Natural selection and genetic diversity in the butterfly Heliconius melpomene

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The stable isotopic composition of Daphnia ephippia reflects changes in d13C and d18O values of food and water

The stable isotopic composition of fossil resting eggs (ephippia) of Daphnia spp. is being used to reconstruct past environmental conditions in lake ecosystems. However, the underlying assumption that the stable isotopic composition of the ephippia reflects the stable isotopic composition of the parent Daphnia, of their diet and of the environmental water have yet to be confirmed in a controlled experimental setting. We performed experiments with Daphnia pulicaria cultures, which included a control treatment conducted at 12 °C in filtered lake water and with a diet of fresh algae and three treatments in which we manipulated the stable carbon isotopic composition (?13C value) of the algae, stable oxygen isotopic composition (?18O value) of the water and the water temperature, respectively. The stable nitrogen isotopic composition (?15N value) of the algae was similar for all treatments. At 12 °C, differences in algal ?13C values and in ?18O values of water were reflected in those of Daphnia. The differences between ephippia and Daphnia stable isotope ratios were similar in the different treatments (?13C: +0.2 ± 0.4 ‰ (standard deviation); ?15N: ?1.6 ± 0.4 ‰; ?18O: ?0.9 ± 0.4 ‰), indicating that changes in dietary ?13C values and in ?18O values of water are passed on to these fossilizing structures. A higher water temperature (20 °C) resulted in lower ?13C values in Daphnia and ephippia than in the other treatments with the same food source and in a minor change in the difference between ?13C values of ephippia and Daphnia (to ?1.3 ± 0.3 ‰). This may have been due to microbial processes or increased algal respiration rates in the experimental containers, which may not affect Daphnia in natural environments. There was no significant difference in the offset between ?18O and ?15N values of ephippia and Daphnia between the 12 and 20 °C treatments, but the ?18O values of Daphnia and ephippia were on average 1.2 ‰ lower at 20 °C than at 12 °C. We conclude that the stable isotopic composition of Daphnia ephippia provides information on that of the parent Daphnia and of the food and water they were exposed to, with small offsets between Daphnia and ephippia relative to variations in Daphnia stable isotopic composition reported from downcore studies. However, our experiments also indicate that temperature may have a minor influence on the ?13C, ?15N and ?18O values of Daphnia body tissue and ephippia. This aspect deserves attention in further controlled experiment

Agent-based simulation of electricity markets - a literature review

Liberalisation, climate policy and promotion of renewable energy are challenges to players of the electricity sector in many countries. Policy makers have to consider issues like market power, bounded rationality of players and the appearance of fluctuating energy sources in order to provide adequate legislation. Furthermore the interactions between markets and environmental policy instruments become an issue of increasing importance. A promising approach for the scientific analysis of these developments is the field of agent-based simulation. The goal of this article is to provide an overview of the current work applying this methodology to the analysis of electricity markets

New methods for energy market modelling. Proceedings of the first european workshop on energy market modelling using agent-based compuational economics 2007: 1st EMMACE workshop 2007, 26th October Karlsruhe, Germany

A growing number of researchers have developed agent-based models to simulate the development of liberalized energy markets. As the field of energy market modelling with agent-based computational economics is very heterogeneous, the overview in this book might help interested researchers to get a sense for the different modelling approaches and to learn about the potential of this valuable modelling approach in different fields of the energy market

Local human pressures influence gene flow in a hybridizing Daphnia species complex

International audienceAnthropogenic environmental changes are considered critical drivers of the genetic structure of populations and communities through, for example, the facilitation of introgressive hybridization between syntopic species. However, the mechanisms by which environmental perturbations trigger changes in the genetic structure of populations and communities, such as the processes that determine the directionality of hybridization and patterns of mitochondrial introgression over many generations, remain largely unexplored. In this study, the changes in genetic structure of hybridizing members of the Daphnia longispina species complex were reconstructed over the last 100years for three large temperate lakes under strong anthropogenic pressures via palaeogenetic analyses of resting egg banks. Drastic changes in the genetic structure of the Daphnia community, associated with hybridization events between D.longispina and D.galeata and subsequent introgression, were detected in Lakes Geneva and Bourget. In Lake Bourget, these changes were induced by the successful establishment of D.galeata with rising phosphorus levels and reinforced by the sensitivity of D.longispina to fish predation pressure. In Lake Geneva, the pattern of hybridization during eutrophication is more likely a function of the original taxonomic composition of the species complex in this lake. Lakes seem to require at least a meso-oligotrophic status to allow D.galeata populations to establish and accordingly no D.galeata genotypes were found in the egg bank of oligotrophic Lake Annecy. In contrast to the generally assumed pattern of unidirectional hybridization in this species complex, bidirectional hybridization was recorded in Lakes Geneva and Bourget. Our results also demonstrate complex genetic trajectories within this species complex and highlight the irreversibility of changes in the genotypic architecture of populations driven by local human pressures. Finally, we show that extensive hybridization and introgression do not necessarily result in a large and homogenous hybrid swarm

Local human pressures influence gene flow in a hybridizing Daphnia species complex

International audienceAnthropogenic environmental changes are considered critical drivers of the genetic structure of populations and communities through, for example, the facilitation of introgressive hybridization between syntopic species. However, the mechanisms by which environmental perturbations trigger changes in the genetic structure of populations and communities, such as the processes that determine the directionality of hybridization and patterns of mitochondrial introgression over many generations, remain largely unexplored. In this study, the changes in genetic structure of hybridizing members of the Daphnia longispina species complex were reconstructed over the last 100years for three large temperate lakes under strong anthropogenic pressures via palaeogenetic analyses of resting egg banks. Drastic changes in the genetic structure of the Daphnia community, associated with hybridization events between D.longispina and D.galeata and subsequent introgression, were detected in Lakes Geneva and Bourget. In Lake Bourget, these changes were induced by the successful establishment of D.galeata with rising phosphorus levels and reinforced by the sensitivity of D.longispina to fish predation pressure. In Lake Geneva, the pattern of hybridization during eutrophication is more likely a function of the original taxonomic composition of the species complex in this lake. Lakes seem to require at least a meso-oligotrophic status to allow D.galeata populations to establish and accordingly no D.galeata genotypes were found in the egg bank of oligotrophic Lake Annecy. In contrast to the generally assumed pattern of unidirectional hybridization in this species complex, bidirectional hybridization was recorded in Lakes Geneva and Bourget. Our results also demonstrate complex genetic trajectories within this species complex and highlight the irreversibility of changes in the genotypic architecture of populations driven by local human pressures. Finally, we show that extensive hybridization and introgression do not necessarily result in a large and homogenous hybrid swarm