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1.
Two important new books by Greg Carter and Kenneth Prewitt provide detailed historical perspectives on how understandings of race and race categories have evolved since the founding of the republic. Prewitt focuses on an analysis of racial classification in the US census – the so-called ‘statistical races’ –and its changing role in US policy, culminating in recommendations for radical change. Carter takes as his theme population mixing across the races, offering a positive, even celebratory, but little known account of the moments and movements that have praised mixing. As pressures mount on the ‘statistical races’ in the late twentieth century, Prewitt uses the political space opened up by these debates to offer fundamental changes to US methods of ethno-racial data collection, including the removal of these questions from the census. The jury is in recess for further deliberations.  相似文献   

2.
The twentieth anniversary of the journal Molecular Ecology was celebrated with a symposium on the current state and the future directions of the field. The event, organized by Tim Vines and Loren Rieseberg, took place on the opening day of the First Joint Congress on Evolutionary Biology organized by the American Society of Naturalists (ASN), the Canadian Society for Ecology and Evolution (CSEE), the European Society for Evolutionary Biology (ESEB), the Society for the Study of Evolution (SSE) and the Society of Systematic Biologists (SSB) in Ottawa (Canada) from 6–10 July 2012. The get together of these five societies created a truly international and exciting “Evolution conference” and the ideal framework for the Molecular Ecology symposium. Its thirteen talks were grouped into the five different subject areas of the journal: Speciation and Hybridization; Landscape Genetics, Phylogeography and Conservation; Ecological Genomics and Molecular Adaptation; Kinship, Parentage and Behaviour; Ecological Interactions. Each session was followed by a panel discussion on the future direction of the subfield. That more than 300 colleagues registered for this special symposium illustrates the broad interest in, and appreciation of, molecular ecology – both the field and the journal.  相似文献   

3.
甘南高原农户对极端天气的适应障碍及适应意向   总被引:1,自引:0,他引:1  
王伟军  赵雪雁  万文玉  李花  薛冰 《生态学报》2017,37(23):8089-8100
基于入户调查数据,探讨了甘南高原农户对极端天气的适应障碍,并采用二元Logistic回归模型分析了适应障碍对农户适应意向的影响。结果发现:(1)甘南高原农户面临的规范性障碍最严重,信息技术障碍次之,再次为制度障碍和认知障碍。不同生计农户面临的适应障碍存在差异,其中,纯农户主要面临信息技术障碍,兼业户和非农户则主要面临规范性障碍。(2)纯农户对极端天气的适应意向主要受认知障碍、信息准确性障碍、适应策略选择时机障碍、政策激励障碍和牲畜拥有量的影响,兼业户主要受认知障碍、技术服务障碍、政策激励障碍影响,非农户主要受认知障碍、资源获取性障碍影响。除适应策略选择时机障碍外,其余适应障碍越小,不同生计农户的积极适应意向均越强。最后,提出了解决农户适应障碍的对策建议。  相似文献   

4.
How might a microbial cell that is entirely metabolically dormant – and which has the ability to remain so for extended periods of time – irreversibly commit itself to resuming vegetative growth within seconds of being exposed to certain amino acids or sugars? That this process takes place in the absence of any detectable ATP or de novo protein synthesis, and relies upon a pre-formed apparatus that is immobilised, respectively, in a semi-crystalline membrane or multi-layered proteinaceous coat, only exacerbates the challenge facing spores of Bacillales species when stimulated to germinate. Whereas the process by which spores are formed in response to nutrient starvation – sporulation – involves the orchestrated interplay between hundreds of distinct proteins, the process by which spores return to life – germination – is a much simpler affair, requiring a handful of receptor and channel proteins complemented with specialized peptidoglycan lysins. Despite this relative simplicity, and research effort spanning many decades, comprehensive understanding of key molecular and biochemical details and, in particular signal transduction mechanisms associated with spore germination, has remained elusive. In this review we provide an up to date overview of the field while identifying what we consider to be the key gaps in knowledge associated with germination of Bacillales spores, suggesting also technical approaches that may provide fresh insight to this unique biological process.  相似文献   

5.
Until relatively recently, in countries such as the U.S.A. and U.K., individuals could only opt for “single race” categories with which they identified. However, in the 2000 decennial census, respondents in the U.S. were able to choose more than one racial category, while in 2001, a “Mixed” box (with further subcategories) was provided in the England and Wales census for the first time. But the very success of this racial project in these countries has spawned a number of questions for policy-makers and academics who theorize, enumerate and study the experiences of multiracial people. With demographic changes such as generational change, who counts as multiracial or mixed race? This question has yet to receive significant attention. Although mixing is becoming more commonplace, the question of who counts as multiracial is far from straightforward, especially as we look down the generational pipeline.  相似文献   

6.
Abstract

This article reviews the ways in which Britain and the USA classify and analyse the integration of immigrants and their descendants. While both societies recognize racial differences in their official statistics and in the academic analyses of change over time, the USA tends to classify immigrants and their descendants by immigrant generation much more than Britain does. The importance of the concept of generation in American immigration research is highlighted and it is suggested that studies built on the importance of generation can illuminate social processes of integration in Britain. The complexities of defining and measuring immigrant generation are reviewed, including new developments in the measurement of generation that take into account age at migration, and historical period and cohort effects. Racial and ethnic minority groups formed through immigration may have very different characteristics depending on the average distance of their members from immigration – including the possibility of ‘ethnic leakage’, as more assimilated, later-generation individuals no longer identify with the group.  相似文献   

7.
Female meiotic drive is the phenomenon where a selfish genetic element alters chromosome segregation during female meiosis to segregate to the egg and transmit to the next generation more frequently than Mendelian expectation. While several examples of female meiotic drive have been known for many decades, a molecular understanding of the underlying mechanisms has been elusive. Recent advances in this area in several model species prompts a comparative re-examination of these drive systems. In this review, we compare female meiotic drive of several animal and plant species, highlighting pertinent similarities.  相似文献   

8.
Population viability has often been assessed by census of reproducing adults. Recently this method has been called into question and estimation of the effective population size (Ne) proposed as a complementary method to determine population health. We examined genetic diversity in five populations of chinook salmon (Oncorhynchus tshawytscha) from the upper Fraser River watershed (British Columbia, Canada) at 11 microsatellite loci over 20 years using DNA extracted from archived scale samples. We tested for changes in genetic diversity, calculated the ratio of the number of alleles to the range in allele size to give the statistic M, calculated Ne from the temporal change in allele frequency, used the maximum likelihood method to calculate effective population size (NeM), calculated the harmonic mean of population size, and compared these statistics to annual census estimates. Over the last two decades population size has increased in all five populations of chinook examined; however, Ne calculated for each population was low (81-691) and decreasing over the time interval measured. Values of NeM were low, but substantially higher than Ne calculated using the temporal method. The calculated values for M were generally low (M < 0.70), indicating recent population reductions for all five populations. Large-scale historic barriers to migration and development activities do not appear to account for the low values of Ne; however, available spawning area is positively correlated with Ne. Both Ne and M estimates indicate that these populations are potentially susceptible to inbreeding effects and may lack the ability to respond adaptively to stochastic events. Our findings question the practice of relying exclusively on census estimates for interpreting population health and show the importance of determining genetic diversity within populations.  相似文献   

9.
Knowing where species occur is fundamental to many ecological and environmental applications. Species distribution models (SDMs) are typically based on correlations between species occurrence data and environmental predictors, with ecological processes captured only implicitly. However, there is a growing interest in approaches that explicitly model processes such as physiology, dispersal, demography and biotic interactions. These models are believed to offer more robust predictions, particularly when extrapolating to novel conditions. Many process–explicit approaches are now available, but it is not clear how we can best draw on this expanded modelling toolbox to address ecological problems and inform management decisions. Here, we review a range of process–explicit models to determine their strengths and limitations, as well as their current use. Focusing on four common applications of SDMs – regulatory planning, extinction risk, climate refugia and invasive species – we then explore which models best meet management needs. We identify barriers to more widespread and effective use of process‐explicit models and outline how these might be overcome. As well as technical and data challenges, there is a pressing need for more thorough evaluation of model predictions to guide investment in method development and ensure the promise of these new approaches is fully realised.  相似文献   

10.
OPINION Manipulating lake community structure: where do we go from here?   总被引:1,自引:0,他引:1  
SUMMARY. 1 More than 10 years experience with whole lake pelagic manipulation has suggested some general trends applicable to all freshwater pelagic communities and some specific trends related to lake depth.
2 Among the general trends is the observation that the trophic cascade is strongly damped. This means that changes in phytoplankton biomass can be assured only when the fish community is strongly manipulated.
3 Among the depth related trends is the observation that in shallow lakes, changes in fish community structure are more likely to have cascading impacts on phytoplankton than are changes in deep lakes.
4 In shallow lakes, fish removal frequently results in decreased turbidity which is associated with the development of dense macrophyte populations and significant reductions of algal standing stocks. The mechanisms involve: increased grazing by zooplankton, the removal of fish induced bioturbation and nutrient recycling, and direct and indirect macrophyte effects (shading, zooplankton refuges and competition for nutrients).
5 In shallow lakes, where planktivore biomass can be regulated and macrophyte development is acceptable, fish biomanipulalions are likely to result in reduced algal populations and improved water quality.
6 In deep lakes, where macrophytes are not as important, long-term effects of fish manipulations are strongly dependent upon the probability of non-grazable algal bloom development. This is determined by many factors (chemical, physical and grazer related) which modify the impact that grazers have on phytoplankton biomass.
7 In deep lakes, successful fish biomanipulations may only be effective when chemical and physical factors are altered to produce algal species compositions that permit strong top-down control of prey by predators.  相似文献   

11.
Melanoma is known as an aggressive tumor which shows an increasing incidence and poor prognosis in the metastatic phase. Hence, it seems that diagnosis and effective management (including early diagnosis, choosing of the effective therapeutic platform, caring, and training of patients for early detection) are major aspects of melanoma therapy. Early detection of melanoma is a key point for melanoma therapy. There are various diagnosis options such as assessing of biopsy, imaging techniques, and biomarkers (i.e., several proteins, polymorphism, and liquid biopsy). Among the various biomarkers, assessing circulating tumor cells, cell-free DNAs, cell-free RNAs, and microRNAs (miRNAs) have emerged as powerful diagnosis tools for melanoma patients. Deregulations of these molecules are associated with melanoma pathogenesis. After detection of melanoma, choosing of effective therapeutic regimen is a key step for recovery of melanoma patients. Several studies indicated that various therapeutic approaches including surgery, immunotherapy, systematic therapy, radiation therapy and antibodies therapy could be used as potential therapeutic candidates for melanoma therapy. Caring for melanoma patients is one of the important components of melanoma therapy. Caring and training for melanoma patients could contribute to better monitoring of patients in response to various therapeutic options. Here, we summarized various diagnosis approaches such as assessing biopsy, imaging techniques, and utilization of various biomarkers (i.e., proteins, CTCs, cfDNAs, and miRNAs) as a diagnostic biomarker for detection and monitoring patients with melanoma. Moreover, we highlighted various therapeutic options and caring aspects in patients with melanoma.  相似文献   

12.
Glycosaminoglycans regulate numerous physiopathological processes such as development, angiogenesis, innate immunity, cancer and neurodegenerative diseases. Cell surface GAGs are involved in cell-cell and cell-matrix interactions, cell adhesion and signaling, and host-pathogen interactions. GAGs contribute to the assembly of the extracellular matrix and heparan sulfate chains are able to sequester growth factors in the ECM. Their biological activities are regulated by their interactions with proteins. The structural heterogeneity of GAGs, mostly due to chemical modifications occurring during and after their synthesis, makes the development of analytical techniques for their profiling in cells, tissues, and biological fluids, and of computational tools for mining GAG-protein interaction data very challenging. We give here an overview of the experimental approaches used in glycosaminoglycomics, of the major GAG-protein interactomes characterized so far, and of the computational tools and databases available to analyze and store GAG structures and interactions.  相似文献   

13.
R. L. Peterson 《Plant biosystems》2013,147(6):1145-1152
Abstract

Ectomycorrhizas are subterranean organs resulting from the alteration in root structure by soil-inhabiting symbiotic fungi. Hyphae of the mycobiont have to contact the root surface, become attached to the root, and subsequently enter the root by growing between epidermal cells (and in some species, cortical cells) to form the Hartig net. A chemotropic stimulus might be involved in early hypha-root contact and recognition-adhesion may involve a polysaccharide-lectin interaction, but further research is needed to confirm this. Fungal hyphae adhering to the root surface change their mode of growth from apical, extension growth to a loss of this pattern resulting in a multi-branched mycelium. A similar change in pattern of branching occurs as hyphae form the Hartig net. In both cases, a change in the cytoskeleton might precede the change in branching. The ingress of hyphae between epidermal cells in angiosperm roots triggers radial rather than axial elongation of these cells; a reorientation of the cytoskeleton and subsequently the cellulose microfibrils is hypothesized to be involved in this process. Wall changes in root cells contiguous to Hartig net hyphae also occur, and these might facilitate nutrient exchange between the symbionts.  相似文献   

14.
Livestock production is an important contributor to sustainable food security for many nations, particularly in low‐income areas and marginal habitats that are unsuitable for crop production. Animal products account for approximately one‐third of global human protein consumption. Here, a range of indicators, derived from FAOSTAT and World Bank statistics, are used to model the relative vulnerability of nations at the global scale to predicted climate and population changes, which are likely to impact on their use of grazing livestock for food. Vulnerability analysis has been widely used in global change science to predict impacts on food security and famine. It is a tool that is useful to inform policy decision making and direct the targeting of interventions. The model developed shows that nations within sub‐Saharan Africa, particularly in the Sahel region, and some Asian nations are likely to be the most vulnerable. Livestock‐based food security is already compromised in many areas on these continents and suffers constraints from current climate in addition to the lack of economic and technical support allowing mitigation of predicted climate change impacts. Governance is shown to be a highly influential factor and, paradoxically, it is suggested that current self‐sufficiency may increase future potential vulnerability because trade networks are poorly developed. This may be relieved through freer trade of food products, which is also associated with improved governance. Policy decisions, support and interventions will need to be targeted at the most vulnerable nations, but given the strong influence of governance, to be effective, any implementation will require considerable care in the management of underlying structural reform.  相似文献   

15.
There are currently several debates taking place in palaeoanthropological circles in which the issue of sexual dimorphism is crucial. During the 60th Jubilee of the discovery of the TaungAustralopithecus skull, the authors concurred that much of the debate was due to differences in perception concerning dimorphism, and it was suggested that a study session dealing principally with sexual dimorphism in Primates should be organised with a view to determining what, if anything, could be observed in extant primates that might be utilised for determining the existence of dimorphism in fossil species. An advertisement was placed in the Journal of Human Evolution, calling for papers. Response was encouraging, suggesting that there was indeed a need for such a meeting, which was organised to take place late in November in Italy. Seventeen scientists sent abstracts, but due to the rather short notice, several were unable to attend the meeting. Nevertheless, papers were received and read at the meeting which form the basis for this issue of the Journal of Human Evolution. What remains to be done now, is for a second meeting to be organised at which the findings of the first meeting can be extended backwards in time into the fossil record.  相似文献   

16.
Understanding recent biogeographic responses to climate change is fundamental for improving our predictions of likely future responses and guiding conservation planning at both local and global scales. Studies of observed biogeographic responses to 20th century climate change have principally examined effects related to ubiquitous increases in temperature – collectively termed a warming fingerprint. Although the importance of changes in other aspects of climate – particularly precipitation and water availability – is widely acknowledged from a theoretical standpoint and supported by paleontological evidence, we lack a practical understanding of how these changes interact with temperature to drive biogeographic responses. Further complicating matters, differences in life history and ecological attributes may lead species to respond differently to the same changes in climate. Here, we examine whether recent biogeographic patterns across California are consistent with a warming fingerprint. We describe how various components of climate have changed regionally in California during the 20th century and review empirical evidence of biogeographic responses to these changes, particularly elevational range shifts. Many responses to climate change do not appear to be consistent with a warming fingerprint, with downslope shifts in elevation being as common as upslope shifts across a number of taxa and many demographic and community responses being inconsistent with upslope shifts. We identify a number of potential direct and indirect mechanisms for these responses, including the influence of aspects of climate change other than temperature (e.g., the shifting seasonal balance of energy and water availability), differences in each taxon's sensitivity to climate change, trophic interactions, and land‐use change. Finally, we highlight the need to move beyond a warming fingerprint in studies of biogeographic responses by considering a more multifaceted view of climate, emphasizing local‐scale effects, and including a priori knowledge of relevant natural history for the taxa and regions under study.  相似文献   

17.
Poleward and upward species range shifts are the most commonly anticipated and studied consequences of climate warming. However, these global responses to climate change obscure more complex distribution change patterns. We hypothesize that the spatial arrangement of mountain ranges and, consequently, climatic gradients in Europe, will result in range disjunctions. This hypothesis was investigated for submountainous forest plant species at two temporal and spatial scales: (i) under future climate change (between 1950–2000 and 2061–2080 periods) at the European scale and (ii) under contemporary climate change (between 1914–1987 and 1997–2013 periods) at the French scale. We selected 97 submountainous forest plant species occurring in France, among which distribution data across Europe are available for 25 species. By projecting future distribution changes for the 25 submountainous plant species across Europe, we demonstrated that range disjunction is a likely consequence of future climate change. To assess whether it is already taking place, we used a large forest vegetation‐plot database covering the entire French territory over 100 years (1914–2013) and found an average decrease in frequency (?0.01 ± 0.004) in lowland areas for the 97 submountainous species – corresponding to a loss of 6% of their historical frequency – along with southward and upward range shifts, suggesting early signs of range disjunctions. Climate‐induced range disjunctions should be considered more carefully since they could have dramatic consequences on population genetics and the ability of species to face future climate changes.  相似文献   

18.
Heart disease including myocardial infarction and ischemia is associated with the irreversible loss of cardiomyocytes and vasculature, both via apoptosis or necrosis. However, the native capacity for the renewal and repair of myocardial tissue is inadequate as have been current therapeutic measures to prevent left ventricular remodeling. Cell transplantation has emerged as a potentially viable therapeutic approach to directly repopulate and repair the damaged myocardium. A detailed analysis and a vision for future progress in stem cell applications, both in research and clinical cardiology are presented in this review, highlighting the use of a wide spectrum of stem/progenitor cell types including embryonic or fetal stem cells, myoblasts, and adult bone marrow stem cells. An up-to-date comparison of donor cell-types used, and evaluation of the myocardial disorders that might be most amenable to stem cell therapy are discussed. The roles that myocardial cell fusion and transdifferentiation play in stem cell transplantation, the specific shortcomings of available technologies, and recommendations for practical ways that these concerns might be overcome, are also presented.  相似文献   

19.
Lynch syndrome (LS) is the most common form of inherited predisposition to develop cancer mainly in the colon and endometrium but also in other organ sites. Germline mutations in DNA mismatch repair (MMR) gene cause the transmission of the syndrome in an autosomal dominant manner. The management of LS patients is complicated by the large variation in age at cancer diagnosis which requires these patients to be enrolled in surveillance protocol starting as early as in their second decade of life. Several environmental and genetic factors have been proposed to explain this phenotypic heterogeneity, but the molecular mechanisms remain unknown. Although the presence of genetic anticipation in Lynch syndrome has been suspected since 15 years, only recently the phenomenon has been increasingly reported to be present in different cancer genetic syndromes including LS. While the biological basis of earlier cancer onset in successive generations remains poorly known, recent findings point to telomere dynamics as a mechanism significantly contributing to genetic anticipation in Lynch syndrome and in other familial cancers. In this review, we summarize the clinical and molecular features of Lynch syndrome, with a particular focus on the latest studies that have investigated the molecular mechanisms of genetic anticipation.  相似文献   

20.
Ecosystems and other naturally resilient systems exhibit allometric scaling in the distribution of sizes of their elements. In this paper we define an allometry inspired scaling indicator for cities that is a first step toward quantifying the stability borne of a complex systems’ hierarchical structural composition. The scaling indicator is calculated using large census datasets and is analogous to fractal dimension in spatial analysis. Lack of numerical rigor and the resulting variation in scaling indicators – inherent in the use of box counting mechanism for fractal dimension calculation for cities – has been one of the hindrances in the adoption of fractal dimension as an urban indicator of note. The intra-urban indicator of scaling in population density distribution developed here is calculated for 58 US cities using a methodology that produces replicable results, employing large census-block wise population datasets from the 2010 US Census and the 2007 US Economic Census. We show that rising disparity – as measured by the proposed indicator of population density distribution in census blocks in Metropolitan Statistical Areas adversely affects energy consumption efficiency and carbon emissions in cities and leads to a higher urban carbon footprint. We then define a planning plane as a visual and analytic tool for incorporation of scaling indicator analysis into policy and decision-making.  相似文献   

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