SUMMARY
Radially anisotropic S-wave structures under the permanent seismic stations in Australia are reconstructed using multimode surface waves (SWs) and receiver functions (RFs) in a framework of ...the Bayesian inference. We have developed a fully nonlinear method of joint inversions incorporating P-RFs and multimode Rayleigh and Love waves, based on the transdimensional Hierarchical Bayesian formulation. The method allows us to estimate a probabilistic Earth model taking account of the complexity and uncertainty of Earth structure, by treating the model parameters and data errors as unknowns. The Parallel Tempering algorithm is employed for the effective parameter search based on the reversible-jump Markov Chain Monte Carlo method. The use of higher modes enables us to enhance the sensitivity to the depth below the continental asthenosphere. Synthetic experiments indicate the importance of higher mode SWs for the better recovery of radial anisotropy in the whole depth range of the upper mantle. The method is applied to five Global Seismographic Network stations in Australia. While the S-wave models in eastern Australia show shallow lithosphere–asthenosphere boundary (LAB) above 100 km depth, those in central and Western Australia exhibit both mid-lithosphere discontinuities (MLDs) and LAB. Also, seismic velocity jumps equivalent to the Lehmann discontinuity (L-D) are found in all seismic stations. The L-D under the Australian continents is found at around 200–300 km depth, depending on locations. Radial anisotropy in the depth range between LAB and L-D tends to show faster SH anomalies, which may indicate the effects of horizontal shear underneath the fast-moving Australian plate.
Phylogenetic relationships among the winged orders of Polyneoptera Blattodea, Dermaptera, Embiodea (=Embioptera), Isoptera, Mantodea, Orthoptera, Phasmatodea, Plecoptera and Zoraptera were estimated ...based on morphological data selected from the hindwing base structure. Cladistic analyses were carried out using hindwing base data alone and in combination with other, more general, morphological data. Both datasets resulted in similar trees and recovered the monophyly of Polyneoptera. Deepest phylogenetic relationships among the polyneopteran orders were not confidently estimated, but the monophyly of Mystroptera (= Embiodea + Zoraptera), Orthopterida (= Orthoptera + Phasmatodea) and Dictyoptera (= Blattodea + Mantodea + Isoptera) was supported consistently. In contrast, placements of Plecoptera and Dermaptera were unstable, although independent analysis of the wing base data supported their sister‐group relationship with two nonhomoplasious synapomorphies (unique conditions in the ventral basisubcostale, and in the articulation between the antemedian notal wing process and first axillary sclerite). Results from the combined wing base plus general morphology data were consistent, even if the wingless orders Grylloblattodea and Mantophasmatodea were included in the analysis. Generally, trees obtained from the present analyses were concordant with the results from other morphological and molecular analyses, but Isoptera were placed inappropriately to be the sister of Blattodea + Mantodea by the inclusion of the wing base data, probably as a result of morphological regressions of the order.
In contrast to active continental rifting, which is caused by the thermal erosion of active upwelling plumes, passive continental rifting is attributed to the extensional stress acting on the ...continental lithosphere due to either the basal drag force exerted by the passive mantle flow under the lithosphere or the boundary forces at the continental margins. Although the extension of continental lithosphere by passive continental rifting may cause the breakup of continental margins, such as the separation of Zealandia from Gondwanaland at ca. 100 Ma and the Japanese islands from Eurasia at ca. 25 Ma, the dynamics have not been fully understood from geophysical and geological perspectives. Here, a series of numerical experiments of visco-elasto-plastic thermo-chemical convection with a free surface is performed using 2-D Cartesian models to investigate the localization of strain in the extending continental lithosphere, with an initial depth of 200 km, and the behavior of continental rifting and breakup. Our results demonstrate that when extension rates at the continental margin were set between 1 and 4 cm yr−1, the time taken for seafloor subsidence and subsequent continental breakup under extensional stress is less than a few million years. During continental rifting, high-shear zones (i.e., high-strain-rate zones) develop under the base of the deforming continental lithosphere, with a strain rate of the order of 10−13 s−1, which is approximately two orders larger than the typical value of the mantle interior. Due to accumulating strain along the base of the deforming lithosphere, excess strain is not concentrated on the shallowest part of the underlying mantle; hence, the spreading ridge that breaks the thick continental lithosphere emerges as a locally weak plate boundary on the Earth's surface. This characteristic is more remarkable as the activation volume of the sublithospheric mantle rock and the resultant viscosity are low under hydrous conditions.
•A series of numerical experiments of visco-elasto-plastic thermo-chemical convection in 2-D Cartesian geometry is performed.•Dynamics and mechanism of the passive continental rifting and the breakup of thick continental lithosphere are examined.•Required time for seafloor subsidence and subsequent continental breakup under extensional stress is less than ~20 Myr.•During continental rifting, high-strain-rate zones develop under the base of the deforming continental lithosphere.•Thus, the spreading ridge that breaks the continental lithosphere emerges as a locally weak plate boundary on the surface.
Two end-member scenarios have been proposed for the tectonic situation along the eastern margins of Gondwanaland before Zealandia was formed ca. 100 million years ago (Ma), namely: (1) A subduction ...zone located far from the eastern margin of Zealandia, wherein Zealandia may have separated from Gondwanaland by plume push of an active hotspot plume.; (2) A subduction zone located along the eastern margin of Gondwanaland, wherein Zealandia possibly separated from Gondwanaland via trench/subduction retreat. Assuming that the thermal structure of the deep mantle and source of hotspot plumes remained relatively stationary over the last hundred million years, major hotspot plumes with a large buoyancy flux did not exist under Zealandia; the eastern margins of Gondwanaland were far from two large low-shear-velocity provinces under the Africa–Atlantic and South Pacific regions. Herein, through numerical studies of three-dimensional global mantle convection, we examined the mantle convection and surface tectonic patterns at ~100 Ma. The present model considered the real configuration of Gondwanaland at the model surface to observe long-term variations of mantle convection and the resulting surface tectonic conditions. The results demonstrate that the extensive subduction zones developed preferentially along the eastern margin of Gondwanaland when the temperature anomaly of the lower mantle was primarily dominated by high-temperature regions under present-day Africa–Atlantic and South Pacific regions. The results of this study support one of the proposed hypotheses, where the breakup at the eastern margins of Gondwanaland at ~100 Ma occurred via trench/subduction retreat.
•Mantle convection and surface tectonic patterns along the eastern margin of Gondwanaland at ~100 Ma are examined.•Extensive subduction zones developed preferentially along the eastern margin of Gondwanaland.•The breakup at the eastern margins of Gondwanaland at ~100 Ma may be occurred via trench retreat.
Abstract
The insect order Psocodea is a diverse lineage comprising both parasitic (Phthiraptera) and nonparasitic members (Psocoptera). The extreme age and ecological diversity of the group may be ...associated with major genomic changes, such as base compositional biases expected to affect phylogenetic inference. Divergent morphology between parasitic and nonparasitic members has also obscured the origins of parasitism within the order. We conducted a phylogenomic analysis on the order Psocodea utilizing both transcriptome and genome sequencing to obtain a data set of 2370 orthologous genes. All phylogenomic analyses, including both concatenated and coalescent methods suggest a single origin of parasitism within the order Psocodea, resolving conflicting results from previous studies. This phylogeny allows us to propose a stable ordinal level classification scheme that retains significant taxonomic names present in historical scientific literature and reflects the evolution of the group as a whole. A dating analysis, with internal nodes calibrated by fossil evidence, suggests an origin of parasitism that predates the K-Pg boundary. Nucleotide compositional biases are detected in third and first codon positions and result in the anomalous placement of the Amphientometae as sister to Psocomorpha when all nucleotide sites are analyzed. Likelihood-mapping and quartet sampling methods demonstrate that base compositional biases can also have an effect on quartet-based methods.Illumina; Phthiraptera; Psocoptera; quartet sampling; recoding methods.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Females of the silver-washed fritillary butterfly,
Argynnis paphia
(Linnaeus), and its relatives are known to have a unique genital projection called the cornucopia. Previous observations showed that ...the cornucopia partly penetrates the male genitalia during copulation, but its detailed structures and functions are unknown to date. Our observations using light microscopy, confocal laser scanning microscopy, scanning electron microscopy, and microcomputed tomography suggested that penetration by the female cornucopia occurs passively, and it is hooked and pulled by the male towards the male genitalia using sharp teeth on the uncus. This hooking and pulling causes wounds on the dorsal region of the cornucopia. Artificial amputation of a cornucopia confirmed that it is indispensable for spermatophore transfer from males and functions to break off the male phallic spines (cornuti). The broken spines may be used by females to help the digestion of spermatophores in the female’s corpus bursae. Females with larger body sizes had more broken spines in the corpus bursae, indicating that secure holding of a large female during copulation is challenging for males.
Abstract
The forewing base structure of the orthopteran suborder Ensifera, a group of insects well known for their sound-producing behavior, was examined by using light microscopy, confocal laser ...scanning microscopy, and µCT. We detected significant novel characters, such as functional changes in the tpm9 muscle from the flexor to the extensor of the forewing that are likely associated with the acquisition of sound-producing behavior using forewings. Phylogenetic analysis based on the characters selected from the forewing base structure showed that the character system contains a strong phylogenetic signal supporting the monophyly of Ensifera, Tettigonioidea and Grylloidea as well as the sister-group relationship between Grylloidea and Gryllotalpoidea, but no apomorphies to resolve the deep phylogeny among superfamilies could be determined from this character system.
The diversity of feeding apparatuses in insects far exceeds that observed in any other animal group. Consequently, tracking mouthpart innovation in insects is one of the keys toward understanding ...their diversification. In hemipteroid insects (clade Paraneoptera or Acercaria: lice, thrips, aphids, cicadas, bugs, etc.), the transition from chewing to piercing-and-sucking mouthparts is widely regarded as the turning point that enabled hyperdiversification of the Hemiptera, the fifth largest insect order. However, the transitional process from chewing to piercing-and-sucking in the Paraneoptera was hitherto completely unknown. In this paper, we report a well preserved mid Cretaceous amber fossil of the paraneopteran insect family Archipsyllidae and describe it as Mydiognathus eviohlhoffae gen. et sp. n. This species has elongate mandibles and styliform laciniae similar to Hemiptera but retains functional chewing mouthparts. A number of morphological characters place the Archipsyllidae as the sister group of the thrips plus hemipterans, which strongly suggests that the mouthparts of M. eviohlhoffae represent a transitional condition from primitive chewing to derived piercing-and-sucking mouthparts. The clade composed of Archipsyllidae, thrips, and hemipterans is here named Pancondylognatha, a new supra-ordinal taxon. Based on newly obtained information, we also assess the monophyly of the Paraneoptera, which was called into question by recent phylogenomic analyses. A phylogenetic analysis that includes Mydiognathus strongly supports the monophyly of the Paraneoptera.
Cormopsocidae n. fam. of the psocid suborder Trogiomorpha was proposed for a fossil species from mid‐Cretaceous Burmese amber, Cormopsocus groehni n. gen. & n. sp. This family was estimated to be the ...sister group of all other trogiomorphan taxa, but the possibility of much deeper divergence (i.e. placement as a sister group of all Psocodea) could not be excluded. Cormopsocus groehni retains many plesiomorphic features, which will contribute greatly to elucidating the ancestral state of Psocodea.
Cormopsocus groehni n. gen. & n. sp., representing a new family of the psocid suborder Trogiomorpha was described from mid‐Cretaceous Burmese amber.
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