Ecological Case Study Research Articles

Interpretability-preserving genetic optimization of linguistic terms in fuzzy models for fuzzy ordered classification: An ecological case study

Fuzzy ordered classifiers were used to assign fuzzy labels to river sites expressing their suitability as a habitat for a certain macroinvertebrate taxon, given up to three abiotic properties of the considered river site. The models were built using expert knowledge and evaluated on data collected in the Province of Overijssel in the Netherlands. Apart from a performance measure for crisp classifiers common in the aquatic ecology domain, the percentage of correctly classified instances (% CCI), two performance measures for fuzzy (ordered) classifiers are introduced in this paper: the percentage of correctly fuzzy classified instances (% CFCI) and the average deviation (AD). Furthermore, results of an interpretability-preserving genetic optimization of the linguistic terms, applying once binary encoding and once real encoding, are presented.

Stability and Hopf bifurcation in an approachable haematopoietic stem cells model

We consider the haematopoietic stem cells model (HSC) with one delay introduced by Mackey [M.C. Mackey, Unified hypothesis for the origin of aplastic anemia and periodic hematopoiesis, blood 51 (1978) 5; M.C. Mackey, Mathematical models of haematopoietic cell replication and control, in: The Art of Mathematical Modelling: Case Studies in Ecology, Physiology and Biofluids, H.G. Othmer, F.R. Adler, M.A. Lewis, J.C. Dallon (Eds), Prentice-Hall, New York, 1997, p. 149] and Andersen and Mackey [L.K. Andersen, M.C. Mackey, Resonance in periodic chemotherapy: a case study of acute myelogenous leukemia, J. theor. Biol. 209 (2001) 113]. There are two possible stationary states in the model. One of them is trivial and the second E ∗( τ) depending on the delay is non-trivial . This paper investigates the stability of the non-trivial state and occurrence of the Hopf bifurcation depending on time delay. We prove the existence and uniqueness of a critical values τ 0 and τ ¯ of the delay such that E ∗( τ) is asymptotically stable for τ < τ 0 and unstable for τ 0 < τ < τ ¯ . We show that E ∗( τ 0) is a Hopf bifurcation critical point for an approachable model.

Evolutionary dynamics and highly optimized tolerance

We develop a numerical model of a lattice community based on Highly Optimized Tolerance (HOT), which relates the evolution of complexity to robustness tradeoffs in an uncertain environment. With the model, we explore scenarios for evolution and extinction which are abstractions of processes which are commonly discussed in biological and ecological case studies. These include the effects of different habitats on the phenotypic traits of the organisms, the effects of different mutation rates on adaptation, fitness, and diversity, and competition between generalists and specialists. The model exhibits a wide variety of microevolutionary and macroevolutionary phenomena which can arise in organisms which are subject to random mutation, and selection based on fitness evaluated in a specific environment. Generalists arise in uniform habitats, where different disturbances occur with equal frequency, while specialists arise when the relative frequency of different disturbances is skewed. Fast mutators are seen to play a primary role in adaptation, while slow mutators preserve well-adapted configurations. When uniform and skewed habitats are coupled through migration of the organisms, we observe a primitive form of punctuated equilibrium. Rare events in the skewed habitat lead to extinction of the specialists, whereupon generalists invade from the uniform habitat, adapt to their new surroundings, ultimately leading their progeny to become vulnerable to extinction in a subsequent rare disturbance.

A Study on the Application of Henon with a Case Study of Ecology

This paper deals with the well known Henon map. Its main properties are studied as well as a non deterministic form. Least squares estimates of parameters of the non deterministic model are driven and a case study from animal ecology is studied, where the population size of the Canadian lynx animal is considered as a time series. The embedding dimension of this time series is estimated and then a mathematical model of the form of suggested non deterministic (stochastic) model is fitted . The chaotic property of this series is studied throughout the fitted model.

Inderjit, Mallik, A.U. (eds). Chemical ecology of plants: allelopathy in aquatic and terrestrial ecosystems

Inderjit, Mallik, A.U. (eds). Chemical ecology of plants: allelopathy in aquatic and terrestrial ecosystems

The Ethnography of Landscape: GIS and Remote Sensing in the Study of Forest Change in West African Guinea Savanna

In this paper we explore the application of Amazonian forest change models to the Guinea savanna environment of western Africa. In particular, we examine recent research documenting the growth of peri‐village forest islands in the area of Kissidougou, Guinea, which purports to challenge the pervasive view of Guinea savanna deforestation brought about by human activity. As a more systematic approach to the analysis of human/environmental interactions, we propose an "ethnography of landscape," in which the findings of detailed, local ethnographic and ecological case studies are combined with remotely sensed information on what the wider region looks like as it changes over time. In pursuing this research, we employ aerial photography and Geographic Information Systems (GIS) techniques to examine our study area of Kilimi in northwestern Sierra Leone. We show that a Kissidougou‐type model of peri‐village forest island growth is not applicable to this region, where other environmental change processes are underway. In future work, we propose to employ Landsat satellite image archives to examine, monitor, and compare processes of ecological change throughout the Guinea savanna. [deforestation, ecological anthropology, remote sensing, Sierra Leone, West Africa]

Projecting population-level response of purple sea urchins to lead contamination for an estuarine ecological risk assessment

As part of an ecological risk assessment casestudy at the Portsmouth Naval Shipyard (PNS), Kittery,Maine, USA, the population level effects of leadexposure to purple sea urchin, Arbaciapunctulata, were investigated using a stage-classifiedmatrix population model. The model divided the lifehistory of A. punctulata into five classes,incorporating both, the developmental stages of thisspecies and the endpoints from a laboratory bioassay. Finite population growth rate (λ) was themetric relating population level impact to leadexposure. An inverse relationship was observed betweenlead tissue residues in A. punctulata andλ. Bioassay treatments which resulted insignificant impacts on fertilization success and zygoteviability did not translate into significant effects onλ, unless those treatments also negativelyimpacted adult survival. These results paralleled theelasticity (relative sensitivity) analysis of themodel, which indicated that λ was mostsensitive to adult and subadult survival and wasrelatively insensitive to fecundity, fertilizationsuccess, or zygote survival. Model results indicatedthat the environmental lead levels observed at PNSshould not pose significant ecological risk to seaurchin populations. Additionally, the model resultsindicated that impacts to the early life stagesroutinely used in toxicity testing do not necessarilytranslate directly into impacts at the populationlevel.

Balancing sexual selection through opposing mate choice and male competition

Male–male competition and female mate choice act contemporaneously in the cockroach Nauphoeta cinerea and the social pheromone of males influences the outcome of both forms of sexual selection. We therefore examined the joint and separate effects of male–male competition and female mate choice to determine if the selective optima for the pheromone were the same or different. Dominant males in a newly established hierarchy mated more frequently, but not exclusively. Manipulations of the multi-component social pheromone produced by males of N. cinerea showed that both long- and close-range attraction of females by males were influenced by the quantity and composition of the pheromone. The most attractive composition, however, differed from that which was most likely to confer high status to males. Since the outcome of male–male competition can conflict with mating preferences exhibited by females, there is balancing sexual selection on the social pheromone of N. cinerea. Such balancing selection might act to maintain genetic variation in sexually selected traits. We suggest that the different forms of sexual selection conflict in N. cinerea because females prefer a blend different to that which is most effective in male–male competition in order to avoid mating with overly aggressive males.

The Oil Mallee Project: A Multifaceted Industrial Ecology Case Study

SummaryThe planting on degraded agricultural lands of eucalypts for leaf oil provides a commercial incentive for restoring original vegetation; a sustainable method of controlling groundwater and salinity; a product that is an environmentally benign substitute for a widely used solvent damaging to the ozone layer; and a mechanism for reducing atmospheric carbon dioxide levels. With integrated tree crop systems and improved harvesting and processing technologies, the Western Australian wheatbelt could produce large volumes of high‐cineole eucalyptus oil from mallee eucalypts. With new industrial markets, a scale of planting could be achieved that would result in substantial land rehabilitation benefits. Industrial solvent markets are large and currently in transition following the recent withdrawal of 1,1,1‐trichloroethane as a result of international measures to control ozone depletion. There is a strong preference in these markets for “natural” replacement products. Although large‐scale penetration of these markets would need prices about half those prevailing in traditional eucalyptus oil markets, this goal should be achievable with the potential for economies of scale, genetic advances, and improved harvesting and processing technologies.

Die Veröffentlichungen des deutschen Entomologen und Ökologen Hermann Remmert

The following list includes all publications of the late Professor Dr Hermann Remmert (1931-1994) with early communications during his student's period until his posthum published contributions. This scientific work contains case studies both in field ecology and physiological ecology, review articles on aspects of biological rhythms as well as salinity problems of animals at the interface between sea and land, and last but not least, book publications about Ecology (text-books), Arctic Animal Ecology, Nature Conservation, and the Moasaic-Cycle Concept of Ecosystems.

Destruction of the tropical swamp forest ecosystem and its possibility for rehabilitation : An ecological case study in Thailand

Destruction of the tropical swamp forest ecosystem and its possibility for rehabilitation : An ecological case study in Thailand

Socio-economic ecological models: criteria for evaluation of state-of-the-art models shown on four case studies

Abstract Integrated projects, for example, Global Change, Man and Biosphere or LTER (Long-Term Ecological Research), pose new challenges to construct large, integrated, socio-economic ecological models. Criteria to evaluate and judge models have been around for quite some time, such as quality of calibration, availability of documentation, sb validations, etc. But now additional requirements have to be fulfilled, which are described here. One of the most essential issues may be the partial unpredictability inherent in almost all systems. Here a systematic, encompassing scheme is provided on how to deal with the unexpected. The requirements mentioned before and this scheme are used to evaluate four integrated socio-economic ecological case studies which also involved model construction. The models were also used for predictions. The correctness of predictions and the causes for failures were, for several of these models, repeatedly and thoroughly evaluated. The case studies seem to be representative for the state of the art, also in their weaknesses.

High school pupils' and first-year university students' responses to questions based on data analysis of an ecological case study

Ecological case study data were used to determine high school pupils' and university students' ability to organize and use these data to predict outcomes of interactions between populations within a community. Almost all the pupils and students could reorganize data into satisfactory tables and graphs, but less than 50 per cent of the respondents could integrate clues and predict outcomes acceptably. Students' and pupils' perceptions that the case study enabled them to develop insights into ecological processes support the hypothesis that ecological concepts may be successfully developed through data analysis, but the poor quality of answers given by these respondents suggests that explicit teaching, prior to the use of such an exercise, may greatly enhance its value.

The analysis of national subfields: a case study of Dutch fresh-water ecology

Bibliometric analysis is combined with a psychometric analysis of the perceptions which researchers in a community of Dutch fresh-water ecologists have of their professional environment. The results of these two types of analysis converge and can be understood by an exploration of the institutional and intellectual development of the community and the intellectual continuities in the careers of the researchers involved. International developments appear to be taken up in ways which reflect the particular socio-cognitive organization of the national subfield. The article claims that such national subfields of science constitute a strategic research site for social studies of science which is also directly relevant for science policy analysis. It pleads for the employment of a combination of methods in the synchronic and diachronic analysis of the structures of such subfields.

Options for mission-orientation in ecology

In response to growing concern about environmental problems ecologists have engaged in a variety of “mission-oriented” efforts in which they claim to have taken into account the objective of helping to solve environmental problems in their research strategies. The significance of these efforts is evaluated here in terms of both the theoretical development of the field of ecology and its orientation towards societal objectives. Three examples of mission-orientation are analysed on the basis of a case-study of Dutch fresh-water ecology: (1) ecosystems research within the framework of the International Biological Programme; (2) landscape ecology; and (3) ecological research on the management of fresh-water resources. These examples demonstrate that in principle the scope of mission-orientation in ecology can be broad. In Dutch fresh-water ecology, however, two specific approaches have become particularly institutionalized. The ecologists tended to opt either for theory-centered approaches close to the type of research carried out by ecologists developing the field regardless of any societal mission, or for problem-centered approaches without much emphasis on theory-development. Types of mission-orientation which can be placed between these extremes have been established to a limited extent in Dutch fresh-water ecology. Conclusions are drawn as to why only certain approaches have been successfully institutionalized in the Dutch research setting. On the basis of these results the implications for science policy are discussed. Moreover generalizations are made with respect to the usefulness of the concept of mission-orientation.

The Efficiency of Simulation-Based Multiple Comparisons

A frequently encountered problem in practice is that of simultaneous interval estimation of p linear combinations of a parameter beta in the setting of (or equivalent to) a univariate linear model. This problem has been solved adequately only in a few settings when the covariance matrix of the estimator is diagonal; in other cases, conservative solutions can be obtained by the methods of Scheffé, Bonferroni, or Sidák (1967, Journal of the American Statistical Association 62, 626-633). Here we investigate the efficiency of using a simulated critical point for exact intervals, which has been suggested before but never put to serious test. We find the simulation-based method to be completely reliable and essentially exact. Sample size savings are substantial (in our settings): 3-19% over the Sidák method, 4-37% over the Bonferroni method, and 27-33% over the Scheffé method. We illustrate the efficiency and flexibility of the simulation-based method with case studies in physiology and marine ecology.

The scope of mission-orientation in Dutch fresh-water ecology

In response to growing concern about environmental problems ecologists have engaged in a variety of ‘mission-oriented” efforts in which they claim to have taken into account the objective of helping to solve environmental problems in their research strategies or research programmes. The significance of these efforts is evaluated here in terms of both the theoretical development of the field of ecology and its orientation towards social objectives. Three examples of mission-orientation are analyzed on the basis of a case-study of Dutch fresh-water ecology; (1) ecosystems research within the framework of the International Biological Programme; (2) landscape ecology, and (3) ecological research on the management of fresh-water resources. These examples demonstrate that in principle the scope of missionorientation in ecology can be broad. In Dutch fresh-water ecology, however, two specific approaches have become particularly institutionalized. The ecologists tended to opt either for theory-centered approaches close to the type of research carried out by ecologists developing the field regardless of any societal mission or for problem-centered approaches without much emphasis on theory development. Types of mission-orientation which can be placed between these extremes have been established only to a limited extent in Dutch fresh-water ecology.

The Impact of Screening and Referral Practices in Early Childhood Special Education: Policy Considerations and Research Directions

Ecological case study methods were used in an exploratory investigation of four early childhood special education (ECSE) screening programs. Possible influences on screening outcomes were identified. The screening outcomes selected for comparing ECSE programs included (a) the percentage of eligible preschoolers screened (participation rate) and (b) the percentage of screened children referred for further developmental assessment (referral rate). Observations, interviews, file searches, and parent surveys were used to obtain multidimensional descriptions of outreach, screening, and referral practices. Results suggested that few screening and referral practices influenced screening outcomes in a consistent manner. Participation rates were related to school district size and the accessibility of screening to the public. Referral rates appeared to be influenced by screening purposes, second-level referral decisions, and subjective judgment. Relationships among community agencies appeared to influence both participation and referral rates. Policy considerations and directions for research are discussed.

Sexual Selection and Variance in Reproductive Success

Sexual Selection and Variance in Reproductive Success

Crisis and Development: An Ecological Case Study of the Forest of Arden, 1570-1674

During the Tudor and Stuart periods the population of England doubled, increasing from perhaps 2.5 to 5 million. When the total had last reached the 4–5 million mark, in the early fourteenth century, there had been a sharp Malthusian cut-back. How then did the country manage to break through this crucial barrier at its second attempt? Victor Skipp throws light on this question by constructing a detailed model of demographic, economic and social change for a sample group of English communities. After examing the effect of the ecological adjustments on social structure, domestic and cultural life, Mr Skipp turns to the wider implications of his model, considering the possibilities of adapting it to the analysis of sixteenth and seventeenth century developments in other English communities; how it might be related to the 'general European crisis', particularly as expounded in the regional studies of French historians; and to the political alignment of local inhabitants during the English civil war.