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Alternative Explanation (alternative + explanation)
Selected AbstractsEVALUATION OF ELEVATED PLOIDY AND ASEXUAL REPRODUCTION AS ALTERNATIVE EXPLANATIONS FOR GEOGRAPHIC PARTHENOGENESIS IN EUCYPRIS VIRENS OSTRACODSEVOLUTION, Issue 4 2010Sofia Adolfsson Transitions from sexual to asexual reproduction are often coupled with elevations in ploidy. As a consequence, the importance of ploidy per se for the maintenance and spread of asexual populations is unclear. To examine the effects of ploidy and asexual reproduction as independent determinants of the success of asexual lineages, we sampled diploid sexual, diploid asexual, and triploid asexual Eucypris virens ostracods across a European wide range. Applying nuclear and mitochondrial markers, we found that E. virens consists of genetically highly differentiated diploid sexual populations, to the extent that these sexual clades could be considered as cryptic species. All sexual populations were found in southern Europe and North Africa and we found that both diploid asexual and triploid asexual lineages have originated multiple times from several sexual lineages. Therefore, the asexual lineages show a wide variety of genetic backgrounds and very strong population genetic structure across the wide geographic range. Finally, we found that triploid, but not diploid, asexual clones dominate habitats in northern Europe. The limited distribution of diploid asexual lineages, despite their shared ancestry with triploid asexual lineages, strongly suggests that the wider geographic distribution of triploids is due to elevated ploidy rather than to asexuality. [source] An Alternative Explanation for the Origin of the Resistivity Anomaly in La-Doped BaTiO3JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2001Finlay D. Morrison Semiconductivity in La-doped BaTiO3 ceramics after high-temperature firing, e.g., 1350°C in air, is attributed to oxygen nonstoichiometry. In more heavily doped compositions, the observed resistivity rise is attributed to surface oxidation of the grains during cooling. [source] The Struggle between Security and Democracy: An Alternative Explanation of the Democratization of South KoreaPACIFIC FOCUS, Issue 1 2010Dongsoo Kim South Korea experienced democratic reform relatively recently. Before its significant democratic reform in 1987, South Korea had been dominated by a series of authoritarian regimes over a few decades since its liberation from Japanese colonial rule. This study aims to uncover a set of variables that helped the democratic development of South Korea. For that purpose, I will demonstrate that prior to democratization the politics of South Korea were characterized by the struggle between democracy and security, and that the authoritarian leaders were successful in utilizing the unstable international security environment to strengthen their power during those years. I will also show that the favorably changing security environment played a significant role in the process of democratic transition. In so doing, I will argue that consideration of the external security environment is essential in the discussion of democratization. [source] The Distribution of Subsidized Agricultural Credit in Brazil: Do Interest Groups Matter?DEVELOPMENT AND CHANGE, Issue 3 2001Steven M. Helfand This article examines the unequal distribution of credit and credit subsidies in the Brazilian agricultural sector from 1969 to 1990. Total credit subsidies exceeded US$ 40 billion in this period. The distribution across crops is studied econometrically. After controlling for area, the crops that benefited most had superior access to credit institutions, were tradeable, had high prices, and were not perennials. Proxies for collective action by crop were an unimportant determinant of credit policy, while a bias in favour of large producers was evident. Alternative explanations for this bias are discussed, including collective action by farm size and transaction costs in lending. [source] Opposite shell-coiling morphs of the tropical land snail Amphidromus martensi show no spatial-scale effectsECOGRAPHY, Issue 4 2006Paul G. Craze Much can be learned about evolution from the identification of those factors maintaining polymorphisms in natural populations. One polymorphism that is only partially understood occurs in land snail species where individuals may coil clockwise or anti-clockwise. Theory shows that polymorphism in coiling direction should not persist yet species in several unrelated groups of land snails occur in stably polymorphic populations. A solution to this paradox may advance our understanding of evolution in general. Here, we examine two possible explanations: firstly, negative frequency-dependent selection due to predation; secondly, random fixation of alternative coiling morphs in tree-sized demes, giving the impression of wider polymorphism. We test these hypotheses by investigating morph-clustering of empty shells at two spatial scales in Amphidromus martensi populations in northern Borneo: the spatial structure of snail populations is relatively easy to estimate and this information may support one or other of the hypotheses under test. For the smaller scale we make novel use of a statistic previously used in botanical studies (the K-function statistic), which allows clustering of more than one morph to be simultaneously investigated at a range of scales and which we have corrected for anisotropy. We believe this method could be of more general use to ecologists. The results show that consistent clustering or separation of morphs cannot be clearly detected at any spatial scale and that predation is not frequency-dependent. Alternative explanations that do not require strong spatial structuring of the population may be needed, for instance ones involving a mechanism of selection actively maintaining the polymorphism. [source] Shifting Imperatives: An Integrative View of Resource Scarcity and Agency Reasons for FranchisingENTREPRENEURSHIP THEORY AND PRACTICE, Issue 1 2006Gary J. Castrogiovanni Alternative explanations of franchising offer contrasting predictions as to how the proportion of franchised outlets changes as franchisors age. We propose that two dominant views,resource-scarcity and agency theory,can be integrated by delineating when each is most relevant. Data from 102 franchisors over a 21-year period suggest that resource-scarcity considerations take precedence when franchisors are young, but that agency considerations prevail as franchisors age. Thus, the proportion franchised exhibits a cubic pattern as franchisors age,increasing rapidly at first, decreasing, and then increasing again. Future researchers and practitioners alike can benefit from understanding how the relative influences of resource and agency considerations shift over time. [source] FROM MICRO- TO MACROEVOLUTION THROUGH QUANTITATIVE GENETIC VARIATION: POSITIVE EVIDENCE FROM FIELD CRICKETSEVOLUTION, Issue 10 2004Mattieu Bégin Abstract . -Quantitative genetics has been introduced to evolutionary biologists with the suggestion that microevolution could be directly linked to macroevolutionary patterns using, among other parameters, the additive genetic variance/ covariance matrix (G) which is a statistical representation of genetic constraints to evolution. However, little is known concerning the rate and pattern of evolution of G in nature, and it is uncertain whether the constraining effect of G is important over evolutionary time scales. To address these issues, seven species of field crickets from the genera Gryllus and Teleogryllus were reared in the laboratory, and quantitative genetic parameters for morphological traits were estimated from each of them using a nested full-sibling family design. We used three statistical approaches (T method, Flury hierarchy, and Mantel test) to compare G matrices or genetic correlation matrices in a phylogenetic framework. Results showed that G matrices were generally similar across species, with occasional differences between some species. We suggest that G has evolved at a low rate, a conclusion strengthened by the consideration that part of the observed across-species variation in G can be explained by the effect of a genotype by environment interaction. The observed pattern of G matrix variation between species could not be predicted by either morphological trait values or phylogeny. The constraint hypothesis was tested by comparing the multivariate orientation of the reconstructed ancestral G matrix to the orientation of the across-species divergence matrix (D matrix, based on mean trait values). The D matrix mainly revealed divergence in size and, to a much smaller extent, in a shape component related to the ovipositor length. This pattern of species divergence was found to be predictable from the ancestral G matrix in agreement with the expectation of the constraint hypothesis. Overall, these results suggest that the G matrix seems to have an influence on species divergence, and that macroevolution can be predicted, at least qualitatively, from quantitative genetic theory. Alternative explanations are discussed. [source] On linking interannual tree ring variability with observations of whole-forest CO2 fluxGLOBAL CHANGE BIOLOGY, Issue 8 2006ADRIAN V. ROCHA Abstract We used a 10-year record of the CO2 flux by an old growth boreal forest in central Manitoba (the Northern Old Black Spruce Site (NOBS)), a ,150-year-old Picea mariana [Mill.] stand) to determine whether and how whole-forest CO2 flux is related to tree ring width. We compared a 37-year ring width chronology collected at NOBS to a second chronology that was collected at a nearby Black Spruce stand with a different disturbance history, and also to three measures of annual whole-forest photosynthesis [gross ecosystem production (GEP)], two measures of annual respiration (R), and one measure of annual carbon balance [net ecosystem production (NEP)]. The year-to-year ring width fluctuations were well correlated between the two sites; increasing our confidence in the NOBS chronology and implying that ring width variation is driven and synchronized by the physical environment. Both chronologies exhibited serial correlation, with a fluctuation in ring width that had an apparent periodicity of ,7 years. Neither chronology was correlated with variation in annual precipitation or temperature. Ring width and NEP increased, while R decreased from 1995 to 2004. GEP either remained constant or decreased from 1995 to 2004, depending on which measure was considered. The lack of relationship between ring width and GEP may indicate that ring growth is controlled almost entirely by something other than carbon uptake. Alternative explanations for the ring width chronologies include the possibility that wood production varies as a result of shifts in respiration, or that an unidentified aspect of the environment, rather than the balance between GEP and respiration, controls wood production. The serial correlation in ring width may be related to increases and decreases in carbohydrate pools, or to gradual changes in nutrient availability, pathogens, herbivores, soil frost or soil water table. The cause or causes of serial correlation, and the controls on the allocation of photosynthate to wood production, emerge as critical uncertainties for efforts in predicting the carbon balance of boreal ecosystems and inferring past climate from tree rings. [source] Social Interactions and Entrepreneurial ActivityJOURNAL OF ECONOMICS & MANAGEMENT STRATEGY, Issue 3 2009Mariassunta Giannetti We show that individuals residing in highly entrepreneurial neighborhoods are more likely to become entrepreneurs and invest more into their own businesses, even though their entrepreneurial profits are lower and their alternative job opportunities more attractive. Our results suggest that peer effects create nonpecuniary benefits from entrepreneurial activity and play an important role in the decision to become an entrepreneur. Alternative explanations, such as entry costs, social learning, and informal credit markets, are not supported by the data. [source] Verbal short-term memory in Down's syndrome: An articulatory loop deficit?JOURNAL OF INTELLECTUAL DISABILITY RESEARCH, Issue 2 2004S. Vicari Abstract Background Verbal short-term memory, as measured by digit or word span, is generally impaired in individuals with Down's syndrome (DS) compared to mental age-matched controls. Moving from the working memory model, the present authors investigated the hypothesis that impairment in some of the articulatory loop sub-components is at the base of the deficient maintenance and recall of phonological representations in individuals with DS. Methods Two experiments were carried out in a group of adolescents with DS and in typically developing children matched for mental age. In the first experiment, the authors explored the reliance of these subjects on the subvocal rehearsal mechanism during a word-span task and the effects produced by varying the frequency of occurrence of the words on the extension of the word span. In the second experiment, they investigated the functioning of the phonological store component of the articulatory loop in more detail. Results A reduced verbal span in DS was confirmed. Neither individuals with DS nor controls engaged in spontaneous subvocal rehearsal. Moreover, the data provide little support for defective functioning of the phonological store in DS. Conclusions No evidence was found suggesting that a dysfunction of the articulatory loop and lexical-semantic competence significantly contributed to verbal span reduction in subjects with DS. Alternative explanations of defective verbal short-term memory in DS, such as a central executive system impairment, must be considered. [source] A strategic response to class size reduction: Combination classes and student achievement in CaliforniaJOURNAL OF POLICY ANALYSIS AND MANAGEMENT, Issue 3 2008David Sims The California class size reduction program provided schools with cash rewards for K,3 classes of 20 or fewer students. I show how program rules made it possible for schools to save money by using mixed-grade classes to meet class size reduction obligations while maintaining larger average class sizes. I also show that this smoothing of students across grades is associated with a significant test score gap for certain second and third grade students. My estimates suggest that class size reduction may lead to lower test scores for students placed in combination classes. Alternative explanations of teacher experience and credentialing changes cannot explain the test score pattern. This result spotlights both the underappreciated role of age heterogeneity in classroom learning and the difficulty of replicating the success of policy experiments in statewide reform. © 2008 by the Association for Public Policy Analysis and Management. [source] Party Identification in Emotional and Political Context: A ReplicationPOLITICAL PSYCHOLOGY, Issue 6 2007Francis Neely While testing an affective measure of party identification Burden and Klofstad (2005) found that using the phrase, "feel that you are," in place of, "think of yourself as," significantly shifted PID in a Republican direction. I adopt the theoretical framework of Affective Intelligence (Marcus, Neuman, & MacKuen, 2000) to specify how the timing of their question-wording experiment may have influenced the results. I suggest that the outcome was a function of (a) anxiety present during the survey, which ran just after 9/11 of 2001, coupled with (b) a political environment that favored Republicans. In a 2005 survey I replicate the experiment and collect new measures with which to test expectations. I find no significant shift in PID, and provisional support for the Affective Intelligence explanation. The results validate Burden and Klofstad's measure, qualify their findings, and test the application of the theory of Affective Intelligence to party dispositions. Alternative explanations and directions for further research are discussed. [source] Is Under-Employment due to Labour Hoarding?THE ECONOMIC RECORD, Issue 246 2003Evidence from the Australian Workplace Industrial Relations Survey In this paper, Australian data are used to study the characteristics of workers who are constrained in their hours of work. Matched employer,employee data allow us to control for their employers' characteristics as well. In particular, the information on the firms' state of demand provides useful evidence on the underlying cause of under-employment. The labour hoarding model cannot explain the observed patterns involving under-employment. Alternative explanations are offered. [source] Early indicators of child abuse and neglect: a multi-professional Delphi studyCHILD ABUSE REVIEW, Issue 1 2003Catherine Powell Abstract Through the application of the Delphi technique, this study draws on the expertise of British child protection academics and practitioners from a wide range of disciplines in seeking to develop a consensus opinion on possible early indicators of child abuse and neglect. The search for early indicators is described in the context of a secondary preventative approach to the problem of child maltreatment. A very tentative conclusion arising from the study is that the early indicators of child abuse and neglect that achieved consensus of agreement may help in diagnosing child abuse and neglect at an earlier stage, although they are not necessarily diagnostic. Alternative explanations, differential diagnoses and information-gathering are paramount, as is a willingness and ability to act on concerns. Although great caution is urged, it is suggested that the findings from the study are credible and of interest to those who are working towards more timely recognition and referral of abused and neglected children. Copyright © 2003 John Wiley & Sons, Ltd. [source] Measuring the Time Inconsistency of US Monetary PolicyECONOMICA, Issue 297 2008PAOLO SURICO This paper offers an alternative explanation for the great inflation of the 1970s by measuring a novel source of monetary policy time inconsistency. In the presence of asymmetric preferences, the monetary authorities generate a systematic inflation bias through the private-sector expectations of a larger policy response in recessions than in booms. The estimated Fed's implicit target for inflation has declined from the pre- to the post-Volcker regime. The average inflation bias was about 1% before 1979, but this has disappeared over the last two decades, because the preferences on output stabilization were large and asymmetric only in the former period. [source] The individual tolerance concept is not the sole explanation for the probit dose-effect model,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2000Michael C. Newman Abstract Predominant methods for analyzing dose- or concentration-effect data (i.e., probit analysis) are based on the concept of individual tolerance or individual effective dose (IED, the smallest characteristic dose needed to kill an individual). An alternative explanation (stochasticity hypothesis) is that individuals do not have unique tolerances: death results from stochastic processes occurring similarly in all individuals. These opposing hypotheses were tested with two types of experiments. First, time to stupefaction (TTS) was measured for zebra fish (Brachydanio rerio) exposed to benzocaine. The same 40 fish were exposed during five trials to test if the same order for TTS was maintained among trials. The IED hypothesis was supported with a minor stochastic component being present. Second, eastern mosquitofish (Gambusia holbrooki) were exposed to sublethal or lethal NaCl concentrations until a large portion of the lethally exposed fish died. After sufficient time for recovery, fish sublethally exposed and fish surviving lethal exposure were exposed simultaneously to lethal NaCl concentrations. No statistically significant effect was found of previous exposure on survival time but a large stochastic component to the survival dynamics was obvious. Repetition of this second type of test with pentachlorophenol also provided no support for the IED hypothesis. We conclude that neither hypothesis alone was the sole or dominant explanation for the lognormal (probit) model. Determination of the correct explanation (IED or stochastic) or the relative contributions of each is crucial to predicting consequences to populations after repeated or chronic exposures to any particular toxicant. [source] Evaluating the impact of pollution on plant,Lepidoptera relationshipsENVIRONMETRICS, Issue 4 2005Christian Mulder Abstract We monitored the biodiversity of plants, adult butterflies and leaf-miners in a Dutch nature reserve over a period of six years (1994,1999) within the International Co-operative Programme on Integrated Monitoring on Air Pollution Effects (ICP-IM). Butterfly abundance decreased steadily over the period, indicating a negative diversity trend, while the number of leaf-mining larvae of Microlepidoptera remained fairly constant. Also the concentration of pollutants (NH4, NO3, SO4, Cd, Cu and Zn) was determined in air, leaves, litter, throughfall and stemflow. We have no reason to expect a negative impact of acidification in rainwater or climate change, as temperature and ozone show no significant trends across the six years. It is shown that the nectar-plants of adult butterflies are much more sensitive to heavy metals than the nectar-plants of moths and other pollinating insects. It is hypothesized that the butterfly decline is a secondary effect of heavy metal stress on local plants, not resulting in a decrease in the number of host-plants, but in a selective pressure of pollutants on the plant vigour, subsequently affecting their pollinators (p,<,0.001). An alternative explanation, such as the possible coexistence of a direct effect of xenobiotics on the adult Lepidoptera occurring in the study area, is not supported by our data (p,>,0.05). Copyright © 2005 John Wiley & Sons, Ltd. [source] Comparative study on antibodies to human and bacterial 60 kDa heat shock proteins in a large cohort of patients with coronary heart disease and healthy subjectsEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 4 2001Z. Prohászka Background Recent observations indicate an association between antibodies against mycobacterial heat shock protein (hsp65) and coronary heart disease (CHD). Previously, we reported on marked differences in antigen specificity and complement activating ability of anti-hsp65 antibodies and auto-antibodies against human heat shock protein, hsp60. Here, we investigated whether there are differences between antih-sp65 and anti-hsp60 antibodies in their association with CHD. Design We measured by ELISA the levels of antibodies to hsp65, hsp60 and E. coli -derived GroEL in three groups: Group I, 357 patients with severe CHD who underwent by-pass surgery; Group II, 67 patients with negative coronary angiography; Group III, 321 healthy blood donors. Antibodies against Helicobacter pylori were also measured by commercial ELISA. Results As calculated by multiple regression analysis, the levels of anti-hsp60 auto-antibodies were significantly higher in Group I compared to Group II (P = 0·007) or Group III (P < 0·0001). By contrast, although concentrations of anti-hsp65 and anti-GroEL antibodies in Group I were higher than in Group III, no significant differences between Group I and Group II were found. Antibodies to the two bacterial hsp strongly correlated to each other, but either did not correlate or weakly correlated to hsp60. In Group I, serum concentrations of anti- H.pylori antibodies significantly correlated with those of anti-hsp65 and anti-GroEL antibodies but they did not correlate with the anti-hsp60 antibodies. Conclusion As to their clinical relevance, a remarkable difference become evident between antibodies to human hsp60 and antibodies against bacterial hsp in the extent of association with CHD. On the basis of these findings and some pertinent literature data, an alternative explanation for the association between high level of anti-hsp antibodies and atherosclerotic vascular diseases is raised. [source] PRECLINICAL STUDY: Is withdrawal hyperalgesia in morphine-dependent mice a direct effect of a low concentration of the residual drug?ADDICTION BIOLOGY, Issue 4 2009Vardit Rubovitch ABSTRACT Withdrawal of opioid drugs leads to a cluster of unpleasant symptoms in dependent subjects. These symptoms are stimulatory in nature and oppose the acute, inhibitory effects of opiates. The conventional theory that explains the opioid withdrawal syndrome assumes that chronic usage of opioid drugs activates compensatory mechanisms whose stimulatory effects are revealed upon elimination of the inhibitory opioid drug from the body. Based on previous studies that show a dose-dependent dual activity of opiates, including pain perception, we present here an alternative explanation to the phenomenon of withdrawal-induced hyperalgesia. According to this explanation, the residual low concentration of the drug that remains after cessation of its administration elicits the stimulatory withdrawal hyperalgesia. The goal of the present study was to test this hypothesis. In the present study we rendered mice dependent on morphine by a daily administration of the drug. Cessation of morphine application elicited withdrawal hyperalgesia that was completely blocked by a high dose of the opiate antagonist naloxone (100 mg/kg). Similarly, naloxone (2 mg/kg)-induced withdrawal hyperalgesia was also blocked by 100 mg/kg of naloxone. The blockage of withdrawal hyperalgesia by naloxone suggested the involvement of opioid receptors in the phenomenon and indicated that withdrawal hyperalgesia is a direct effect of a residual, low concentration of morphine. Acute experiments that show morphine- and naloxone-induced hyperalgesia further verified our hypothesis. Our findings offer a novel, alternative approach to opiate detoxifications that may prevent withdrawal symptoms by a complete blockage of the opioid receptors using a high dose of the opioid antagonist. [source] An Investigation of the Reactivity of [(diimine)(dithiolato)M] Complexes Using the Fukui Functions ConceptEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2006Christodoulos Makedonas Abstract Fukui functions are widely used when investigating the reactivity of organic molecules, but rarely with metal complexes. Here, we investigate the reactivity of [(diimine)(dithiolato)M] complexes with different types of reagents and upon oxidation employing this concept. Mixed-ligand complexes of this type have a peculiar electronic description due to the mixed-metal-ligand-to-ligand charge-transfer band, which is why they are considered as very promising candidates for non-linear optical (NLO) materials and molecular photochemical devices (MPD). As a result, their reactivity is of crucial importance for their potential applications. The obtained results of f+ and f, for the neutral [(diimine)(dithiolato)M] complexes (M = Pd, Ni and Pt) not only predict that the sulfur atom is the preferable active site for electrophilic attack but also reveal the different tunability of these complexes when they are subjected to an oxidation process, in agreement with experimental results. Under the framework of the Fukui indices we also provide an alternative explanation for crystal packing that could find widespread application. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Issue salience in regional party manifestos in SpainEUROPEAN JOURNAL OF POLITICAL RESEARCH, Issue 1 2009LISELOTTE LIBBRECHT It is based on a content analysis of the party manifestos of the Spanish PP and PSOE in eight regional elections held between 2001 and 2003. It provides an innovative coding scheme for analysing regional party manifestos and on that basis seeks to account for inter-regional, intra-party and inter-party differences in regional campaigning. The authors have tried to explain the inter-regional variation of the issue profiles of state-wide parties in regional elections on the basis of a model with four independent variables: the asymmetric nature of the system, the electoral cycle, the regional party systems and the organisation of the state-wide parties. Three of their hypotheses are rejected, but the stronger variations in the regional issue profiles of the PSOE corroborate the assumption that parties with a more decentralised party organisation support regionally more diverse campaigning. The article concludes by offering an alternative explanation for this finding and by suggesting avenues for further research. [source] How fatiguing is dispositional suppression?EUROPEAN JOURNAL OF SOCIAL PSYCHOLOGY, Issue 2 2007Disentangling the effects of procedural rebound, ego-depletion Recent work has shown that correcting a dispositional inference may lead social observers to over-emphasize the role of dispositional factors in subsequent judgments. This effect has been explained as a procedural rebound following a phase of dispositional suppression. We conducted two experiments to test an alternative explanation in terms of ego-depletion. In Experiment 1, we compared the effects of ego-depletion and dispositional rebound by relying on the attitude attribution paradigm and the cookie paradigm. In Experiment 2, we turned to a difficult math task in order to induce fatigue. We were able to replicate the dispositional rebound and the ego-depletion effects but none of the experiments supported an ego-depletion explanation of post-suppression dispositional rebound. Copyright © 2006 John Wiley & Sons, Ltd. [source] EFFECTS OF MIGRATION ON THE GENETIC COVARIANCE MATRIXEVOLUTION, Issue 10 2007Frédéric Guillaume In 1996, Schluter showed that the direction of morphological divergence of closely related species is biased toward the line of least genetic resistance, represented by gmax, the leading eigenvector of the matrix of genetic variance,covariance (the G -matrix). G is used to predict the direction of evolutionary change in natural populations. However, this usage requires that G is sufficiently constant over time to have enough predictive significance. Here, we explore the alternative explanation that G can evolve due to gene flow to conform to the direction of divergence between incipient species. We use computer simulations in a mainland,island migration model with stabilizing selection on two quantitative traits. We show that a high level of gene flow from a mainland population is required to significantly affect the orientation of the G -matrix in an island population. The changes caused by the introgression of the mainland alleles into the island population affect all aspects of the shape of G (size, eccentricity, and orientation) and lead to the alignment of gmax with the line of divergence between the two populations' phenotypic optima. Those changes decrease with increased correlation in mutational effects and with a correlated selection. Our results suggest that high migration rates, such as those often seen at the intraspecific level, will substantially affect the shape and orientation of G, whereas low migration (e.g., at the interspecific level) is unlikely to substantially affect the evolution of G. [source] Dividend Initiations and Asymmetric Information: A Hazard ModelFINANCIAL REVIEW, Issue 3 2003Sanjay Deshmukh G35 Abstract This paper investigates the dynamics of dividend policy using a hazard model. Specifically, the paper examines dividend initiations for a sample of firms that went public between 1990 and 1997. These dividend initiations are examined in the context of an alternative explanation based on the pecking order theory. The results indicate that the probability or the hazard rate of a dividend initiation is negatively related to both the level of asymmetric information and growth opportunities and positively related to the level of cash flow. These results are consistent with a pecking order explanation but inconsistent with a signaling explanation. [source] Leaf size and foraging for light in a sclerophyll woodlandFUNCTIONAL ECOLOGY, Issue 5 2002J. G. Bragg Summary 1It has been suggested that leaf size may represent a foraging scale, with smaller-leaved species exploiting and requiring higher resource concentrations that are available in smaller patches. 2Among 26 shrub species from a sclerophyll woodland community in New South Wales, Australia, species with smaller leaves tended to occur in better light environments, after controlling for height. The dark respiration rates of small-leaved species tended to exceed those of larger-leaved species. 3However, the higher-light environments where smaller-leaved species tended to occur had a patch scale larger than whole plants. There would not have been any foraging-scale impediment to large-leaved species occupying these higher-light patches. An alternative explanation for small-leaved species being more successful in higher-light patches, in this vegetation with moderate shading, might be that they were less prone to leaf overheating. 4Such relationships of leaf size to light across species at a given height may be important contributors to the wide spread of leaf sizes among species within a vegetation type, along with patterns down the light profile of the canopy, and effects associated with architecture and ramification strategy. [source] On the empirical association between poor health and low socioeconomic status at old ageHEALTH ECONOMICS, Issue 3 2002Christian Salas Abstract Epidemiologic studies using mortality rates as indicators of health fail to find any meaningful association between poor health and low socioeconomic status in older age-groups, whereas economic studies using self-assessed health consistently find a significant positive correlation, even after controlling for self-reporting errors. Such contradictory results have not been reported for working age individuals. A simple explanation might be that the elderly samples on which the epidemiologic and economic studies are based come from different populations. However, this paper shows that similar contradictory results are obtained even when the same samples are used, simply by switching between self-assessed health and mortality as health indicators. An alternative explanation is proposed, namely that these health indicators yield different results because they relate to different ranges of the latent health variable at old age. Copyright © 2002 John Wiley & Sons, Ltd. [source] The distribution of skeletal lesions in treponemal disease: is the lymphatic system responsible?INTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 3 2002Hallie R. Buckley Abstract The differential diagnosis of bone lesions in treponemal disease is well established in palaeopathology. However, the actual mechanism responsible for the characteristic distribution of bone involvement is not as clear. Two mechanisms are proposed in the literature. Firstly, that bone lesions are the result of direct extension from the skin rash of the secondary stage of disease. Secondly, that bones situated closer to the skin are more vulnerable to local trauma and therefore more likely to elicit a subperiosteal bone response. We propose an alternative explanation for the characteristic distribution of bone lesions in treponemal disease. This explanation is based on the close association between the lymphatic and skeletal systems and the pathogenesis of treponemal disease. This paper argues that the position of the lymphatic nodes and vessels, with little soft tissue intervention between bone tissue, mirrors the characteristic pattern of skeletal involvement in treponemal disease. Copyright © 2002 John Wiley & Sons, Ltd. [source] Primed for Violence: The Role of Gender Inequality in Predicting Internal ConflictINTERNATIONAL STUDIES QUARTERLY, Issue 2 2005M. Caprioli We know, most notably through Ted Gurr's research, that ethnic discrimination can lead to ethnopolitical rebellion,intrastate conflict. I seek to discover what impact, if any, gender inequality has on intrastate conflict. Although democratic peace scholars and others highlight the role of peaceful domestic behavior in predicting state behavior, many scholars have argued that a domestic environment of inequality and violence,structural and cultural violence,results in a greater likelihood of violence at the state and the international level. This project contributes to this line of inquiry and further tests the grievance theory of intrastate conflict by examining the norms of violence that facilitate a call to arms. And in many ways, I provide an alternative explanation for the significance of some of the typical economic measures,the greed theory,based on the link between discrimination, inequality, and violence. I test whether states characterized by higher levels of gender inequality are more likely to experience intrastate conflict. Ultimately, the basic link between gender inequality and intrastate conflict is confirmed,states characterized by gender inequality are more likely to experience intrastate conflict, 1960,2001. [source] Cycles and synchrony: two historical ,experiments' and one experienceJOURNAL OF ANIMAL ECOLOGY, Issue 5 2000Ottar N. Bjřrnstad Summary 1.,Theoretical models predict that spatial synchrony should be enhanced in cyclic populations due to nonlinear phase-locking. 2.,This is supported by Rohani et al.,s (1999) comparison of spatial synchrony of epidemics in two childhood diseases prior to and during the vaccination era. Measles is both more synchronous and more cyclic before vaccination. Whooping cough, in contrast, is more synchronous during the vaccination era, during which multiannual fluctuations are also more conspicuous. 3.,Steen et al. (1990) analysed historic records of cyclic rodents, to show that cyclicity was lost during the early part of the 20th century. I reanalyse the data, and find that the loss of cyclicity is associated with loss of regional synchrony. 4.,I use a coupled map lattice model to show that imperfect phase-locking provides an alternative explanation for regionwide synchrony of cyclic populations. [source] The monophyly of island radiations: an evaluation of niche pre-emption and some alternative explanationsJOURNAL OF ECOLOGY, Issue 4 2005JONATHAN SILVERTOWN Summary 1It has been argued that niche pre-emption is not the only possible explanation for monophyly among Macaronesian endemic plants because (i) interspecific competition is diffuse, not species-specific, (ii) the radiations in question may not in fact be monophyletic, and (iii) later colonists may have hybridized with earlier ones, making a small and undetected contribution to the gene pool of lineages that appear to be monophyletic. 2The niche pre-emption mechanism does not, however, require species-specific competitive interactions. It merely proposes that the clade created by adaptive radiation will occupy more niche space than the original colonist could on its own. Members of the clade will then collectively inhibit establishment by new colonists more effectively than can a colonist that has not radiated. 3The monophyly of many larger radiations in the Macaronesian flora is well established and new studies tend to confirm this pattern. 4A few later-arriving colonists may have undetectably hybridized with earlier arrivals, but this is only a genetic interpretation of the essential idea behind pre-emption, i.e. that early arrivals so outnumber later colonists that the latter cannot establish. 5We do not therefore believe that hybridization provides an alternative explanation of why groups with multiple colonization failed to radiate in Macaronesia. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||