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1.
Abstract: Over the last 35 years there has been a shift in university wildlife and fisheries academic programs away from management and toward an ecology or conservation ethos. These university changes have been in both research and education. A similar change has occurred in direction among state and federal natural resource agencies. However, the changes exhibited by both groups have not been to the same degree. I believe university academic programs are now scaled more to the ecology—conservation side, while agencies still average to the management side. This represents a disconnect because university academic programs conduct research for these agencies (and others) and also educate future agency employees and provide technical services to agencies.  相似文献   

2.
3.
The literature on speciation has expanded dramatically in recent years, catalyzed by the emergence of new conceptual frameworks, new theoretical approaches, and new methods for characterizing pattern and inferring process. As a consequence, the language used to describe the speciation process has become more complex. Increasing complexity may be an accurate reflection of current thinking with respect to how phenotypic differences limit gene flow, how selection results in the evolution of reproductive isolation, and genetic changes that contribute to speciation. However, increased language complexity has come at a cost; old definitions have been reconfigured and new terms have been introduced. In some instances, the introduction of new terminology has failed to recognize historical usage, leading to unnecessary ambiguity and redundancy. Although the writings of Mayr and Dobzhansky remain a reference point in the language of speciation, the last decades of the 20th century saw substantial changes in our thinking about the speciation process. During that period, the language of speciation remained relatively stable. In contrast, the first decade of the 21st century has witnessed a remarkable expansion of the language of speciation. Here, the origin and evolution of ideas about speciation are viewed through the lens of changing language use.  相似文献   

4.
Asthma prevalence has increased over the last fifty years, but the more recent changes have not been conclusively determined. Studies in children indicate that a plateau in the prevalence of asthma may have been reached, but this has not yet been confirmed in adults. Epidemiological studies have suggested that the prevalence of asthma in adults is approximately 7-10% in different parts of the western world.We have now performed a large-scale epidemiological evaluation of the prevalence of asthma and respiratory symptoms in adults between the ages of 16-75 in West Sweden. Thirty thousand randomly chosen individuals were sent a detailed questionnaire focusing on asthma and respiratory symptoms, as well possible risk factors. Sixty-two percent of the contacted individuals responded to the questionnaire. Asthma prevalence, defined as asthma diagnosed by a physician, was 8.3%. Moreover, the prevalence of respiratory symptoms was lower compared to previous studies. The most common respiratory symptom was any wheeze (16.6%) followed by sputum production (13.3%). In comparison with studies performed 18 years ago, the prevalence of asthma has not increased, and the prevalence of most respiratory symptoms has decreased. Therefore, our data argues that the continued increase in asthma prevalence that has been observed over the last half century is over.  相似文献   

5.
Species abundance distributions over time   总被引:1,自引:1,他引:0  
It has been known for 50 years that the time period over which data are collected affects the shape of empirical species abundance distributions. However, despite a recent resurgence of interest in characterizing and explaining these patterns the temporal component of species abundance distributions has been largely ignored. I argue that it is essential to take account of time, and not only because sampling duration can have a profound influence on the perceived shape of the distribution. Partitions of species abundance distributions based on temporal occurrence in the record will facilitate tests of both biological and neutral models and may lead to a better understanding of rarity. These temporal partitions also have interesting, but as yet barely explored, parallels with spatial ones such as the core-satellite division. Moreover, changes in abundance distributions across all three of Preston's temporal scales (sampling time, ecological time and evolutionary time) present rich opportunities for ecological research.  相似文献   

6.
A novel synthesis has been elaborated for the pharmacologically remarkable 2-arylapomorphines described and characterized in the last few years. This new procedure contains two alternative synthetic routes and has allowed the preparation of several hitherto unknown compounds as well. The pharmacological profile of the previously published and the novel 2-alkyl- and arylapomorphines has been determined with the application of in vitro and in vivo techniques. For 2-phenyl- (2) and 2-(4-hydroxyphenyl)apomorphines (3) the superior dopamine agonist profile has been confirmed and for the novel compounds some remarkable results have been observed.  相似文献   

7.
Forests soils should be neither sinks nor sources of carbon in a long-term perspective. From a Swedish perspective the time since the last glaciation has probably not been long enough to reach a steady state, although changes are currently very slow. In a shorter perspective, climatic and management changes over the past 100 years have probably created imbalances between litter input to soils and organic carbon mineralisation. Using extant data on forest inventories, we applied models to analyse possible changes in the carbon stocks of Swedish forest soils. The models use tree stocks to provide estimates of tree litter production, which are fed to models of litter decomposition and from which carbon stocks are calculated. National soil carbon stocks were estimated to have increased by 3 Tg yr−1 or 12–13 g m−2 yr−1 in the period 1926–2000 and this increase will continue because soil stocks are far from equilibrium with current litter inputs. The figure obtained is likely to be an underestimation because wet sites store more carbon than predicted here and the inhibitory effect of nitrogen deposition on soil carbon mineralisation was neglected. Knowledge about site history prior to the calculation period determines the accuracy of current soil carbon stocks estimates, although changes can be more accurately estimated. This article has previously been published in issue 82/3, under DOI .  相似文献   

8.
We examined the vertical distributions of total organic carbon (TOC), total nitrogen (TN), total sulfur (TS), and 21 polycyclic aromatic hydrocarbons (PAHs) in a 100-cm-long sediment core collected from Lake Kitaura, a small and shallow eutrophic freshwater lake in central Japan, to elucidate changes in its aquatic environment and the input of PAHs with respect to human activity over the last 1000 years. Using a cross-plot of TOC and TS, the aquatic environment of this lake was well classified into four stages: a marine–brackish water period (≤1321 AD), a brackish–freshwater period (1394–1646 AD), a freshwater period (1726–1958 AD), and a eutrophication period (≥1971 AD). During the current eutrophication period, both TOC and TN have increased dramatically and TOC/TN (which is a useful indicator for distinguishing between aquatic and terrestrial plant sources) has decreased because algal production has markedly increased recently due to eutrophication. The vertical distributions of PAHs (which have derived primarily from combustion over the last 1000 years) showed increases in layers corresponding to periods of volcanic activity in the 18th century, as well as dramatic increases from 1971 to the present. Thus, both the aquatic environment and the input of PAHs in Lake Kitaura have been strongly affected by recent human activity. On the other hand, among all of the PAHs, only perylene—which is known to be of biological origin—was consistently formed via first-order kinetics over the period covered by the core. Its formation was barely influenced by fluctuations in the input of the precursor of perylene or how reductive the environment in the bottom water was.  相似文献   

9.
Populations at the edge of species distributions are especially vulnerable to climate change. Genetic changes as well as modification of their population structure are expected as reactions to global warming. Atlantic salmon ( Salmo salar ) inhabiting south France has been chosen as a model for studying the effect of global warming in marginal populations during the last 15 years. Increased gene flow between neighboring populations and dichotomy of maturation age between sexes have been identified as two main population changes significantly associated with high values of the North Atlantic Oscillation index, a global climate indicator. Although occurrence of isolated populations in each river (or even tributary) is a paradigm for this species, at least in northern areas, increased gene flow between rivers is forecasted as long as climate warming increases, favoring metapopulations at regional level.  相似文献   

10.
The use of habitats by hunting Hen Harriers Circus cyaneus just prior to the settlement period was investigated on Orkney, where numbers have declined by 70% over the last 20 years. Both males and females hunted over areas that were closer to subsequent breeding territories. Neither sex differed in the amount of time they hunted over areas dominated by either intensive pasture, moorland or rough grazing. However, male hunting was significantly related to the amount of unmanaged grass habitat with a litter layer. Female hunting was related negatively to vegetation height, and to the prevalence of both Heather Calluna vulgaris and managed grass; after controlling for these habitat features, female hunting also tended to be associated negatively with Common Starling Sturnus vulgaris abundance. Dramatic changes in land use on Orkney have occurred over the last 40 years, with increases in the amount of intensive pasture and decreases in the amount of rough grazing. These changes, coupled with a doubling in sheep Ovis aries densities over the last 20 years, are likely to have reduced the amount of unmanaged grass. These changes will have been detrimental to hunting male Harriers by reducing the amount of food they can supply to the females prior to egg laying and during the incubation period.  相似文献   

11.
Significant advances have been achieved in testicular cancer treatment for the last 15 years. Almost 100% of the non seminomatous tumors seen at the precocious stages I and II are cured because of the efficacy of chemotherapy in relapses. For clinical stages I, tendancy is to survey after castration without lymphadenectomy. For advanced metastatic stages, platinum has changed chemotherapy performances, allowing to cure 75 to 80% of these patients. The results of a bad pronosis group with large tumor remain to be improved. Seminomas at a localized stage (the most frequent case) are cured by radiotherapy; at an advanced stage, they are as sensitive to chemotherapy as non seminomatous tumors.  相似文献   

12.
Forests soils should be neither sinks nor sources of carbon in a long-term perspective. From a Swedish perspective the time since the last glaciation has probably not been long enough to reach a steady state, although changes are currently very slow. In a shorter perspective, climatic and management changes over the past 100 years have probably created imbalances between litter input to soils and organic carbon mineralisation. Using extant data on forest inventories, we applied models to analyse possible changes in the carbon stocks of Swedish forest soils. The models use tree stocks to provide estimates of tree litter production, which are fed to models of litter decomposition and from which carbon stocks are calculated. National soil carbon stocks were estimated to have increased by 3 Tg yr−1 or 12–13 g m−2 yr−1 in the period 1926–2000 and this increase will continue because soil stocks are far from equilibrium with current litter inputs. The figure obtained is likely to be an underestimation because wet sites store more carbon than predicted here and the inhibitory effect of nitrogen deposition on soil carbon mineralisation was neglected. Knowledge about site history prior to the calculation period determines the accuracy of current soil carbon stocks estimates, although changes can be more accurately estimated.  相似文献   

13.
In this article, a summary of the geologic, paleontological, and human history of an area of the Atlantic coast in the Pampean plain, Argentina is discussed. This area presents very interesting characteristics. On the one hand, the area includes the Monte Hermoso cliffs studied by Charles Darwin in 1832, which compose the set of localities related to the development of the theory of evolution. On the other hand, in the referred area, an extraordinary amount of human and Pleistocene mammal footprints are registered. Also in that section, four diachronic stages have been registered which depict the evolutionary scenario during the last five million years. Four paleontological and archeological sites are described, showing the palaeoenvironmental changes that occurred there regarding fauna associations and human settlement. The first scenario is found at Monte Hermoso cliff, whose sediments contain fossil remains of the autochthonous South American fauna. The second scenario shows a remarkable change in the drainage system where the fauna is composed of immigrated taxa due to the Great American Biotic Interchange. Both last scenarios show human presence; the third one shows faint evidences (one human trackway and two isolated footprints), and in the last one the hunter–gatherers are fully represented as a well-established population on the Pampean coast during the Early Holocene, registered at La Olla and Monte Hermoso I sites. In this way, the sites summarized in this work allow the reconstruction of four remarkable evolutionary scenarios in South America, as regards landscapes, fauna associations, and human population.  相似文献   

14.
Hawkmoths are an important component of tropical ecosystems, with significant roles as herbivores and pollinators. These moths can be used as indicators in biodiversity assessments because they can be easily sampled and identified. However, hawkmoths have seldom been surveyed over the long term for this purpose, especially in the Neotropical region. Considering that long-term datasets are of indisputable importance for understanding and monitoring temporal changes in biodiversity, this study assessed long-term changes in the hawkmoth fauna in a protected Atlantic Rain Forest area over a period of 64 years. We used historical and recent empirical datasets to ask whether faunal-diversity patterns and species composition have changed over time. We used individual- and sample-based rarefaction and extrapolation curves based on Hill number (diversity order of q = 0) to compare species richness, and the probability version of the abundance-based Chao-Jaccard index to assess beta diversity over time. To assess changes in faunal composition, we conducted a nonmetric multidimensional scaling analysis and performed an analysis of similarities to test whether the community composition has changed. Our results clearly showed long-term stability of the hawkmoth community over the 64 years, despite the growing human-induced landscape changes that occurred in the region surrounding the study area during the last 6 decades. This study emphasizes the importance of large remnants of Atlantic Forest for long-term maintenance of both functional diversity and ecosystem functioning.  相似文献   

15.
Over the last several decades, rural Greek society has undergone rapid changes. In large part these changes are due to two interrelated developments: the integration of Greece into the European Union and the arrival of large numbers of Eastern European migrant laborers. Social organization in Greek villages has been influenced by global systems of production and exchange for hundreds of years, if not longer, but since the early 1980’s, with the accession of Greece into the European Union, these relations seem to have been altered in novel ways. As Greece has become integrated into the transnational and global markets through the E.U., social relations are increasingly shaped by a pervasive global trend toward neoliberalism, that is, by a new round of market liberalization that has in effect redefined the way that local communities and international markets interact. This change has had a profound effect on the ways that rural Greeks participate in international markets as both producers and consumers. A related development, in fact a by-product of neoliberal policies in the formerly socialist countries of Eastern Europe, is the introduction of large numbers of immigrant laborers into rural Greece, which has significantly altered rural labor markets and allowed for important changes in patterns of the social reproduction of labor. While these changes have been for the most part not of their own making, except perhaps in an indirect way, Greek agriculturalists are not hapless victims in these developments. Globalization has indeed brought changes to rural society, but not exactly in the ways that policy-makers or others with a “top -- down” perspective have imagined. During ethnographic fieldwork that I conducted in several Greek villages between 2000 and 2004 I found that rural people have engaged these changes in the global political economy through an active process of adaptation, manipulation, resistance and accommodation. Here I will focus on changes in the mobilization of labor and the production of national identity, and the relationship between the two. I will argue that there has been a transformation in how national identities are being produced within the new configuration of nation and state that has important implications for understanding how inequality is structured and reproduced under global capitalism.  相似文献   

16.
In recent years, our understanding of the functioning of ABC (ATP-binding cassette) systems has been boosted by the combination of biochemical and structural approaches. However, the origin and the distribution of ABC proteins among living organisms are difficult to understand in a phylogenetic perspective, because it is hard to discriminate orthology and paralogy, due to the existence of horizontal gene transfer. In this chapter, I present an update of the classification of ABC systems and discuss a hypothetical scenario of their evolution. The hypothetical presence of ABC ATPases in the last common ancestor of modern organisms is discussed, as well as the additional possibility that ABC systems might have been transmitted to eukaryotes, after the two endosymbiosis events that led to the constitution of eukaryotic organelles. I update the functional information of selected ABC systems and introduce new families of ABC proteins that have been included recently into this vast superfamily, thanks to the availability of high-resolution three-dimensional structures.  相似文献   

17.
G B Sancar 《Mutation research》1990,236(2-3):147-160
DNA photolyases catalyze the light-dependent repair of cis,syn-cyclobutane dipyrimidines (pyrimidine dimers). Although the phenomenon of enzymatic photoreactivation was first described 40 years ago and photolyases were the first enzymes shown unequivocally to effect DNA repair, it has only been in the last 8 years that sufficient quantities of the enzymes have been purified to permit detailed studies of their physical properties, identification of their intrinsic chromophores, and elucidation of the mechanisms of dimer recognition and photolysis. In addition several of the genes encoding these enzymes have now been cloned and sequenced. These studies have revealed remarkable functional and structural conservation among these evolutionarily ancient enzymes and have identified a new role for photolyases in dark-repair processes which has implications for the mechanism of nucleotide excision repair in both prokaryotes and eukaryotes.  相似文献   

18.
Although few hunter‐gatherers or foragers exist today, they are well documented in the ethnographic record. Anthropologists have been eager to study them since they assumed foragers represented a lifestyle that existed everywhere before 10,000 years ago and characterized our ancestors into some ill‐defined but remote past. In the past few decades, that assumption has been challenged on several grounds. Ethnographically described foragers may be a biased sample that only continued to exist because they occupied marginal habitats less coveted by agricultural people. 3 In addition, many foragers have been greatly influenced by their association with more powerful agricultural societies. 4 It has even been suggested that Holocene foragers represent a new niche that appeared only with the climatic changes and faunal depletion at the end of the last major glaciation. 5 Despite these issues, the ethnographic record of foragers provides the only direct observations of human behavior in the absence of agriculture, and as such is invaluable for testing hypotheses about human behavioral evolution. 6 .  相似文献   

19.
A deep genetic cline between southern populations of the barnacle Balanus glandula (from about Monterey Bay southward) and northern populations (from northern California through Alaska) has recently been described. If this pattern is due to historical isolation and genetic drift, we expect it to have formed recently and represent a transient, nonequilibrium state. However, this cline appears to have formed well before the last glacial maximum. Our assays of sequence diversity at a region of mitochondrial cytochrome oxidase I, combined with coalescent estimators of the time of separation for these two regions, suggest that a late Pleistocene event more than 100 thousand years ago may be responsible for the initial separation. This suggests that either strong oceanographic mechanisms or natural selection have maintained the cline, because there has clearly been adequate time for this cline or polymorphism to resolve itself by genetic drift and migration. However, reliance on only a single mitochondrial marker for which the substitution rate has been estimated still limits the resolution of our analysis.  相似文献   

20.
Beyond the proteome: non-coding regulatory RNAs   总被引:3,自引:0,他引:3       下载免费PDF全文
Szymański M  Barciszewski J 《Genome biology》2002,3(5):reviews0005.1-reviews00058
  相似文献   

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