Charlotte Louise Jensen

Effects of genetic distance on heterosis in a Drosophila melanogaster model system

Habitat fragmentation and small population sizes can lead to inbreeding and loss of genetic variation, which can potentially cause inbreeding depression and decrease the ability of populations to adapt to altered environmental conditions. One solution to these genetic problems is the implementation of genetic rescue, which re-establishes gene flow between separated populations. Similar techniques are being used in animal and plant breeding to produce superior production animals and plants. To optimize fitness benefits in genetic rescue programs and to secure high yielding domestic varieties in animal and plant breeding, knowledge on the genetic relatedness of populations being crossed is imperative. In this study, we conducted replicated crosses between isogenic Drosophila melanogaster lines from the Drosophila Genetic Reference Panel. We grouped lines in two genetic distance groups to study the effect of genetic divergence between populations on the expression of heterosis in two fitness components; starvation resistance and reproductive output. We further investigated the transgenerational effects of outcrossing by investigating the fitness consequences in both the F1- and the F3-generations. High fitness enhancements were observed in hybrid offspring compared to parental lines, especially for reproductive output. However, the level of heterosis declined from the F1- to the F3-generation. Generally, genetic distance did not have strong impact on the level of heterosis detected, although there were exceptions to this pattern. The best predictor of heterosis was performance of parental lines with poorly performing parental lines showing higher hybrid vigour when crossed, i.e. the potential for heterosis was proportional to the level of inbreeding depression. Overall, our results show that outcrossing can have very strong positive fitness consequences for genetically depauperate populations.

Beyond ‘behaviour’: The institutionalisation of practice and the case of energy-efficient lighting in Denmark:

In contrast with approaches which focus on behaviour relating to purchasing decisions and attitudes of consumers, research on social practices emphasises the analysis of what people routinely do and the elements of practice underpinning institutionalisation of collective conventions. This article contributes to this growing stream of literature by investigating social practices relevant to energy-efficient lighting in Denmark. It reports on data collected from ‘ethnographic interviews’ conducted in 16 Danish households and suggests that drawing on insights from institutional theory could enrich our understanding of social practices, for example, in relation to the emergence and embedding of new practices and shedding of ‘old’ ones. In addition to highlighting the elements of practice previously identified as integral to collective conventions and connections among different domains of practice, this article recognises the importance of phenomena usually examined in work emphasising institutional analysis. It suggests that policy interventions need to recognise various kinds of institutional rules and processes which confer legitimacy to emerging practices, to facilitate their sedimentation and contribute to realising environmentally sustainable systems and societies.