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Sökning: L773:1464 7931 OR L773:1469 185X

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  • Schweiger, Oliver, et al. (författare)
  • Multiple stressors on biotic interactions: how climate change and alien species interact to affect pollination
  • 2010
  • Ingår i: Biological Reviews. - : John Wiley and Sons. - 1469-185X .- 1464-7931. ; 85:4, s. 777-795
  • Forskningsöversikt (refereegranskat)abstract
    • Global change may substantially affect biodiversity and ecosystem functioning but little is known about its effects on essential biotic interactions. Since different environmental drivers rarely act in isolation it is important to consider interactive effects. Here, we focus on how two key drivers of anthropogenic environmental change, climate change and the introduction of alien species, affect plant-pollinator interactions. Based on a literature survey we identify climatically sensitive aspects of species interactions, assess potential effects of climate change on these mechanisms, and derive hypotheses that may form the basis of future research. We find that both climate change and alien species will ultimately lead to the creation of novel communities. In these communities certain interactions may no longer occur while there will also be potential for the emergence of new relationships. Alien species can both partly compensate for the often negative effects of climate change but also amplify them in some cases. Since potential positive effects are often restricted to generalist interactions among species, climate change and alien species in combination can result in significant threats to more specialist interactions involving native species.
  • Wennersten, Lena, et al. (författare)
  • Population-level consequences of polymorphism, plasticity and randomized phenotype switching: a review of predictions
  • 2012
  • Ingår i: Biological Reviews. - 1464-7931 .- 1469-185X. ; 87:3, s. 756-767
  • Forskningsöversikt (refereegranskat)abstract
    • The consequences of among-individual phenotypic variation for the performance and ecological success of populations and species has attracted growing interest in recent years. Earlier reviews of this field typically address the consequences for population processes of one specific source of variation (plasticity or polymorphism), or consider one specific aspect of population performance, such as rate of speciation. Here we take a broader approach and study earlier reviews in order to summarize and compare predictions regarding several population-level consequences of phenotypic variation stemming from genetic polymorphism, developmental plasticity or randomized phenotype switching. Unravelling cause-dependent consequences of variation may increase our ability to understand the ecological dynamics of natural populations and communities, develop more informed management plans for protection of biodiversity, suggest possible routes to increased productivity and yield in natural and managed biological systems, and resolve inconsistencies in patterns and results seen in studies of different model systems. We find an overall agreement regarding the effects of higher levels of phenotypic variation generated by different sources, but also some differences between fine-grained and coarse-grained environments, modular and unitary organisms, mobile and sessile organisms, and between flexible and fixed traits. We propose ways to test the predictions and identify issues where current knowledge is limited and future lines of investigation promise to provide important novel insights.
  • Bengtsson, Jan (författare)
  • Landscape moderation of biodiversity patterns and processes - eight hypotheses
  • 2012
  • Ingår i: Biological Reviews. - : Wiley: 12 months. - 1464-7931 .- 1469-185X. ; 87, s. 661-685
  • Forskningsöversikt (refereegranskat)abstract
    • Understanding how landscape characteristics affect biodiversity patterns and ecological processes at local and landscape scales is critical for mitigating effects of global environmental change. In this review, we use knowledge gained from human-modified landscapes to suggest eight hypotheses, which we hope will encourage more systematic research on the role of landscape composition and configuration in determining the structure of ecological communities, ecosystem functioning and services. We organize the eight hypotheses under four overarching themes. Section A: landscape moderation of biodiversity patterns' includes (1) the landscape species pool hypothesisthe size of the landscape-wide species pool moderates local (alpha) biodiversity, and (2) the dominance of beta diversity hypothesislandscape-moderated dissimilarity of local communities determines landscape-wide biodiversity and overrides negative local effects of habitat fragmentation on biodiversity. Section B: landscape moderation of population dynamics' includes (3) the cross-habitat spillover hypothesislandscape-moderated spillover of energy, resources and organisms across habitats, including between managed and natural ecosystems, influences landscape-wide community structure and associated processes and (4) the landscape-moderated concentration and dilution hypothesisspatial and temporal changes in landscape composition can cause transient concentration or dilution of populations with functional consequences. Section C: landscape moderation of functional trait selection includes (5) the landscape-moderated functional trait selection hypothesislandscape moderation of species trait selection shapes the functional role and trajectory of community assembly, and (6) the landscape-moderated insurance hypothesislandscape complexity provides spatial and temporal insurance, i.e. high resilience and stability of ecological processes in changing environments. Section D: landscape constraints on conservation management' includes (7) the intermediate landscape-complexity hypothesislandscape-moderated effectiveness of local conservation management is highest in structurally simple, rather than in cleared (i.e. extremely simplified) or in complex landscapes, and (8) the landscape-moderated biodiversity versus ecosystem service management hypothesislandscape-moderated biodiversity conservation to optimize functional diversity and related ecosystem services will not protect endangered species. Shifting our research focus from local to landscape-moderated effects on biodiversity will be critical to developing solutions for future biodiversity and ecosystem service management.
  • Gotzenberger, Lars, et al. (författare)
  • Ecological assembly rules in plant communities-approaches, patterns and prospects
  • 2012
  • Ingår i: Biological Reviews. - 1464-7931 .- 1469-185X. ; 87:1, s. 111-127
  • Tidskriftsartikel (refereegranskat)abstract
    • Understanding how communities of living organisms assemble has been a central question in ecology since the early days of the discipline. Disentangling the different processes involved in community assembly is not only interesting in itself but also crucial for an understanding of how communities will behave under future environmental scenarios. The traditional concept of assembly rules reflects the notion that species do not co-occur randomly but are restricted in their co-occurrence by interspecific competition. This concept can be redefined in a more general framework where the co-occurrence of species is a product of chance, historical patterns of speciation and migration, dispersal, abiotic environmental factors, and biotic interactions, with none of these processes being mutually exclusive. Here we present a survey and meta-analyses of 59 papers that compare observed patterns in plant communities with null models simulating random patterns of species assembly. According to the type of data under study and the different methods that are applied to detect community assembly, we distinguish four main types of approach in the published literature: species co-occurrence, niche limitation, guild proportionality and limiting similarity. Results from our meta-analyses suggest that non-random co-occurrence of plant species is not a widespread phenomenon. However, whether this finding reflects the individualistic nature of plant communities or is caused by methodological shortcomings associated with the studies considered cannot be discerned from the available metadata. We advocate that more thorough surveys be conducted using a set of standardized methods to test for the existence of assembly rules in data sets spanning larger biological and geographical scales than have been considered until now. We underpin this general advice with guidelines that should be considered in future assembly rules research. This will enable us to draw more accurate and general conclusions about the non-random aspect of assembly in plant communities.
  • Johansson, Björn, et al. (författare)
  • The role of chemical communication in mate choice
  • 2007
  • Ingår i: Biological Reviews. - 1464-7931 .- 1469-185X. ; 82:2, s. 265-289
  • Forskningsöversikt (refereegranskat)abstract
    • Chemical signals are omnipresent in sexual communication in the vast majority of living organisms. The traditional paradigm was that their main purpose in sexual behaviour was to coordinate mate and species recognition and thus pheromones were conserved in structure and function. In recent years, this view has been challenged by theoretical analyses on the evolution of pheromones and empirical reports of mate choice based on chemical signals. The ability to measure precisely the quantity and quality of chemicals emitted by single individuals has also revealed considerable individual variation in chemical composition and release rates, and there is mounting evidence that prospecting mates respond to this variation. Here, we review the evidence for pheromones as indicators of mate quality and examine the extent of their use in individual mate assessment. We begin by briefly defining the levels of mate choice – species recognition, mate recognition and mate assessment. We then explore the degree to which pheromones satisfy the key criteria necessary for their evolution and maintenance as cues in mate assessment; that is, they should exhibit variation across individuals within a sex and species; they should honestly reflect an individual's quality and thus be costly to produce and/or maintain; they should display relatively high levels of heritability. There is now substantial empirical evidence that pheromones can satisfy all these criteria and, while measurements of the actual metabolic cost of pheromone production remain to some degree lacking, trade-offs between pheromone production and various fitness-related characters such as growth rate, immunocompetence and longevity have been reported for a range of species. In the penultimate section, we outline the growing number of studies where the consequences of chemical-based mate assessment have been investigated, specifically focussing on the reported direct and genetic benefits accrued by the receiver. Finally, we highlight potential areas for future research and in particular emphasise the need for interdisciplinary research that combines exploration of chemical, physiological and behavioural processes to further our understanding of the role of chemical cues in mate assessment.
  • Morrow, Edward H., et al. (författare)
  • Female postmating immune responses, immune system evolution and immunogenic males
  • 2012
  • Ingår i: Biological Reviews. - 1464-7931 .- 1469-185X. ; 87:3, s. 631-638
  • Forskningsöversikt (refereegranskat)abstract
    • Females in many taxa experience postmating activation of their immune system, independently of any genital trauma or pathogenic attack arising from male-female genital contact. This response has always been interpreted as a product of natural selection as it either prepares the female immune system for antigens arising from an implanted embryo (in the case of placental mammals), or is a pre-emptive strike against infection or injury acquired during mating. While the first hypothesis has empirical support, the second is not entirely satisfactory. Recently, studies that have experimentally dissected the postmating responses of Drosophila melanogaster females point to a different explanation: male reproductive peptides/proteins that have evolved in response to postmating male-male competition are directly responsible for activating particular elements of the female immune system. Thus, in a broad sense, males may be said to be immunogenic to females. Here, we discuss a possible direct role of sexual selection/sexual conflict in immune system evolution, in contrast to indirect trade-offs with other life-history traits, presenting the available evidence from a range of taxa and proposing ways in which the competing hypotheses could be tested. The major implication of this review is that immune system evolution is not only a product of natural selection but also that sexual selection and potentially sexual conflict enforces a direct selective pressure. This is a significant shift, and will compel researchers studying immune system evolution and ecological immunity to look beyond the forces generated by parasites and pathogens to those generated by the male ejaculate.
  • Nakagawa, Shinichi, et al. (författare)
  • Repeatability for Gaussian and non-Gaussian data : a practical guide for biologists
  • 2010
  • Ingår i: Biological Reviews. - 1464-7931 .- 1469-185X. ; 85:4, s. 935-956
  • Tidskriftsartikel (refereegranskat)abstract
    • Repeatability (more precisely the common measure of repeatability, the intra-class correlation coefficient, ICC) is an important index for quantifying the accuracy of measurements and the constancy of phenotypes. It is the proportion of phenotypic variation that can be attributed to between-subject (or between-group) variation. As a consequence, the non-repeatable fraction of phenotypic variation is the sum of measurement error and phenotypic flexibility. There are several ways to estimate repeatability for Gaussian data, but there are no formal agreements on how repeatability should be calculated for non-Gaussian data (e.g. binary, proportion and count data). In addition to point estimates, appropriate uncertainty estimates (standard errors and confidence intervals) and statistical significance for repeatability estimates are required regardless of the types of data. We review the methods for calculating repeatability and the associated statistics for Gaussian and non-Gaussian data. For Gaussian data, we present three common approaches for estimating repeatability: correlation-based, analysis of variance (ANOVA)-based and linear mixed-effects model (LMM)-based methods, while for non-Gaussian data, we focus on generalised linear mixed-effects models (GLMM) that allow the estimation of repeatability on the original and on the underlying latent scale. We also address a number of methods for calculating standard errors, confidence intervals and statistical significance; the most accurate and recommended methods are parametric bootstrapping, randomisation tests and Bayesian approaches. We advocate the use of LMM- and GLMM-based approaches mainly because of the ease with which confounding variables can be controlled for. Furthermore, we compare two types of repeatability (ordinary repeatability and extrapolated repeatability) in relation to narrow-sense heritability. This review serves as a collection of guidelines and recommendations for biologists to calculate repeatability and heritability from both Gaussian and non-Gaussian data.
  • Nilsson, Christer, et al. (författare)
  • The role of hydrochory in structuring riparian and wetland vegetation
  • 2010
  • Ingår i: Biological Reviews. - 1464-7931 .- 1469-185X. ; 85:4, s. 837-858
  • Tidskriftsartikel (refereegranskat)abstract
    • Hydrochory, or the passive dispersal of organisms by water, is an important means of propagule transport, especially forplants. During recent years, knowledge about hydrochory and its ecological consequences has increased considerablyand a substantial body of literature has been produced. Here, we review this literature and define the state of the art ofthe discipline. A substantial proportion of species growing in or near water have propagules (fruits, seeds or vegetativeunits) able to disperse by water, either floating, submerged in flowing water, or with the help of floating vessels.Hydrochory can enable plants to colonize sites out of reach with other dispersal vectors, but the timing of dispersaland mechanisms of establishment are important for successful establishment. At the population level, hydrochorymay increase the effective size and longevity of populations, and control their spatial configuration. Hydrochory isalso an important source of species colonizing recruitment-limited riparian and wetland communities, contributing tomaintenance of community species richness. Dispersal by water may even influence community composition in differentlandscape elements, resulting in landscape-level patterns. Genetically, hydrochory may reduce spatial aggregation ofgenetically related individuals, lead to high gene flow among populations, and increase genetic diversity in populationsreceiving many propagules. Humans have impacted hydrochory in many ways. For example, dams affect hydrochoryby reducing peak flows and hence dispersal capacity, altering the timing of dispersal, and by presenting physical barriersto dispersal, with consequences for riverine plant communities. Hydrochory has been inferred to be an important vectorfor the spread of many invasive species, but there is also the potential for enhancing ecosystem restoration by improvingor restoring water dispersal pathways. Climate change may alter the role of hydrochory by modifying the hydrology ofwater-bodies as well as conditions for propagule release and plant colonization.
  • Andersen, Jesper H., et al. (författare)
  • Long-term temporal and spatial trends in eutrophication status of the Baltic Sea
  • 2017
  • Ingår i: Biological Reviews. - : John Wiley and Sons. - 1464-7931 .- 1469-185X. ; 92:1, s. 135-149
  • Tidskriftsartikel (refereegranskat)abstract
    • Much of the Baltic Sea is currently classified as 'affected by eutrophication'. The causes for this are twofold. First, current levels of nutrient inputs (nitrogen and phosphorus) from human activities exceed the natural processing capacity with an accumulation of nutrients in the Baltic Sea over the last 50-100 years. Secondly, the Baltic Sea is naturally susceptible to nutrient enrichment due to a combination of long retention times and stratification restricting ventilation of deep waters. Here, based on a unique data set collated from research activities and long-term monitoring programs, we report on the temporal and spatial trends of eutrophication status for the open Baltic Sea over a 112-year period using the HELCOM Eutrophication Assessment Tool (HEAT 3.0). Further, we analyse variation in the confidence of the eutrophication status assessment based on a systematic quantitative approach using coefficients of variation in the observations. The classifications in our assessment indicate that the first signs of eutrophication emerged in the mid-1950s and the central parts of the Baltic Sea changed from being unaffected by eutrophication to being affected. We document improvements in eutrophication status that are direct consequences of long-term efforts to reduce the inputs of nutrients. The reductions in both nitrogen and phosphorus loads have led to large-scale alleviation of eutrophication and to a healthier Baltic Sea. Reduced confidence in our assessment is seen more recently due to reductions in the scope of monitoring programs. Our study sets a baseline for implementation of the ecosystem-based management strategies and policies currently in place including the EU Marine Strategy Framework Directives and the HELCOM Baltic Sea Action Plan.
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