retroviruses (ERVs) are vertically transmitted intragenomic elements derived from integrated retroviruses. ERVs can proliferate within the genome of their host until they either acquire inactivating mutations or are lost by recombinational deletion. We present a model that unifies current knowledge of ERV biology into a single evolutionary framework. The model predicts the possible long-term outcomes of retroviral germline infection and can account for the variable patterns of observed ERV genetic diversity. We hope the model will provide a useful framework for understanding ERV evolution, enabling the testing of evolutionary hypotheses and the estimation of parameters governing ERV proliferation.

Endogenous Retroviruses↗
PubMed2006

Unifying evolutionary dynamics: from individual stochastic processes to macroscopic models.

A distinctive signature of living systems is Darwinian evolution, that is, a propensity to generate as well as self-select individual diversity. To capture this essential feature of life while describing the dynamics of populations, mathematical models must be rooted in the microscopic, stochastic description of discrete individuals characterized by one or several adaptive traits and interacting with each other. The simplest models assume asexual reproduction and haploid genetics: an offspring usually inherits the trait values of her progenitor, except when a mutation causes the offspring to take a mutation step to new trait values; selection follows from ecological interactions among individuals. Here we present a rigorous construction of the microscopic population process that captures the probabilistic dynamics over continuous time of birth, mutation, and death, as influenced by the trait values of each individual, and interactions between individuals. A by-product of this formal construction is a general algorithm for efficient numerical simulation of the individual-level model. Once the microscopic process is in place, we derive different macroscopic models of adaptive evolution. These models differ in the renormalization they assume, i.e. in the limits taken, in specific orders, on population size, mutation rate, mutation step, while rescaling time accordingly. The macroscopic models also differ in their mathematical nature: deterministic, in the form of ordinary, integro-, or partial differential equations, or probabilistic, like stochastic partial differential equations or superprocesses. These models include extensions of Kimura's equation (and of its approximation for small mutation effects) to frequency- and density-dependent selection. A novel class of macroscopic models obtains when assuming that individual birth and death occur on a short timescale compared with the timescale of typical population growth. On a timescale of very rare mutations, we establish rigorously the models of "trait substitution sequences" and their approximation known as the "canonical equation of adaptive dynamics". We extend these models to account for mutation bias and random drift between multiple evolutionary attractors. The renormalization approach used in this study also opens promising avenues to study and predict patterns of life-history allometries, thereby bridging individual physiology, genetic variation, and ecological interactions in a common evolutionary framework.

Algorithms↗
PubMed2006

Echocardiographic evaluation of the evolutionary changes after heart transplantation.

AIM: To undertake an evolutionary analysis of echocardiographic examinations carried out during follow-up of cardiac transplant patients. MATERIALS AND METHODS: The study included 193 consecutive patients transplanted between August 1998 and December 2004. We excluded pediatric, cardiopulmonary, and repeat transplants. Four echocardiographic examinations were analyzed per patient (first, second, third quarter and the last study carried out; average time from transplant: 1115 +/- 681 days). The total number of examinations was 772. The evaluated variables were thickness of walls and diameters of the cavities, systolic and diastolic functions, pericardial effusion, and number of rejections. RESULTS: The isovolumetric relaxation time showed reduced values during early echocardiography with subsequent increases during evolution (first echocardiogram: 92 +/- 16 vs final echocardiogram 101 +/- 16 ms; P < .0001). Right ventricular function showed initial deterioration with subsequent recovery (first echocardiogram: 16% vs final echocardiogram: 8%; P < .05); moreover, the existence of delayed malfunction of the right ventricle was correlated with a higher incidence of transplant rejection (P < .01). Pericardial effusion was initially present with a tendency to reduce over time (first echocardiogram: 58% vs final echocardiogram: 12%; P < .0001). There was no difference in the other variables. CONCLUSIONS: Cardiac transplant patients undergo evolutionary echocardiogram alterations that were mainly early and normalized as of the first quarter. The most usual changes in this period were restrictive isovolumetric behavior accompanied by some degree of depressed right ventricular function. Right ventricular malfunction during late evolution was correlated with a higher incidence of transplant rejection during follow-up.

Electrocardiography↗
PubMed2004

Ecological and evolutionary consequences of biotic homogenization.

Biotic homogenization, the gradual replacement of native biotas by locally expanding non-natives, is a global process that diminishes floral and faunal distinctions among regions. Although patterns of homogenization have been well studied, their specific ecological and evolutionary consequences remain unexplored. We argue that our current perspective on biotic homogenization should be expanded beyond a simple recognition of species diversity loss, towards a synthesis of higher order effects. Here, we explore three distinct forms of homogenization (genetic, taxonomic and functional), and discuss their immediate and future impacts on ecological and evolutionary processes. Our goal is to initiate future research that investigates the broader conservation implications of homogenization and to promote a proactive style of adaptive management that engages the human component of the anthropogenic blender that is currently mixing the biota on Earth.

Journal Article↗
PubMed2004

Vicious circles: positive feedback in major evolutionary and ecological transitions.

Evolutionary biologists and ecologists often focus on equilibrium states that are subject to forms of negative feedback, such as optima for phenotypic traits or regulation of population sizes. However, recent theoretical and empirical studies show how positive feedback can be instrumental in driving many of the most important and spectacular processes in evolutionary ecology, including the evolution of sex and genetic systems, mating systems, life histories, complex cooperation in insects and humans, ecological specialization, species diversity, species ranges, speciation and extinction. Taken together, this work suggests that positive feedback is more common than is generally appreciated, and that its self-reinforcing dynamics generate the conditions for changes that might otherwise be difficult or impossible for selection or other mechanisms to achieve. Testing for positive feedback requires analysing each causal link in feedback loops, tracking genetic, character and population-dynamic changes across generations, and elucidating the conditions that can result in self-reinforcing change.

Journal Article↗
PubMed2004

Towards an evolutionary ecology of life in soil.

The soil-microbe system is one of the most diverse components of the terrestrial ecosystem. The origin of this diversity, and its relation to the life-sustaining processes that are mediated by the resident microbial community, is still poorly understood. The inherent complexities necessitate a theoretical framework that integrates ecological and evolutionary approaches and which embraces the physical heterogeneity of the soil environment. Such a framework is currently lacking, although recent advances in theory and experimentation are beginning to identify the essential ingredients. Here, we review and evaluate the relevance of current modelling approaches, and propose a new synthesis of an evolutionary ecology of life in soil. Key elements include an account of dispersal, horizontal gene transfer, and the consideration of the physical and biological components of soil as an integrated complex adaptive system.

Journal Article↗
PubMed2005

The evolutionary and ecological benefits of asteroid and comet impacts.

Commonly viewed solely as agents of destruction, asteroid and comet impact events can also have a beneficial influence on processes from the molecular to the evolutionary scale. On the heavily bombarded early Earth, impacts might have delivered and caused the synthesis of prebiotic compounds that eventually led to life. At the organismal and ecosystem level, impact events can provide new habitats through the shock processing of target materials and by enhancing water availability, such as within intracrater lakes. At the evolutionary level, by destroying entire groups of organisms, impacts might have been instrumental in enabling the rise of new groups, such as the dinosaurs and mammals. Here, we synthesize the emerging literature on the beneficial effects of impacts to provide a novel perspective on these extraterrestrial agents of biological change.

Journal Article↗
PubMed2005

Information and its use by animals in evolutionary ecology.

Information is a crucial currency for animals from both a behavioural and evolutionary perspective. Adaptive behaviour relies upon accurate estimation of relevant ecological parameters; the better informed an individual, the better it can develop and adjust its behaviour to meet the demands of a variable world. Here, we focus on the burgeoning interest in the impact of ecological uncertainty on adaptation, and the means by which it can be reduced by gathering information, from both 'passive' and 'responsive' sources. Our overview demonstrates the value of adopting an explicitly informational approach, and highlights the components that one needs to develop useful approaches to studying information use by animals. We propose a quantitative framework, based on statistical decision theory, for analysing animal information use in evolutionary ecology. Our purpose is to promote an integrative approach to studying information use by animals, which is itself integral to adaptive animal behaviour and organismal biology.

Journal Article↗
PubMed2005

Evolutionary biology of cancer.

Cancer is driven by the somatic evolution of cell lineages that have escaped controls on replication and by the population-level evolution of genes that influence cancer risk. We describe here how recent evolutionary ecological studies have elucidated the roles of predation by the immune system and competition among normal and cancerous cells in the somatic evolution of cancer. Recent analyses of the evolution of cancer at the population level show how rapid changes in human environments have augmented cancer risk, how strong selection has frequently led to increased cancer risk as a byproduct, and how anticancer selection has led to tumor-suppression systems, tissue designs that slow somatic evolution, constraints on morphological evolution and even senescence itself. We discuss how applications of the tools of ecology and evolutionary biology are poised to revolutionize our understanding and treatment of this disease.

Journal Article↗