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1.
Despite a recent explosion of works emphasizing the increasingly plural and complex character of identity, political and social elites' interpretations of identities have continued to be dominated by the paradigm of monistic authenticity. In the face of this resilience, theorists must say more about the formation, meaning and implications of plural and complex identities. They must provide social and political actors with a credible alternative language to make sense of the actual or potential plurality of their allegiances. This article aims at contributing to the task by relying on the complementary merits of two traditions that used to ignore each other: post-imperialism and federalism. First, we suggest that post-imperialism may provide a language for redefining communities and individual-community relationships in a pluralist way. Second, we argue that the language of federalism has a high – and neglected – potential to answer the political and normative questions raised by post-imperialism.  相似文献   

2.
The classification of the Catesbaeeae and Chiococceae tribes, along with that of the entire Rubiaceae, has long been debated. The Catesbaeeae-Chiococceae complex (CCC) includes approximately 28 genera and 190 species primarily concentrated in the Greater Antilles (nearly 70% of the species), Central and South America, and in the western Pacific (three genera). Previous molecular studies, with broad sampling of the Rubiaceae, have shown the CCC to be a monophyletic group. The present study is a more detailed examination of the generic relationships within the CCC using two data sets, the nuclear ribosomal ITS regions and the trnL-F chloroplast intron and spacer. Maximum parsimony analyses lend further support to the previous hypotheses that the CCC is monophyletic and sister to Strumpfia maritima. However, within the complex several genera do not form monophyletic groups. Previous studies of the Rubiaceae suggest that the ancestral fruit type in the CCC is a multiseeded capsule. Indehiscent, fleshy fruits appear to have evolved three to four times within this lineage. Changes in floral morphologies within the complex tend to correspond to cladogenesis among and within genera. Finally, molecular analyses suggest one or possibly two long-distance dispersals from the Americas to the western Pacific.  相似文献   

3.
Abstract

Taxonomic concepts (sensu Berendsohn) embody the underlying meanings of scientific names as stated in a particular publication, thus offering a new way to resolve semantic ambiguities that result from multiple revisions of a taxonomic name. This paper presents a comprehensive and powerful language for representing the relationships among taxonomic concepts. The language features terms and symbols for concept relationships within a single taxonomic hierarchy, or between two related but independently published hierarchies. Taxonomic concepts pertaining to a single hierarchy are characterised by parent/child relationships, whereas those pertaining to two independent hierarchies may have the following basic relationships: congruence, inclusion (non‐symmetrical, relative to the side of comparison), overlap, and exclusion. The relationships are asserted by specialists who have the option to add or subtract concepts on one or both sides of a relationship equation in order to reconcile differences between non‐congruent taxonomic perspectives. The terms ‘and’, ‘or’ and ‘not’ are available, respectively, to connect multiple simultaneously or alternatively valid relationship assessments, or to explicitly negate the validity of a relationship. The language also permits the decomposition of a relationship according to the intensional (property referencing) and ostensive (member pointing) aspects of the compared taxonomic concepts. Adopting the concept relationship language will facilitate a more precise documentation of similarities and differences in multiple succeeding taxonomic perspectives, thereby preparing the stage for an ontology‐based integration of taxonomic and related biological information.  相似文献   

4.
Elucidating how complex regulatory networks have assembled during evolution requires a detailed understanding of the evolutionary dynamics that follow gene duplication events, including changes in post‐translational modifications. We compared the phosphorylation profiles of paralogous proteins in the budding yeast Saccharomyces cerevisiae to that of a species that diverged from the budding yeast before the duplication of those genes. We found that 100 million years of post‐duplication divergence are sufficient for the majority of phosphorylation sites to be lost or gained in one paralog or the other, with a strong bias toward losses. However, some losses may be partly compensated for by the evolution of other phosphosites, as paralogous proteins tend to preserve similar numbers of phosphosites over time. We also found that up to 50% of kinase–substrate relationships may have been rewired during this period. Our results suggest that after gene duplication, proteins tend to subfunctionalize at the level of post‐translational regulation and that even when phosphosites are preserved, there is a turnover of the kinases that phosphorylate them.  相似文献   

5.
Using data from the 1992 NESTOR-survey 'Living arrangements and social networks of older adults' (N = 4494), the aim of the present study is to identify specific categories of older adults who are most vulnerable to loneliness. By looking at different types of partner relationships (first, second, and third marriages; consensual unions; partners who are not household members) and at partner histories (never married, ever divorced, ever widowed, remarried), this study elaborates on previous research which has tended to look only at the presence versus the absence of partner relationships. Findings indicate that different types of partner relationships provide differential protection against loneliness. There appears to be a 'shadow of the past' of a previous divorce or widowhood in second and third partnerships, which accounts for generally higher levels of loneliness. Single men tend to be more lonely than single women. Moreover, there are no differences in loneliness between men who have always been single and those previously married. Among single women, differences in partner history are relevant: never married single women tend to be least vulnerable to loneliness. The differences in loneliness between older adults with different types of partner relationships and partner histories are only partially attributable to network and social participation differences. The latter independently contribute to the explanation of loneliness. The role of non-social determinants (health and socioeconomic position) is also examined. The results underscore the socially isolating effects of sensory impairments. Older adults with functional limitations, and those with visual or auditory problems tend to be more lonely, findings which are only partially attributable to differences in the number and quality of social relationships. Socioeconomic circumstances primarily have an indirect influence on loneliness. Those with higher levels of educational attainment and higher incomes tend to have more extensive social networks and are therefore less prone to loneliness.  相似文献   

6.
Taxonomic relationships within the Old World fruit bat genus, Cynopterus, have been equivocal for the better part of a century. While nomenclature has been revised multiple times on the basis of phenotypic characters, evolutionary relationships among taxa representing the entire geographic range of the genus have not been determined. We used mitochondrial DNA sequence data to infer phylogenetic relationships among the three most broadly distributed members of the genus: C. brachyotis, C. horsfieldi, and C. sphinx, and to assess whether C. brachyotis represents a single widespread species, or a complex of distinct lineages. Results clearly indicate that C. brachyotis is a complex of lineages. C. sphinx and C. horsfieldi haplotypes formed monophyletic groups nested within the C. brachyotis species complex. We identified six divergent mitochondrial lineages that are currently referred to C. brachyotis. Lineages from India, Myanmar, Sulawesi, and the Philippines are geographically well-defined, while in Malaysia two lineages, designated Sunda and Forest, are broadly sympatric and may be ecologically distinct. Demographic analyses of the Sunda and Forest lineages suggest strikingly different population histories, including a recent and rapid range expansion in the Sunda lineage, possibly associated with changes in sea levels during the Pleistocene. The resolution of the taxonomic issues raised in this study awaits combined analysis of morphometric characters and molecular data. However, since both the Indian and Malaysian Forest C. brachyotis lineages are apparently ecologically restricted to increasingly fragmented forest habitat, we suggest that reevaluation of the conservation status of populations in these regions should be an immediate goal.  相似文献   

7.
The growing independence of infant common marmosets from their caregivers is promoted primarily by their caregivers, who increasingly often prevent the infants from climbing onto them and decreasingly often pick the infants up. Infants achieve independence from their mothers, fathers, and older siblings at different rates and develop characteristically different relationships with them. Infants that are most rejected by caregivers spend the least time on them. When rejected by their parents, infants tend to spend their time with their twins, rather than seeking to climb onto other caregivers. Caregivers do not compensate for unduly large or small amounts of care given by other members of the group. It is argued that if we are to understand the development of caregiver-infant relationships in species with multiple caregivers, we must discover the rules by which infants assess the amount of care they perceive themselves to have received and caregivers assess the amount of care they perceive themselves to have offered. The implications of a simple model based on expected levels of caregiving and careseeking are explored, particularly with respect to competition and compensation.  相似文献   

8.
The handicap principle has been applied to a number of different traits in the last three decades, but it is difficult to characterize its record, or even its perceived relevance, when it comes to an important human attribute—spoken language. In some cases, assumptions regarding the energetic cost of speech, and the veracity of linguistically encoded messages, have failed to recognize critical aspects of human development, cognition, and social ecology. In other cases, the fact that speech contains honest (physiological) information, and tends to be used honestly with family and friends, has been overlooked. Speech and language are functionally related but they involve different resources. Individuals can increase the attractiveness of their speech, and of more stylized vocal and verbal performances, without enhancing linguistic structure or content; and they can modify their use of language without significant changes in the physical form of speech. That its production costs are normally low enables speech to be produced extravagantly in bids for status and mating relationships, and in evolution, may have allowed its content—linguistic knowledge and structure—to become complex.  相似文献   

9.
Several captive chimpanzees and bonobos have learned to use symbols and to comprehend syntax. Thus, compared with other nonhumans, these animals appear to have unusual cognitive powers that can be recruited for communicative behavior. This raises the possibility that wild chimpanzee vocal communication is more complex than heretofore demonstrated. To examine this possibility, I investigated whether wild chimpanzee vocal exchanges exhibit uniquely human conversational attributes. The results indicate that wild chimpanzees vocalize at low rates, tend not to respond to calls that they hear, and, when they do respond, tend to give calls that are similar to the ones they have heard. Thus, chimpanzee vocal interactions resemble those of other primate species, and show no special similarity to human conversations. The results support the view that we need to explore cognitive and social continuities and discontinuities with nonhuman primates to understand the origin and evolution of language, but also emphasize the need for fine-grained analyses of wild chimpanzee vocal interactions.  相似文献   

10.
Neural networks as robust tools in drug lead discovery and development   总被引:1,自引:0,他引:1  
Empirical methods for building predictive models of the relationships between molecular structure and useful properties are becoming increasingly important. This has arisen because drug discovery and development have become more complex. A large amount of biological target information is becoming available though molecular biology. Automation of chemical synthesis and pharmacological screening has also provided a vast amount of experimental data. Tools for designing libraries and extracting information from molecular databases and high-throughput screening (HTS) experiments robustly and quickly enable leads to be discovered more effectively. As drug leads progress down the development pipeline, the ability to predict physicochemical, pharmacokinetic, and toxicological properties of these leads is becoming increasingly important in reducing the number of expensive, late-development failures. Neural network methods have much to offer in these areas. This review introduces the concepts behind neural networks applied to quantitative structure-activity relationships (QSARs), points out problems that may be encountered, suggests ways of avoiding the pitfalls, and introduces several exciting new neural network methods discovered during the last decade.  相似文献   

11.
Communication in nature is not restricted to the transmitter-receiver pair. Unintended listeners, or eavesdroppers, can intercept the signal and possibly utilize the received information to their benefit, which may confer a certain cost to the communicating pair. In this paper we explore (computationally and mathematically) such situations with the goal of uncovering their effect on language evolution. We find that in the presence of eavesdropping, languages exhibit a tendency to become more complex. On the other hand, if eavesdroppers belong to a different (competing) population, the languages used by the two populations tend to converge, if the cost of eavesdropping is sufficiently high; otherwise the languages synchronize. These findings are discussed in the context of animal communication and human language. In particular, the emergence of synonyms is predicted. We demonstrate that a small associated cost can suppress synonyms in the absence of eavesdropping, but that their likelihood increases strongly with the probability of eavesdropping.  相似文献   

12.
Chloroplast DNA (cpDNA) sequence variation is currently the most widely used tool for the inference of phylogenetic relationships among plants at all taxonomic levels. Generally, noncoding regions tend to evolve faster than coding sequences and have recently been applied to the study of phylogenetic relationships among closely related taxa. An implicit assumption of many of these studies is that intraspecific cpDNA variation is either absent or low and therefore will not interfere with the reconstruction of interspecific relationships. A survey of cpDNA sequence variation in the common alpine plant species Draba aizoides L. was undertaken to assess levels of intraspecific cpDNA sequence variation. These levels were compared to levels of interspecific sequence divergence between D. aizoides and related alpine Draba species. Intraspecific cpDNA sequence divergence was extensive in D. aizoides, and intraspecific differences were often larger than interspecific differences. cpDNA haplotype relationships were explored using a maximum parsimony approach and minimum-spanning networks. Results from both methods were largely congruent but comparisons provided interesting insights into the presumed evolutionary history of cpDNA haplotypes. A combined effect of cpDNA introgression and complex lineage sorting was inferred to explain the pattern of cpDNA variation found in D. aizoides. Our results suggest that intraspecific cpDNA variation can be extensive and that intraspecific variation needs to be taken into account when inferring phylogenetic relationships among closely related taxa.  相似文献   

13.
Infants are frequently with their mothers when troop members initiate interaction with them. To what extent are the infants' companions attracted specifically to them rather than to the mother? A simple method is presented for approaching this question and for assessing the extent to which the relationships of 11 free-ranging rhesus (Macaca mulatta) infants on Cayo Santiago have acquired qualities independent of (differentiated from) those of the mother. Companions of all ages tend to be attracted specifically to infants between 1 and 14 weeks of age and not simply to their mothers. However, this tendency is less marked for sibling companions than for more distantly related companions. No differences are found between infants of high- and low-ranking mothers. Infantile attractiveness is not necessarily sustained when infants are 17 to 30 weeks of age. The degree to which relationships with infant companions and with older female companions have, differentiated by 17 to 30 weeks is negatively related to the companion's age. Infants show early and increasingly marked tendencies to develop differentiated relationships with one another; however, they show no signs of doing so with adult female companions by 30 weeks of age.  相似文献   

14.
1.  The abundance and distribution of species tend to be linked, such that species declining in abundance often tend also to show declines in the number of sites they occupy, while species increasing in abundance tend also to be increasing in occupancy. Therefore, intraspecific abundance–occupancy relationships are commonly positive.
2.  The intraspecific pattern is mirrored by more general positive interspecific abundance–occupancy relationships: widespread species tend to be abundant, and narrowly distributed species rare.
3.  Here, we review recent research on these patterns based on the flora and fauna of the British Isles. We assess their generality, describe what is currently known about their structure, and summarize the results of tests of the several hypotheses proposed to explain their existence.
4.  The positive form generally exhibited by abundance–occupancy relationships, intraspecific or interspecific, has consequences for several areas of applied ecology, including conservation, harvesting, biological invasions and biodiversity inventorying. These implications are discussed briefly.  相似文献   

15.
Bottlenose dolphins exhibit complex social affiliations that may be shaped by interactions among individuals. Affiliative body contact among dolphins may repair deteriorated relationships or reduce tension within the group following aggressive interactions. We investigated the time-series association between one type of contact behavior (flipper-rubbing) and aggression by continuous observation of three captive bottlenose dolphins. For all three dolphin pairs, the elapsed time to aggressive events was significantly greater following flipper-rubbing. In two dolphin pairs comprised of a young male and an adult female, one-zero score of inter-opponent flipper-rubbing was higher for 10 min following aggressive bouts (post-AG periods) than for the same length of control (Ctrl) periods. For all three focal pairs, one-zero score of third-party rubbing was higher for post-AG than Ctrl periods. Neither the direction of rubbing nor the identity of the partner that approached prior to rubbing showed any significant tendencies. Flipper-rubbing may contribute to restore friendly relationships between former opponents or reduce conflicts in at least juvenile-adult female associations. Our results also give preliminary suggestions of the functions of third-party flipper-rubbing among bottlenose dolphins, including tension easing by the third party, or displacement as a result of aggressive interactions.  相似文献   

16.
Listening habits are strongly influenced by two opposing aspects, the desire for variety and the demand for uniformity in music. In this work we quantify these two notions in terms of instrumentation and production technologies that are typically involved in crafting popular music. We assign an ‘instrumentational complexity value’ to each music style. Styles of low instrumentational complexity tend to have generic instrumentations that can also be found in many other styles. Styles of high complexity, on the other hand, are characterized by a large variety of instruments that can only be found in a small number of other styles. To model these results we propose a simple stochastic model that explicitly takes the capabilities of artists into account. We find empirical evidence that individual styles show dramatic changes in their instrumentational complexity over the last fifty years. ‘New wave’ or ‘disco’ quickly climbed towards higher complexity in the 70s and fell back to low complexity levels shortly afterwards, whereas styles like ‘folk rock’ remained at constant high instrumentational complexity levels. We show that changes in the instrumentational complexity of a style are related to its number of sales and to the number of artists contributing to that style. As a style attracts a growing number of artists, its instrumentational variety usually increases. At the same time the instrumentational uniformity of a style decreases, i.e. a unique stylistic and increasingly complex expression pattern emerges. In contrast, album sales of a given style typically increase with decreasing instrumentational complexity. This can be interpreted as music becoming increasingly formulaic in terms of instrumentation once commercial or mainstream success sets in.  相似文献   

17.
While the relationship between food web complexity and stability has been well documented, how complexity affects productivity remains elusive. In this study, we combine food web theory and a data set of 149 aquatic food webs to investigate the effect of complexity (i.e. species richness, connectance, and average interaction strength) on ecosystem productivity. We find that more complex ecosystems tend to be more productive, although different facets of complexity have contrasting effects. A higher species richness and/or average interaction strength increases productivity, whereas a higher connectance often decreases it. These patterns hold not only between realized complexity and productivity, but also characterize responses of productivity to simulated declines of complexity. Our model also predicts a negative association between productivity and stability along gradients of complexity. Empirical analyses support our predictions on positive complexity-productivity relationships and negative productivity-stability relationships. Our study provides a step forward towards reconciling ecosystem complexity, productivity and stability.  相似文献   

18.
Earlier reports suggest a distinct pattern of genetic variation linked to both language and geographic distance in Island Melanesia. Inland Papuan-speaking populations from different islands tend to share one allelic profile, while shore-based or more cosmopolitan populations share another, related to Southeast Asian influence over the past 3000 years. In the present paper, we report the genotypes and allele frequencies of an informative 9.1-thousand-base-pairs (kb) insertion/deletion polymorphism in 19 populations living in Island Melanesia. The populations studied inhabit the islands of New Britain, New Ireland, New Hanover, and Mussau in the Bismarck Archipelago, and speak either Austronesian or Papuan languages. We also include for reference a collection from New Guinea and Bougainville. The data show a marked fluctuation in the allele frequency among the different isolates, with the 9.1-kb(-) allele frequency ranging from 0.67 to 0.98. The deletion allele reaches fixation in some Papuan-speaking interior populations of New Britain, as well as in the interiors of New Guinea and Bougainville. However, certain inland Austronesian-speaking populations also share a similar high frequency of the deletion. Our data suggest that language distinctions are generally, but not invariably, indicative of diverse allelic patterns in this complex region, where inland groups on large islands tend to be often distinctive from shore-based populations.  相似文献   

19.
Despite extensive research efforts, the controversy over diversity–productivity (D–P) patterns in natural communities still looms large. Recent meta‐analyses suggest that unimodal D–P relationships tend to pre‐dominate in plant studies, while positively linear relationships are more common in animal studies. These patterns, however, are based on studies in which productivity is estimated either directly, based on the biomass or energy of the studied organisms, or indirectly, according to the productivity of lower trophic levels, and various surrogates. Our analysis shows that the distribution of D–P patterns is sensitive to the directness of productivity estimates in animal studies but not in plant studies. Analysis of D–P patterns should be based on direct productivity estimates of the studied organisms, especially in comparative meta‐analyses of communities from multiple trophic levels, where productivity is often affected nonlinearly by indirect factors or when complex feedback interactions are expected between productivity and diversity.  相似文献   

20.
Cancer progression is mediated by complex epigenetic, protein and structural influences. Critical among them are the biochemical, mechanical and architectural properties of the extracellular matrix (ECM). In recognition of the ECM's important role, cancer biologists have repurposed matrix mimetic culture systems first widely used by tissue engineers as new tools for in vitro study of tumor models. In this review we discuss the pathological changes in tumor ECM, the limitations of 2D culture on both traditional and polyacrylamide hydrogel surfaces in modeling these characteristics and advances in both naturally derived and synthetic scaffolds to facilitate more complex and controllable 3D cancer cell culture. Studies using naturally derived matrix materials like Matrigel and collagen have produced significant findings related to tumor morphogenesis and matrix invasion in a 3D environment and the mechanotransductive signaling that mediates key tumor–matrix interaction. However, lack of precise experimental control over important matrix factors in these matrices have increasingly led investigators to synthetic and semi-synthetic scaffolds that offer the engineering of specific ECM cues and the potential for more advanced experimental manipulations. Synthetic scaffolds composed of poly(ethylene glycol) (PEG), for example, facilitate highly biocompatible 3D culture, modular bioactive features like cell-mediated matrix degradation and complete independent control over matrix bioactivity and mechanics. Future work in PEG or similar reductionist synthetic matrix systems should enable the study of increasingly complex and dynamic tumor–ECM relationships in the hopes that accurate modeling of these relationships may reveal new cancer therapeutics targeting tumor progression and metastasis.  相似文献   

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