Consequences of food distribution for optimal searching behavior: an evolutionary model

Resource distribution can vary greatly in space and time. Consequently, animals should adjust their searching tactics to such spatio–temporal patterns in accordance with their innate capabilities, or alternatively, they should use a genetically fixed searching tactic that has been evolved in response to the specific pattern of the food they experience. Using a simulation model and a genetic algorithm, we show how optimal searching tactics change as a function of food spatial pattern. Searching tactics for hidden prey can be approximated using the following three components: (1) Extensive search mode (ESM), the type of movement before encountering a food item; (2) Intensive search mode (ISM), the type of movement after encountering a food item; and (3) ISM duration. Both ESM and ISM are characterized by movement tortuosity. We show that searching behavior adaptively changes as a function of food pattern. When food is distributed in a regular pattern, ISM is more directional than ESM, but under a clumped food pattern, ISM is much more tortuous than ESM. It may suggest that animals with larger spectra of searching tactics should experience greater variance or seasonal changes in their food pattern than animals with narrow spectra of searching tactics. Increased forager attack radius diminishes the differences between ESM and ISM, and thus the use of these three components to model searching in animals with higher attack radii is not appropriate. Increased handling time, which is a surrogate of reducing habitat profitability results in longer patch residency time as expected by optimal foraging theory. To conclude, we suggest that using such a combined approach of simulation models and genetic algorithms may improve our understanding of how extrinsic and intrinsic factors interact to influence searching behavior.     

Explanation and prediction in vegetation science

A definition of vegetation science is given, spanning 6 levels of integration and stressing the interrelations among them. The problems of realism are discussed. The selection of levels is related to the adequate correspondence between conceptualization and research aims. Pattern and process are introduced as the central concepts of vegetation science. The perception of reality is dependent on the spatial and temporal scale chosen. The concept of noise is discussed in relation to stochasticity and randomness of events. Traces of essentialism are found both in classification of communities and habitat ecology. Classification is important, particularly the coexistence of alternative classification approaches. Organicism as a basis of vegetation research is rejected because the organismic view is inadequate on higher integration levels. The concept of function is redefined in a non-teleologic way.Present vegetation ecological research is inductivistic. One possible alternative to inductivism is falsificationism. The major domain of this approach is hypothesis testing, which will become more important. Progress can only be reached by a maximum degree of communication among scientific individuals.Predictive ecology is partly based on historic explanation, partly on complementary approaches. Characters of vegetation worthwhile to be predicted are listed and the necessary requirements for vegetation science to become predictive are discussed. A major requirement is the development of succession and life-history theory. A further elaboration of the individualistic concept will be a main task of vegetation science in the near future.     

The role of visual and olfactory plant cues in aphid behaviour and the development of non-persistent virus management strategies

Non-persistent viruses are transmitted by aphids in short feeding probes during the initial stages of aphid host plant selection behaviour. To control the transmission of these viruses, farmers rely on pesticides and cultural control practices, with varying success rates. As a result, there is a need for novel management practices that are more robust and specific to reducing aphid landing rates in crops. Aphid–plant–virus interactions involve a number of behaviours and processes to ensure survival of the insect vector and virus. So far, virus management tactics focused on reducing immigrating aphids in crops have emphasized the manipulation of visual rather than olfactory stimuli. An improved understanding of the synergistic or additive effects in which aphids use visual and olfactory stimuli to locate host plants could be used to improve on current non-persistent virus management tactics and develop novel strategies. The aim of this review is to evaluate current understanding of aphid vector behaviour and the ways that these behaviours have been exploited to develop management strategies, and to identify areas of research needed to further improve virus management.     

Biochemical systems theory: operational differences among variant representations and their significance

An appropriate language or formalism for the analysis of complex biochemical systems has been sought for several decades. The necessity for such a formalism results from the large number of interacting components in biochemical systems and the complex non-linear character of these interactions. The Power-Law Formalism, an example of such a language, underlies several recent attempts to develop an understanding of integrated biochemical systems. It is the simplest representation of integrated biochemical systems that has been shown to be consistent with well-known growth laws and allometric relationships--the most regular, quantitative features that have been observed among the systemic variables of complex biochemical systems. The Power-Law Formalism provides the basis for Biochemical Systems Theory, which includes several different strategies of representation. Among these, the synergistic-system (S-system) representation is the most useful, as judged by a variety of objective criteria. This paper first describes the predominant features of the S-system representation. It then presents detailed comparisons between the S-system representation and other variants within Biochemical Systems Theory. These comparisons are made on the basis of objective criteria that characterize the efficiency, power, clarity and scope of each representation. Two of the variants within Biochemical Systems Theory are intimately related to other approaches for analyzing biochemical systems, namely Metabolic Control Theory and Flux-Oriented Theory. It is hoped that the comparisons presented here will result in a deeper understanding of the relationships among these variants. Finally, some recent developments are described that demonstrate the potential for further growth of Biochemical Systems Theory and the underlying Power-Law Formalism on which it is based.     

Classification of vegetation: Past,present and future

Abstract. This paper is a report on the past, status-quo and perspectives of vegetation classification, still a major occupation of many vegetation scientists. The history of vegetation classification is discussed against a background of several controversial issues such as the problem of continuum vs. discontinuum, naturalness vs. arbitrariness of the nature of plant communities, universality vs. ad hoc character of syntaxonomic schemes, as well as classical versus numerical approaches to data analysis for classification purposes. The development of the methodology of vegetation science and the present image of vegetation classification is documented by a bibliometric analysis of the publication record of four majorjournals: Journal of Vegetation Science, Vegetatio, Phytocoenologia and Tuexenia. This analysis revealed a persisting controversy between traditional and numerical approaches to vegetation classification. A series of important changes in vegetation science (foundation of new journals, change of editorial policy by the established, important meetings) punctuate a period called the ‘Innovation period’. Several trends in the development of methods of vegetation systematics are summarized under the headings formalism, pluralism, functionalism, pragmatism and indeterminism. Some new features, such as the development and improvement of numerical tools, use of large data banks and attempts to summarize the theory of vegetation classification are discussed. The new growth-form system of Barkman initiated a revival of physiognomy-based vegetation classification. Within this framework the use of the character-type concept and the development of new numerical methods for studying the hierarchical structure of character-set types seems to be a promising approach. The achievements of population biology and ecophysiology have affected vegetation science by emphasizing the functionality of species within plant communities. The use of guilds and other functional groups has experienced an increasing interest from vegetation scientists. Applied in vegetation science, fuzzy-set theory has bridged the techniques of classification and ordination of plant communities.     

Monological versus dialogical consciousness: two epistemological views on the use of theory in clinical ethical practice

In this article, we argue that a critical examination of epistemological and anthropological presuppositions might lead to a more fruitful use of theory in clinical-ethical practice. We differentiate between two views of conceptualizing ethics, referring to Charles Taylors' two epistemological models: 'monological' versus 'dialogical consciousness'. We show that the conception of ethics in the model of 'dialogical consciousness' is radically different from the classical understanding of ethics in the model of 'monological consciousness'. To reach accountable moral judgments, ethics cannot be conceptualized as an individual enterprise, but has to be seen as a practical endeavor embedded in social interactions within which moral understandings are being negotiated. This view has specific implications for the nature and the role of ethical theory. Theory is not created in the individual mind of the ethicist; the use of theory is part of a joint learning process and embedded in a cultural context and social history. Theory is based upon practice, and serves practical purposes. Thus, clinical ethics support is both practical and theoretical.     

Universal Optimization of Flight Initiation Distance and Habitat-Driven Variation in Escape Tactics in a Namibian Lizard Assemblage

Some aspects of escape predicted by theoretical models are intended to apply universally. For example, flight initiation distance (distance between an approaching predator and prey when escape begins) is predicted from predation risk and the costs of escaping. Escape tactics and refuge selection are not currently predicted by theoretical models, but are expected to vary with structural features of the habitat. One way of studying such variation is to compare aspects of antipredatory behavior among sympatric species that differ in habitat or microhabitat use. In an assemblage of lizards in northwestern Namibia, we conducted experiments to test predictions of escape theory for three risk factors in representatives of three families and observed escape tactics in additional species. As predicted by escape theory, flight initiation distance increased with directness of a predator's approach and predator speed in Agama planiceps, Mabuya acutilabris, and Rhotropus boultoni, and with distance from refuge in M. acutilabris. As predicted by theory, the probability of entering refuge increased with risk in R. boultoni. All available data indicate that flight initiation distance and refuge entry by lizards conform to theoretical predictions. Escape tactics varied greatly as a function of habitat type: (1) arboreal species fled up and around trees and sometimes entered tree holes; (2) saxicolous species used rock crevices as refuges, but differed in tactics prior to entering refuges; and (3) terrestrial species fled into bushes or other vegetation, often to the far sides of them. Some M. acutilabris entered small animal burrows or buried themselves in sand beneath bushes. Escape tactics varied even among congeners in Mabuya, highlighting the important effect of habitat structure on them. Although habitat partitioning has traditionally been viewed as favoring species coexistence, an interesting by‐product appears to be structuring of escape tactics in lizard communities.     

Managing vegetation in surface-flow wastewater-treatment wetlands for optimal treatment performance

Constructed wetlands that mimic natural marshes have been used as low-cost alternatives to conventional secondary or tertiary wastewater treatment in the U.S. for at least 30 years. However, the general level of understanding of internal treatment processes and their relation to vegetation and habitat quality has not grown in proportion to the popularity of these systems. We have studied internal processes in surface-flow constructed wastewater-treatment wetlands throughout the southwestern U.S. since 1990. At any given time, the water quality, hydraulics, water temperature, soil chemistry, available oxygen, microbial communities, macroinvertebrates, and vegetation each greatly affect the treatment capabilities of the wetland. Inside the wetland, each of these components plays a functional role and the treatment outcome depends upon how the various components interact. Vegetation plays a uniquely important role in water treatment due to the large number of functions it supports, particularly with regard to nitrogen transformations. However, it has been our experience that vegetation management is critical for achieving and sustaining optimal treatment function. Effective water treatment function and good wildlife quality within a surface-flow constructed wetland depend upon the health and sustainability of the vegetation. We suggest that an effective tool to manage and sustain healthy vegetation is the use of hummocks, which are shallow emergent plant beds within the wetland, positioned perpendicular to the water flow path and surrounded by water sufficiently deep to limit further emergent vegetation expansion. In this paper, we describe the use of a hummock configuration, in conjunction with seasonal water level fluctuations, to manage the vegetation and maintain the treatment function of wastewater-treatment wetlands on a sustainable basis.     

中国常绿阔叶林分类试行方案

植被分类是植被生态学研究中最复杂、充满着争论的问题之一,直到现在并没有一个能为植被学家共同接受的、统一的分类系统。常绿阔叶林的复杂性仅次于热带雨林,加之在人类长期干扰下,变化极大,过渡性群落极多,更增加了分类的困难。中国常绿阔叶林分类经历了漫长的道路,20世纪50年代学习苏俄学派,60年代初引进威斯康星学派的“重要值"概念,在研究云南滇青冈(Cyclobalanopsis glaucoides)林时也曾试用过法瑞学派的理论和方法。80年代《中国植被》(1980)一书的作者们提出,对于“南方某些类型"在“群系(Formation)"和“群丛(Association)"划分时应采用“标志种(Diagnostic species)"的原则,当时由于资料所限,这一原则并未得到贯彻。本文在总结以往分类方案的基础上,根据高级单位以生态外貌、中级单位以优势度类型、低级单位以特征种组的分类原则,构建了从“群丛"、“群系"、“群系组"到“植被亚型"和“植被型"的中国常绿阔叶林分类系统。将中国常绿阔叶林划分出3个植被型、8个植被亚型、14个群系组和53个群系。这些群系大都占据一定的地理区域,并与一定的生境相联系。     

What determines the normal water content of a living cell?

Most living cells contain a large amount of water. To improve our understanding of this fundamental phenomenon of cell physiology, five theories are critically examined in the light of three sets of relevant experimental findings. These findings are: (1) the diversity and specificity of the percentage water content to tissue type; (2) the limitation imposed by the Law of the Conservation of Energy on postulating membrane pumps and (3) the non-extractability of cell water from the open ends of muscle cells whose membrane covering has been surgically removed. Two of the five theories examined are called respectively the accidental theory (Theory I) and the direct water pump-leak theory (Theory III); both are introduced for the first time here as working hypotheses. Three others theories examined were published; they comprise the Donnan membrane equilibrium theory (Theory II), the indirect pump-leak (Theory IV) and the polarized-oriented multilayer (PM) theory of cell water (Theory V.) The PM (Theory V) alone is in harmony with, and supported by all three sets of the experimental findings. The remaining theories are shown to be non-applicable to cell water by at least two of the findings     

An inter-regional approach to intraspecific variation in habitat association: Rock Buntings Emberiza cia as a case study

The habitat association approach has been increasingly used in ecology to resolve problems in wildlife conservation and management. One problem related to habitat association studies is that they are restricted to small geographical areas within a species' range, and thus they are applicable to only a limited set of environmental conditions utilized by the species. In addition, very few studies address why the preference for specific habitat components may be adaptive for the species in question. The objective of this study was to examine how consideration of populations of a species from two dramatically different environments affects the results of habitat association modelling for a ground-nesting passerine, the Rock Bunting Emberiza cia . At a regional scale, a trend to defending breeding habitat patches with relatively higher stone cover was confined to birds from a temperate region in Slovakia. In contrast, in a semi-arid region in southeastern Spain, Rock Buntings preferred to use breeding habitat patches that had relatively higher grass cover. Combining data from both regions, breeding Rock Buntings showed a general pattern of using habitat patches close to hedges, with low bush cover, high ditch density and a steep slope. Whereas regional habitat association models appear to be sensitive to the particularities of the breeding environment, our study suggests that Rock Bunting breeding habitat association is constrained by the adults' tactics to protect themselves against predators. Although the birds prefer to nest in patches of low vegetation, the better to see nearby predators, these patches are ideally close to taller vegetation that can be used to provide cover when evading predators, and they are also of a rugged profile that helps the birds to approach and leave the nest stealthily.     

The Importance of Understanding the Nature of Science for Accepting Evolution

Many students reject evolutionary theory, whether or not they adequately understand basic evolutionary concepts. We explore the hypothesis that accepting evolution is related to understanding the nature of science. In particular, students may be more likely to accept evolution if they understand that a scientific theory is provisional but reliable, that scientists employ diverse methods for testing scientific claims, and that relating data to theory can require inference and interpretation. In a study with university undergraduates, we find that accepting evolution is significantly correlated with understanding the nature of science, even when controlling for the effects of general interest in science and past science education. These results highlight the importance of understanding the nature of science for accepting evolution. We conclude with a discussion of key characteristics of science that challenge a simple portrayal of the scientific method and that we believe should be emphasized in classrooms.     

Lack of Evolution Acceptance Inhibits Students’ Negotiation of Biology-based Socioscientific Issues

The purpose of this study was to explore science content used during college students’ negotiation of biology-based socioscientific issues (SSI) and examine how it related to students’ conceptual understanding and acceptance of biological evolution. The Socioscientific Issues Questionnaire (SSI-Q) was developed to measure depth of evolutionary science content use during SSI negotiation. Fifty-two upper level undergraduate biology and non-biology majors completed the SSI-Q and also the Conceptual Inventory of Natural Selection to assess evolution understanding and the Measure of Acceptance of the Theory of Evolution to appraise evolution acceptance. A multiple regression analysis tested for interaction effects between the predictor variables, evolution understanding and evolution acceptance. Results indicate that college students primarily use science concepts related to evolution to negotiate biology-based SSI including variation in a population, inheritance of traits, differential success, and change through time. The hypothesis that the extent of one’s acceptance of evolution is a mitigating factor in how science content related to evolution is evoked during SSI negotiation was supported by the data, in that such content was consistently evoked by participants for each of the three SSI scenarios used in this study.     

Ecology of Australia: the effects of nutrient-poor soils and intense fires

Australia, the flattest, driest, and geologically oldest vegetated continent, has a uniquely high proportion of nutrient-poor soils. We develop a "Nutrient-Poverty/Intense-Fire Theory," which postulates that most anomalous features of organisms and ecosystems of Australia are the evolutionary consequences of adaptations to nutrient poverty, compounded by intense fire that tends to occur as a result of nutrient poverty. The fundamental tenet of the theory is that plants growing in environments with plentiful light and periodic adequate moisture, but on soils poor in phosphorus, zinc, and other indispensible nutrients, can synthesize carbohydrates in excess of the amount that can be combined with, or catalyzed by, these nutrients for metabolism and production of nutrient-rich foliage and reproductive tissues. They use this "expendable energy" to produce well-defended foliage, large quantities of lignified tissues, and readily digestible exudates. Rapid accumulation of nutrient-poor biomass, a result of low rates of herbivory, provides fuel for intense fire. Intense fire exacerbates nutrient poverty by volatilizing certain micronutrients critical for animals. Anomalous features of organisms of Australia that can be explained by this theory, rather than by climate or phylogenetic history alone, include the following: most woody plants have long-lived, durable foliage; plants defend their tissues primarily with carbon-rich but nutrient-poor compounds; an unusually high proportion of plants protects seeds from fire and granivores in sturdy, woody capsules or follicles; plants allocate unusually large amounts of expendable energy to production of carbon-based exudates, such as nectar and gums; an unusually high proportion of plant species is pollinated by vertebrates that average larger size than pollinators on other continents; herbivores are small and have slow metabolism; there are no ruminants, mammals that eat mainly subterranean plant matter, or fungus-culturing termites and ants; vegetation dominated by leaf-spinescent plants is more extensive than vegetation dominated by stem-spinescent plants; nitrogen-fixing plants are major components of most vegetation types; there is a higher proportion of myrmecochorous plant species than on any other continent; there are hardly any stem-succulent and few leaf-succulent, perennial, non-halophytic plant species; and an unusually high proportion of bird species breeds cooperatively. Although the Nutrient-Poverty/Intense-Fire Theory can provide plausible explanations for these anomalous features, some puzzles remain, among them the great success of introduced herbivores, the lack of grazers on extensive grasslands on cracking clays, the apparently low productivity of ants, and the prominence of the parasitic plants of Australia. By examining the ratios of available energy to nutrients, particularly scarce nutrients, ecologists may identify processes not previously recognized as important for life forms or biotic adaptation on other continents.     

Relationships among Teachers’ Knowledge and Beliefs Regarding the Teaching of Evolution: A Case for Turkey

The research study investigated the possible associations among science and biology teachers?? knowledge and belief variables concerning teaching evolution in science and biology classes. Specifically, this study examined how a set of variables including teachers?? understanding of evolution and nature of science (NOS) is related to the set of variables including teachers?? acceptance of evolution and perceptions of teaching evolution (i.e., perceptions of the necessity of addressing evolution in their classrooms, perceptions of the factors that impede addressing evolution in their classrooms, and personal science teaching efficacy beliefs regarding evolution). Data were collected from science and biology teachers through administration of Evolution Content Knowledge Test, Measure of Acceptance of the Theory of Evolution, Nature of Science as Argument Questionnaire and Teachers?? Perceptions of Teaching Evolution Scale. Canonical correlation analysis findings suggested that teachers who had thorough understanding of evolution and NOS were likely to both accept the scientific validity of evolution and believe the necessity of addressing evolution in the classrooms. On the other hand, teachers with thorough understanding of evolution and NOS did not necessarily believe that they have a stronger sense of self-efficacy beliefs regarding teaching evolution and that there are fewer obstacles to addressing evolution in the classroom. The research is significant in that it provides empirical evidence clarifying the interactions between teachers?? understanding and beliefs in teaching evolution. Implications for science teacher education are discussed.     

Evasion of innate and adaptive immunity by flaviviruses

After a virus infects an animal, antiviral responses are generated that attempt to prevent dissemination. Interferons, antibody, complement, T and natural killer cells all contribute to the control and eradication of viral infections. Most flaviviruses, with the exception of some of the encephalitic viruses, cause acute disease and do not establish persistent infection. The outcome of flavivirus infection in an animal is determined by a balance between the speed of viral replication and spread, and the immune system response. Although many of the mechanistic details require further elucidation, flaviviruses have evolved specific tactics to evade the innate and adaptive immune response. A more thorough understanding of these principles could lead to improved models for viral pathogenesis and to strategies for the development of novel antiviral agents.     

Ecological Monitoring and Health Research in Luambe National Park,Zambia: Generation of Baseline Data Layers

Classifying, describing and understanding the natural environment is an important element of studies of human, animal and ecosystem health, and baseline ecological data are commonly lacking in remote environments of the world. Human African trypanosomiasis is an important constraint on human well-being in sub-Saharan Africa, and spillover transmission occurs from the reservoir community of wild mammals. Here we use robust and repeatable methodology to generate baseline datasets on vegetation and mammal density to investigate the ecology of warthogs (Phacochoerus africanus) in the remote Luambe National Park in Zambia, in order to further our understanding of their interactions with tsetse (Glossina spp.) vectors of trypanosomiasis. Fuzzy set theory is used to produce an accurate landcover classification, and distance sampling techniques are applied to obtain species and habitat level density estimates for the most abundant wild mammals. The density of warthog burrows is also estimated and their spatial distribution mapped. The datasets generated provide an accurate baseline to further ecological and epidemiological understanding of disease systems such as trypanosomiasis. This study provides a reliable framework for ecological monitoring of wild mammal densities and vegetation composition in remote, relatively inaccessible environments.     

Reproductive-tactic-specific variation in sperm swimming speeds in a shell-brooding cichlid

Theory predicts that males experiencing elevated levels of sperm competition will invest more in gonads and produce faster-swimming sperm. Although there is ample evidence in support of the first prediction, few studies have examined sperm swimming speed in relation to sperm competition. In this study, we tested these predictions from sperm competition theory by examining sperm characteristics in Telmatochromis vittatus, a small shell-brooding cichlid fish endemic to Lake Tanganyika. Males exhibit four different reproductive tactics: pirate, territorial, satellite, and sneaker. Pirate males temporarily displace all other competing males from a shell nest, whereas sneaker males always release sperm in the presence of territorial and satellite males. Due to the fact that sneakers spawn in the presence of another male, sneakers face the highest levels of sperm competition and pirates the lowest, whereas satellites and territorials experience intermediate levels. In accordance with predictions, sperm from sneakers swam faster than sperm from males adopting the other reproductive tactics, whereas sperm from pirates was slowest. Interestingly, we were unable to detect any variation in sperm tail length among these reproductive tactics. Thus, sperm competition appears to have influenced sperm energetics in this species without having any influence on sperm size.