Morphological Discontinuities Research Articles

Analysis of electrochemical corrosion performance of 316L stainless steel fabricated and textured by selective laser melting

Textured surfaces were used to increase the electrochemical corrosion resistance of the laser powder bed fusion, corrosion performance, DC corrosion and electrochemical impedance spectroscopy techniques were examined. Corrosion resistance could be optimized as a result of changing the surface energy on modified surfaces and eliminating selective laser melting (SLM)-induced morphological discontinuities. The corrosion resistance of optimum textured surfaces is higher than that of forged samples. Results close to texture-free surface performance were obtained on surfaces where texture density reached maximum. Increasing texture weakened the corrosion resistance. Thus the best corrosion resistance; icorr = 156 nA/cm2 with Ecorr = −327 mV observed at 5CR. Material losses are 49.40 mpy × 10−3 for 5CR, 63.48 mpy × 10−3 for 5SQ, 382.60 mpy × 10−3 for 15CR, 63.33 mpy × 10−3 for 15SQ, 394.6 mpy × 10−3 for 25CR and 174.80 mpy × 10−3 for 25SQ, respectively. The highest performance in terms of material losses was found to be 5CR. No significant change in the context of texture geometry was observed in the SEM images. According to quantitative evaluation in electrochemical corrosion tests, the differences are quite close to each other.

Unbiased analyses of ITS folding motifs in a taxonomically confusing lineage: Anagnostidinema visiae sp. nov. (CYANOBACTERIA).

Cyanobacteria are diverse prokaryotic, photosynthetic organisms present in nearly every known ecosystem. Recent investigations around the world have recovered vast amounts of novel biodiversity in seldom sampled habitats. One phylogenetically significant character, the secondary folding structures of the 16S-23S ITS rDNA region, has allowed an unprecedented capacity to erect new species. However, two questions arise: is this feature as informative as is proposed, and how do we best employ these features? Submerged sinkholes with oxygen-poor, sulfur-rich ground water in Lake Huron (USA) contain microbial mats dominated by both oxygenic and anoxygenic cyanobacteria. We sought to document some of this unique cyanobacterial diversity. Using culture-based investigations, we recovered 45 strains, of which 23 were analyzed employing 16S-23S rDNA sequences, ITS folding patterns, ecology, and morphology. With scant morphological discontinuities and nebulous 16S rDNA gene sequence divergence, ITS folding patterns were effective at articulating cryptic biodiversity. However, we would have missed these features had we not folded all the available motifs from the strains, including those with highly similar 16S rDNA gene sequences. If we had relied solely on morphological or 16S rDNA gene data, then we might well have missed the diversity of Anagnostidinema. Thus, in order to avoid conformation basis, which is potentially common when employing ITS structures, we advocate clustering strains based on ITS rDNA region patterns independently and comparing them back to 16S rDNA gene phylogenies. Using a total evidence approach, we erected a new taxon according to the International Code of Nomenclature for Algae, Fungi, and Plants: Anagnostidinema visiae.

(2943) Proposal to conserve Selaginella, nom. cons., (Selaginellaceae) with a conserved type

(2943) Proposal to conserve <i>Selaginella</i>, nom. cons., (<i>Selaginellaceae</i>) with a conserved type

Debris flows and debris avalanches initiation and runout susceptibility assessment in Campania region (Italy)

Sectors of the Campania region (southern Italy), where pyroclastic airfall deposits cover carbonate slopes, have frequently experienced debris avalanches and debris flows. These landslides are triggered by heavy rainfall and in the last century caused severe destruction and hundreds of deaths. Their occurrence is controlled by the interaction of several factors, both natural and human induced. The initial failure is linked with the presence of morphological discontinuities such as rocky scarps and road cuts, which interrupt the stratigraphical continuity of an “infinite slope”. Here the main criteria for susceptibility analysis are defined trying to develop a procedure for identify highly-susceptible sources, runout and invasion areas.

Insight into the Experimental Error in the Mapping of Electrical Properties with Electrostatic Force Microscopy.

Electrostatic force microscopy (EFM) is an emergent, powerful technique for nanoscale detection of electrical properties such as permittivity and charge distribution. However, the surface irregularity of samples has been unfortunately overlooked in most EFM studies. Herein, we use a polymer nanocomposite dielectric (PND) as the showcase and demonstrate that the morphological discontinuity at the matrix/particle interface can lead to major discrepancies or even incorrect results in the EFM study. First, the influence of the morphology, permittivity, and charge density of the interface is quantitively analyzed with a numerical method, proving that linking EFM results directly to sample properties is impracticable in the research based on classical interface configuration. Then, two methods are proposed to address the issue. The first method is numerical inversion, which takes heterogeneous materials and irregular surfaces into consideration. In this method, the influence of several experimental uncertainties, such as the radius of the nanoparticle and the permittivity of the matrix, is estimated. It is shown that the uncertainties related to geometry have a great impact on inversion and should be determined preferentially. In the second method, two standard configurations of the interface are recommended and compared for the interface study to bypass the morphological issue. This work provides quantitative results regarding the long-overlooked error in the EFM detection of the microregion with heterogeneous composition and surface irregularities and offers methods to tackle this issue.

A Graphical Generalization of Localized Morphological Discontinuities on Medium-Scale State Topographic Maps

A Graphical Generalization of Localized Morphological Discontinuities on Medium-Scale State Topographic Maps

Resolving the Tetrastigma loheri s. l. Species Complex (Vitaceae) in the Philippines: No Evidence for Recognizing More than One Species

Abstract— Tetrastigma loheri (Vitaceae) is a vine species native to Borneo and the Philippines. Because it is a commonly encountered forest species in the Philippines, T. loheri is potentially suitable for studying patterns of genetic diversity and connectivity among fragmented forest ecosystems in various parts of this country. However, previous research suggests that T. loheri is part of a species complex in the Philippines (i.e. the T. loheri s. l. complex) that potentially also contains Philippine plants identified as T. diepenhorstii, T. philippinense, T. stenophyllum, and T. trifoliolatum. This uncertainty about its taxonomic delimitation can make it challenging to draw conclusions that are relevant to conservation from genetic studies using this species. Here, we tested the hypothesis that T. loheri s. l. is composed of more than one species in the Philippines. For this, we used generalized mixed Yule coalescent (GMYC) and Poisson tree process (PTP) species delimitation models to identify clades within DNA sequence phylogenies of T. loheri s. l. that might constitute species within this complex. Although these methods identified several putative species, these are statistically poorly supported and subsequent random forest analyses using a geometric morphometric leaf shape dataset and several other vegetative characters did not result in the identification of characters that can be used to discriminate these putative species morphologically. Furthermore, the results of principal component and principal coordinates analyses of these data suggest the absence of morphological discontinuities within the species complex. Under a unified species concept that uses phylogenetic and morphological distinction as operational criteria for species recognition, we therefore conclude that the currently available data do not support recognizing multiple species in the T. loheri s. l. complex. This implies that T. loheri is best considered as a single, morphologically variable species when used for studying patterns of genetic diversity and connectivity in the Philippines.

Quantitative morphometrics suggest that the widespread Neotropical Humiria balsamifera (Aubl.) St. Hil. is a species complex

Humiria balsamifera is an infraspecific complex of high phenotypic variation and widely distributed in northern South America. Leaf traits are traditionally considered the most relevant taxonomic characters for varietal level delimitation in the group. However, substantial phenotypic overlap among vegetative characters complicates taxonomic diagnoses in this complex. The objective of this study was to quantify and analyze phenotypic variation among individuals of the complex at a continental scale using uni- and multivariable analyses to assess whether morphometric analyses detect discontinuities. Secondarily, these quantitative data were used to test whether phenotypic similarity was related to geographic distance. Twenty- five quantitative and 27 qualitative character traits did not overtly reveal a topology corresponding to traditional varietal classification, nor to geographic structure. However, petiole length alone revealed a definitive separation of H. balsamifera var. guianensis (together with another recognized species Humiria wurdackii, and variety H. balsamifera var. laurina) from the rest of the taxa. Our results highlight substantial morphological overlap among vegetative and reproductive characters including those used in identification keys, and no morphological discontinuities suitable for clearly separating taxa within the complex were encountered demonstrating a future need to integrate multiple sources of information, including molecular data, to resolve this complex.

Application of multivariate morphometrics to delimit three Japanese species of Arisaema sect. Pistillata (Araceae)

The Arisaema serratum group sensu stricto (Araceae) is a Japanese species assemblage characterized by a well‐developed leaf rachis and a long pseudostem. It has been regarded as a complex including many species with few decisive traits. They were previously considered as a single species due to their wide intraspecific variation, but recent monographs have recognized about 13 species. In this group, A. maekawae and A. pseudoangustatum var. pseudoangustatum were recently divided from A. angustatum from the type localities. An earlier study found sympatric populations of the three species in the Chugoku region, far from the type localities, and distinguished them by qualitative observations, but there are no quantitative data to delimit the species boundaries objectively. Since high phenotypic plasticity hinders species delimitation in the A. serratum group s.s. using just a few quantitative traits, I investigated the morphological discontinuity among them using principal component analysis with eleven quantitative characters. In an ordination space including the three species, the morphological variation was roughly divided into A. maekawae and the others, and largely overlapped between A. angustatum and A. pseudoangustatum var. pseudoangustatum. However, the morphological variation clearly distinguished the two latter species when A. maekawae was excluded from the PCA. To conclude, the three Arisaema species appeared to be morphologically distinct. The strong reproductive isolation reported previously also ensures the species distinction according to the biological species concept. The discriminating traits between A. angustatum and the other two species partly differed from those in the type localities, suggesting that examination of intraspecific variation is needed between geographically isolated populations. This study showed that a combination of quantitative traits effectively supports tentative species identifications using qualitative traits and reinforces the usefulness of multivariate morphometrics for future systematic studies.

Research in Boraginaceae: A new variety of Cryptantha maritima, Cryptantha pondii resurrected, and Johnstonella echinosepala transferred back to Cryptantha

A review of the species Cryptantha maritima (Boraginaceae) supports the continued recognition of the three varieties, these differing in corolla size, ovule and nutlet number, and calyx vestiture. Mapping of these taxa from verified specimens demonstrates some geographic trends, but also some overlap in ranges. In the process of our study, we discovered a new taxonomic entity. Cryptantha maritima var. vizcainensis is described as new. This variety is restricted to the Vizcaíno Desert of Baja California Sur, Mexico and should be considered rare, as it is known to date from only eleven collections. It differs from the other three varieties of the species in having a canescent, appressed-strigose stem vestiture lacking spreading trichomes, in having a relatively large corolla, and in having a fruit derived from two 1-ovuled ovary lobes, developing into two heteromorphic nutlets. We also discovered that the species Cryptantha pondii, previously treated as a synonym of C. patula, should be resurrected as a distinct taxon. Cryptantha pondii is restricted to the western Vizcaíno Desert and to Natividad Island of Baja California Sur. It is morphologically distinctive in having bracteate flowers, relatively large corollas, and four smooth nutlets heteromorphic by size. It is to date known from only three collections and should be considered extremely rare. We also reviewed the morphological and phylogenetic status of Johnstonella echinosepala. This taxon shows similarities to Cryptantha maritima and also exhibits some morphological discontinuity between Pacific and Gulf populations in Baja California Sur. Evidence from both morphological and phylogenetic studies supports the transfer of this species from the genus Johnstonella back to the genus Cryptantha. Finally, we propose that both C. pondii and C. echinosepala are likely close relatives of C. maritima, all of the “Maritimae clade,” a group distantly related to the main core of the genus Cryptantha. This study confirms the great importance of studying herbarium specimens in taxonomic research.

Hydrological control of soil thickness spatial variability on the initiation of rainfall-induced shallow landslides using a three-dimensional model

Thickness and stratigraphic settings of soils covering slopes potentially control susceptibility to initiation of rainfall-induced shallow landslides due to their local effect on slope hydrological response. Notwithstanding the relevance of the assessment of hazard to shallow landsliding at a distributed scale by approaches based on a coupled modelling of slope hydrological response and slope stability, the spatial variability of soil thickness and stratigraphic settings are factors poorly considered in the literature. Under these premises, this paper advances the well-known case study of rainfall-induced shallow landslides involving ash-fall pyroclastic soils covering the peri-Vesuvian mountains (Campania, southern Italy). In such a unique geomorphological setting, the soil covering is formed by alternating loose ash-fall pyroclastic deposits and paleosols, with high contrasts in hydraulic conductivity and total thickness decreasing as the slope angle increases, thus leading to the establishment of lateral flow and an increase of pore water pressure in localised sectors of the slope where soil horizon thickness is less. In particular, we investigate the effects, on hillslope hydrological regime and slope stability, of irregular bedrock topography, spatial variability of soil thickness and vertical hydraulic heterogeneity of soil horizons, by using a coupled three-dimensional hydrological and a probabilistic infinite slope stability model. The modelling is applied on a sample mountain catchment, located on Sarno Mountains (Campania, southern Italy), and calibrated using physics-based rainfall thresholds derived from the literature. The results obtained under five simulated constant rainfall intensities (2.5, 5, 10, 20 and 40 mm h−1) show an increase of soil pressure head and major failure probability corresponding to stratigraphic and morphological discontinuities, where a soil thickness reduction occurs. The outcomes obtained from modelling match the hypothesis of the formation of lateral throughflow due to the effect of intense rainfall, which leads to the increase of soil water pressure head and water content, up to values of near-saturation, in narrow zones of the slope, such as those of downslope reduction of total soil thickness and pinching out of soil horizons. The approach proposed can be conceived as a further advance in the comprehension of slope hydrological processes at a detailed scale and their effects on slope stability under given rainfall and antecedent soil hydrological conditions, therefore in predicting the most susceptible areas to initiation of rainfall-induced shallow landslides and the related I-D rainfall thresholds. Results obtained demonstrate the occurrence of a slope hydrological response depending on the spatial variability of soil thickness and leading to focus slope instability in specific slope sectors. The approach proposed is conceived to be potentially exportable to other slope environments for which a spatial modelling of soil thickness would be possible.

Broken into Pieces: ATLAS and Aliqa Uma as One Single Stream

Abstract We present the first spectroscopic measurements of the ATLAS and Aliqa Uma streams from the Southern Stellar Stream Spectroscopic Survey (S 5), in combination with the photometric data from the Dark Energy Survey and astrometric data from Gaia. From the coherence of spectroscopic members in radial velocity and proper motion, we find that these two systems are extremely likely to be one stream with discontinuity in morphology and density on the sky (the “kink” feature). We refer to this entire stream as the ATLAS-Aliqa Uma stream, or the AAU stream. We perform a comprehensive exploration of the effect of baryonic substructures and find that only an encounter with the Sagittarius dwarf ∼0.5 Gyr ago can create a feature similar to the observed “kink.” In addition, we also identify two gaps in the ATLAS component associated with the broadening in the stream width (the “broadening” feature). These gaps have likely been created by small mass perturbers, such as dark matter halos, as the AAU stream is the most distant cold stream known with severe variations in both the stream surface density and the stream track on the sky. With the stream track, stream distance, and kinematic information, we determine the orbit of the AAU stream and find that it has been affected by the Large Magellanic Cloud, resulting in a misalignment between the proper motion and stream track. Together with the Orphan-Chenab Stream, AAU is the second stream pair that has been found to be a single stream separated into two segments by external perturbation.

An integrative taxonomic approach resolves the

The diagnostic characteristics and distinctiveness of plant taxa have traditionally been based on a combination of geographic and morphological discontinuity. Implicit within these concepts is the notion that morphological variation is fixed and that gene flow among taxa is limited. However, species complexes that comprise a range of more-or-less continuous morphotypes often confound such assumptions and resist formal taxonomic treatment. A range of independent data sources, namely, nucleotide sequences, volatile oils and traditional morphology, were used in an integrative approach to resolve the taxonomic structure within the geographically widespread species complex of Prostanthera lasianthos Labill. We concluded that no dataset has primacy in defining segregate taxa, and that a combination of morphological and molecular data was required to determine the taxa within. As a result, we amended the description of P. lasianthos sens. strict. and recognise the following five new segregate species: Prostanthera largiflorens B.J.Conn &amp; K.Proft, P. lasiangustata J.Carrick ex B.J.Conn &amp; K.Proft, P. rupicola B.J.Conn &amp; K.Proft, P. subalpina B.J.Conn &amp; K.Proft, and P. williamsii B.J.Conn &amp; K.Proft.

Species delimitation and phylogeography of African tree populations of the genus Parkia (Fabaceae)

In the pantropical mimosoid legume genus Parkia, taxonomic classification has remained controversial in Africa due to clinal phenotypic variations. Three species (P. biglobosa, P. bicolor, and P. filicoidea) are currently recognized, ranging from West to East Africa, with partially overlapping ranges across different floristic regions. However, additional taxa (species or varieties) have been suggested by different authors. To assess species boundaries of African Parkia and phylogeographic patterns within species, we genotyped 889 individuals using 10 microsatellite markers and compared our results with existing morphological descriptions. Bayesian genetic clustering confirmed the species boundaries assessed from morphological traits and did not reveal introgression but identified genetic discontinuities within each species. Six moderately differentiated genetic clusters were recovered in P. biglobosa (pairwise FST: 0.05–0.19), while P. bicolor and P. filicoidea, each, displayed four well-differentiated clusters (FST: 0.18–0.41 and 0.11–0.34, respectively). Within each species, genetic clusters occurred in parapatry. Parkia biglobosa clusters were congruent with the longitudinal clinal variation in leaflets sizes but 26% of individuals presented admixed genotypes. Genetic clusters in P. bicolor and P. filicoidea followed environmental gradients as well as phytogeographic subdivisions. They were also largely congruent with morphological discontinuities described in previous taxonomic studies and < 10% individuals showed admixed genotypes. We conclude that only one species (P. biglobosa) should be considered in the Guineo-Sudanian savanna. However, P. bicolor and P. filicoidea might each represent a complex of (sub)species. Thus, the hypotheses of cryptic species within P. bicolor and P. filicoidea should be further investigated by testing reproductive barriers.

Are the implications for conservation of a major taxonomic revision of the world’s birds’ simply serendipity?

Are the implications for conservation of a major taxonomic revision of the world’s birds’ simply serendipity?

New subspecies of fir dwarf mistletoe (Arceuthobium abietinum: Viscaceae) from the western United States and northern Mexico

Two new subspecies of fir dwarf mistletoe (Arceuthobium abietinum, Viscaceae) are described herein: Arceuthobium abietinum subsp. mathiasenii (Mathiasen’s dwarf mistletoe) and Arceuthobium abietinum subsp. grandae (grand fir dwarf mistletoe). The former dwarf mistletoe—Mathiasen’s dwarf mistletoe—parasitizes Rocky Mountain white fir in Nevada, Utah, and Arizona and Durango fir in northern Mexico; whereas, grand fir dwarf mistletoe parasitizes grand fir as well grand fir × white fir hybrids in California, Oregon and Washington. The recognition of these subspecies and, hence, their classification is based on morphological discontinuities and host range differences when compared to white fir dwarf mistletoe (Arceuthobium abietinum subsp. abietinum), red fir dwarf mistletoe (A. abietinum subsp. magnificae), and Wiens’ dwarf mistletoe (A. abietinum subsp. wiensii). The combined analyses of plant height, third internode length and width, fruit dimensions, staminate spike and petal dimensions, and anther distance to tip, contributed most to the discrimination of subsp. grandae and mathiasenii from subsp. abietinum and magnificae. The flowers of Mathiasen's dwarf mistletoe were larger than all of the other taxa classified under A. abietinum. The shoot color of Mathiasen’s dwarf mistletoe was frequently blue-green, brown, yellow-brown, or red-brown, and plants were often highly glaucous, while the shoot color of the other subspecies were typically yellow-green or yellow, except for Wiens' dwarf mistletoe whose shoots are often green-brown or red-brown. Differences in host specificity and geographic distribution also distinguish the new subspecies from the other taxa of A. abietinum.

Delimiting a constellation: integrative taxonomy of a star-shaped Hydrocotyle species complex (Araliaceae) from the Brazilian Atlantic forest

Species delimitation must overcome the inconsistency among the different delimitation criteria to maintain species as reliable units for biological research and conservation. The general lineage species (GLS) concept embraces different methods of species delimitation and thus provides an integrative framework for taxonomy. The Hydrocotyle stella complex contains six morphotypes that occur along mountain ranges within the Brazilian Atlantic forest, possibly representing undescribed species. In this study, we adopted the GLS concept to assess whether H. stella would be a single species or not, in which we considered genetic structure and morphological discontinuity as evidences for species delimitation. We applied ISSR-based population genetics and morphometrics to 12 populations of H. stella, representing all morphotypes across their main geographical range. Population genetics revealed three genetically structured groups (ΦST > 0.22), each associated with different mountain range regions. Morphometrics indicated significant (p < 0.001) morphological divergence among genetically structured groups, but not for all of the traditional leaf morphotypes. Based on congruency between genetic structure and morphological discontinuity, we recognized three species within the complex, H. alpina, H. palacea, and H. quinqueradiata, and provided their due taxonomic treatment.

Imaging phonon dynamics with ultrafast electron microscopy: Kinematical and dynamical simulations.

Ultrafast x-ray and electron scattering techniques have proven to be useful for probing the transient elastic lattice deformations associated with photoexcited coherent acoustic phonons. Indeed, femtosecond electron imaging using an ultrafast electron microscope (UEM) has been used to directly image the influence of nanoscale structural and morphological discontinuities on the emergence, propagation, dispersion, and decay behaviors in a variety of materials. Here, we describe our progress toward the development of methods ultimately aimed at quantifying acoustic-phonon properties from real-space UEM images via conventional image simulation methods extended to the associated strain-wave lattice deformation symmetries and extents. Using a model system consisting of pristine single-crystal Ge and a single, symmetric Lamb-type guided-wave mode, we calculate the transient strain profiles excited in a wedge specimen and then apply both kinematical- and dynamical-scattering methods to simulate the resulting UEM bright-field images. While measurable contrast strengths arising from the phonon wavetrains are found for optimally oriented specimens using both approaches, incorporation of dynamical scattering effects via a multi-slice method returns better qualitative agreement with experimental observations. Contrast strengths arising solely from phonon-induced local lattice deformations are increased by nearly an order of magnitude when incorporating multiple electron scattering effects. We also explicitly demonstrate the effects of changes in global specimen orientation on the observed contrast strength, and we discuss the implications for increasing the sophistication of the model with respect to quantification of phonon properties from UEM images.

Local climate and latitude affect flower form of Ophrys fuciflora (Orchidaceae): evidence for clinal variation

ABSTRACTThe widely accepted approach – the use of morphometrics – often reveals gradients without clear morphological discontinuities, which can be explained as clinal variability. The Ophrys fuciflora complex from South-eastern Europe (Slovenia and Croatia) was morphologically evaluated. Classical morphology was performed on specimens from 18 populations. Each individual plant is represented with a set of 19 floral characters obtained from a single flower. Altogether, 221 flowers were measured. According to PCA results, a high proportion of specimens shows intermediate character values, specimens belonging to different morphological entities overlap. The first morphological principal component was considered as a flower form (size and shape) vector. Correlation tests were performed based on 19 bioclimatic variables and the first morphological principal component. Nine bioclimatic variables show statistically significant, strong correlation with the flower form. Results indicate that the observed floral continuous quantitative characters, traditionally utilized to differentiate taxa in the Ophrys fuciflora complex are affected by the local climatic conditions and latitude, and exhibit clinal variability. An integrative taxonomical approach to the genus Ophrys should also take into account site-specific ecological conditions, to investigate and prove possible clinal variability first, but also taxa-specific phenology.

Linear and geometric morphometrics as tools to resolve species circumscription in the Pseudolaelia vellozicola complex (Orchidaceae, Laeliinae)

Background and aims – Pseudolaelia is a genus endemic to eastern Brazil, with 12 accepted species predominantly distributed across granitic inselbergs of the Brazilian Atlantic Forest. The aim of the present study was to distinguish between the very similar taxa P. aguadocensis, P. oliveirana, P. regentii and P. vellozicola, using morphometric data acquired as linear measurements and outlines capture with Elliptic Fourier Analysis (EFA) of the floral parts. Material and methods – We sampled 208 specimens from 11 natural populations of the above taxa. We measured 20 floral variables and for the EFA, and we extracted 24 shape variables from the Fourier coefficient matrices, which describe the outlines of the floral parts. In both cases the data were analyzed with multivariate methods (both ordination and clustering). Key results – We could not find morphological discontinuities with sufficient magnitude to consider P. aguadocensis, P. oliveirana and P. regentii as distinct species from P. vellozicola. Conclusions – We propose that P. vellozicola should be considered a polymorphic and widely distributed species, generally supported by both methods.