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Abstract: We examined six historical specimens of the endangered North Atlantic right whale ( Eubalaena glacialis ) using DNA isolated from documented baleen plates from the late nineteenth and early twentieth centuries. Sequences from the mitochondrial DNA (mtDNA) control region from these samples were compared with those from a near-exhaustive survey (269 of approximately 320 individuals) of the remaining right whales in the western North Atlantic Ocean. Our results suggest that there has been only relatively modest change in maternal lineage diversity over the past century in the North Atlantic right whale population. Any significant reduction in genetic variation in the species most likely occurred prior to the late nineteenth century. One historical specimen was from the last documented female capable of propagating one of the maternal lineages in the population today; no females in the existing population have been found to carry this mtDNA haplotype. Analysis of the only specimens from the eastern North Atlantic right whale population ever to be examined revealed that eastern and western North Atlantic right whales may not have been genetically differentiated populations. Loss of gene diversity experienced by North Atlantic right whales over the last century has been modest, and the six decades of protection have been successful in maintaining much of the maternal lineage diversity that was present in the late nineteenth century.  相似文献   
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We develop a spectral framework for testing the hypothesis of complete spatial randomness (CSR) for a spatial point pattern. Five formal tests based on the periodogram (sample spectrum) proposed in Mugglestone (1990) are considered. A simulation study is used to evaluate and compare the power of the tests against clustered, regular and inhomogeneous alternatives to CSR. A subset of the tests is shown to be uniformly more powerful than the others against the alternatives considered. The spectral tests are also compared with three widely used space-domain tests that are based on the mean nearest-neighbor distance, the reduced second-order moment function (K-function), and a bivariate Cramér-von Mises statistic. The test based on the scaled cumulative R-spectrum is more powerful than the space-domain tests for detecting clustered alternatives to CSR, especially when the number of events is small.  相似文献   
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Some recently emerged brook charr (Salvelinus fontinalis) inhabiting still-water pools along the sides of streams are sedentary and eat crustaceans from the lower portion of the water column. Others are more active and eat insects from the upper portion of the water column. We provide evidence that this divergent foraging behavior reflects short-term divergent selection brought about by intraspecific competition in the presence of alternative food sources. Rates of encounters and interactions between individuals were density dependent, and encounter and interaction events were closely timed with prey capture attempts. In addition, aggressive fish made more foraging attempts per minute than nonaggressive fish. Aggressive fish were also either inactive or very active, while nonaggressive fish exhibited intermediate levels of activity. Growth rate potential, an important component of fitness during the early life stages of brook charr, was assessed using tissue concentrations of RNA and found to be highest for sedentary fish and for active fish making frequent foraging attempts, and lower for fish exhibiting intermediate levels of activity. Our findings support contentions that individual behavior plays an important role during initial steps in the evolution of resource polymorphisms. Received: 27 July 1998 / Accepted after revision: 16 November 1998  相似文献   
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In this paper we examine and compare communication processes aimed at building social networks and increasing citizen engagement in two communities participating in a municipal sustainability planning (MSP) pilot programme in Alberta, Canada, initiated by the Alberta Urban Municipalities Association (AUMA). Data were gathered through qualitative semi-structured interviews and documentary review. In soliciting citizen engagement, each community utilised a variety of communication methods, based on available resources and on-going evaluation of community responses. In both cases, citizens developed a shared vision of a preferred future for their community, aided by a reconfiguration of their internal and external social networks. In addition to drawing upon and strengthening bonding relationships within the community, bridging relationships with external actors and agencies promoted knowledge mobilisation that aided in planning and transitioning towards sustainability. Both communities faced challenges as well, which the authors discuss in relation to the sustainability of MSP planning.  相似文献   
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For an integrated assessment of the vulnerability of societies to drought it is necessary to set the benchmark at a level where the impacts of droughts lead to a state of affairs that departs from normal conditions, i.e. a crisis event. This article aims to improve the understanding of drought-related crisis events on the basis of a twofold media content analysis. This approach enables us to test when increased vulnerability in fact leads to a crisis situation and offers an improved understanding of the intensity and the extent of crisis events. To this end, we first outline our perspective on crisis and give an overview on existing approaches to identify crisis events. We then outline our two-step approach of media content analysis aimed at developing a crisis data set for the case study regions Andhra Pradesh (India), Southern Portugal and the Volga region (Russia). Using the Factiva news database and information by regional newspapers, a crisis data set is generated enabling us to define the occurrence and extent of drought-related crisis events in the case study regions. Moreover, based on attributes of drought impacts reported by news sources, we categorize the extensiveness of a specific drought. As a key result, our findings suggest that Southern Portugal, the case study region which is expected to be less susceptible to drought events than the other case study regions, faced the most extended crisis events.  相似文献   
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Halting forest loss and achieving sustainable development in an equitable manner require state, non-state actors, and entire societies in the Global North and South to tackle deeply established patterns of inequality and power relations embedded in forest frontiers. Forest and climate governance in the Global South can provide an avenue for the transformational change needed—yet, does it? We analyse the politics and power in four cases of mitigation, adaptation, and development arenas. We use a political economy lens to explore the transformations taking place when climate policy meets specific forest frontiers in the Global South, where international, national and local institutions, interests, ideas, and information are at play. We argue that lasting and equitable outcomes will require a strong discursive shift within dominant institutions and among policy actors to redress policies that place responsibilities and burdens on local people in the Global South, while benefits from deforestation and maladaptation are taken elsewhere. What is missing is a shared transformational objective and priority to keep forests standing among all those involved from afar in the major forest frontiers in the tropics.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01602-1.  相似文献   
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We report a study which examined whether the decision of 135 couples to accept prenatal cystic fibrosis (CF) carrier screening would be influenced by the advent of gene therapy. A majority (91 couples; 67 per cent) felt that gene therapy for CF would not influence their decision to be screened. Twenty-two couples (16 per cent) stated that they would decline to be screened and an equal number felt ambivalent. Even if the life expectancy of a CF sufferer were increased by gene therapy to normal, 78 per cent of couples would still wish to avail themselves of prenatal carrier screening. A majority of women who decline screening do so because they are opposed to termination of pregnancy. The availability of gene therapy could increase the proportion of couples who accept screening.  相似文献   
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