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Ecological Experiments (ecological + experiment)
Selected AbstractsConservation genetics of a critically endangered Iberian minnow: evidence of population decline and extirpationsANIMAL CONSERVATION, Issue 2 2010V. Sousa Abstract The endangered minnow Iberochondrostoma almacai is an endemic Iberian cyprinid with a restricted and fragmented distribution. Here, we describe the genetic structure of the species and infer its demographic history from six nuclear-encoded microsatellite loci and mitochondrial cytochrome b sequences. Genetic diversity was low (microsatellite He<0.45; mtDNA ,<0.0015), and both markers resolved two groups: one from the northern Mira drainage and one from the Arade and Bensafrim drainages. The relatively low differentiation between these groups (0.09 Functional redundancy in heterogeneous environments: implications for conservationECOLOGY LETTERS, Issue 3 2001Todd Wellnitz It has been argued that one of the best ways to conserve biological diversity is to maintain the integrity of functional processes within communities, and this can be accomplished by assessing how much ecological redundancy exists in communities. Evidence suggests, however, that the functional roles species play are subject to the influences of local environmental conditions. Species may appear to perform the same function (i.e. be redundant) under a restricted set of conditions, yet their functional roles may vary in naturally heterogeneous environments. Incorporating the environmental context into ecological experiments would provide a critical perspective for examining functional redundancy among species. [source] Responses of riparian plants to flooding in free-flowing and regulated boreal rivers: an experimental studyJOURNAL OF APPLIED ECOLOGY, Issue 6 2002M. E. Johansson Summary 1The long history of river regulation has resulted in extensively changed ecosystem structures and processes in rivers and their associated environments. This fact, together with changing climatic and hydrological conditions, has increased the need to recover the natural functions of rivers. To develop guidelines for river restoration, comparative ecological experiments at contrasting water-level regimes are needed. We compared growth and survival of transplanted individuals of four riparian plant species (Betula pubescens, Carex acuta, Filipendula ulmaria and Leontodon autumnalis) over 2 years on four free-flowing and four regulated riverbank sites in northern Sweden. The species were chosen as representatives of dominating life-forms and species traits on different elevations of the riverbanks. 2In Betula and Filipendula, mean proportional growth rates were significantly higher at free-flowing sites than at regulated sites, whereas no consistent differences between free-flowing and regulated sites were found in Carex and Leontodon. Differences among species were generally in accordance with natural distribution patterns along riverbank elevation gradients and with experimental evidence on flooding tolerance, although plants of all species survived and even showed positive growth rates on elevations below their natural range of occurrence. 3Partial least squares regression was used to relate plant performance (growth and survival) to duration, frequency and timing of flooding at the different sites. Flood duration and frequency typically reduced performance in all species and during all time periods, although to various degrees. Flood events early in the experiment determined the outcome to a high degree at all sites. Variables indicating a regulated regime were mostly negatively related to plant performance, whereas free-flowing regime variables were positively related to plant performance. 4We used two of the regression models generated from our data with an acceptably high predictive power to simulate a hypothetical re-regulation scenario in run-of-river impoundments. With an overall reduction in flooding duration and frequency of 50,75%, plant performance of Filipendula at low riverbank elevations showed predicted increases of about 20,30%, levelling off to zero at the highest elevations. Reductions in summer floods represented about one-third to half of this increase. 5We conclude that for a range of species individual plant performance is clearly reduced on banks of impoundments and storage reservoirs due to changes in the water-level regime. Furthermore, our model simulation suggests that rather substantial reductions of flood duration and frequency are needed to improve plant performance on riverbanks upstream from dams in impounded rivers. River restoration principles should, however, be based on a combination of experimental data on plant performance of individual species and observed long-term changes in plant communities of regulated rivers. Consequently, successful re-regulation schemes in boreal rivers should include both reductions of summer and winter floods as well as re-introduced spring floods. [source] Large-scale ecology and hydrology: an introductory perspective from the editors of the Journal of Applied EcologyJOURNAL OF APPLIED ECOLOGY, Issue 2000S.J. Ormerod 1. Five key features characterize large-scale factors in ecology: (a) they incorporate some of the most major of all ecological phenomena , the ranges of organisms, patterns of diversity, variations in ecosystem character and environmental processes such as climate, biogeochemical cycles, dispersal and migration; (b) they involve interactions across scales through both top-down and bottom-up processes; (c) they are multifaceted, and hence require an interdisciplinary perspective; (d) they reflect the cumulative effects of anthropogenic change across all scales, and so have direct relevance to environmental management; (e) they invariably exceed the range of classical ecological experiments, and so require alternative approaches to hypothesis testing. 2. Against this background, a recent research initiative on large-scale ecology and hydrology was funded jointly by the Natural Environment Research Council (NERC) and the Scottish Executive Rural Affairs Department (SERAD). Outputs from this programme are reported in this special issue of the Journal of Applied Ecology, and they illustrate some of the ecological research that is currently in progress in the UK at large spatio-temporal scales. 3. The spatial scales investigated in the papers range from hectares to whole continents, and much of the work reported here involves modelling. Although the model outputs are intrinsically valuable, several authors express the need for improved validation and testing. We suggest that this is an area requiring much development, and will need considerable innovation due to the difficulties at the scales involved (see 1d). Possible methods include: model applications to new circumstances; large-scale environmental manipulations; large-scale surveys that mimic experimental protocols; support from process studies at smaller scales. These alternatives are not mutually exclusive, and all can allow robust hypothesis testing. 4. Much of the work reported here is interdisciplinary linking, for example, geographical, mathematical, hydrological, hydrochemical and ecological concepts (see 1c). We suggest that even stronger links between environmental disciplines will further aid large-scale ecological research. 5. Most important in the context of the Journal of Applied Ecology, the work reported in this issue reveals that large-scale ecology already has applied value. Sectors benefiting include the conservation of biodiversity, the control of invasive species, and the management of land and water resources. 6. Large-scale issues continue to affect many applied ecologists, with roughly 30,40% of papers published in the Journal of Applied Ecology typically confronting such problems. This special issue adds to the growing body of seminal contributions that will add impetus to further large-scale work. Moreover, occurring in a period when other areas of biology are increasingly reductionist, this collection illustrates that, at least with respect to large-scale environmental problems, ecology still holds centre ground. [source] Design and analysis of ecological experiments: philosophy and practiceJOURNAL OF BIOGEOGRAPHY, Issue 2 2003Glenn De'ath No abstract is available for this article. [source] MYSTERIES OF ADAPTATION TO HYPOXIA AND PRESSURE IN MARINE MAMMALS The Kenneth S. Norris Lifetime Achievement Award LectureMARINE MAMMAL SCIENCE, Issue 3 2006Gerald L. Kooyman Presented on 12 December 2005 San Diego, California Abstract This paper reviews past and current work on diving behavior, effects of pressure, and the aerobic diving limit from the perspective of the Ken Norris Lifetime Achievement Award. Because of the influence of Norris to marine mammalogy in general, and to my career in particular, I want to emphasize the important tradition of mentors and colleagues as keystones to a successful career in science, and ultimately to the success of science itself. These two related activities are illustrated by studies on marine mammals that were conducted in an endeavor to understand: (1) the behavioral traits associated with deep diving, (2) the mechanical and physiological effects of pressure during routine dives to great depth, and (3) the degree of oxygen depletion that they routinely endure while diving. The search for answers has resulted in numerous physiological and ecological experiments, along with accompanying theoretical analyses. Currently it appears that some deep-diving mammals may suffer from bends, and some may resort more often than what seems physiologically possible to anaerobic metabolism while diving. Above all, the way divers manage their nitrogen and oxygen stores remains a mystery. [source] Scale as a lurking factor: incorporating scale-dependence in experimental ecologyOIKOS, Issue 9 2009Brody Sandel Ecologists have recognized for decades the importance of spatial scale in ecological processes and patterns, as well as the complications scale poses for understanding ecological mechanisms. Here we highlight the opportunity attention to scale offers experimental ecology. Despite many advantages to considering scale, a review of the literature indicates that multi-scale experimental studies are rare. Although much work has focused on scale as a primary factor (e.g. island size), we draw attention to scale as a ,lurking' variable: one which influences the relationship between two or more variables that are not usually understood to be scale-dependent. We highlight three basic observations from which scale-dependence arises: abundance increases with area, environmental conditions vary across space, and the effect of an organism on its environment is spatially limited. From these arise first-order scale-dependence, which relates an ecological variable of interest to a measure of scale. Combining first-order relationships together, we can produce second-order scale-dependencies, which occur when the relationship between two or more variables is mediated by scale. It is these relationships that are of particular interest, as they have the potential to confound experimental results. Most ecological experiments have incorporated scale either implicitly or not at all. We suggest that an explicit consideration of scale could help resolve some long-standing debates when scale is turned from a lurking variable into a working variable. Finally, we review and evaluate four different experimental sampling designs and corresponding statistical analyses that can be used to address the effects of scale in ecological experiments. [source] Empirical tests for ecological exchangeabilityANIMAL CONSERVATION, Issue 3 2005Russell B. Rader The concept of ecological exchangeability, together with genetic exchangeability, is central to both the Cohesion Species Concept as well as to some definitions of Evolutionarily Significant Units. While there are well-established criteria for measuring genetic exchangeability, the concept of ecological exchangeability has generated considerable confusion. We describe a procedure that uses the complementary strengths, while recognising the limitations, of both molecular genetic data and ecological experiments to determine the ecological exchangeability of local populations within a species. This is the first synthesis of a combined approach (experiments and genetics) and the first explicit discussion of testing ecological exchangeability. Although it would be ideal to find functional genes that interact to influence quantitative traits resulting in ecological differences (e.g. growth, size, fecundity), we suggest that our current knowledge of functional markers is too limited for most species to use them to differentiate adaptively different local populations. Thus, we argue that ecological experiments using whole organisms combined with neutral markers that indicate evolutionary divergence, provide the strongest case for detecting adaptive differences among local populations. Both genetic divergence and ecological experiments provide the best information for infering ecological exchangeability. This procedure can be used to decide which local populations should be preserved to maintain intraspecific variation and to determine which populations would enhance captive-breeding programs, augment endangered local populations and could best be used to re-introduce native species into historically occupied areas. [source]
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