The influence of pool volume and summer desiccation on the production of the resting and dispersal stage in a Daphnia metapopulation

Dispersal is a key process in metapopulations, as migrants genetically connect populations and enable the colonization of empty habitat patches. Sub-populations may differ in their numerical contribution of migrants within a metapopulation. This has strong implications on evolutionary and ecological dynamics and has led to two different hypotheses about the Daphnia metapopulation studied here: the assessment by some authors is that sub-populations contribute equally to the production of migrants, while others have postulated long-lived core populations in large "mainland” habitat patches as the dominant source of migrants. We have studied the resting and dispersal stage (ephippium) in a natural Daphnia metapopulation and in mesocosm experiments, and tested for effects of habitat size and summer desiccation. We found that a 1000-fold increase in rock pool volume resulted on average in only in a 2.8-fold increase in ephippium production. Mesocosm experiments confirmed these results: a 1000-fold increase of the mesocosms' volume resulted in a 7.2-fold increase in ephippium production. Additionally, we showed that ephippium production did not depend on the initial population size. Thus, populations in small pools may contribute only marginal fewer potential migrants in the whole metapopulation than populations in large pools. In a second mesocosm experiment we found that summer desiccation, which is a typical occurrence in small pools, is not detrimental for the populations. Daphnia hatched out of ephippia that were produced earlier within the same season and built up viable populations again. The substantial production of ephippia by populations in small pools suggests that these populations might be important for both the dynamics and global stability of metapopulation

Partial Clustering in Binary Two-Dimensional Colloidal Suspensions

Strongly interacting binary mixtures of superparamagnetic colloidal particles confined to a two-dimensional water-air interface are examined by theory, computer simulation and experiment. The mixture exhibits a partial clustering in equilibrium: in the voids of the matrix of unclustered big particles, the small particles form subclusters with a sponge-like topology which is accompanied by a characteristic small-wave vector peak in the small-small structure factor. This partial clustering is a general phenomenon occurring for strongly coupled negatively non-additive mixtures.Comment: 12 pages, 5 figures, submitted 200

Solving the TTC 2011 Reengineering Case with GReTL

This paper discusses the GReTL reference solution of the TTC 2011 Reengineering case. Given a Java syntax graph, a simple state machine model has to be extracted. The submitted solution covers both the core task and the two extension tasks.Comment: In Proceedings TTC 2011, arXiv:1111.440

Parasites promote host gene flow in a metapopulation

Local adaptation is a powerful mechanism to maintain genetic diversity in subdivided populations. It counteracts the homogenizing effect of gene flow because immigrants have an inferior fitness in the new habitat. This picture may be reversed in host populations where parasites influence the success of immigrating hosts. Here we report two experiments testing whether parasite abundance and genetic background influences the success of host migration among pools in a Daphnia magna metapopulation. In 22 natural populations of D. magna, immigrant hosts were found to be on average more successful when the resident populations experienced high prevalences of a local microsporidian parasite. We then determined whether this success is due to parasitism per se, or the genetic background of the parasites. In a common garden competition experiment, we found that parasites reduced the fitness of their local hosts relatively more than the fitness of allopatric host genotypes. Our experiments are consistent with theoretical predictions based on coevolutionary host-parasite models in metapopulations. A direct consequence of the observed mechanism is an elevated effective migration rate for the host in the metapopulatio

Business and human rights in the data economy: A mapping and research study

Digitalization is gaining importance rapidly. However, neither companies nor states have yet developed a sufficient understanding of the data economy’s human rights impacts. The study suggests that addressing the corporate responsibility of technology companies through a business and human rights lens has the benefit of anchoring the debate in internationally established norms and universally accepted human rights. Furthermore, discussing human rights in the data economy from this angle opens the possibility for companies to use or learn from managerial toolkits that have already been developed in this field

Multispecies coexistence in fragmented landscapes

Spatial dynamics have long been recognized as an important driver of biodiversity. However, our understanding of species’ coexistence under realistic landscape configurations has been limited by lack of adequate analytical tools. To fill this gap, we develop a spatially explicit metacommunity model of multiple competing species and derive analytical criteria for their coexistence in fragmented heterogeneous landscapes. Specifically, we propose measures of niche and fitness differences for metacommunities, which clarify how spatial dynamics and habitat configuration interact with local competition to determine coexistence of species. We parameterize our model with a Bayesian approach using a 36-y time-series dataset of three Daphnia species in a rockpool metacommunity covering >500 patches. Our results illustrate the emergence of interspecific variation in extinction and recolonization processes, including their dependencies on habitat size and environmental temperature. We find that such interspecific variation contributes to the coexistence of Daphnia species by reducing fitness differences and increasing niche differences. Additionally, our parameterized model allows separating the effects of habitat destruction and temperature change on species extinction. By integrating coexistence theory and metacommunity theory, our study provides platforms to increase our understanding of species’ coexistence in fragmented heterogeneous landscapes and the response of biodiversity to environmental changes

Multispecies coexistence in fragmented landscapes

Publisher Copyright: Copyright © 2022 the Author(s). Published by PNAS.Spatial dynamics have long been recognized as an important driver of biodiversity. However, our understanding of species’ coexistence under realistic landscape configurations has been limited by lack of adequate analytical tools. To fill this gap, we develop a spatially explicit metacommunity model of multiple competing species and derive analytical criteria for their coexistence in fragmented heterogeneous landscapes. Specifically, we propose measures of niche and fitness differences for metacommunities, which clarify how spatial dynamics and habitat configuration interact with local competition to determine coexistence of species. We parameterize our model with a Bayesian approach using a 36-y time-series dataset of three Daphnia species in a rockpool metacommunity covering >500 patches. Our results illustrate the emergence of interspecific variation in extinction and recolonization processes, including their dependencies on habitat size and environmental temperature. We find that such interspecific variation contributes to the coexistence of Daphnia species by reducing fitness differences and increasing niche differences. Additionally, our parameterized model allows separating the effects of habitat destruction and temperature change on species extinction. By integrating coexistence theory and metacommunity theory, our study provides platforms to increase our understanding of species’ coexistence in fragmented heterogeneous landscapes and the response of biodiversity to environmental changes.Peer reviewe

Ultra-fast quenching of binary colloidal suspensions in an external magnetic field

An ultra-fast quench is applied to binary mixtures of superparamagnetic colloidal particles confined at a two-dimensional water-air interface by a sudden increase of an external magnetic field. This quench realizes a virtually instantaneous cooling which is impossible in molecular systems. Using real-space experiments, the relaxation behavior after the quench is explored. Local crystallites with triangular and square symmetry are formed on different time scales and the correlation peak amplitude of the small particles evolves nonmonotonically in time in agreement with Brownian dynamics computer simulations.Comment: 4 pages, 4 figure

Business and human rights in the data economy : a mapping and research study

This study identifies novel challenges for human rights protection emerging from data-driven business conduct. It offers an overview of the current policy debate and emerging best practices for business to mitigate the impacts of data-driven business on human rights. A strong emphasis lies on the dynamic interlinkages between human rights issues in a data ecosystem, in particular addressing systemic bias in data models and establishing genuine stakeholder engagement. This mapping study serves as a conversation starter and aims at raising awareness regarding the data economy’s impact on human rights. On the one hand, the study could be used in a public policy context, e.g. to convince ministerial staff that “digital” human rights issues should also be part of National Action Plans on Business and Human Rights, or why the EU Digital Strategy can benefit from a rights-based approach. On the other hand, companies can use the study to engage in a dialogue with senior management on why a rights-based approach is relevant and should be mainstreamed across business, e.g. for a product counsel or a public affairs specialist. The study thus provides exploratory guidance for human rights impact and risk assessments and human rights due diligence. It addresses some core phenomena and technologies of the data economy and situates them within the social, cultural, and political contexts that explain their effects on human rights. The study presents the following key recommendations: − Business needs a life cycle approach to capture emerging and systemic human rights problems. This would allow it to identify, address and eradicate systematic distortions that have negative impacts on human rights in datafied environments. “Data universalism” needs to be replaced with context-specific, robust human rights due diligence processes that keep companies’ local embeddedness in mind. − Civil society may need to develop new methods to hold companies accountable for “digital” human rights violations. This point is closely connected to the public policy debate on the state duty to protect human rights, including digital rights. − Policymakers should take digital rights into account in policy proposals on human rights due diligence for business and revisit whether existing protection can still cover emerging digital issues. Legislators should strengthen digital rights in the coming years and strategically connect them to other legislative debates on human rights due diligence. This mapping can serve as a basis for a deeper examination of what all actors-states, companies, civil society organizations, national human rights institutions-can do to guarantee that digitalization and technological progress go hand in hand with the enjoyment and protection of human rights