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Selected AbstractsFIELD AND EXPERIMENTAL EVIDENCE FOR COMPETITION'S ROLE IN PHENOTYPIC DIVERGENCEEVOLUTION, Issue 2 2007David W. Pfennig Resource competition has long been viewed as a major cause of phenotypic divergence within and between species. Theory predicts that divergence arises because natural selection favors individuals that are phenotypically dissimilar from their competitors. Yet, there are few conclusive tests of this key prediction. Drawing on data from both natural populations and a controlled experiment, this paper presents such a test in tadpoles of two species of spadefoot toads (Spea bombifrons and S. multiplicata). These two species show exaggerated divergence in trophic morphology where they are found together (mixed-species ponds) but not where each is found alone (pure-species ponds), suggesting that they have undergone ecological character displacement. Moreover, in pure-species ponds, both species exhibit resource polymorphism. Using body size as a proxy for fitness, we found that in pure-species ponds disruptive selection favors extreme trophic phenotypes in both species, suggesting that intraspecific competition for food promotes resource polymorphism. In mixed-species ponds, by contrast, we found that trophic morphology was subject to stabilizing selection in S. multiplicata and directional selection in S. bombifrons. A controlled experiment revealed that the more similar an S. multiplicata was to its S. bombifrons tankmate in resource use, the worse was its performance. These results indicate that S. multiplicata individuals that differ from S. bombifrons would be selectively favored in competition. Our data therefore demonstrate how resource competition between phenotypically similar individuals can drive divergence between them. Moreover, our results indicate that how competition contributes to such divergence may be influenced not only by the degree to which competitors overlap in resource use, but also by the abundance and quality of resources. Finally, our finding that competitively mediated disruptive selection may promote resource polymorphism has potentially important implications for understanding how populations evolve in response to heterospecific competitors. In particular, once a population evolves resource polymorphism, it may be more prone to undergo ecological character displacement. [source] Mindscapes And Internet-mediated CommunicationJOURNAL OF COMPUTER-MEDIATED COMMUNICATION, Issue 3 2002John Gammack Cultures are considered to be epistemologically heterogeneous, and it is assumed that epistemologically similar individuals exist across distinct cultures. Epistemological type is viewed as prior to, and transcendent of, nationality and culture. Identifying a shared epistemological basis for communication will be more likely to succeed in dialogical contexts where conformity to prevailing national stereotypes may fail. Two levels of communication are distinguished: explicate (here seen as conformity to social and cultural symbolic norms and conventions), and implicate (the level at which implicit, abstract communicative intention originates). Cyberspatial interactions potentially undermine normative cultural influences and permit multicultural or transcultural environments in which new codes extending from epistemological types (rather than cultural) become possible, limited only by media potential and symbolization itself. Drawing upon Maruyama's (1980) theory, implications for an alternative to the homogenization of verbal communication, and potential elements of codes for universal understandings are considered. [source] Aggressiveness is associated with genetic diversity in landlocked salmon (Salmo salar)MOLECULAR ECOLOGY, Issue 9 2003Katriina Tiira Abstract The amount of intraindividual genetic variation has often been found to have profound effects on life history traits. However, studies concerning the relationship between behaviour and genetic diversity are scarce. Aggressiveness is an important component of competitive ability in juvenile salmonids affecting their later performance and survival. In this study, we used an experimental approach to test the prediction that juveniles with low estimated genetic diversity should be less aggressive than juveniles with high estimated genetic diversity in fry from a highly endangered population of land-locked salmon (Salmo salar). This was achieved by using a method enabling the accurate estimation of offspring genetic diversity based on parental microsatellite genotype data. This allowed us to create two groups of offspring expected to have high or low genetic diversity in which aggressive behaviour could be compared. Salmon fry with low estimated genetic diversity were significantly less aggressive than fry with high estimated genetic diversity. Closer analysis of the data suggested that this difference was due to differences in more costly acts of aggression. Our result may reflect a direct effect of genetic variation on a fitness-related trait; however, we cannot rule out an alternative explanation of allele-specific phenotype matching, where lowered aggression is expressed towards genetically more similar individuals. [source] Fiscal Federalism in AustraliaPUBLIC ADMINISTRATION, Issue 1 2004Iain McLean Australia displays high vertical fiscal imbalance (VFI) for historical and constitutional reasons. It also attempts to achieve the highest degree of horizontal fiscal equalization (HFE) to be found in any democratic federation. The Commonwealth Grants Commission (CGC), a non-partisan body at arm's length from politicians, oversees the regime. A recent report claims that equity, efficiency and transparency would all improve if the regime were abolished. Such a change is politically unachievable, but it raises interesting issues in public finance and public administration, which carry over to other federations and union states. An economically efficient system would: minimize perverse incentives, especially incentives to seek rent; encourage states to grow; discourage suboptimal location decisions; minimize transaction costs. An equitable system would maximize equity between relevantly similar individuals. Aspects of the Australian system that should be copied include the non-partisan agency and the target of HFE between component parts of the country. Aspects that should be discussed and perhaps copied include the very extensive equalization, including the feature of equalizing away the effects of grants for special purposes. Aspects that should probably not be copied include the cumbersome formulae and some of the perverse methods of calculating for ,needs'. All abbreviations and acronyms are spelt out in the Appendix on page 37. [source] Exploiting a Rare Communication Shift to Document the Persuasive Power of the News MediaAMERICAN JOURNAL OF POLITICAL SCIENCE, Issue 2 2009Jonathan McDonald Ladd Using panel data and matching techniques, we exploit a rare change in communication flows,the endorsement switch to the Labour Party by several prominent British newspapers before the 1997 United Kingdom general election,to study the persuasive power of the news media. These unusual endorsement switches provide an opportunity to test for news media persuasion while avoiding methodological pitfalls that have plagued previous studies. By comparing readers of newspapers that switched endorsements to similar individuals who did not read these newspapers, we estimate that these papers persuaded a considerable share of their readers to vote for Labour. Depending on the statistical approach, the point estimates vary from about 10% to as high as 25% of readers. These findings provide rare evidence that the news media exert a powerful influence on mass political behavior. [source] | |||||||||||||