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PubMed1996

Ecological factors rather than temporal factors dominate the evolution of vesicular stomatitis virus.

Vesicular stomatitis New Jersey virus (VSV-NJ) is a rhabdovirus that causes economically important disease in cattle and other domestic animals in endemic areas from southeastern United States to northern South America. Its negatively stranded RNA genome is capable of undergoing rapid evolution, which allows phylogenetic analysis and molecular epidemiology studies to be performed. Previous epidemiological studies in Costa Rica showed the existence of at least two distinct ecological zones of high VSV-NJ activity, one located in the highlands (premontane tropical moist forest) and the other in the lowlands (tropical dry forest). We wanted to test the hypothesis that the viruses circulating in these ecological zones were genetically distinct. For this purpose, we sequenced the hypervariable region of the phosphoprotein gene for 50 VSV-NJ isolates from these areas. Phylogenetic analysis showed that viruses from each ecological zone had distinct genotypes. These genotypes were maintained in each area for periods of up to 8 years. This evolutionary pattern of VSV-NJ suggests an adaptation to ecological factors that could exert selective pressure on the virus. As previous data indicated an absence of virus adaptation to factors related to the bovine host (including immunological pressure), it appears that VSV genetic divergence represents positive selection to adapt to specific vectors and/or reservoirs at each ecological zone.

Animals↗
PubMedDate not supplied

Selection of ecologic covariates in the American Cancer Society study.

The American Cancer Society (ACS) Study of the effects of long-term exposure to ambient air pollution on mortality used metropolitan areas to assign exposures to individual cohort members (Pope et al., 1995); these authors did not, however, control for any other place-specific variables in their analysis. Consequently, the study has been criticized on the basis that the association observed between air pollution and mortality may be confounded by other unmeasured ecologic covariates. To address this criticism, the reanalysis team selected a set of place-specific variables that measured determinants of health ranging from the biophysical environment to the social environment and the healthcare system. This article outlines the process by which place-specific ecologic covariates were selected; data measuring these variables were obtained and geographic boundaries for places were delineated. Issues involved in obtaining and using geographically based ecological data are examined within the context of the reanalysis of the ACS study. Both the ecological fallacy and the atomistic fallacy are addressed and an argument is made for the importance of studying the effects of place-specific variables that are integral or contextual in nature. Issues relating to the Modifiable Areal Unit Problem (MAUP) are explored with reference to using ZIP codes and data from a variety of sources. It is argued that differences in the geographical scale of variability for various pollutants may prove to be the key to distinguishing between their relative impacts on health and that multilevel analyses are essential for understanding the impact of social and environmental determinants of health. A number of determinants of health are then briefly examined in terms of their association with mortality, the appropriateness of their being measured at the metropolitan scale, and the availability of data for the 1980s from U.S. sources. Finally, the article presents the database of place-specific ecologic covariates that was incorporated into the ACS models during the reanalysis in order to account for the influence that place may have above and beyond ambient air pollution.

Air Pollutants↗
PubMedDate not supplied

Spatial analysis of the air pollution-mortality relationship in the context of ecologic confounders.

Lack of control for confounding by ecological covariates that may relate to sulfate air pollution and mortality was a key criticism of the two studies that were the focus of the Particle Reanalysis Project. To assess the validity of this criticism, we address the question: "Does sulfate air pollution exert health effects when the impact of other individual and ecologic variables thought to influence health is taken into account?" A related question arises from the possibility of autocorrelation in the mortality risks and ecologic covariates. Failure to control for autocorrelation can lead to false positive significance tests and may indicate bias resulting from a missing variable or group of variables. We control for more than 25 individual risk factors and for 20 ecologic variables representing environmental, socioeconomic, demographic, health- care, and lifestyle determinants of health in a two-stage multilevel analysis. Four modeling strategies are used to control for spatial autocorrelation. Of the 20 ecologic variables tested, only sulfate and sulfur dioxide are significant in models that incorporate spatial autocorrelation. Accounting for autocorrelation also reduces the size and certainty of the sulfate effect on mortality when compared to results generated from Cox models where independent observations are assumed. Confidence limits for the sulfate relative risk include unity in models that simultaneously control for sulfur dioxide and autocorrelation.

Air Pollution↗
PubMedDate not supplied

Human ecology, crime, and crime control: linking individual behavior and aggregate crime.

The paper extends previous research published by Cohen, Machalek, Vila, and others on the evolutionary-ecological paradigm for understanding criminal behavior. After reviewing literature related to human ecology and crime, the paper focuses on elements relevant to human ecology-biology, development, and ecological factors--and their role in criminal behavior. Major emphasis is placed on the linkages between individual factors and macro-level crime using chronic offending as a case in point. The principles of evolutionary ecology then are used to discuss counterstrategies to crime, and the prospects for protection/avoidance, deterrent, and nurturant strategies in light of evidence on chronic offending.

Biological Evolution↗
PubMed1989

Ecological causes for the evolution of sexual dimorphism: a review of the evidence.

Can sexual dimorphism evolve because of ecological differences between the sexes? Although several examples of this phenomenon are well known from studies on birds, the idea has often been dismissed as lacking general applicability. This dismissal does not stem from contradictory data so much as from the difficulties inherent in testing the hypothesis, and its apparent lack of parsimony, in comparison to the alternative explanation of sexual selection. The only unequivocal evidence for the evolution of sexual dimorphism through intersexual niche partitioning would be disproportionate dimorphism in trophic structures (e.g., mouthparts). This criterion offers a minimum estimate of the importance of ecological causes for dimorphism, because it may fail to identify most cases. A review of published literature reveals examples of sexually dimorphic trophic structures in most animal phyla. Many of these examples seem to be attributable to sexual selection, but others reflect adaptations for niche divergence between the sexes. For example, dwarf non-feeding males without functional mouthparts have evolved independently in many taxa. In other cases, males and females differ in trophic structures apparently because of differences in diets. Such divergence may often reflect specific nutritional requirements for reproduction in females, or extreme (sexually selected?) differences between males and females in habitats or body sizes. Ecological competition between the sexes may be responsible for intersexual niche divergence in some cases, but the independent evolution of foraging specializations by each sex may be of more general importance. If ecological causation for dimorphism can be demonstrated in so many cases, despite the inadequacies of the available criteria, the degree of sexual size dimorphism in many other animal species may well also have been influenced by ecological factors. Hence, it may be premature to dismiss this hypothesis, despite the difficulty of testing it.

Animals↗
PubMed2004

Community ecology: is it time to move on? (An American Society of Naturalists presidential address).

Because of the contingency and complexity of its subject matter, community ecology has few general laws. Laws and models in community ecology are highly contingent, and their domain is usually very local. This fact does not mean that community ecology is a weak science; in fact, it is the locus of exciting advances, with growing mechanistic understanding of causes, patterns, and processes. Further, traditional community ecological research, often local, experimental, and reductionist, is crucial in understanding and responding to many environmental problems, including those posed by global changes. For both scientific and societal reasons, it is not time to abandon community ecology.

Animals↗
PubMed2026

Concurrent ecological and evolutionary processes contribute to mutualism breakdown between legumes and rhizobia.

Though they jointly shape community responses to environmental perturbations, ecology and evolution are often examined separately, even in microorganisms where both occur over short timescales. Here we examine ecological and evolutionary responses to 33 years of nitrogen fertilization using the legume-rhizobium mutualism. Pairing a manipulative inoculation study with full-length 16S rRNA gene amplicon sequencing and structural equation modeling allows us to synthesize across biological scales: whole bacterial community, genus Rhizobium, Rhizobium ASVs, and symbiosis plasmids. Clover's preferred partner decreases in N-addition soils, limiting host growth, while a diverse and largely uncharacterized Rhizobium community increases. This ecological change is compounded by a concurrent evolutionary degradation of symbiont partner quality via changing frequencies of symbiotic plasmids. Ecological (rarer symbionts) and evolutionary (inferior symbionts) processes each accounted for roughly half of this loss of host benefit, revealing that ecology and evolution jointly shape mutualism breakdown over the short timescales typical of microbial systems.

ecology↗
PubMed1994

Invited commentary: ecologic studies--biases, misconceptions, and counterexamples.

Many authors have pointed out that relative-risk estimates derived from ecologic data are vulnerable to biases not found in estimates derived from individual-level data. Nevertheless, biases in ecologic studies still are often dealt with in the same manner as biases in other observational studies, and so are not given adequate treatment. This commentary reviews and illustrates some of the more recent findings about bias in ecologic estimates. Special attention is given to problems of ecologic confounder control when individual risks follow a nonlinear model, and to misconceptions about ecologic bias that have appeared in the literature.

Bias↗
PubMed2002

Population growth rate as a basis for ecological risk assessment of toxic chemicals.

Assessing the ecological risks of toxic chemicals is most often based on individual-level responses such as survival, reproduction or growth. Such an approach raises the following questions with regard to translating these measured effects into likely impacts on natural populations. (i) To what extent do individual-level variables underestimate or overestimate population-level responses? (ii) How do toxicant-caused changes in individual-level variables translate into changes in population dynamics for species with different life cycles? (iii) To what extent are these relationships complicated by population-density effects? These issues go to the heart of the ecological relevance of ecotoxicology and we have addressed them using the population growth rate as an integrating concept. Our analysis indicates that although the most sensitive individual-level variables are likely to be equally or more sensitive to increasing concentrations of toxic chemicals than population growth rate, they are difficult to identify a priori and, even if they could be identified, integrating impacts on key life-cycle variables via population growth rate analysis is nevertheless a more robust approach for assessing the ecological risks of chemicals. Populations living under density-dependent control may respond differently to toxic chemicals than exponentially growing populations, and greater care needs to be given to incorporating realistic density conditions (either experimentally or by simulation) into ecotoxicological test designs. It is impractical to expect full life-table studies, which record changes in survival, fecundity and development at defined intervals through the life cycle of organisms under specified conditions, for all relevant species, so we argue that population growth rate analysis should be used to provide guidance for a more pragmatic and ecologically sound approach to ecological risk assessment.

Animals↗
PubMed2006

Wood density and vessel traits as distinct correlates of ecological strategy in 51 California coast range angiosperms.

Wood density and vessel characteristics are functionally interrelated, yet they may have distinct ecological associations. In a comparative study of 51 angiosperm species ranging from chaparral shrubs to riparian trees, we examined relationships among wood density and vessel traits and their ecological correlates. Mean vessel lumen area and vessel density (number mm(-2)) varied widely (7- to 10-fold). In multivariate analyses, both vessel traits were negatively correlated with wood density, which varied more narrowly (< 2-fold). Vessel density and lumen area were inversely related across species, allowing a broad range of vessel traits within a narrow range of wood density. Phylogenetic independent contrasts indicated correlated inverse evolutionary change in vessel traits. Each trait had a distinct pattern of ecological correlation -- wood density was most strongly associated with soil water, and vessel traits showed contrasting relationships with plant height. Within a narrow range of wood density, there was significant variation in vessel traits. Given their particular ecological associations, the results suggest that wood density and vessel traits describe two distinct ecological axes.

Biological Evolution↗
PubMed1995

An approach for balancing health and ecological risks at hazardous waste sites.

Human health and ecological risks must be balanced at hazardous waste sites in order to ensure that remedial actions prevent unacceptable risks of either type. Actions that are designed to protect humans may fail to protect nonhuman populations and ecosystems or may damage ecosystems. However, there is no common scale of health and ecological risk that would allow comparisons to be performed. This paper presents an approach to addressing this problem based on classifying all risks (i.e., health and ecological risks due contaminants and remediation) as insignificant (de minimis), highly significant (de manifestis), or intermediate. For health risks the classification is based on standard criteria. However, in the absence of national guidance concerning the acceptability of ecological risks, new ecological criteria are proposed based on an analysis of regulatory precedents. Matrices and flow charts are presented to guide the use of these risk categories in remedial decision making. The assessment of mercury contamination of the East Fork Poplar Creek is presented as an example of the implementation of the approach.

Algorithms↗
PubMed1999

Suicide, religion, and socioeconomic conditions. An ecological study in 26 countries, 1990.

STUDY OBJECTIVE: Relative risks are frequently assumed to be stable across populations but this may not apply in psychiatric epidemiology where sociocultural context may modify them. Such ecological effect modification will give curved associations between aggregated risk factor and outcome. This was examined in connection with the ecological association between suicide rates and an aggregate index of religiosity. DESIGN: Ecological study of associations between suicide rates and an index of religiosity, adjusted for socioeconomic variation. The effect of stratification of the study sample according to levels of religiosity, was examined. SETTING: 26 European and American countries. SUBJECTS: Interview data from 37,688 people aggregated by country. OUTCOME MEASURES: Age and sex specific (1986-1990) suicide rates. MAIN RESULT: Adjusted for socioeconomic variation, negative associations of male suicide rates with religiosity were apparent in the 13 least religious countries only (test for interaction F (1, 25) = 5.6; p = 0.026). Associations between religiosity and female suicide rates did not vary across countries. CONCLUSION: The bent ecological association was apparent only after adjustment for socioeconomic variation suggesting that, rather than confounding, ecological modification of individual level links between religion and male (but not female) suicide risk is the responsible mechanism. This concurs with micro-level findings suggesting that suicide acceptance depends not only on personal but also on contextual levels of religious belief, and that men are more sensitive to this phenomenon than women. In psychiatric epidemiology, relative risks vary with the exposure's prevalence. This has important implications for research and prevention.

Adolescent↗
PubMed2001

Ammonia-oxidizing bacteria: a model for molecular microbial ecology.

The eutrophication of many ecosystems in recent decades has led to an increased interest in the ecology of nitrogen transformation. Chemolitho-autotrophic ammonia-oxidizing bacteria are responsible for the rate-limiting step of nitrification in a wide variety of environments, making them important in the global cycling of nitrogen. These organisms are unique in their ability to use the conversion of ammonia to nitrite as their sole energy source. Because of the importance of this functional group of bacteria, understanding of their ecology and physiology has become a subject of intense research over recent years. The monophyletic nature of these bacteria in terrestrial environments has facilitated molecular biological approaches in studying their ecology, and progress in this field has been rapid. The ammonia-oxidizing bacteria of the beta-subclass Proteobacteria have become somewhat of a model system within molecular microbial ecology, and this chapter reviews recent progress in our knowledge of their distribution, diversity, and ecology.

Ammonia↗
PubMed2004

Microarrays in ecological research: a case study of a cDNA microarray for plant-herbivore interactions.

BACKGROUND: Microarray technology allows researchers to simultaneously monitor changes in the expression ratios (ERs) of hundreds of genes and has thereby revolutionized most of biology. Although this technique has the potential of elucidating early stages in an organism's phenotypic response to complex ecological interactions, to date, it has not been fully incorporated into ecological research. This is partially due to a lack of simple procedures of handling and analyzing the expression ratio (ER) data produced from microarrays. RESULTS: We describe an analysis of the sources of variation in ERs from 73 hybridized cDNA microarrays, each with 234 herbivory-elicited genes from the model ecological expression system, Nicotiana attenuata, using procedures that are commonly used in ecologic research. Each gene is represented by two independently labeled PCR products and each product was arrayed in quadruplicate. We present a robust method of normalizing and analyzing ERs based on arbitrary thresholds and statistical criteria, and characterize a "norm of reaction" of ERs for 6 genes (4 of known function, 2 of unknown) with different ERs as determined across all analyzed arrays to provide a biologically-informed alternative to the use of arbitrary expression ratios in determining significance of expression. These gene-specific ERs and their variance (gene CV) were used to calculate array-based variances (array CV), which, in turn, were used to study the effects of array age, probe cDNA quantity and quality, and quality of spotted PCR products as estimates of technical variation. Cluster analysis and a Principal Component Analysis (PCA) were used to reveal associations among the transcriptional "imprints" of arrays hybridized with cDNA probes derived from mRNA from N. attenuata plants variously elicited and attacked by different herbivore species and from three congeners: N. quadrivalis, N. longiflora and N. clevelandii. Additionally, the PCA revealed the contribution of individual gene ERs to the associations among arrays. CONCLUSIONS: While the costs of 'boutique' array fabrication are rapidly declining, familiar methods for the analysis of the data they create are still missing. The case history illustrated here demonstrates the ease with which this powerful technology can be adapted to ecological research.

Animals↗
PubMed2006

The evolutionary consequences of ecological interactions mediated through phenotypic plasticity.

Phenotypic plasticity describes the capacity of a genotype to exhibit a range of phenotypes in response to variation in the environment. Environmental variation encompasses both abiotic and biotic components of the environment, including interactions among organisms. The strength and outcome of many ecological interactions, ranging from antagonism to mutualism, are mediated through the phenotypically plastic responses of one or more players in the interaction. Herein, three broadly defined, non-mutually exclusive, evolutionary consequences of ecological interactions mediated through phenotypic plasticity are discussed. (1) The predictable plastic response of one partner can favor behaviors, physiological responses, and life history traits of an interacting partner that manipulate, circumvent, or ameliorate the response of that partner. (2) Phenotypic plasticity can generate substantial spatial and temporal variation within and among populations. Such phenotypic variation can depend on the density and identity of interacting players in an ecological community, and can ultimately affect the evolutionary outcome of ecological interactions. (3) Phenotypic plasticity affects the strength and direction of natural selection. Ecological interactions mediated through phenotypic plasticity are ubiquitous in nature, and the potential evolutionary consequences of these interactions illustrate the complexity inherent in understanding evolution in a community context.

Adaptation, Physiological↗
PubMed1999

Ecological biomechanics of benthic organisms: life history, mechanical design and temporal patterns of mechanical stress.

We can gain biomechanical insights if we couple knowledge of the environments, ecological roles and life history strategies of organisms with our laboratory analyses of their mechanical function or fluid dynamics, as illustrated by studies of the mechanical design of bottom-dwelling marine organisms. Obviously, measurements of the spatial and temporal distribution of loads on an organism in nature reveal the magnitudes and rates at which biomechanical tests should be performed in the laboratory. Furthermore, knowledge of the population biology and ecological interactions of the organisms being studied is crucial to determine when during the life of an individual particular aspects of mechanical performance should be measured; not only can the size, shape and material properties of an individual change during ontogeny, but so can its habitat, activities and ecological role. Such ecological information is also necessary to determine whether the aspects of mechanical performance being studied are biologically important, i.e. whether they affect the survivorship or fitness of the organisms. My point in raising these examples is to illustrate how ecological studies can enhance or change our understanding of biomechanical function.

Animals↗
PubMed1976

Nutritional determinants of the ecology of the oral flora.

Consideration of nutritional factors as determinants of oral microbial ecology leads to the conclusion that endogenous factors play a dominant role. It is the interactions between specific microorganisms and nutritional and other factors provided by the host that selectively determine the kinds of microorganisms which willinitially reside in the oral cavity and the sites which they will colonize. The persistence of these original "colonists" in their respective ecologic niches will depend in part on the accessibility of endogenous nutrients variously provided by saliva, tissue exudates, crevicular fluids, or degenerating host cells. It will also depend on their response to and interaction with microorganisms which immigrate to that site subsequently. The microbial ecology of a given site is therefore rarely uncomplicated, the notable exception occurring at the most microscopic level where one may encounter microcolonies of individual species within more heterogenous populations of microorganisms. The extent of this heterogeneity quantitatively and qualitatively is a reflection of the degree to which the interactions between the resident flora and the new arrivals, plus the local environmental changes which they both generate, serve to promote or to discourage the survival and growth of the individual species. This element of heterogeneity in a dynamic system with its inherent potential for variation makes it possible for relatively minor changes in local environmental conditions to result in significant differences in the microflora between one site and another even though they may be in close proximity to each other. Once this concept is appreciated it becomes easy to understand how disease processes such as dental caries may affect specific areas of a tooth while nearby areas are unaffected. The effects of exogenous nutrients on the ecology of the oral microbiota, nevertheless cannot be ignored. The diet may modulate such endogenous factors as the salivary secretions and the local resistance of the gingival tissues to infections. Although at our present state of knowledge the direct influence of dietary proteins and fats on the oral microbiota is thought to be of relatively minor consequence, dietary carbohydrates are of major ecological significance. Dietary sugars provide readily available substrates for the oral microorganisms, most of which depend on carbohydrates for energy sources. The metabolism of dietary sucrose by S. sanguis and S. mutans with the productions of acids and intracellular and extracellular polysaccharides has specific influence on the microbial composition, metabolic activities, and mass of coronal plaque. The ready availability of dietary carbohydrates undoubtedly influences the microflora of other parts of the oral cavity as well, eic species or indirectly through the interactions of other organisms with them...

Adhesiveness↗
PubMed2001

[Nitrate and nitrite content in potatoes from ecological and conventional farms].

The aim of this investigation was to determine nitrate and nitrite content in potatoes from ecological and conventional farms. The influence of variety on nitrate and nitrite content was also evaluated. Vegetables and potatoes from ecological cultures are supposed to contain less nitrates and nitrites and on this basis could have been advised for children, sick and people in special physiological stages. Nitrite content was determined colorimetrically, with sulfanilic acid, nitrate content was determined following reduction of nitrites by means of metallic cadmium. The results showed significantly lower nitrate content in potatoes from ecological farms, and almost twice higher in those from conventional farms. The nitrite content showed no differentiation in conventional and ecological farms. Within three varieties of potatoes (sokół, bryza, ania) significantly highest content of nitrate was determined in bryza. Considering low nitrate level potatoes from ecological farms could be advised for children and sick people, but for the complete safety evaluation also content of other contaminants (i.e. heavy metals) have to be assessed.

Colorimetry↗