Discrete Character Research Articles

Functional and Character Disparity Are Decoupled in Turtle Mandibles

ABSTRACTTurtles have high shape variation of their mandibles, likely reflecting adaptations to a broad variety of food items and ingestion strategies. Here, we compare functional disparity measured by biomechanical proxies and character disparity measured by discrete morphological characters. Functional and character disparities vary between clades and ecological groups and are thus decoupled. Comparisons with cranial disparity also indicate decoupled patterns within the turtle skull. Exploration of mandibular patterns reveals that several biomechanical configurations or character state combinations can lead to the same feeding type (i.e., convergence) or that high functional disparity can be achieved at a low exhaustion of character state combinations (e.g., cryptodires). Dietary specialists show larger functional disparity than generalists, but the phylogenetically widespread generalist ecology leads to high character disparity signals in the ecotype. Whereas character disparity generally shows high phylogenetic signal, functional disparity patterns correspond to dietary specializations, which may occur convergently across different groups. Despite this, individual functional measurements have overlapping ranges across ecogroups and do not always conform to biomechanical expectations. Jaw opening and closing biomechanical advantages model trade‐offs between force transmission and opening/closing speeds, and turtles show a variety of combinations of values that we try to synthesize into several “jaw types”. Closing mechanical advantage shows that turtles retain high levels of force transmission at the anterior jaw end compared with other groups (e.g., pseudosuchians). This can possibly be explained as an evolutionary adaptation to retain high bite forces at small head sizes.

A new Boulenophrys species (Anura, Megophryidae) from the coastal hills of eastern Fujian Province, China.

A new species of the genus Boulenophrys is described from the coastal hills of eastern Fujian Province, China. The new taxon can be distinguished from all recognized congeners by a combination of discrete morphological character state differences and genetic divergences in the combined mitochondrial 16S + CO1 genes. We also provide a map showing the distribution pattern of Boulenophrys species in Fujian and a provincial-specific key, which will aid their conservation by helping the local authorities accurately identify species during field identifications and data collection efforts.

Do morphometric data improve phylogenetic reconstruction? A systematic review and assessment

BackgroundIsolating phylogenetic signal from morphological data is crucial for accurately merging fossils into the tree of life and for calibrating molecular dating. However, subjective character definition is a major limitation which can introduce biases that mislead phylogenetic inferences and divergence time estimation. The use of quantitative data, e.g., geometric morphometric (GMM; shape) data can allow for more objective integration of morphological data into phylogenetic inference. This systematic review describes the current state of the field in using continuous morphometric data (e.g., GMM data) for phylogenetic reconstruction and assesses the efficacy of these data compared to discrete characters using the PRISMA-EcoEvo v1.0. reporting guideline, and offers some pathways for approaching this task with GMM data. A comprehensive search string yielded 11,123 phylogenetic studies published in English up to Oct 2023 in the Web of Science database. Title and abstract screening removed 10,975 articles, and full-text screening was performed for 132 articles. Of these, a total of twelve articles met final inclusion criteria and were used for downstream analyses.ResultsPhylogenetic performance was compared between approaches that employed continuous morphometric and discrete morphological data. Overall, the reconstructed phylogenies did not show increased resolution or accuracy (i.e., benchmarked against molecular phylogenies) as continuous data alone or combined with discrete morphological datasets.ConclusionsAn exhaustive search of the literature for existing empirical continuous data resulted in a total of twelve articles for final inclusion following title/abstract, and full-text screening. Our study was performed under a rigorous framework for systematic reviews, which showed that the lack of available comparisons between discrete and continuous data hinders our understanding of the performance of continuous data. Our study demonstrates the problem surrounding the efficacy of continuous data as remaining relatively intractable despite an exhaustive search, due in part to the difficulty in obtaining relevant comparisons from the literature. Thus, we implore researchers to address this issue with studies that collect discrete and continuous data sets with directly comparable properties (i.e., describing shape, or size).

Parallel evolution of unusual ‘harpiform’ morphologies in distantly related trilobites

Abstract Harpetid and trinucleid trilobites share a similar and unusual morphology, the most striking feature of which is a wide, flattened cephalic brim with many pits or holes. This similarity was once interpreted as a sign that these two groups of trilobites were closely related, but in recent years it has instead been assumed that the ‘harpiform’ brim arose in both groups independently. However, relatedness and similarity can be difficult to disentangle in fossil taxa without close living relatives, and this assumption about the harpiform brim has never been explicitly tested. Our study re-evaluates the relationship between Harpetida and Trinucleioidea in order to test a longstanding assumption about trilobite relationships and as a case study in evaluating different kinds of morphological similarity in extinct groups. We inferred a new phylogenetic tree using parsimony methods and discrete morphological character data from a broad sampling of harpetids, trinucleids, and their relatives. Despite their gross morphological similarities, we found that harpetids and trinucleids were readily distinguished in our analyses, a result consistent with a hypothesis of multiple origins for the harpiform brim. By mapping brim-related characters across our new phylogeny, we identified a sequence of morphological innovations that arose in parallel in both groups and led ultimately in each case to the evolution of the harpiform brim. These results indicate that harpiform brims are a prime example of parallel evolution—the similar development of a morphological trait in distantly related taxa that nevertheless share a similar original morphology. In addition, our phylogeny supports the idea that trinucleids are specialized, harpiform asaphids, rather than an independent order of trilobites. We also provide new information on the relationships of the putative ‘basal-most’ members of Trinucleioidea, the Liostracinidae, and confirm recent assessments that this family is more distantly related to trinucleids.

The issue of continuous characters in the copulatory bulb of Neodiplothele spiders: a morpho-geometric approach

ABSTRACT The definition of species boundaries in mygalomorph spiders is historically based on morphological characters, which can be problematic due to the homogeneous morphology and continuous variation across species. The male copulatory bulb of Neodiplothele, as of many mygalomorphs, is phenotypically diverse and the differences are displayed mostly by subtle shape variations. The purpose of this research was to evaluate the traditional morphology-based delimitation of species informal groups and assess the significance of morphological characters in the systematics of the highly variable and widespread mygalomorph spiders of the barychelid genus Neodiplothele. We conducted a geometric morphometric analysis on the bulb of specimens of Neodiplothele using Fourier descriptors. The results show that the bulb is rather difficult to apply as a discrete character in a taxonomic context and show the proximity of a group of undescribed species of Neodiplothele to both groups proposed in a previous revision, indicating a continuous variation. As a taxonomic character, the use of the copulatory bulb shape as a discrete character may be uninformative in the case of species that present one or more intermediate states, when the incorrect treatment of the character can result in a misrepresentation of shape diversity and equivocate inference of evolutionary relationships.https://zoobank.org/urn:lsid:zoobank.org:author:471C6BE5-D24C-4805-B2DE-EB89B6D1D8FA https://zoobank.org/urn:lsid:zoobank.org:author:D4955FF5-FE7F-4E68-AB2F-4A89593F9850

Assessing the Adequacy of Morphological Models using Posterior Predictive Simulations.

Reconstructing the evolutionary history of different groups of organisms provides insight into how life originated and diversified on Earth. Phylogenetic trees are commonly used to estimate this evolutionary history. Within Bayesian phylogenetics a major step in estimating a tree is in choosing an appropriate model of character evolution. While the most common character data used is molecular sequence data, morphological data remains a vital source of information. The use of morphological characters allows for the incorporation fossil taxa, and despite advances in molecular sequencing, continues to play a significant role in neontology. Moreover, it is the main data source that allows us to unite extinct and extant taxa directly under the same generating process. We therefore require suitable models of morphological character evolution, the most common being the Mk Lewis model. While it is frequently used in both palaeobiology and neontology, it is not known whether the simple Mk substitution model, or any extensions to it, provide a sufficiently good description of the process of morphological evolution. In this study we investigate the impact of different morphological models on empirical tetrapod data sets. Specifically, we compare unpartitioned Mk models with those where characters are partitioned by the number of observed states, both with and without allowing for rate variation across sites and accounting for ascertainment bias. We show that the choice of substitution model has an impact on both topology and branch lengths, highlighting the importance of model choice. Through simulations, we validate the use of the model adequacy approach, posterior predictive simulations, for choosing an appropriate model. Additionally, we compare the performance of model adequacy with Bayesian model selection. We demonstrate how model selection approaches based on marginal likelihoods are not appropriate for choosing between models with partition schemes that vary in character state space (i.e., that vary in Q-matrix state size). Using posterior predictive simulations, we found that current variations of the Mk model are often performing adequately in capturing the evolutionary dynamics that generated our data. We do not find any preference for a particular model extension across multiple data sets, indicating that there is no 'one size fits all' when it comes to morphological data and that careful consideration should be given to choosing models of discrete character evolution. By using suitable models of character evolution, we can increase our confidence in our phylogenetic estimates, which should in turn allow us to gain more accurate insights into the evolutionary history of both extinct and extant taxa.

Testing for heterogeneous rates of discrete character evolution on phylogenies

Abstract Many hypotheses in the field of phylogenetic comparative biology involve specific changes in the rate or process of trait evolution. This is particularly true of approaches designed to connect macroevolutionary pattern to microevolutionary process. We present a method to test whether the rate of evolution of a discrete character has changed in one or more clades, lineages, or time periods. This method differs from other related approaches (such as the “covarion” model) in that the “regimes” in which the rate or process is postulated to have changed are specified a priori by the user, rather than inferred from the data. Similarly, it differs from methods designed to model a correlation between two binary traits in that the regimes mapped onto the tree are fixed. We apply our method to investigate the rate of dewlap colour and/or caudal vertebra number evolution in Caribbean and mainland clades of the diverse lizard genus Anolis. We find little evidence to support any difference in the evolutionary process between mainland and island evolution for either character. We also examine the statistical properties of the method more generally and show that it has acceptable type I error, parameter estimation, and power. Finally, we discuss some general issues of frequentist hypothesis testing and model adequacy, as well as the relationship of our method to existing models of heterogeneity in the rate of discrete character evolution on phylogenies.

A Late Devonian coelacanth reconfigures actinistian phylogeny, disparity, and evolutionary dynamics

The living coelacanth Latimeria (Sarcopterygii: Actinistia) is an iconic, so-called ‘living fossil’ within one of the most apparently morphologically conservative vertebrate groups. We describe a new, 3-D preserved coelacanth from the Late Devonian Gogo Formation in Western Australia. We assemble a comprehensive analysis of the group to assess the phylogeny, evolutionary rates, and morphological disparity of all coelacanths. We reveal a major shift in morphological disparity between Devonian and post-Devonian coelacanths. The newly described fossil fish fills a critical transitional stage in coelacanth disparity and evolution. Since the mid-Cretaceous, discrete character changes (representing major morphological innovations) have essentially ceased, while meristic and continuous characters have continued to evolve within coelacanths. Considering a range of putative environmental drivers, tectonic activity best explains variation in the rates of coelacanth evolution.

New Approaches in Finite Control Set Model Predictive Control for Grid-Connected Photovoltaic Inverters: State of the Art

Grid-connected PV inverters require sophisticated control procedures for smooth integration with the modern electrical grid. The ability of FCS-MPC to manage the discrete character of power electronic devices is highly acknowledged, since it enables direct manipulation of switching states without requiring modulation techniques. This review discusses the latest approaches in FCS-MPC methods for PV-based grid-connected inverter systems. It also classifies these methods according to control objectives, such as active and reactive power control, harmonic suppression, and voltage regulation. The application of FCS-MPC particularly emphasizing its benefits, including quick response times, resistance to changes in parameters, and the capacity to manage restrictions and nonlinearities in the system without the requirement for modulators, has been investigated in this review. Recent developments in robust and adaptive MPC strategies, which enhance system performance despite distorted grid settings and parametric uncertainties, are emphasized. This analysis classifies FCS-MPC techniques based on their control goals, optimal parameters and cost function, this paper also identifies drawbacks in these existing control methods and provide recommendation for future research in FCS-MPC for grid-connected PV-inverter systems.

Is the Current Systematic Subdivision of the Subfamily Neanurinae (Collembola, Neanuridae) Still Valid? Testing the Monophyly and Phylogenetic Relationships of Currently Established Tribes of the Neanurinae.

The subfamily Neanurinae is the largest in the family, with almost 800 described species. These springtails differ significantly from all other Collembola in their morphology, behaviour, and natural habitats. A systematic division of the Neanurinae into tribes was proposed more than 30 years ago by Cassagnau (1989), but it has not yet been tested using cladistic methods. Recent studies, both phylogenetic analyses of individual tribes or genera and descriptions of new taxa, suggest that the currently recognised tribes may not be monophyletic. The phylogenetic relationships among major lineages of the Neanurinae were explored by analysing a dataset of 101 discrete morphological characters. Bayesian and maximum parsimony analyses yielded similar tree topologies. The relationships among the Neanurinae were not resolved in any of the analyses, except for the support for the monophyly of the tribe Lobellini. The results indicate that the taxonomic characters used in the classification of Neanurinae are shared among members of the different tribes, which may have resulted in a classification with little phylogenetic basis. The article discusses the phylogenetic significance of morphological characters, including those recognised as key to the evolution and history of Neanurinae.

Investigating historical drivers of latitudinal gradients in polyploid plant biogeography: A multiclade perspective.

The proportion of polyploid plants in a community increases with latitude, and different hypotheses have been proposed about which factors drive this pattern. Here, we aimed to understand the historical causes of the latitudinal polyploidy gradient using a combination of ancestral state reconstruction methods. Specifically, we assessed whether (1) polyploidization enables movement to higher latitudes (i.e., polyploidization precedes occurrences in higher latitudes) or (2) higher latitudes facilitate polyploidization (i.e., occurrence in higher latitudes precedes polyploidization). We reconstructed the ploidy states and ancestral niches of 1032 angiosperm species at four paleoclimatic time slices ranging from 3.3 million years ago to the present, comprising taxa from four well-represented clades: Onagraceae, Primulaceae, Solanum (Solanaceae), and Pooideae (Poaceae). We used ancestral niche reconstruction models alongside a customized discrete character evolution model to allow reconstruction of states at specific time slices. Patterns of latitudinal movement were reconstructed and compared in relation to inferred ploidy shifts. No single hypothesis applied equally well across all analyzed clades. While significant differences in median latitudinal occurrence were detected in the largest clade, Poaceae, no significant differences were detected in latitudinal movement in any clade. Our preliminary study is the first to attempt to connect ploidy changes to continuous latitudinal movement, but we cannot favor one hypothesis over another. Given that patterns seem to be clade-specific, more clades must be analyzed in future studies for generalities to be drawn.

A new Paleogene fossil and a new dataset for waterfowl (Aves: Anseriformes) clarify phylogeny, ecological evolution, and avian evolution at the K-Pg Boundary.

Despite making up one of the most ecologically diverse groups of living birds, comprising soaring, diving and giant flightless taxa, the evolutionary relationships and ecological evolution of Anseriformes (waterfowl) remain unresolved. Although Anseriformes have a comparatively rich, global Cretaceous and Paleogene fossil record, morphological datasets for this group that include extinct taxa report conflicting relationships for all known extinct taxa. Correct placement of extinct taxa is necessary to understand whether ancestral anseriform feeding ecology was more terrestrial or one of a set of diverse aquatic ecologies and to better understand avian evolution around the K-T boundary. Here, we present a new morphological dataset for Anseriformes that includes more extant and extinct taxa than any previous anseriform-focused dataset and describe a new anseriform species from the early Eocene Green River Formation of North America. The new taxon has a mediolaterally narrow bill which is rarely found in previously described anseriform fossils. The matrix created to assess the placement of this taxon comprises 41 taxa and 719 discrete morphological characters describing skeletal morphology, musculature, syringeal morphology, ecology, and behavior. We additionally combine the morphological dataset with published sequences using Bayesian methods and perform ancestral state reconstruction for select morphological, ecological and behavioral characters. We recover the new Eocene taxon as the sister taxon to (Anseranatidae+Anatidae) across all analyses, and find that the new taxon represents a novel ecology within known Anseriformes and the Green River taxa. Results provide insight into avian evolution during and following the K-Pg mass extinction and indicate that Anseriformes were likely ancestrally aquatic herbivores with rhamphothecal lamellae..

Exploring Phylogenetic Relationships of the Mecocephala Group (Hemiptera: Pentatomidae) Using Continuous and Discrete Characters, with Notes on Taxonomy.

The Mecocephala group comprises about 50 species, restricted to the Neotropics and with the highest species richness in Neotropical South America. Several species use rice as host plants and their identification is facilitated by the presence of exaggerated head proportions and a unique male genitalic morphology. The taxonomy of the group has been extensively explored, but inferring its monophyly and especially its internal phylogenetic relationships has been challenging. Here, we inferred the phylogenetic relationships for the group assembling the most complete taxonomic sampling to date, analyzing discrete and continuous morphological characters through equal and implied weighted parsimony analyses. The monophyly of the group was recovered, but internal relationships varied slightly according to the dataset tested. Thus, we propose internal arrangements for the group and provide a formal description of the Mecocephala group, diagnoses for each genus, a dichotomous key to identify its genera, and illustrations of the morphological characters and type species.

Measuring homoplasy I: comprehensive measures of maximum and minimum cost under parsimony across discrete cost matrix character types.

Here, we propose, prove mathematically and discuss maximum and minimum measures of maximum parsimony evolution across 12 discrete phylogenetic character types, classified across 4467 morphological and molecular datasets. Covered character types are: constant, binary symmetric, multistate unordered (non-additive) symmetric, multistate linear ordered symmetric, multistate non-linear ordered symmetric, binary irreversible, multistate irreversible, binary Dollo, multistate Dollo, multistate custom symmetric, binary custom asymmetric and multistate custom asymmetric characters. We summarize published solutions and provide and prove a range of new formulae for the algebraic calculation of minimum (m), maximum (g) and maximum possible (gmax) character cost for applicable character types. Algorithms for exhaustive calculation of m, g and gmax applicable to all classified character types (within computational limits on the numbers of taxa and states) are also provided. The general algorithmic solution for minimum steps (m) is identical to a minimum spanning tree on the state graph or minimum weight spanning arborescence on the state digraph. Algorithmic solutions for character g and gmax are based on matrix mathematics equivalent to optimization on the star tree, respectively for given state frequencies and all possible state frequencies meeting specified numbers of taxa and states. We show that maximizing possible cost (gmax) with given transition costs can be equivalent to maximizing, across all possible state frequency combinations, the lowest implied cost of state transitions if any one state is ancestral on the star tree, via the solution of systems of linear equations. The methods we present, implemented in the Claddis R package, extend to a comprehensive range, the fundamental character types for which homoplasy may be measured under parsimony using m, g and gmax, including extra cost (h), consistency index (ci), retention index (ri) or indices based thereon.

Comparative geometric morphometrics of male genitalia in Xiphocentron subgenera (Trichoptera: Xiphocentronidae): new species, revision and phylogenetic systematics of the subgenus Sphagocentron

Geometric morphometric statistics have been employed to reduce the subjectivity of visual evaluations in taxonomy. Taxonomy in most insect groups relies strongly on male genitalia morphology which is often the structure with most data available, which is also true to caddisfly taxonomy. Here we revise the caddisfly subgenus Xiphocentron (Sphagocentron) adding five new species after 40 years: X. dactylumsp. nov., X. eurybrachiumsp. nov., X. tapantisp. nov., and X. tuxtlasp. nov.Additionally, we describe a new X. (Antillotrichia): X. drepanumsp. nov. from French Guiana and provide new species records of Xiphocentronidae from Bolivia, Costa Rica and Ecuador. We performed exploratory geometric morphometric analysis on the male genitalia’s preanal appendage to characterize the shape differences among the species, and to investigate its utility to classify species to subgenera. In order to infer species relationship and assess if shape congruences are due to phylogenetic signal or convergence data from 100 landmarks and semilandmarks, and 30 discrete characters were used to generate a phylogenetic hypothesis. The morphometry partially supports the subgenera delimitations, but the Antillotrichia subgenus greatly overlapped with other subgenera. The discriminant analysis overall classification correctness was 64%. Some suggested phenotypic groups were due to convergence. According to the preanal appendage morphometry, X. (Antillotrichia) fuscum is a Sphagocentron species. The phylogenetic analysis recovered Sphagocentron as monophyletic, but not Antillotrichia. Sphagocentron subgenus was placed within a clade of several Antillotrichia species, with X. (A.) fuscum as the sister of the other Sphagocentron species, although support values were low.

A systematic comparative description of extant turtle humeri, with comments on humerus disparity and evolution based on fossil comparisons.

The humerus is central for locomotion in turtles as quadrupedal animals. Osteological variation across testudine clades remains poorly documented. Here, we systematically describe the humerus anatomy for all major extant turtle clades based on 38 species representing the phylogenetic and ecological diversity of crown turtles. Three Late Triassic species of shelled stem turtles (Testudindata) are included to establish the plesiomorphic humerus morphology. Our work is based on 3D models, establishing a publicly available digital database. Previously defined terms for anatomical sides of the humerus (e.g., dorsal, ventral) are often not aligned with the respective body sides in turtles and other quadrupedal animals with sprawling gait. We propose alternative anatomical directional terms to simplify communication: radial and ulnar (the sides articulating with the radius/ulna), capitular (the side bearing the humeral head), and intertubercular (opposite to capitular surface). Turtle humeri show low morphological variation with exceptions concentrated in locomotory specialists. We propose 15 discrete characters to summarize osteological variation for future phylogenetic studies. Disparity analyses comparing non-shelled and shelled turtles indicate that the presence of the shell constrains humerus variation. Flippered aquatic turtles are released from this constraint and significantly increase overall disparity. Ontogenetic changes of turtle humeri are related to increased ossification and pronunciation of the proximal processes, the distal articulation areas, and the closure of the ectepicondylar groove to a foramen. Some turtle species retain juvenile features into adulthood and provide evidence for paedomorphic evolution. We review major changes of turtle humerus morphology throughout the evolution of its stem group.

Macroevolutionary Dynamics in Micro-organisms: Generalists Give Rise to Specialists Across Biomes in the Ubiquitous Bacterial Phylum Myxococcota.

Prokaryotes dominate the Tree of Life, but our understanding of the macroevolutionary processes generating this diversity is still limited. Habitat transitions are thought to be a key driver of prokaryote diversity. However, relatively little is known about how prokaryotes successfully transition and persist across environments, and how these processes might vary between biomes and lineages. Here, we investigate biome transitions and specialization in natural populations of a focal bacterial phylum, the Myxococcota, sampled across a range of replicated soils and freshwater and marine sediments in Cornwall (UK). By targeted deep sequencing of the protein-coding gene rpoB, we found >2,000 unique Myxococcota lineages, with the majority (77%) classified as biome specialists and with only <5% of lineages distributed across the salt barrier. Discrete character evolution models revealed that specialists in one biome rarely transitioned into specialists in another biome. Instead, evolved generalism mediated transitions between biome specialists. State-dependent diversification models found variation in speciation rates across the tree, but this variation was independent of biome association or specialization. Our findings were robust to phylogenetic uncertainty, different levels of species delineation, and different assumed amounts of unsampled diversity resulting in an incomplete phylogeny. Overall, our results are consistent with a "jack-of-all-trades" tradeoff where generalists suffer a cost in any individual environment, resulting in rapid evolution of niche specialists and shed light on how bacteria could transition between biomes.

Mind the gap: new records of Caenolestes in the Western Andes of Colombia challenge its current biogeographic patterns

Abstract The genus Caenolestes is the most species-rich of the marsupial order Paucituberculata. Two species inhabit Colombia (and also occur in Ecuador) with a discontinuous distribution that has not been accounted for in previous studies—Caenolestes fuliginosus known from the Central and Eastern Andes, and C. convelatus restricted to the Western Andes. Here, we present new and noteworthy records of Caenolestes from the Western Andes at the distributional gap of C. convelatus, and outside the known range of C. fuliginosus. We present detailed comparisons using discrete and continuous diagnostic morphological characters, with type material and additional specimens collected nearby, to assess the identity of the new specimens. We performed statistical analyses at species and subspecies levels, and used a principal components analysis to explore the ordination of the new specimens in morphological space. We found that although these specimens are from the Western Andes, they present traits similar to C. fuliginosus and show great overlap with the morphospace of that species. The new records did not differ statistically with C. fuliginosus or any of its subspecies, but they differed in 20 craniodental measurements from C. convelatus. We also report differences at subspecies level within and between species. Based on these observations, we identified these records as C. fuliginosus, expanding its known distribution to the midportion of the Western Andes, across de Cauca valley. We discuss the biogeography of these 2 species in light of the new data and the context of high Andean habitats, especially regarding the contrasting biogeographical patterns found in other taxa in the Northern Andes. Finally, we discuss the need for a new and exhaustive review of the systematics and biogeography of the genus.

ВПЛИВ ДИСКРЕТНОГО ХАРАКТЕРУ СИГНАЛУ ШВИДКОСТІ НА ПРОЦЕСИ КЕРУВАННЯ МОМЕНТОМ ВЕКТОРНО-КЕРОВАНОГО АСИНХРОННОГО ДВИГУНА

The paper presents the investigation of the impact of the discrete character of the measured by incremental encoder speed signal on the induction motor torque vector control in traction electrical drive. The study is based on mathemati-cal simulations for a direct vector flux-torque control system which provides direct asymptotic field-orientation, asymp-totic flux-torque trajectory tracking, and asymptotic decoupling of the torque and flux subsystems. The parameters of the induction motor and encoder used in the study correlate with used in the real traction electromechanical systems of trolleybuses. It is shown that introduction of first order filter in the speed measurement channel reduces the induction motor’s current and torque spikes, but leads to an error in torque control and degradation of the rotor flux field-orientation conditions. Combined utilization of filtered and unfiltered speed signal is proposed in order to avoid this disadvantage. Ref. 7, fig. 6.

Phylogeny and historical biogeography of the leafhopper subfamily Coelidiinae (Hemiptera: Cicadellidae) based on morphological and molecular data

AbstractThe phylogenetic relationships among major lineages of the globally distributed leafhopper subfamily Coelidiinae were reconstructed by analysis of 2903 nucleotide positions from two mitochondrial genes (COI and 16S), four nuclear genes (28S, H3, H2A and Wingless) and 102 discrete morphological characters, compiled for 86 species representing 52 genera within 9 coelidiine tribes broadly representative of the world fauna in addition to 12 outgroup taxa. Maximum likelihood and Bayesian analyses yielded well‐resolved phylogenetic estimates that were highly congruent with most branches receiving strong support. The results indicate Coelidiinae sensu stricto (=Coelidiinae sensu lato without Equeefini and Macroceratogoniini), Thagriini, Tharrini, Tinobregmini and Equeefini are monophyletic. However, the two largest tribes, Coelidiini and Teruliini, are paraphyletic, as well as Youngolidiini and most genera of Oriental Coelidiini. Fossil‐calibrated molecular divergence time analysis indicates that the Coelidiinae sensu stricto originated ca. 149 Ma, prior to the complete separation of the Gondwanan continents, and the tribe‐level lineages diverged between the Lower and Upper Cretaceous (92.77–138.03 Ma). The major lineages of Coelidiinae arose in the Oriental and Neotropical regions, and Oriental Coelidiini arose as a result of dispersal and colonisation from the Afrotropical region.