Phylogenomics Reveals Ancient Gene Tree Discordance in the Amphibian Tree of Life

Molecular phylogenies have yielded strong support for many parts of the amphibian Tree of Life, but poor support for the resolution of deeper nodes, including relationships among families and orders. To clarify these relationships, we provide a phylogenomic perspective on amphibian relationships by developing a taxon-specific Anchored Hybrid Enrichment protocol targeting hundreds of conserved exons which are effective across the class. After obtaining data from 220 loci for 286 species (representing 94% of the families and 44% of the genera), we estimate a phylogeny for extant amphibians and identify gene tree–species tree conflict across the deepest branches of the amphibian phylogeny. We perform locus-by-locus genealogical interrogation of alternative topological hypotheses for amphibian monophyly, focusing on interordinal relationships. We find that phylogenetic signal deep in the amphibian phylogeny varies greatly across loci in a manner that is consistent with incomplete lineage sorting in the ancestral lineage of extant amphibians. Our results overwhelmingly support amphibian monophyly and a sister relationship between frogs and salamanders, consistent with the Batrachia hypothesis. Species tree analyses converge on a small set of topological hypotheses for the relationships among extant amphibian families. These results clarify several contentious portions of the amphibian Tree of Life, which in conjunction with a set of vetted fossil calibrations, support a surprisingly younger timescale for crown and ordinal amphibian diversification than previously reported. More broadly, our study provides insight into the sources, magnitudes, and heterogeneity of support across loci in phylogenomic data sets

A global phylogeny of butterflies reveals their evolutionary history, ancestral hosts and biogeographic origins

Butterflies are a diverse and charismatic insect group that are thought to have evolved with plants and dispersed throughout the world in response to key geological events. However, these hypotheses have not been extensively tested because a comprehensive phylogenetic framework and datasets for butterfly larval hosts and global distributions are lacking. We sequenced 391 genes from nearly 2,300 butterfly species, sampled from 90 countries and 28 specimen collections, to reconstruct a new phylogenomic tree of butterflies representing 92% of all genera. Our phylogeny has strong support for nearly all nodes and demonstrates that at least 36 butterfly tribes require reclassification. Divergence time analyses imply an origin similar to 100 million years ago for butterflies and indicate that all but one family were present before the K/Pg extinction event. We aggregated larval host datasets and global distribution records and found that butterflies are likely to have first fed on Fabaceae and originated in what is now the Americas. Soon after the Cretaceous Thermal Maximum, butterflies crossed Beringia and diversified in the Palaeotropics. Our results also reveal that most butterfly species are specialists that feed on only one larval host plant family. However, generalist butterflies that consume two or more plant families usually feed on closely related plants

Experimentelle und numerische Untersuchung eines Radialverdichters mit Pipe Diffusor und Umlenkbeschaufelung für eine Triebwerksanwendung

The subject of this study is the analysis of three different diffuser configurations in a centrifugal compressor stage for a jet engine application. The nominal geometric configuration of the diffusing system contained a unique type of passage diffuser, a pipe diffuser, and a deswirler with axial prismatic vanes. In the second configuration, the pipe diffuser was radially truncated by approximately half its diametral extent. In a third step, the downstream deswirler was redesigned. To adapt the deswirler to the new diffuser, a tandem design with two stator rows was introduced. For the experimental investigations, a state-of-the-art centrifugal compressor test rig was used. It is located at the Institute of Jet Propulsion and Turbomachinery and was built up in cooperation with General Electric Aviation. In this study, the effects of the three configurations on the stage performance are investigated. These differences are explained by local flow phenomena. For this purpose, detailed measurements with multi-hole probes, unsteady pressure transducers and particle image velocimetry (PIV) have been performed. Finally, the impact on the whole system of a jet engine is analyzed. It was found that the diffuser truncation increases the centrifugal stage performance by 0.3% and enlarges the surge margin by 10%. PIV measurements show a significantly decreased flow separation in the diffuser passage. The changed flow direction due to the diffuser truncation implies, however, an increased incidence flow angle to the deswirler causing extensive losses. This higher incidence angle was the motivation for the deswirler redesign. The first row of this tandem deswirler was introduced into the channel bend for the first time in a test rig. It is shown that the tandem deswirler has lower total pressure losses and thus an improved static pressure rise compared to the nominal deswirler. These lower deswirler losses result in an additional increase of the centrifugal compressor stage efficiency of 1%. Moreover, the relative position of the two tandem rows is investigated. An optimal clocking position regarding stage efficiency and static pressure rise was found. This study gives fundamental insight into the aerodynamic mechanisms of the influence of three geometric configurations in a centrifugal compressor stage, especially in the pipe diffuser and the deswirler. Thus, this study is highly beneficial in furthering knowledge of the fundamental principles of the flow phenomena in the diffusing system of a centrifugal compressor

Experimentelle und numerische Untersuchung eines Radialverdichters mit Pipe Diffusor und Umlenkbeschaufelung für eine Triebwerksanwendung

The subject of this study is the analysis of three different diffuser configurations in a centrifugal compressor stage for a jet engine application. The nominal geometric configuration of the diffusing system contained a unique type of passage diffuser, a pipe diffuser, and a deswirler with axial prismatic vanes. In the second configuration, the pipe diffuser was radially truncated by approximately half its diametral extent. In a third step, the downstream deswirler was redesigned. To adapt the deswirler to the new diffuser, a tandem design with two stator rows was introduced. For the experimental investigations, a state-of-the-art centrifugal compressor test rig was used. It is located at the Institute of Jet Propulsion and Turbomachinery and was built up in cooperation with General Electric Aviation. In this study, the effects of the three configurations on the stage performance are investigated. These differences are explained by local flow phenomena. For this purpose, detailed measurements with multi-hole probes, unsteady pressure transducers and particle image velocimetry (PIV) have been performed. Finally, the impact on the whole system of a jet engine is analyzed. It was found that the diffuser truncation increases the centrifugal stage performance by 0.3% and enlarges the surge margin by 10%. PIV measurements show a significantly decreased flow separation in the diffuser passage. The changed flow direction due to the diffuser truncation implies, however, an increased incidence flow angle to the deswirler causing extensive losses. This higher incidence angle was the motivation for the deswirler redesign. The first row of this tandem deswirler was introduced into the channel bend for the first time in a test rig. It is shown that the tandem deswirler has lower total pressure losses and thus an improved static pressure rise compared to the nominal deswirler. These lower deswirler losses result in an additional increase of the centrifugal compressor stage efficiency of 1%. Moreover, the relative position of the two tandem rows is investigated. An optimal clocking position regarding stage efficiency and static pressure rise was found. This study gives fundamental insight into the aerodynamic mechanisms of the influence of three geometric configurations in a centrifugal compressor stage, especially in the pipe diffuser and the deswirler. Thus, this study is highly beneficial in furthering knowledge of the fundamental principles of the flow phenomena in the diffusing system of a centrifugal compressor

DO PROFIT MAXIMISERS TAKE COLD SHOWERS? ANOTHER LOOK AT PROTECTION AND TECHNICAL EFFICIENCY

In this paper we consider whether a 'cold shower' is possible if the firm we are analysing is a conventional neoclassical profit-maximising firm facing competitively determined prices. In the context of this analysis, the term 'cold shower' refers to a situation where the removal of a protective subsidy induces investment in a cost-reducing technology. First we show that if the investment lowers marginal cost everywhere, then our firm will never respond to the removal of the subsidy by making the investment. We then use this result to carefully construct examples where the investment does not lower marginal cost everywhere. These examples are devised to illustrate a cold shower scenario where, with no protection in place, the firm makes the investment, that would have been rejected, if the protection had have been in place. Copyright Blackwell Publishing Ltd/ University of Adelaide and Flinders University 2005..