Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ECOLOGY”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 343 records · Page 19Linked to original sources
PubMed2000

Chemical ecology of host-plant selection by herbivorous arthropods: a multitrophic perspective.

Most herbivorous arthropods are specialists that feed on one or a few related plant species. To understand why this is so, both mechanistic and functional studies have been carried out, predominantly restricted to bitrophic aspects. Host-selection behaviour of herbivorous arthropods has been intensively studied and this has provided ample evidence for the role of secondary plant chemicals as source of information in behavioural decisions of herbivores. Many evolutionary studies have regarded co-evolution between plants and herbivores to explain the diversity of secondary plant chemicals and host specialisation of herbivores. However, many cases remain unexplained where herbivores select host plants that are suboptimal in terms of fitness returns. A stimulating paper by Bernays and Graham [(1988) Ecology 69, 886-892)] has initiated a discussion on the need of a multitrophic perspective to understand the evolution of host-plant specialisation by herbivorous arthropods. However, this has hardly resulted in ecological studies on host-selection behaviour that take a multitrophic perspective. Yet, evidence is accumulating that constitutive and induced infochemicals from natural enemies and competitors can affect herbivore behaviour. These cues may constitute important information on fitness prospects, just as plant cues can do. In this paper I selectively review how information from organisms at different trophic levels varies in space and time and how herbivores can integratively exploit this information during host selection. In doing so, research areas are identified that are likely to provide important new insights to explain several of the questions in herbivore host selection that remain unanswered so far. These research areas are at the interface of evolutionary ecology, behavioural ecology and chemical ecology.

Journal Article↗
PubMed2001

On developing bioindicators for human and ecological health.

Risk assessors and risk managers generally either examine ecological health (using bioindicators) or human health (using biomarkers of exposure or effect). In this paper we suggest that it is possible and advantageous to develop bioindicators that can be used to assess exposure and effect for both human and non-human receptors. We describe the characteristics of suitable bioindicators for both human and ecological health, using mourning doves (Zenaida macroura), raccoons (Procyon lotor), and bluefish (Pomatomus saltatrix) as examples, and list the general characteristics of other species that would make them useful indicators for assessing both human and ecological health. Bioindicators can be used cross-sectionally to assess the status of ecosystems and risk as well as longitudinally for monitoring changes or evaluating remediation. For both human and ecological risk assessment, there are three sets of characteristics to consider when selecting bioindicators: biological relevance, methodological relevance, and societal relevance. An indicator which fails to fulfill these is not likely to be considered cost-effective and is likely to be abandoned. The indicator should be readily measured and must measure an important range of impacts. For long-term support of a bioindicator, the indicator should be easily understood, and be cost effective. We suggest that bioindicators that can also be used for both ecological and human health risk assessment are optimal.

Animals↗
PubMed2003

The ecological validity of neuropsychological tests: a review of the literature on everyday cognitive skills.

Evaluating the ecological validity of neuropsychological tests has become an increasingly important topic over the past decade. In this paper, we provide a comprehensive review of the research on the ecological validity of neuropsychological tests, as it pertains to everyday cognitive skills. This review is presented in the context of several theoretical issues facing ecological validity research. Overall, the research suggests that many neuropsychological tests have a moderate level of ecological validity when predicting everyday cognitive functioning. The strongest relationships were noted when the outcome measure corresponded to the cognitive domain assessed by the neuropsychological tests. Several other factors that may moderate the degree of ecological validity established for neuropsychological tests are in need of further exploration. These factors include the effects of the population being tested, the approach utilized (verisimilitude vs. veridicality), the person completing the outcome measure (significant other vs. clinician), illness severity, and time from injury until evaluation. In addition, a standard measurement of outcome for each cognitive domain is greatly needed to allow for comparison across studies.

Cognition Disorders↗
PubMed1998

Molecular phylogeny and ecological diversification in a clade of New World songbirds (genus Vireo).

We constructed a molecular phylogeny for a clade of eye-ringed vireos (Vireo flavifrons and the V. solitarius complex) to examine existing hypotheses of speciation and ecological diversification. Complete sequences of the mtDNA cytochrome b gene were obtained from 47 individuals of this group plus four vireonid outgroups. Mean levels of sequence divergence in the clade varied from 0.29% to 5.7%. Differences were greatest between V. flavifrons and four taxa of 'V. solitarius'. The latter separated into three taxonomic, geographical and ecological groups: V. plumbeus plumbeus, V. cassinii cassinii, and V. solitarius solitarius plus V. solitarius alticola. These differed by an average of 2.6-3.2%. Populations within each group revealed low levels of sequence variation (x = 0.20%) and little geographical structuring. The mtDNA data generally corroborate results from allozymes. V. plumbeus shows a loss of yellow-green carotenoid pigmentation from the ancestral condition. The occupancy of relatively dry habitats by this species and V. cassinii represents a derived ecological shift from more-humid environments occupied by other species of vireonids. Ecological divergence in this clade occurred in allopatry and is associated with generic-level stability in morphometrics and foraging styles. Migratory behaviour and seasonal habitat shifts apparently evolved multiple times in vireos breeding in temperate environments. Present geographical and ecological distributions, and low levels of intrataxon genetic divergence, are hypothesized to be the result of postglacial regionalization of climate-plant associations and rapid northward expansion of breeding ranges.

Animals↗
PubMed2002

On ochratoxin A and fungal flora in Polish cereals from conventional and ecological farms - Part 1: occurrence of ochratoxin A and fungi in cereals in 1997.

Over 200 samples of Polish cereal grain from the 1997 harvest obtained from conventional and ecological farms were tested for the presence of ochratoxin A as well as for contamination by microscopic fungi. Ochratoxin A contamination of rye from ecological farms was over six times more frequent than that from conventional cultivation. The ochratoxin A content in wheat and barley samples from ecological farms was also higher. No wheat sample from conventional farms contained the mycotoxin. In the group of ecological farms, there were differences in the percentage of cereal samples containing ochratoxin A. The ochratoxin A levels ranged from 0.2 to 57 microg kg(-1). The mean concentration of ochratoxin A in investigated cereal grain was 5.7 microg kg(-1). From samples containing detectable amounts of ochratoxin A, fungi producing ochratoxin A under laboratory conditions were isolated. They were classified as belonging to the species Penicillium cyclopium, P. viridicatum, P. chrysogenum and also Aspergillus alliaceus, A. versicolor, A. glaucus and A. flavus. Penicillium strains - producers of ochratoxin A - were isolated from 93% of the samples; in 7% of samples, only Aspergillus strains producing this mycotoxin were noted. Rye samples mainly from one farm with an ecological type of cultivation and from one conventional farm were contaminated with both Aspergillus and Penicillium mycotoxigenic strains.

Aspergillus↗
PubMed2004

Ecology of congruence: past meets present.

Phylogenetic congruence is governed by various macroevolutionary events, including cospeciation, host switching, sorting, duplication, and failure to speciate. The relative frequency of these events may be influenced by factors that govern the distribution and abundance of the interacting groups; i.e., ecological factors. If so, it may be possible to predict the degree of phylogenetic congruence between two groups from information about their ecology. Unfortunately, adequate comparative ecological data are not available for many of the systems that have been subjected to cophylogenetic analysis. An exception is provided by chewing lice (Insecta: Phthiraptera), which parasitize birds and mammals. For a few genera of these lice, enough data have now been published to begin exploring the relationship between ecology and congruence. In general, there is a correspondence between important ecological factors and the degree of phylogenetic congruence. Careful comparison of these genera suggests that dispersal is a more fundamental barrier to host switching among related hosts than is establishment. Transfer experiments show that host-specific lice can survive and reproduce on novel hosts that are similar in size to the native host as long as the lice can disperse to these hosts. To date, studies of parasite dispersal have been mainly inferential. A better understanding of the role of dispersal will require more direct data on dispersal frequency and distances.

Animals↗
PubMed2006

Trade-offs in thermal adaptation: the need for a molecular to ecological integration.

Through functional analyses, integrative physiology is able to link molecular biology with ecology as well as evolutionary biology and is thereby expected to provide access to the evolution of molecular, cellular, and organismic functions; the genetic basis of adaptability; and the shaping of ecological patterns. This paper compiles several exemplary studies of thermal physiology and ecology, carried out at various levels of biological organization from single genes (proteins) to ecosystems. In each of those examples, trade-offs and constraints in thermal adaptation are addressed; these trade-offs and constraints may limit species' distribution and define their level of fitness. For a more comprehensive understanding, the paper sets out to elaborate the functional and conceptual connections among these independent studies and the various organizational levels addressed. This effort illustrates the need for an overarching concept of thermal adaptation that encompasses molecular, organellar, cellular, and whole-organism information as well as the mechanistic links between fitness, ecological success, and organismal physiology. For this data, the hypothesis of oxygen- and capacity-limited thermal tolerance in animals provides such a conceptual framework and allows interpreting the mechanisms of thermal limitation of animals as relevant at the ecological level. While, ideally, evolutionary studies over multiple generations, illustrated by an example study in bacteria, are necessary to test the validity of such complex concepts and underlying hypotheses, animal physiology frequently is constrained to functional studies within one generation. Comparisons of populations in a latitudinal cline, closely related species from different climates, and ontogenetic stages from riverine clines illustrate how evolutionary information can still be gained. An understanding of temperature-dependent shifts in energy turnover, associated with adjustments in aerobic scope and performance, will result. This understanding builds on a mechanistic analysis of the width and location of thermal windows on the temperature scale and also on study of the functional properties of relevant proteins and associated gene expression mechanisms.

Acclimatization↗
PubMed2003

Psychology and the internet: a social ecological analysis.

This paper proposes a research strategy based on a social ecological analysis of the Internet and its psychological impact as an option to generate original research to answer the follow ing question: What is the psycho-environmental meaning of the Internet? This paper has two objectives: first, to analyze Computer Mediated Communication (CMC) linked to the use of the Internet from a social ecological approach, and second, to propose some relationships among variables from a social ecological perspective, which can help to clarify the variability and magnitude of the psychosocial effect associated with the Internet. This article is divided into three sections. The first briefly describes the origins and development of the Internet. It identifies some technological features and specifies some of the cutting-edge breakthroughs that have facilitated its expansion. The second section proposes a conceptual scheme from the social ecological perspective, which analyzes the subject-environmental binomial associated with the Internet. It identifies the basic assumption, the conceptual richness, and possibilities for research on the Internet, using a social ecological approach. Finally, the last section describes the scope and limitations of this perspective, and discusses its heuristic utility for the development and consolidation of a new area in psychological research: "digital psychology or cyber psychology."

Communication↗
PubMed1992

Effects of nondifferential exposure misclassification in ecologic studies.

Although many authors have argued against inferring individual-level exposure-disease relations from ecologic data because of the potential "ecological fallacy." the availability of data from diverse populations promotes the continued use of this rapid and inexpensive study design. In ecologic studies, the exposure status of groups is often defined by the proportion of individuals exposed. In these studies, nondifferential exposure misclassification of individuals is shown to produce overestimation of exposure-disease associations that may be extreme when the ecologically derived rate ratios are applied to individuals. This overestimation contrasts with the bias toward the null resulting from nondifferential misclassification of a binary exposure in epidemiologic studies conducted at the individual level. Given the magnitude of the potential bias from nondifferential exposure misclassification and other sources, quantitative estimates of individual-level rate ratios from ecologic data should be interpreted with extreme caution.

Environmental Health↗
PubMed1998

Residential 222Rn exposure and lung cancer: testing the linear no-threshold theory with ecologic data.

In most rigorous epidemiologic studies, such as case-control and cohort studies, the basic unit of analysis is the individual. Each individual is classified in terms of exposure and disease status. However, in ecologic epidemiologic studies, the unit of analysis is some aggregate group of individuals. Summary measures of exposure and disease frequency are obtained for each aggregate, and the analyses focus on determining whether or not the aggregates with high levels of exposure also display high disease rates. The ecologic study design has major limitations, including ecologic confounding and cross level bias. Cohen has attempted to circumvent these limitations by invoking the linear no-threshold theory of radiation carcinogenesis to derive aggregate "exposures" from individual-level associations. He asserts that, "while an ecologic study cannot determine whether radon causes lung cancer, it can test the validity of a linear-no threshold relationship between them." Cohen compares his testing of the linear no-threshold relationship between radon exposure and lung cancer to the practice of estimating the number of deaths from the person-rem collective dose, dividing the person-rem by the number of individuals in the population to derive the individual average dose, and then determining individual average risk by dividing the number of deaths by the number of individuals in the population. We show that Cohen's erroneous assumptions concerning occupancy rates and smoking effects result in the use of the wrong model to test the linear no-threshold theory. Because of these assumptions, the ecologic confounding and cross level bias associated with Cohen's model invalidate his findings. Furthermore, when more recent Iowa county lung cancer incidence rates are regressed on Cohen's mean radon levels, the reported large negative associations between radon exposure and lung cancer are no longer obtained.

Air Pollutants, Radioactive↗
PubMed1998

Rainforest frogs of the Australian Wet Tropics: guild classification and the ecological similarity of declining species.

Rainforest frogs are classified into nine ecological guilds based on features of reproduction, habitat use, temporal activity, microhabitat and body size. The largest ecological differences are between the microhylid frogs and the rest of the frog species. Within the non-microhylids, there are two primary groups consisting of (i) regionally endemic rainforest specialists, and (ii) a more ecologically diverse group of species that are less specialized in their habitat requirements. Most of the regionally endemic rainforest specialists, which includes species in three ecological guilds, have declined or gone missing in recent years. Multivariate analyses of the ecological characteristics of these species show that it is not a single characteristic that isolates those species that have declined from those which have not. The guilds that have undergone significant population declines in the Wet Tropics are all characterized by the combination of low fecundity, a high degree of habitat specialization and reproduction in flowing streams. These results have important implications for the determination of the causal factors in the unexplained global decline of many amphibian species.

Animals↗
PubMed2002

Ecosystem management and ecological modeling.

It is the intention of this paper to demonstrate that environmental technology must be supplemented by other tools to be able to solve environmental problems properly. Five cases are used to illustrate the possibilities of ecological engineering, a new engineering field based on ecology, as chemical engineering is based on chemistry. It encompasses restoration of ecosystems, utilization of ecosystems to the benefit of both mankind and nature, construction of ecosystems, and ecologically sound planning of ecosystems from a holistic point of view. Ecological engineering requires a good knowledge of the system properties of ecosystems to be able to fully utilize the possibilities that ecosystem management offers. Models reflecting the ecosystem properties are furthermore needed to be able to quantify the effects of the ecological engineering solutions to the environmental problems. This is clearly demonstrated in two of the five case studies presented in the paper.

Algorithms↗
PubMed2002

Ecological bistability and evolutionary reversals under asymmetrical competition.

How does the process of life-history evolution interplay with population dynamics? Almost all models that have addressed this question assume that any combination of phenotypic traits uniquely determine the ecological population state. Here we show that if multiple ecological equilibria can exist, the evolution of a trait that relates to competitive performance can undergo adaptive reversals that drive cyclic alternation between population equilibria. The occurrence of evolutionary reversals requires neither environmentally driven changes in selective forces nor the coevolution of interactions with other species. The mechanism inducing evolutionary reversals is twofold. First, there exist phenotypes near which mutants can invade and yet fail to become fixed; although these mutants are eventually eliminated, their transitory growth causes the resident population to switch to an alternative ecological equilibrium. Second, asymmetrical competition causes the direction of selection to revert between high and low density. When ecological conditions for evolutionary reversals are not satisfied, the population evolves toward a steady state of either low or high abundance, depending on the degree of competitive asymmetry and environmental parameters. A sharp evolutionary transition between evolutionary stasis and evolutionary reversals and cycling can occur in response to a smooth change in ecological parameters, and this may have implications for our understanding of size-abundance patterns.

Animals↗
PubMed2006

Divergence in mating signals correlates with ecological variation in the migratory songbird, Swainson's thrush (Catharus ustulatus).

Song divergence among populations of passerine birds is recognized as a potentially important premating isolation mechanism and may represent the first step in speciation. Because song divergence may be influenced by an array of acoustic, ecological, and genetic factors, the study of its origin requires a multifaceted approach. Here we describe the relationship between acoustic, neutral genetic and ecological variation in five populations of the Swainson's thrush: two from coastal temperate rainforest habitat representing the 'russet-backed' subspecies group, two from inland coniferous forest habitat representing the 'olive-backed' subspecies group, and one mixed locality that resides within a contact zone between the two groups. Song in the five populations is analysed using a multivariate analysis of spectral and temporal measurements, population genetic structure is assessed using an analysis of five microsatellite loci and ecological differences between populations are quantified using an analysis of climatic parameters. Matrix correspondence tests are used to distinguish between the potential for drift and selection in driving song divergence. No significant correlation was found between acoustic and genetic distance suggesting that song divergence cannot be explained by drift alone. A significant correlation between ecological and acoustic distance after accounting for genetic distance, suggests a potential role for ecological selection on divergence in spectral and temporal components of Swainson's thrush song.

Acoustics↗
PubMed1997

Perception of ecological risk to water environments.

This paper examines lay and expert perceptions of the ecological risks associated with a range of human activities that could adversely affect water resource environments. It employs the psychometric paradigm pioneered in characterizing perceptions of human health risks, which involves surveys to obtain judgments from subjects about risk items in terms of several important characteristics of the risks. The paper builds on a previous study that introduced ecological risk perception. This second study employs a larger, more diverse sample, a more focused topic area, and comparisons between lay and expert judgments. The results confirm that a small set of underlying factors explain a great deal of variability in lay judgments about ecological risks. These have been termed Ecological Impact, Human Benefits, Controllability, and Knowledge. The results are useful in explaining subjects' judgments of the general riskiness of, and need for regulation of, various risk items. The results also indicate several differences and areas of agreement among the lay and expert samples that point to potential key issues in future ecological risk management efforts for water resources.

Adult↗
PubMed2004

Life history trade-offs assemble ecological guilds.

Ecological theory predicts that competition for a limiting resource will lead to the exclusion of species unless the within-species effects outweigh the between-species effects. Understanding how multiple competitors might coexist on a single resource has focused on the prescriptive formalism of a necessary niche width and limiting similarity. Here, we show how continuously varying life histories and trade-offs in these characteristics can allow multiple competitors to coexist, and we reveal how limiting similarity emerges and is shaped by the ecological and evolutionary characteristics of competitors. In this way, we illustrate how the interplay of ecological and evolutionary processes acts to shape ecological communities in a unique way. This leads us to argue that evolutionary processes (life-history trait trade-offs) are fundamental to the understanding of the structure of ecological communities.

Animals↗
PubMed2001

Diastolic blood pressure and area of residence: multilevel versus ecological analysis of social inequity.

STUDY OBJECTIVES: To study geographical differences in diastolic blood pressure and the influence of the social environment (census percentage of people with low educational achievement) on individual diastolic blood pressure level, after controlling for individual age and educational achievement. To compare the results of multilevel and ecological analyses. DESIGN: Cross sectional analysis performed by multilevel linear regression modelling, with women at the first level and urban areas at the second level, and by single level ecological regression using areas as the unit of analysis. SETTING: Malmö, Sweden (population 250 000). PARTICIPANTS: 15 569 women aged 45 to 73, residing in 17 urban areas, who took part in the Malmö Diet and Cancer Study (1991-1996). MAIN RESULTS: In the "fixed effects" multilevel analysis, low educational achievement at both individual (beta=1.093, SE=0.167) and area levels (beta=2.966, SE=1.250) were independently associated with blood pressure, although in the "random effects" multilevel analysis almost none of the total variability in blood pressure across persons was attributable to areas (intraclass correlation=0.3%). The ecological analysis also found an association between the area educational variable and mean diastolic blood pressure (beta=4.058, SE=1.345). CONCLUSIONS: The small intraclass correlation found indicated very marginal geographical differences and almost no influence of the urban area on individual blood pressure. However, these slight differences were enough to detect an effect of the social environment on blood pressure. The ecological study overestimated the associations found in the "fixed" effects multilevel analysis, and neither distinguished individual from area levels nor provided information on the intraclass correlation. Ecological analyses are inadequate to evaluate geographical differences in health.

Age Factors↗
PubMed2026

Genetic diversity and antifungal susceptibility among ecological niche populations of Aspergillus flavus in Yaoundé, Cameroon.

Aspergillus flavus is a ubiquitous fungus commonly found in a variety of ecological niches including soil, crops, the air, and humans. In humans, it is the second leading cause of invasive aspergillosis (IA) and is linked to other illnesses through contamination of agricultural products with aflatoxins. As such, A. flavus threatens food safety, economic wellbeing, and human health, particularly in less developed regions and countries such as Cameroon. To mitigate these effects, farmers and clinicians rely on triazoles to reduce aflatoxin contamination and treat IA. However, a consequence of increasing triazole use is the emergence and spread of triazole resistance in both agriculture and clinics. To identify the prevalence of triazole resistance and the potential genetic relationships among triazole resistant and susceptible strains, this study investigated antifungal susceptibility to both clinical and agricultural triazoles and analyzed genetic variation among various ecological niche populations of A. flavus in Cameroon. Strain genotypes were obtained through analysis of six polymorphic microsatellite markers. Our analyses revealed that 30.3% (17/56) of the strains were resistant to at least one of the four triazoles, with increased minimum inhibitory concentrations found among crop-isolated strains. A Permutational Multivariate Analysis of Variance suggested limited ecological niche-based clustering of genotypes, consistent with frequent gene flow and dispersal among ecological niches. A multilocus linkage disequilibrium analysis revealed evidence of non-random recombination in A. flavus. Overall, this study elucidates the interplay between ecological pressures, antifungal resistance, and genetic differentiation, and invites alternative methods to control aflatoxin contamination in foods without the use of agricultural fungicides.

Aspergillus flavus↗