The genetic architecture of petal number in Cardamine hirsuta

International audienceInvariant petal number is a characteristic of most flowers and is generally robust to genetic and environmental variation. We took advantage of the natural variation found in Cardamine hirsuta petal number to investigate the genetic basis of this trait in a case where robustness was lost during evolution. We used quantitative trait locus (QTL) analysis to characterize the genetic architecture of petal number. Αverage petal number showed transgressive variation from zero to four petals in five C. hirsuta mapping populations, and this variation was highly heritable. We detected 15 QTL at which allelic variation affected petal number. The effects of these QTL were relatively small in comparison with alleles induced by mutagenesis, suggesting that natural selection may act to maintain petal number within its variable range below four. Petal number showed a temporal trend during plant ageing, as did sepal trichome number, and multi-trait QTL analysis revealed that these age-dependent traits share a common genetic basis. Our results demonstrate that petal number is determined by many genes of small effect, some of which are age-dependent, and suggests a mechanism of trait evolution via the release of cryptic variation

Stochastic variation in Cardamine hirsuta petal number

Background and Aims Floral development is remarkably robust in terms of the identity and number of floral organs in each whorl, whereas vegetative development can be quite plastic. This canalization of flower development prevents the phenotypic expression of cryptic genetic variation, even in fluctuating environments. A cruciform perianth with four petals is a hallmark of the Brassicaceae family, typified in the model species Arabidopsis thaliana. However, variable petal loss is found in Cardamine hirsuta, a genetically tractable relative of A. thaliana. Cardamine hirsuta petal number varies in response to stochastic, genetic and environmental perturbations, which makes it an interesting model to study mechanisms of decanalization and the expression of cryptic variation. Methods Multitrait quantitative trait locus (QTL) analysis in recombinant inbred lines (RILs) was used to identify whether the stochastic variation found in C. hirsuta petal number had a genetic basis. Key Results Stochastic variation (standard error of the average petal number) was found to be a heritable phenotype, and four QTL that influenced this trait were identified. The sensitivity to detect these QTL effects was increased by accounting for the effect of ageing on petal number variation. All QTL had significant effects on both average petal number and its standard error, indicating that these two traits share a common genetic basis. However, for some QTL, a degree of independence was found between the age of the flowers where allelic effects were significant for each trait. Conclusions Stochastic variation in C. hirsuta petal number has a genetic basis, and common QTL influence both average petal number and its standard error. Allelic variation at these QTL can, therefore, modify petal number in an age-specific manner via effects on the phenotypic mean and stochastic variation. These results are discussed in the context of trait evolution via a loss of robustness

Inverse Medea as a Novel Gene Drive System for Local Population Replacement: A Theoretical Analysis

One strategy to control mosquito-borne diseases, such as malaria and dengue fever, on a regional scale is to use gene drive systems to spread disease-refractory genes into wild mosquito populations. The development of a synthetic Medea element that has been shown to drive population replacement in laboratory Drosophila populations has provided encouragement for this strategy but has also been greeted with caution over the concern that transgenes may spread into countries without their consent. Here, we propose a novel gene drive system, inverse Medea, which is strong enough to bring about local population replacement but is unable to establish itself beyond an isolated release site. The system consists of 2 genetic components—a zygotic toxin and maternal antidote—which render heterozygous offspring of wild-type mothers unviable. Through population genetic analysis, we show that inverse Medea will only spread when it represents a majority of the alleles in a population. The element is best located on an autosome and will spread to fixation provided any associated fitness costs are dominant and to very high frequency otherwise. We suggest molecular tools that could be used to build the inverse Medea system and discuss its utility for a confined release of transgenic mosquitoes

The S-Cycle performance matrix : supporting comprehensive sustainability performance evaluation of technical systems

The work reported in this paper consolidates and rationalises disparate evaluation methods in a novel, generic framework to support the selection of comprehensive material/energetic sustainability performance indicators (SPIs) for technical systems. The S-Cycle Performance Matrix (S-CPMatrix) is comprised of 6 generic sustainability goals, 11 SPI archetypes, and 23 corresponding metrics identified from a model of technical system sustainability (the S-Cycle). The matrix was evaluated by interpreting and classifying 324 indicators currently applied to evaluate technical system sustainability performance in the literature, with 94.1% found to be fully classifiable with respect to the matrix following several refinements. The remaining 5.9% suggested additional SPI archetypes and a goal that were not initially identified. The matrix is intended to support decision makers in meeting three criteria for comprehensiveness identified from the literature: (C1) inclusion of indicators measuring performance at all relevant scales; (C2) inclusion of efficiency and effectiveness indicators; and (C3) coverage of all system sustainability goals. It may be applied to different systems in conjunction with different evaluation methods, thereby contributing to more consistent guidance on the selection of comprehensive SPIs for technical systems. In addition to industrial evaluation and comparison with existing evaluation methods, four avenues for future research were identified: (i) use of the S-CPMatrix to support systems comparison/benchmarking; (ii) further investigation of unsupported metrics; (iii) the nature and measurement of contaminants; and (iv) the comprehensiveness of SPI sets currently used in sustainability performance evaluation of technical systems

Morphogenetic Theory and the Constructivist Institutionalist Challenge

This article engages with two meta-theoretical approaches to social analysis, ‘morphogenetic theory’ and ‘constructivist institutionalism’, and specifically explores how the former fares under the critical scrutiny of the latter. The key proponent of constructivist institutionalism, Colin Hay, has offered two detailed critiques of morphogenesis that criticise its position on the foundational sociological issues of structure-agency and material-ideational. Although Hay’s critiques are largely rejected in an overall defence of the morphogenetic approach, the process of engagement is seen to be particularly useful for morphogenetic theory because it allows a number of important clarifications to be made and it also opens up space for theoretical development. In the course of this debate, accessible introductions are given to both theories, and the similarities and differences between them are outlined, providing clarity to both. Therefore, although this article ultimately operates as a defence of morphogenetic theory, especially in the form proposed by Margaret Archer and Douglas Porpora, it finds a great deal of fruitful discussion in the constructivist institutionalist challenge

Geographic Market Definition in an International Context

Market definition is generally regarded as a key step in antitrust analysis. Market definition has two components. Product market definition seeks to include all products that are meaningful substitutes. Geographic market definition seeks to incorporate all relevant sources of the product in question. This paper is concerned with geographic market definition and, in particular, how geographic markets are defined in situations where competition may, at least to some extent, transcend national boundaries. The subject of the paper may be of some current interest for two reasons. First, the perception is widespread that, over the past twenty or so years, competition in many products and services has become increasingly international in scope and that this trend will continue. Second, the way in which foreign competition is taken into account in performing the antitrust analysis can have a dramatic impact on the legal or policy conclusions that are reached in a particular instance. The legality of a proposed merger, for example, may turn entirely on how competition from foreign sellers is treated. For antitrust purposes, when we say that competition has become more international in scope, we mean primarily that the range of possible suppliers for many goods and services to U.S. consumers increasingly includes sellers who do not produce or are not primarily headquartered in the United States or that an increasing portion of sales by American-based firms are to customers abroad. Many aspects of antitrust are potentially affected by these changes. Some of the more complex issues involve jurisdictional considerations and these will not be discussed here. As we will see, however, the subject of market definition exposes almost all of the substantive (as opposed to jurisdictional) considerations that come into play when we take account of the international aspect of certain markets. The paper has three main parts. The first focuses on the role market definition plays in antitrust analysis and, in particular, the link between market definition and market power. The second explores the particular issues that are raised with respect to market definition when there is an international aspect to competition. The final section addresses some of the empirical questions raised by the largely theoretical analysis of the first two parts of the paper

Geographic Market Definition in an International Context

Market definition is generally regarded as a key step in antitrust analysis. Market definition has two components. Product market definition seeks to include all products that are meaningful substitutes. Geographic market definition seeks to incorporate all relevant sources of the product in question. This paper is concerned with geographic market definition and, in particular, how geographic markets are defined in situations where competition may, at least to some extent, transcend national boundaries. The subject of the paper may be of some current interest for two reasons. First, the perception is widespread that, over the past twenty or so years, competition in many products and services has become increasingly international in scope and that this trend will continue. Second, the way in which foreign competition is taken into account in performing the antitrust analysis can have a dramatic impact on the legal or policy conclusions that are reached in a particular instance. The legality of a proposed merger, for example, may turn entirely on how competition from foreign sellers is treated. For antitrust purposes, when we say that competition has become more international in scope, we mean primarily that the range of possible suppliers for many goods and services to U.S. consumers increasingly includes sellers who do not produce or are not primarily headquartered in the United States or that an increasing portion of sales by American-based firms are to customers abroad. Many aspects of antitrust are potentially affected by these changes. Some of the more complex issues involve jurisdictional considerations and these will not be discussed here. As we will see, however, the subject of market definition exposes almost all of the substantive (as opposed to jurisdictional) considerations that come into play when we take account of the international aspect of certain markets. The paper has three main parts. The first focuses on the role market definition plays in antitrust analysis and, in particular, the link between market definition and market power. The second explores the particular issues that are raised with respect to market definition when there is an international aspect to competition. The final section addresses some of the empirical questions raised by the largely theoretical analysis of the first two parts of the paper

Globalization, the ambivalence of European integration and the possibilities for a post-disciplinary EU studies

Using the work of Manuel Castells as a starting point, this article explores the ambivalent relationship between globalization and European integration and the variety of ways in which the mainstream political science of the EU has attempted to deal with this issue. The analysis here suggests that various 'mainstreaming' disciplinary norms induce types of work that fail to address fully the somewhat paradoxical and counter-intuitive range of possible relationships between globalization and European integration. The article explores critically four possible analytical ways out of this paradox—abandonment of the concept of globalization, the development of definition precision in globalization studies, the reorientation of work to focus on globalization as discourse, and inter- and post-disciplinarity. The argument suggests that orthodox discussions of the relationship require a notion of social geography that sits at odds with much of the literature on globalization and while greater dialogue between disciplines is to be welcomed, a series of profound epistemological questions need to be confronted if studies of the interplay between global and social process are to be liberated from their disciplinary chains