University of Konstanz

About: University of Konstanz is a education organization based out in Konstanz, Baden-Württemberg, Germany. It is known for research contribution in the topics: Population & Visualization. The organization has 12115 authors who have published 27401 publications receiving 951162 citations. The organization is also known as: University of Constance & Universität Konstanz.

Adaptive phenotypic plasticity in the Midas cichlid fish pharyngeal jaw and its relevance in adaptive radiation

Abstract: Phenotypic evolution and its role in the diversification of organisms is a central topic in evolutionary biology. A neglected factor during the modern evolutionary synthesis, adaptive phenotypic plasticity, more recently attracted the attention of many evolutionary biologists and is now recognized as an important ingredient in both population persistence and diversification. The traits and directions in which an ancestral source population displays phenotypic plasticity might partly determine the trajectories in morphospace, which are accessible for an adaptive radiation, starting from the colonization of a novel environment. In the case of repeated colonizations of similar environments from the same source population this "flexible stem" hypothesis predicts similar phenotypes to arise in repeated subsequent radiations. The Midas Cichlid (Amphilophus spp.) in Nicaragua has radiated in parallel in several crater-lakes seeded by populations originating from the Nicaraguan Great Lakes. Here, we tested phenotypic plasticity in the pharyngeal jaw of Midas Cichlids. The pharyngeal jaw apparatus of cichlids, a second set of jaws functionally decoupled from the oral ones, is known to mediate ecological specialization and often differs strongly between sister-species. We performed a common garden experiment raising three groups of Midas cichlids on food differing in hardness and calcium content. Analyzing the lower pharyngeal jaw-bones we find significant differences between diet groups qualitatively resembling the differences found between specialized species. Observed differences in pharyngeal jaw expression between groups were attributable to the diet's mechanical resistance, whereas surplus calcium in the diet was not found to be of importance. The pharyngeal jaw apparatus of Midas Cichlids can be expressed plastically if stimulated mechanically during feeding. Since this trait is commonly differentiated - among other traits - between Midas Cichlid species, its plasticity might be an important factor in Midas Cichlid speciation. The prevalence of pharyngeal jaw differentiation across the Cichlidae further suggests that adaptive phenotypic plasticity in this trait could play an important role in cichlid speciation in general. We discuss several possibilities how the adaptive radiation of Midas Cichlids might have been influenced in this respect.

Fostering Team Innovation: Why Is It Important to Combine Opposing Action Strategies?

Abstract: We develop a framework that provides a general theoretical rationale for the claim made by several authors that combining opposing action strategies fosters team innovation. We distinguish between open and closed strategies and posit that these are opposing but complementary in that each fosters one of two processes necessary for team innovation: open action strategies (e.g., delegative leadership) promote knowledge generation, and closed action strategies (e.g., directive leadership) enhance knowledge integration. We argue that each pole of a pair of opposing action strategies both energizes and detracts from elements of innovation. Thus, it could be expected that combining opposing action strategies leads to an impasse, as the negative effects of each strategy might offset the positive effects of the opposite strategy. There is currently no viable explanation in the literature for why this mutual neutralization may not occur. We aim to fill this gap by explicating why and how opposing action strategies, when implemented simultaneously, do not countervail each other's positive effects, but rather yield positive synergies that fuel team innovation.

Novel Relationships Among Ten Fish Model Species Revealed Based on a Phylogenomic Analysis Using ESTs

Abstract: The power of comparative phylogenomic analyses also depends on the amount of data that are included in such studies. We used expressed sequence tags (ESTs) from fish model species as a proof of principle approach in order to test the reliability of using ESTs for phylogenetic inference. As expected, the robustness increases with the amount of sequences. Although some progress has been made in the elucidation of the phylogeny of teleosts, relationships among the main lineages of the derived fish (Euteleostei) remain poorly defined and are still debated. We performed a phylogenomic analysis of a set of 42 of orthologous genes from 10 available fish model systems from seven different orders (Salmoniformes, Siluriformes, Cypriniformes, Tetraodontiformes, Cyprinodontiformes, Beloniformes, and Perciformes) of euteleostean fish to estimate divergence times and evolutionary relationships among those lineages. All 10 fish species serve as models for developmental, aquaculture, genomic, and comparative genetic studies. The phylogenetic signal and the strength of the contribution of each of the 42 orthologous genes were estimated with randomly chosen data subsets. Our study revealed a molecular phylogeny of higher-level relationships of derived teleosts, which indicates that the use of multiple genes produces robust phylogenies, a finding that is expected to apply to other phylogenetic issues among distantly related taxa. Our phylogenomic analyses confirm that the euteleostean superorders Ostariophysi and Acanthopterygii are monophyletic and the Protacanthopterygii and Ostariophysi are sister clades. In addition, and contrary to the traditional phylogenetic hypothesis, our analyses determine that killifish (Cyprinodontiformes), medaka (Beloniformes), and cichlids (Perciformes) appear to be more closely related to each other than either of them is to pufferfish (Tetraodontiformes). All 10 lineages split before or during the fragmentation of the supercontinent Pangea in the Jurassic.

In Search of Co‐variance, Causal Mechanisms or Congruence? Towards a Plural Understanding of Case Studies

Abstract: Methodological reflections about case study research have increased within recent years. According to our account, there are three distinct approaches to case studies: co-variational, causal process tracing, and congruence analysis. The main goals of this article are to lay out the distinct ways in which causal inferences are drawn for the cases under study and to scrutinize the different understandings and directions of generalization within these three approaches. By doing so we highlight two aspects: First, causal process tracing and congruence analysis should be seen as two distinct alternatives to the dominant co-variational template. Second, the main characteristics of case studies, their thickness, provides only an unavoidable dilemma if we aim to generalize the findings towards a wider population of similar cases as in the co-variational template. If we would like to get deeper insights â-“ as the causal process tracing approach does â-“ or if we would like to use the empirical evidence for a broader theoretical discourse â-“ as the congruence analysis does â-“ case studies do not face a trade-off.