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- Volume 32, 2001
Annual Review of Ecology, Evolution, and Systematics - Volume 32, 2001
Volume 32, 2001
- Review Articles
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Chemical Detection of Natural Enemies by Arthropods: An Ecological Perspective
Marcel Dicke, and Paul GrostalVol. 32 (2001), pp. 1–23More Less▪ AbstractFood webs are overlaid with infochemical webs that mediate direct and indirect interactions. The infochemicals may result in shifts in trait values, which affect the strength of species interactions. As a consequence, population dynamics and evolutionary changes can be affected. Chemical information can mediate the interactions between animals and their resources, competitors and enemies. Of all chemical information gathered by animals, cues about predation risk are of special significance because predation risk usually has important and immediate consequences on fitness. In this paper we selectively review the role of chemical information in enemy avoidance by arthropods. Arthropods not only constitute important components of food webs, being the largest group in numbers and species diversity; they also make excellent models for ecological studies. We discuss the evidence, the key mechanisms, and the trade-offs involved in chemical detection of enemies by potential arthropod prey. Further, we address the variation in prey responses and the evidence for learning in avoiding enemies by arthropods. Finally, we identify and prioritize major questions to be tackled by future studies.
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Sex Chromosome Meiotic Drive
Vol. 32 (2001), pp. 25–49More Less▪ AbstractSex chromosome drive refers to the unequal transmission of X and Y chromosomes from individuals of the heterogametic sex, resulting in biased sex ratios among progeny and within populations. The presence of driving sex chromosomes can reduce mean fitness within a population, bring about intragenomic conflict between the X chromosome, the Y, and the autosomes, and alter the intensity or mode of sexual selection within species. Sex chromosome drive, or its genetic equivalent, is known in plants, mammals, and flies. Many species harboring driving X chromosomes have evolved Y-linked and autosomal suppressors of drive. If a drive polymorphism is not stable, then driving chromosomes may spread to fixation and cause the extinction of a species. Certain characteristics of species, such as population density and female mating rate, may affect the probability of fixation of driving chromosomes. Thus, sex chromosome drive could be an agent of species-level selection.
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Environmental Influences on Regional Deep-Sea Species Diversity1
Vol. 32 (2001), pp. 51–93More Less▪ AbstractMost of our knowledge of biodiversity and its causes in the deep-sea benthos derives from regional-scale sampling studies of the macrofauna. Improved sampling methods and the expansion of investigations into a wide variety of habitats have revolutionized our understanding of the deep sea. Local species diversity shows clear geographic variation on spatial scales of 100–1000 km. Recent sampling programs have revealed unexpected complexity in community structure at the landscape level that is associated with large-scale oceanographic processes and their environmental consequences. We review the relationships between variation in local species diversity and the regional-scale phenomena of boundary constraints, gradients of productivity, sediment heterogeneity, oxygen availability, hydrodynamic regimes, and catastrophic physical disturbance. We present a conceptual model of how these interdependent environmental factors shape regional-scale variation in local diversity. Local communities in the deep sea may be composed of species that exist as metapopulations whose regional distribution depends on a balance among global-scale, landscape-scale, and small-scale dynamics. Environmental gradients may form geographic patterns of diversity by influencing local processes such as predation, resource partitioning, competitive exclusion, and facilitation that determine species coexistence. The measurement of deep-sea species diversity remains a vital issue in comparing geographic patterns and evaluating their potential causes. Recent assessments of diversity using species accumulation curves with randomly pooled samples confirm the often-disputed claim that the deep sea supports higher diversity than the continental shelf. However, more intensive quantitative sampling is required to fully characterize the diversity of deep-sea sediments, the most extensive habitat on Earth. Once considered to be constant, spatially uniform, and isolated, deep-sea sediments are now recognized as a dynamic, richly textured environment that is inextricably linked to the global biosphere. Regional studies of the last two decades provide the empirical background necessary to formulate and test specific hypotheses of causality by controlled sampling designs and experimental approaches.
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The Physiology of Life History Trade-Offs in Animals
Vol. 32 (2001), pp. 95–126More Less▪ AbstractThe functional causes of life history trade-offs have been a topic of interest to evolutionary biologists for over six decades. Our review of life history trade-offs discusses conceptual issues associated with physiological aspects of trade-offs, and it describes recent advances on this topic. We focus on studies of four model systems: wing polymorphic insects, Drosophila, lizards, and birds. The most significant recent advances have been: (a) incorporation of genetics in physiological studies of trade-offs, (b) integration of investigations of nutrient input with nutrient allocation, (c) development of more sophisticated models of resource acquisition and allocation, (d) a shift to more integrated, multidisciplinary studies of intraspecific trade-offs, and (e) the first detailed investigations of the endocrine regulation of life history trade-offs.
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Urban Ecological Systems: Linking Terrestrial Ecological, Physical, and Socioeconomic Components of Metropolitan Areas1
Vol. 32 (2001), pp. 127–157More Less▪ AbstractEcological studies of terrestrial urban systems have been approached along several kinds of contrasts: ecology in as opposed to ecology of cities; biogeochemical compared to organismal perspectives, land use planning versus biological, and disciplinary versus interdisciplinary. In order to point out how urban ecological studies are poised for significant integration, we review key aspects of these disparate literatures. We emphasize an open definition of urban systems that accounts for the exchanges of material and influence between cities and surrounding landscapes. Research on ecology in urban systems highlights the nature of the physical environment, including urban climate, hydrology, and soils. Biotic research has studied flora, fauna, and vegetation, including trophic effects of wildlife and pets. Unexpected interactions among soil chemistry, leaf litter quality, and exotic invertebrates exemplify the novel kinds of interactions that can occur in urban systems. Vegetation and faunal responses suggest that the configuration of spatial heterogeneity is especially important in urban systems. This insight parallels the concern in the literature on the ecological dimensions of land use planning. The contrasting approach of ecology of cities has used a strategy of biogeochemical budgets, ecological footprints, and summaries of citywide species richness. Contemporary ecosystem approaches have begun to integrate organismal, nutrient, and energetic approaches, and to show the need for understanding the social dimensions of urban ecology. Social structure and the social allocation of natural and institutional resources are subjects that are well understood within social sciences, and that can be readily accommodated in ecosystem models of metropolitan areas. Likewise, the sophisticated understanding of spatial dimensions of social differentiation has parallels with concepts and data on patch dynamics in ecology and sets the stage for comprehensive understanding of urban ecosystems. The linkages are captured in the human ecosystem framework.
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Dispersal in Freshwater Invertebrates
Vol. 32 (2001), pp. 159–181More Less▪ AbstractMovement between discrete habitat patches can present significant challenges to organisms. Freshwater invertebrates achieve dispersal using a variety of mechanisms that can be broadly categorized as active or passive, and which have important consequences for processes of colonization, gene flow, and evolutionary divergence. Apart from flight in adult freshwater insects, active dispersal appears relatively uncommon. Passive dispersal may occur through transport by animal vectors or wind, often involving a specific desiccation-resistant stage in the life cycle. Dispersal in freshwater taxa is difficult to study directly, and rare but biologically significant dispersal events may remain undetected. Increased use of molecular markers has provided considerable insight into the frequency of dispersal in freshwater invertebrates, particularly for groups such as crustaceans and bryozoans that disperse passively through the transport of desiccation-resistant propagules. The establishment of propagule banks in sediment promotes dispersal in time and may be particularly important for passive dispersers by allowing temporal escape from unfavorable conditions. Patterns that apply to dispersal in freshwater invertebrates can be readily extended to other freshwater taxa, since common challenges arise from the colonization of isolated aquatic systems.
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Applied Evolution
J. J. Bull, and H. A. WichmanVol. 32 (2001), pp. 183–217More Less▪ AbstractEvolutionary biology is widely perceived as a discipline with relevance that lies purely in academia. Until recently, that perception was largely true, except for the often neglected role of evolutionary biology in the improvement of agricultural crops and animals. In the past two decades, however, evolutionary biology has assumed a broad relevance extending far outside its original bounds. Phylogenetics, the study of Darwin's theory of “descent with modification,” is now the foundation of disease tracking and of the identification of species in medical, pharmacological, or conservation settings. It further underlies bioinformatics approaches to the analysis of genomes. Darwin's “evolution by natural selection” is being used in many contexts, from the design of biotechnology protocols to create new drugs and industrial enzymes, to the avoidance of resistant pests and microbes, to the development of new computer technologies. These examples present opportunities for education of the public and for nontraditional career paths in evolutionary biology. They also provide new research material for people trained in classical approaches.
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Mistletoe—A Keystone Resource in Forests and Woodlands Worldwide
Vol. 32 (2001), pp. 219–249More Less▪ AbstractMistletoes are a diverse group of parasitic plants with a worldwide distribution. The hemiparasitic growth form is critical to understanding their biology, buffering variation in resource availability that constrains the distribution and growth of most plants. This is manifested in many aspects of mistletoe life history, including extended phenologies, abundant and high-quality fruits and nectar, and few chemical or structural defenses. Most mistletoe species rely on animals for both pollination and fruit dispersal, and this leads to a broad range of mistletoe-animal interactions. In this review, I summarize research on mistletoe biology and synthesize results from studies of mistletoe-animal interactions. I consolidate records of mistletoe-vertebrate interactions, incorporating species from 97 vertebrate families recorded as consuming mistletoe and from 50 using mistletoe as nesting sites. There is widespread support for regarding mistletoe as a keystone resource, and all quantitative data are consistent with mistletoe functioning as a determinant of alpha diversity. Manipulative experiments are highlighted as a key priority, and six explicit predictions are provided to guide future experimental research.
The facts which kept me longest scientifically orthodox are those of adaptation—the pollen-masses in Asclepias—the misseltoe, with its pollen carried by insects and seed by Birds—the woodpecker, with its feet and tail, beak and tongue, to climb the tree and secure insects. To talk of climate or Lamarckian habit producing such adaptation to other organic beings is futile. This difficulty, I believe I have surmounted.
From a letter to Asa Gray by Charles Darwin, 1857.
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The Role of Disturbance in the Ecology and Conservation of Birds1
Vol. 32 (2001), pp. 251–276More Less▪ AbstractNatural ecological disturbance creates habitats that are used by diverse groups of birds. In North America, these habitats or ecosystems include grasslands or prairies, shrublands, savannas, early successional forests, and floodplains. Whereas the extent of all natural habitats has diminished significantly owing to outright loss from agriculture and development, the suppression of disturbance by agents such as fire and flooding has led to further losses. Accordingly, the abundances of many bird species adapted to disturbance-mediated habitats have declined as well. In North America, these declines have been more severe and common than those of species associated with less frequently disturbed habitats such as mature or closed-canopy forests. Field studies consistently reveal the direct role of disturbance and successional processes in structuring avian habitats and communities. Conservation strategies involving the management of disturbance through some combination of flooding, application of fire, or the expression of wildfire, and use of certain types of silviculture have the potential to diversify avian habitats at the local, landscape, and regional scale. Many aspects of the disturbance ecology of birds require further research. Important questions involve associations between the intensity and frequency of disturbance and the viability of bird populations, the scale of disturbance with respect to the spatial structure of populations, and the role of natural vs. anthropogenic disturbance. The effects of disturbance and ensuing successional processes on birds are potentially long-term, and comprehensive monitoring is essential.
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Approaches to the Study of Territory Size and Shape
Vol. 32 (2001), pp. 277–303More Less▪ AbstractIntraspecific variation in territory size and shape can have strong effects on population structure and dynamics. The traditional theoretical approach to the study of territory size is based on optimality models that analyze decisions of focal residents as responses to the costs and benefits of defense. These models have stimulated numerous empirical studies showing that territory holders adjust their behavior according to rates of intrusion and availability of food. However, models of optimal territory size are applicable only in limited circumstances because they focus on unilateral decisions rather than on interactions. Furthermore, observational and experimental studies often find that territory sizes are insensitive to food supply. Recently, greater emphasis has been placed on two alternative approaches. The first concerns interactions among contiguous neighbors and how these affect use of space. In these models territory size and shape are determined by the balance of pressure exerted at boundaries or arise as the results of local rules of movement and interaction. The second alternative approach views territory size as the outcome of interactions between established residents and potential settlers attempting to acquire territories. By considering the simultaneous actions of multiple competitors, these models allow quantitative prediction of the effects of territory defense on population density and spatial patterns as well as responses to environmental change.
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The Population Biology of Invasive Species
Vol. 32 (2001), pp. 305–332More Less▪ AbstractContributions from the field of population biology hold promise for understanding and managing invasiveness; invasive species also offer excellent opportunities to study basic processes in population biology. Life history studies and demographic models may be valuable for examining the introduction of invasive species and identifying life history stages where management will be most effective. Evolutionary processes may be key features in determining whether invasive species establish and spread. Studies of genetic diversity and evolutionary changes should be useful for understanding the potential for colonization and establishment, geographic patterns of invasion and range expansion, lag times, and the potential for evolutionary responses to novel environments, including management practices. The consequences of biological invasions permit study of basic evolutionary processes, as invaders often evolve rapidly in response to novel abiotic and biotic conditions, and native species evolve in response to the invasion.
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Streams in the Urban Landscape
Vol. 32 (2001), pp. 333–365More Less▪ AbstractThe world's population is concentrated in urban areas. This change in demography has brought landscape transformations that have a number of documented effects on stream ecosystems. The most consistent and pervasive effect is an increase in impervious surface cover within urban catchments, which alters the hydrology and geomorphology of streams. This results in predictable changes in stream habitat. In addition to imperviousness, runoff from urbanized surfaces as well as municipal and industrial discharges result in increased loading of nutrients, metals, pesticides, and other contaminants to streams. These changes result in consistent declines in the richness of algal, invertebrate, and fish communities in urban streams. Although understudied in urban streams, ecosystem processes are also affected by urbanization. Urban streams represent opportunities for ecologists interested in studying disturbance and contributing to more effective landscape management.
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Integrating Function and Ecology in Studies of Adaptation: Investigations of Locomotor Capacity as a Model System
Vol. 32 (2001), pp. 367–396More Less▪ AbstractUnderstanding adaptation in morphological and physiological traits requires elucidation of how traits relate to whole-organism performance and how performance relates to fitness. A common assumption is that performance capacities are utilized by and important to organisms. For some systems, it is assumed that high levels of physical fitness, as indexed by measures of locomotor performance, lead to high fitness levels. Although biologists have appreciated this, little attention has been paid to quantifying how organisms use their performance capacities in nature. We argue that for the study of adaptation to proceed, greater integration of laboratory studies of performance and behavioral/ecological studies is needed, and we illustrate this approach by examining two questions. First, how does the environment affect locomotor function in nature? Second, what percentage of locomotor capacities do animals use in nature? A review of studies in several animal groups shows widespread effects of the environment on measures of locomotor function.
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The Southern Conifer Family Araucariaceae: History, Status, and Value for Paleoenvironmental Reconstruction
Vol. 32 (2001), pp. 397–414More Less▪ AbstractThe Araucariaceae are important to biogeography because they have an ancient origin and are a distinctive and sometimes dominant component of southern hemisphere forest communities. This paper examines recent information on ecology and phylogeny and on pollen and macrofossil assemblages to assess the history and present-day status of the family and its potential for refinement of past environmental, particularly climatic, conditions. From an origin in the Triassic, the family expanded and diversified in both hemispheres in the Jurassic and Early Cretaceous and remained a significant component of Gondwanan vegetation until the latter part of the Cenozoic. The development of angiosperms in the Middle Cretaceous probably assisted in the demise of some araucarian components but there was also evolution of new genera. Recorded diversity in the early Cenozoic of Australia is as high as it was in the Early Cretaceous. Continental separation and associated climatic drying, cooling, and increased variability progressively reduced the ranges of conifers to moist, predominantly mesothermal climates on continents. However, tectonic and volcanic activity, partially associated with Australia's collision with Southeast Asia, provided new opportunities for some araucarian components on Asia-Pacific islands. Araucarians provide information on climatic conditions suitable for rainforest vegetation throughout their recorded period, even prior to the recognition or even existence of these forests in the fossil record. High pollen abundance is also indicative of marginal rainforest environments where these canopy emergents can compete effectively with angiosperm forest taxa. Despite their apparent relictual status in many areas, they provide precise paleoclimatic estimates in late Quaternary pollen records and have particular value in providing evidence of climatic variability that has otherwise been difficult to detect.
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The Units of Selection on Mitochondrial DNA
Vol. 32 (2001), pp. 415–448More Less▪ AbstractMitochondrial DNA (mtDNA) exists in a nested hierarchy of populations. There are multiple mtDNAs within each mitochondrion, a population of mitochondria in each cell, multiple oocytes within each reproductive female, multiple females in each population, and so on up through species and higher clades. The metabolic properties of mitochondria make them highly mutagenic environments for the naked, circular mtDNAs that lie within them. This mutational pressure introduces mtDNA variation (i.e., heteroplasmy) into the cytoplasmic population of cell lineages that are particularly prone to mutational decay and Muller's ratchet owing to the asexual, maternal inheritance of mtDNA. Neutrality tests show that deleterious mutations are common in mtDNA evolution. Population cage experiments further show that mtDNA fitnesses are influenced by nuclear-mitochondrial interactions. These selective processes are pervasive despite the long-standing use of mtDNA as a neutral marker in population and evolutionary biology. These evolutionary dynamics are also unique in the nested hierarchy of mtDNA populations because mutation, selection, and drift can act—and interact—at multiple levels. Multi-level selection can facilitate the escape from Muller's ratchet and help resolve intragenomic conflicts. This review addresses recent advances in the transmission genetics, population genetics, and evolution of mtDNA. A primary goal of the review is to motivate additional empirical studies that might clarify the many units of selection acting on mtDNA.
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Evolutionary Patterns Among Permo-Triassic Therapsids*
Vol. 32 (2001), pp. 449–480More Less▪ AbstractA rich fossil record documents nonmammalian evolution. In recent years, the application of cladistic methodology has shed valuable light on the relationships within the therapsid clades Biarmosuchia, Dinocephalia, Anomodontia, and Cynodontia. Recent discoveries from South Africa suggest that Gondwana, rather than Laurasia, was the center of origin and radiation for many early therapsids. Because of their relative abundance and global distribution, therapsids have enjoyed widespread use in biostratigraphy, basin analysis, and paleo-environmental and -continental reconstructions. Synapsids (including therapsids) form the bulk of tetrapod diversity (in terms of both number of species and abundance) from Early Permian to Middle Triassic times and thus can provide critical information on the nature of the Permo-Triassic extinction in the terrestrial realm. Quantitative techniques have produced headway into understanding the relative importance of homoplasy and convergent evolution in the origin of mammals.
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Ecology, Conservation, and Public Policy
Vol. 32 (2001), pp. 481–517More Less▪ AbstractA new sense of urgency about environmental problems has changed the relationship between ecology, other disciplines, and public policy. Issues of uncertainty and scientific inference now influence public debate and public policy. Considerations that formerly may have appeared to be mere technicalities now may have decisive influence. It is time to re-examine our methods to ensure that they are adequate for these new requirements. When science is used in support of policy-making, it cannot be separated from issues of values and equity. In such a context, the role of specialists diminishes, because nobody can be an expert in all the aspects of complicated environmental, social, ethical, and economic issues. The disciplinary boundaries that have served science so well in the past are not very helpful in coping with the complex problems that face us today, and ecology now finds itself in intense interaction with a host of other disciplines. The next generation of ecologists must be prepared to interact with such disciplines as history, religion, philosophy, geography, economics, and political science. The requisite training must involve not only words, but core skills in these disciplines. A sense of urgency has affected not only ecology but other disciplines that influence environmental problems: they are undergoing a similar transformation of their outlook and objectives.
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Male-Killing, Nematode Infections, Bacteriophage Infection, and Virulence of Cytoplasmic Bacteria in the GenusWolbachia
Vol. 32 (2001), pp. 519–545More Less▪ AbstractWolbachia bacteria are cytoplasmic endosymbionts with a wide range of effects on their hosts and are known to infect two major invertebrate groups, arthropods and nematodes. In arthropods Wolbachia alter host reproduction, causing unidirectional and bidirectional cytoplasmic incompatibility, parthenogenesis, feminization, and embryonic male killing. Wolbachia variation in reproductive effects is indicative of a high degree of evolutionary plasticity. As many as 75% of arthropods may be infected with Wolbachia, which in addition to affecting reproduction, can also directly affect host fitness by either increasing or decreasing survival and fecundity. We review the dynamics of embryonic male-killing, including effects on insect mating behavior, as well as the distribution and implication of Wolbachia infections in filarial nematodes.
Arthropod host–Wolbachia phylogenies are not congruent, which is suggestive of horizontal transmission. The opposite has been shown in nematode-Wolbachia phylogenies, indicative of long-term association and vertical transmission. Multiple levels of parasitism within arthropods may promote horizontal transmission. Bacteriophage WO has recently been identified and is found in all Wolbachia-infected insect hosts so far examined. Extensive horizontal transmission of the phage occurs between different Wolbachia strains within a host as well as between Wolbachia in different hosts. The phage genome may carry genes important in determining both the effect of Wolbachia on arthropod host reproduction and host fitness and fecundity. The extensive horizontal transmission of the phage may explain the plasticity of Wolbachia's effect on arthropod hosts.
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Biospheric Trace Gas Fluxes and Their Control Over Tropospheric Chemistry
Vol. 32 (2001), pp. 547–576More Less▪ AbstractTerrestrial and marine ecosystems function as sources and sinks for reactive trace gases, and in doing so, profoundly influence the oxidative photochemistry in the troposphere. Principal biogenic processes include microbial methane production and oxidation, the emission of volatile organic compounds from forest ecosystems, the emission of nitric oxide from soils, the emission of reactive sulfur compounds and carbon monoxide from marine ecosystems, control over the production of hydroxyl radical concentration by regional hydrologic processes, and deposition of ozone and nitrogen oxides to ecosystems. The combined influence of these processes is to affect the tropospheric concentrations of ozone, hydroxyl radicals, reactive nitrogen oxides, carbon monoxide, and inorganic acids, all of which constitute fundamental components of oxidative photochemistry. In this review we discuss the recent literature related to the primary controls over the biosphere-atmosphere exchange of reactive trace gases, and also to efforts to model the dominant biospheric influences on oxidative dynamics of the troposphere. These studies provide strong support for the paradigm that biospheric processes exert the dominant control over oxidative chemistry in the lower atmosphere. Improvements in our ability to model biospheric influences on tropospheric chemistry, and its susceptibility to global change, will come from inclusion of more explicit information on the processes that control the emission and uptake of reactive trace gases and the impact of changes in ecosystem cover and land-use change.
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Previous Volumes
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Volume 55 (2024)
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Volume 54 (2023)
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Volume 53 (2022)
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Volume 52 (2021)
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Volume 51 (2020)
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Volume 50 (2019)
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Volume 49 (2018)
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Volume 48 (2017)
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Volume 47 (2016)
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Volume 46 (2015)
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Volume 45 (2014)
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Volume 44 (2013)
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Volume 43 (2012)
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Volume 42 (2011)
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Volume 41 (2010)
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Volume 40 (2009)
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Volume 39 (2008)
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Volume 38 (2007)
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Volume 37 (2006)
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Volume 36 (2005)
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Volume 35 (2004)
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Volume 34 (2003)
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Volume 33 (2002)
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Volume 32 (2001)
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Volume 31 (2000)
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Volume 30 (1999)
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Volume 29 (1998)
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Volume 28 (1997)
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Volume 27 (1996)
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Volume 26 (1995)
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Volume 25 (1994)
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Volume 24 (1993)
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Volume 23 (1992)
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Volume 22 (1991)
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Volume 21 (1990)
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Volume 20 (1989)
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Volume 19 (1988)
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Volume 18 (1987)
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Volume 17 (1986)
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Volume 16 (1985)
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Volume 15 (1984)
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Volume 14 (1983)
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Volume 13 (1982)
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Volume 12 (1981)
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Volume 11 (1980)
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Volume 10 (1979)
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Volume 9 (1978)
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Volume 8 (1977)
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Volume 7 (1976)
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Volume 6 (1975)
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Volume 5 (1974)
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Volume 4 (1973)
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Volume 3 (1972)
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Volume 2 (1971)
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Volume 1 (1970)
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Volume 0 (1932)