9-Genes Reinforce the Phylogeny of Holometabola and Yield Alternate Views on the Phylogenetic Placement of Strepsiptera

Background: The extraordinary morphology, reproductive and developmental biology, and behavioral ecology of twisted wing parasites (order Strepsiptera) have puzzled biologists for centuries. Even today, the phylogenetic position of these enigmatic “insects from outer space” [1] remains uncertain and contentious. Recent authors have argued for the placement of Strepsiptera within or as a close relative of beetles (order Coleoptera), as sister group of flies (order Diptera), or even outside of Holometabola.Methodology/Principal Findings Here, we combine data from several recent studies with new data (for a total of 9 nuclear genes and ∼13 kb of aligned data for 34 taxa), to help clarify the phylogenetic placement of Strepsiptera. Our results unequivocally support the monophyly of Neuropteroidea ( = Neuropterida + Coleoptera) + Strepsiptera, but recover Strepsiptera either derived from within polyphagan beetles (order Coleoptera), or in a position sister to Neuropterida. All other supra-ordinal- and ordinal-level relationships recovered with strong nodal support were consistent with most other recent studies. Conclusions/Significance: These results, coupled with the recent proposed placement of Strepsiptera sister to Coleoptera, suggest that while the phylogenetic neighborhood of Strepsiptera has been identified, unequivocal placement to a specific branch within Neuropteroidea will require additional study.Organismic and Evolutionary Biolog

Strain profiles in overcritical (001) ZnSe GaAs heteroepitaxial layers

ZnSe layers of various thicknesses have been grown epitaxially on (001)-oriented GaAs substrates by metalorganic vapor phase epitaxy and studied by x-ray diffraction and Raman scattering. Consistent results have been found for the in-plane strains of both, ZnSe layers below and above the critical value of plastic relaxation. The experimental results are well described by strain profiles which are evaluated by an energy model and a geometrical model including the effects of strain and work hardening. The thickness-dependent full widths at half maximum of the x-ray reflections and the Raman resonances are accounted for by assuming uncorrelated misfit dislocations in the layers. (C) 1999 American Institute of Physics. [S0021-8979(99)00813-0]