Range Of Species Research Articles

Habitat fragmentation strongly restricts gene flow in endangered ectomycorrhizal fungal populations: Evidence from Rhizopogon togasawarius, specific to Pseudotsuga japonica, across the entire distribution range.

Habitat fragmentation reduces gene flow, causing genetic differentiation and diversity loss in endangered species through genetic drift and inbreeding. However, the impact of habitat fragmentation on ectomycorrhizal (ECM) fungi remains unexplored, despite their critical roles in forest ecosystems. Here, we investigated the population genetic structure and the demographic history of Rhizopogon togasawarius, the ECM fungus specifically colonizing the host tree Pseudotsuga japonica, across its entire distribution range (>200 km). These two species are designated as endangered species on the IUCN Red List since they are found only in small, fragmented forests in Japan. We analysed 236 R. togasawarius individuals from five remaining populations across the Kii Peninsula and the Shikoku Island, separated by a sea channel. Simple sequence repeat analyses using 20 loci revealed strong genetic differentiation among populations (FST = 0.255), even significant in the nearest population pair separated by a distance of only 8 km (FST = 0.075), indicating extremely limited gene flow between populations. DIYABC-RF analyses implied that population divergence occurred approximately 6000 generations ago between the two regions, and nearly 1500 generations ago between the nearest populations within Shikoku Island, related to past climate events. Because of prolonged genetic isolation, significant inbreeding was confirmed in four of five populations, where effective population sizes became very small (Ne = 9.0-58.0). Although evaluation of extinction risks for microorganisms is challenging, our conservation genetic results indicated that habitat fragmentation increases extinction risk through population genetic mechanisms, and therefore should not be overlooked in biodiversity conservation efforts.

Disaster mechanism of large-diameter shield tunnel segments under multi-source load coupling: A case study

The deflection squeezing of the shield shell and the eccentric jack thrust significantly impact the segment dislocation and damage. Based on summarizing the derivative relationship between engineering factors and disasters, this study established a 3D numerical calculation model under the multi-source load coupling. Then, this study explored the displacement and dislocation distribution of segments, as well as their derivative relationship with bolt failure. Furthermore, this study analyzed the spatial distribution and evolution characteristics of segment damage. Further revealing the disaster mechanism and proposing the engineering treatment measures. The research results indicate that as the deflection angle increases, the vertical relative compression deformation of the segment that is detaching from the shield tail (segment-DFST) becomes more significant. The plastic strain of the internal bolts inside the two segments in direct contact with the shield shell is mainly related to the radial and longitudinal dislocation. The increase in the deflection angle will lead to a more significant increase in the adjacent dislocation on both sides and the internal dislocation. The plastic strain of the internal bolts of the segment that is completely in the shield shell (segment-CSS) is more influenced by joint opening and longitudinal dislocation under the lower eccentric compression (LEC) state. The plastic strain of the internal bolts in segment-DFST is more influenced by radial dislocation and joint opening under the LEC state. The tension damage of the segments mainly occurs on both sides of the circumferential joint and the lower part of the segment-CSS. The compression damage of the segments is mainly distributed at the top and bottom of the segment-CSS. The eccentric distribution of jack thrust has the most significant impact on the block damage of the lower part of the segment-CSS. With the increase of the deflection angle, the compression damage and distribution range of the blocks at the bottom of the segment-DFST increase sharply. The compression damage and distribution range of the segment-CSS gradually spread from the upper and lower parts to the middle of the segment. The increase in deflection angle will promote the influence of the thrust in LEC state on the compression damage of the lower block of the segment-CSS, and on the tension damage of the upper block of the segment- DFST.

A study on the diversity of phlebotomine sand flies (Diptera, Psychodidae) in karstic limestone areas in Vientiane Province, Laos, with a description of two new species of Sergentomyia França and & Parrot

BackgroundSoutheast Asia is well known as a hotspot of biodiversity. However, very little is known about cave-dwelling hematophagous insects that are medically important. Taxonomic knowledge and ecology of phlebotomine sand flies are very poorly studied in Laos, as well as in other countries in the region. Herein, we report species diversity data and some notes on the ecology of the detected species from these karstic limestone areas of Laos.MethodsPhlebotomine sand flies were collected using Centers for Disease Control and Prevention (CDC) light traps from limestone cave locations in three districts of Vientiane Province, Laos. Both morphological and molecular techniques were used for sand fly identification. Species diversity and abundance were analyzed according to sites, locations, collection seasons, and trapping positions.ResultsA total of 6564 sand flies, of which 5038 were females and 1526 were males, were morphologically identified into 20 species belonging to five genera (Chinius, Idiophlebotomus, Phlebotomus, Sergentomyia, and Grassomyia). The most abundant species were Chinius eunicegalatiae, Phlebotomus stantoni, Sergentomyia hivernus, Se. siamensis, and Idiophlebotomus longiforceps. Cytochrome b analysis results supported the morphological identification and revealed that Se. siamensis was separated from other members of the Se. barraudi group. Two new species, Se. dvoraki n. sp. and Se. marolii n. sp., were described. Sand fly density was generally high except in a cave in Vangvieng, with species richness ranging from 14 to 18 across different caves. Outside caves had higher species richness (R = 20) and diversity (H = 2.50) than cave entrances (R = 18, H = 2.41) and interiors (R = 16, H = 2.13). Seasonal variations showed high sand fly density in Feung and Hinheup during both dry and rainy seasons, while Vangvieng had a notable decrease in density during the dry season (D = 6.29).ConclusionsThis study revealed that the diversity of phlebotomine sand fly fauna in Laos, particularly in karstic limestone areas, is greater than previously known. However, the taxonomic status of many species in Laos, as well as Southeast Asia, still needs more in-depth study using both morphological characters and molecular methods. Many species could be found from inside, at the entrance, and outside of caves, indicating a wide range of host-seeking behavior or possible natural breeding in the karstic cave areas.Graphical abstract

Discovery and biological confirmation of a highly divergent Tacaribe virus in metatranscriptomic data from neotropical bats.

Clade B New World arenaviruses (NWA) include rodent-borne lethal hemorrhagic fever viruses, whereas Tacaribe virus (TCRV) stands out because of its detection in bats and its presumably low zoonotic potential. However, the bat association of TCRV was put into question by lethal experimental neotropical fruit bat infections and rare TCRV detection in bats. Scarce genomic data include near-identical viruses from Caribbean bats and ticks from the US sampled 50 years later. The prototype TCRV isolate used for experimental risk assessments has an extensive passage history in suckling mouse brains. Exploring the true genetic diversity, geographic distribution, and host range of bat-borne NWA is pivotal to assess their zoonotic potential and transmission cycles. We analyzed metatranscriptomic data for evidence of NWA identifying a highly divergent TCRV in bats and confirmed virus detection in original biological materials, supporting the association of TCRV with neotropical bats and warranting investigation of strain-associated TCRV pathogenicity.

Integrative taxonomy and biogeography of the genus Oxytrechus (Coleoptera: Carabidae: Trechini) in the tropical alpine ecosystem of Ecuadorian Andes, with the description of six new species

Summary This study presents a taxonomic revision of the species of the ground beetle genus Oxytrechus Jeannel, 1927 that inhabit the superpáramo of the Andes of Ecuador, which constitutes the uppermost zone of the tropical alpine ecosystem, above 4200 m. Sixteen species, displayed in three clades, were recorded in this environment, six of which are described as new: Oxytrechus antisanae n. sp. (Mt Antisana), O. giachinoi n. sp. (Mt Illiniza), O. hamatus n. sp. (Mt Atacazo and Pichincha), O. prunai n. sp. (Mt Guamaní), O. reflexus n. sp. (Mt Illiniza and Mt Corazón), and O. robbiolai n. sp. (Mt Pichincha). New distributional data are presented for O. chioriae Quéinnec & Ollivier, 2019, O. lallemandi Jeannel, 1927, O. moreti Mateu, 1988 and O. zoiai Casale & Sciaky, 1985. The first molecular phylogeny of the group, based on fragments of four mitochondrial and two nuclear genes, is given. Dichotomous identification keys are provided to the species groups and the included species. Based on systematic sampling, Oxytrechus exhibits the highest degree of microendemism among páramo ground beetles. No species has been found in more than two sky islands, and half of the species recorded in the superpáramo are single-mountain endemics. As regards their conservation status, eight species (two thirds) can be classified as vulnerable or endangered, due to a mix of low abundance, narrow distribution range, microendemism, limited ecological tolerance, habitat destruction and effects of climate change.

Towards a unifying model for B-cell receptor triggering.

Antibodies are exceptionally versatile molecules with remarkable flexibility in their binding properties. Their natural targets range from small-molecule toxins, across viruses of different sizes, to bacteria and large multicellular parasites. The molecular determinants bound by antibodies include proteins, peptides, carbohydrates, nucleic acids, lipids and even synthetic molecules that have never existed in nature. Membrane-anchored antibodies also serve as receptors on the surface of the B cells that produce them. Despite recent structural insights, there is still no unifying molecular mechanism to explain how antibody targets (antigens) trigger the activation of these B-cell receptors(BCRs). After cognate antigen encounter, somatic hypermutation and class-switch recombination allow BCR affinity maturation and immunoglobulin class-specific responses, respectively. This raises the fundamental question of how one receptor activation mechanism can accommodate a plethora of variant receptors and ligands, and how it can ensure that individual B cells remain responsive to antigen after somatic hypermutation and class switching. There is still no definite answer. Here we give a brief historical account of the different models proposed to explain BCR triggering and discuss their merit in the context of the current knowledge of the structure of BCRs, theirdynamic membrane distribution, and recent biochemical and cell biological insights.

Investigation of local mechanical behavior during the shear process of rough rock joints using DEM

Rough joints are prevalent in natural rock masses, and their shear mechanical properties are crucial for ensuring the safety and stability of these masses. Existing studies often neglect the contribution of various joint asperities to shear stress resistance. This study addresses this gap by eluci-dating the local shear mechanisms of different asperities in rough joints throughout the shear process. This was achieved through a combination of quantitative and qualitative analyses using the Discrete Element Method (DEM). Initially, Barton's ten standard roughness joint profiles were dig-itized, and rough joints were modeled using the Modified Smooth Joint Model (MSJM). Direct shear tests on joint specimens under constant nor-mal stress were performed using servo-controlled methods. Subsequently, the shear stress behavior was analyzed in relation to the test results. The failure modes of the joint specimens were examined in detail using crack tracking and force chain analysis. The study also explored the relation-ship between the number of cracks and shear stress. Additionally, variations in average stress across ten different segments of joints during shear were monitored using the measuring circle function. The shear resistance contributions of local joint segments were quantitatively assessed using three stress indices: maximum stress, upper limit of maximum stress, and the distribution range of maximum stress. The Joint Roughness Coeffi-cient (JRC) of joints was found to correlate well with these indices. Overall, the progressive failure of local joint segments was analyzed both qual-itatively and quantitatively. The study confirmed that the local shear mechanisms of different joint segments during the shear process are distinct.

Rapid Risk Assessment of the Detection of Listeria Monocytogenes in Enoki Mushrooms

This rapid assessment has been requested to inform a decision by FSA Policy whether a temporary overarching risk management response to the commodity (enoki mushrooms) is necessary. Cultivated enoki mushrooms are deprived of light and grown in a CO2-rich environment. Commercially grown enoki mushrooms are grown in hard wood sawdust that is impregnated with the spores. The sawdust is usually good for four or five crops of mushrooms. The mushrooms are encouraged to grow long and thin by placing glass tubes over them. This produces a pale white mushroom with long, slender stems, up to five inches in length, and small caps. Whilst specific practices may vary, generally the initial growing environment is humid with a temperature between 22°C – 25°C, followed by lowering the temperature to 7°C – 12°C whilst maintaining humidity. It is this change in temperature that causes the mycelium to form fruiting bodies that grow into mature mushrooms which are harvested after about 90 days (Pereira et al., 2023). The species Flammulina filiformis, known and sold in different regions as “enoki”/“enokitake” Japan, “jingu” (China), “futu” (India), “paengi beoseot” (Korea), “nám kim cham” (Vietnam) also grows wild throughout a broad natural range on the rotting wood of a range of common trees, although wild-growing mushrooms appear quite different. The majority of enoki mushrooms on sale appear to be commercially cultivated and fresh rather than wild mushrooms. It is unknown if wild enoki mushrooms present a similar L. monocytogenes risk to cultivated mushrooms. Listeria spp., including L. monocytogenes, can be present in the soil (Linke et al., 2014), and are common in natural and urban environments (Orsi and Wiedmann, 2016). Contamination and proliferation is possible during cultivation but also during harvesting and packing (uncertainty).

Sod farms drive habitat selection of a migratory grassland shorebird during a critical stopover period

Migratory shorebirds are one of the fastest declining groups of North American avifauna. Yet, relatively little is known about how these species select habitat during migration. We explored the habitat selection of Buff-breasted Sandpipers (Calidris subruficollis) during spring and fall migration through the Texas Coastal Plain, a major stopover region for this species. Using tracking data from 118 birds compiled over 4 years, we found Buff-breasted Sandpipers selected intensively managed crops such as sod and short-stature crop fields, but generally avoided rangeland and areas near trees and shrubs. This work supports prior studies that also indicate the importance of short-stature vegetation for this species. Use of sod and corn varied by season, with birds preferring sod in spring, and avoiding corn when it is tall, but selecting for corn in fall after harvest. This dependence on cropland in the Texas Coastal Plain is contrary to habitat use observed in other parts of their non-breeding range, where rangelands are used extensively. The species' almost complete reliance on a highly specialized crop, sod, at this critical stopover site raises concerns about potential exposure to contaminants as well as questions about whether current management practices are providing suitable conditions for migratory grassland birds.

Spatial and Ontogenetic Patterns in the Trophic Ecology of Two Predatory Fishes in a Large River

ABSTRACTFishes use a variety of physical and biological resources that shift ontogenetically, seasonally and spatially. Quantifying what resources such as prey are required for persistence can improve understanding of ecological needs of fishes and riverine macrosystem functioning. Bowfin (Amia ocellicauda) and largemouth bass (Micropterus nigricans) cohabitate in their native range and potentially compete with one another. Yet, there have been no direct comparisons of their diets across spatial gradients to assess whether they partition resources or shift in prey use. We used multiple univariate and multivariate analyses to compare diet composition, diet overlap, feeding strategy, prey importance and diet partitioning between largemouth bass and bowfin across three reaches of the Upper Mississippi River. Largemouth bass ontogenetically shifted their diet from aquatic invertebrates to fishes and a more diverse assemblage of aquatic invertebrates. Bowfin and adult largemouth bass were top predators which consumed mostly crayfish and fish and overlapped in their diets. Despite overlapping diets, predators partitioned resources by consuming different lengths and abundances of prey, and largemouth bass had greater trophic plasticity. Within a predator group, few differences in diets existed spatially, underscoring the relative homogeneity in resource use potentially from similarities in the river's physical structure. Combined, prey use likely differed sufficiently to reduce potential competition between largemouth bass and bowfin, allowing long‐term coexistence in this system. Our results also highlighted the importance of crayfishes to riverine food webs and underscored the use of multiple prey and habitat types that sustain these predators.

Characteristics of Phenotypic Variation of Malus Pollen at Infrageneric Scale.

Pollen carries extensive genetic information, which may provide clues regarding the kinship of Malus, whose genetic relationships are complex. In this study, the phenotypic variation of pollen from 107 Malus taxa was investigated using combined methods of intraspecific/interspecific uniformity testing, cluster analysis, and Pearson correlation analysis. The family aggregation distributions in Malus sections, species, and cultivars were analyzed to infer their pedigree relationships. The results showed that (1) compared with pollen size and morphology, aberrant pollen rate and ornamentation were highly interspecifically differentiated, but ornamentation was also intraspecifically unstable, especially perforation densities (c.v.¯ > 15%). (2) The pollen alteration direction from the original to the evolutionary population of Malus was large to small, with elliptic to rectangular morphologies, large and compact to small and sparse ridges, and low to high perforation densities. However, there was no significant change in pollen size. (3) The 107 studied taxa were divided into four groups. Malus species were relatively clustered in the same section, while homologous cultivars showed evidence of family aggregation distribution characteristics (92.60% of cultivars were clustered with their parents). (4) M. baccata and M. pumilar var. neidzwetzkyana were high-frequency parents, participating in 38.7% and 20.7% of cross-breeding, respectively. Overall, this study provides a reference for identifying Malus' pedigree relationship.

Expanding the boundaries in the face of global warming: A lesson from genetic and ecological niche studies of Centaurium erythraea in Europe

Climate change affects plant species, especially those with restricted ecology and distribution. Centaurium erythraea is a flowering plant species in the Gentianaceae family, native to Europe, with its centre of diversity in the Mediterranean and western Asia. Of the 11 infraspecific taxa distinct from C. erythraea, only two are common in Europe: C. erythraea subsp. erythraea (widespread nominal subspecies) and C. erythraea subsp. majus (mainly distributed in the western Mediterranean region). Freshly collected samples of 36 plants from 11 localities across Lower Silesia (Central Europe) were utilised for taxonomic and genetic analysis. The barcode sequences of chloroplast DNA region matK were used for molecular analysis. Data deposited in GenBank was also used. Five haplotypes were identified among the analysed specimens. Species Distribution Modelling (SDM) techniques were applied to predict the current and future (short- and long-term projections) potential distribution of C. erythraea subsp. majus and to identify the most influential climatic factors. Despite the typical Mediterranean distribution, the presence of C. erythraea subsp. majus outside its natural range in SW Poland has been confirmed by morphological and genetic studies. The mean monthly precipitation of the wettest quarter and the mean daily temperatures of the warmest quarter were identified as the key climatic factors. Short-term scenarios suggest that C. erythraea subsp. majus will maintain most of its current suitable habitats and potentially expand into the lowlands of Central Europe. However, long-term projections indicate a potential reduction in its currently suitable areas, especially in the southern parts of its range, with a possible expansion into north-western Europe. The results of these studies provide clear evidence of the impact of ongoing climate change on species range changes. These findings suggest that climate change may create new opportunities for Mediterranean species to spread to new regions, using C. erythraea subsp. majus as an example.

Petrography and geochemistry of aplites from the Seridó Pegmatite Province, NE Brazil: Petrogenetic Implications

In the Seridó Pegmatite Province (SPP) there are thousands of granitic pegmatite intrusions, including unzoned and barren, and zoned and mineralized ones. The whole rock chemical analysis of pegmatite is usually unfeasible because of its large grain size. However, fine-grained aplites syn crystallized with pegmatites should allow them to be used as proxies to assess pegmatite melt differentiation. We selected 15 representative aplite occurrences within unzoned pegmatite intrusions, including 7 intrusions with the grayish muscovite-aplite type and 8 with the reddish magnetite-aplite type. We also used for new trace element analysis samples of medium-to coarse-grained facies of host unzoned pegmatites. These pegmatites occur as NE-SW and N-S dykes and sills intruding mica schist and paragneiss from the Seridó Belt. Both aplite types contain along with quartz and feldspars accessory apatite, zircon, monazite, and xenotime. Tourmaline, muscovite, and garnet occur in the grayish aplites, whereas biotite and opaque minerals occur in the reddish aplites. The grayish aplites are slightly to strong peraluminous, while the reddish aplites are slightly metaluminous to slightly peraluminous. The reddish aplites and their host pegmatites are enriched in Ba, Sr, U and Th, while the grayish aplites and their host pegmatites are enriched in B, Li and Cs. The K/Rb ratios of the aplites varies from 11 to 44 with similar ranges in both reddish and grayish aplites. Normalized to the average upper continental crust composition, both aplite types present positive anomalies of Rb, Pb, U, and Hf, and negative anomalies of Ba, Sr and Ti. K, Nb and Ta show variable enrichment and depletion. They usually show HREE enrichment in relation to LREE and negative Eu anomaly, but positive Eu anomaly and tetrad patterns occur in few samples. In the normative QAP diagram the aplites show a wide range of compositions with a trend from quartz-plagioclase-rich tonalite to quartz-poor K-feldspars-rich alkali granite. Such trend is inverted in relation to the characteristic trends of melt differentiation by crystal fractionation. The albite/K-feldspar ratio of aplites shows a wide distribution range that would be related to the compositional variety of the partially melted protoliths and/or the variation in melting rate during prograde anatexis. The trace element compositions of the medium-to coarse-grained facies of the unzoned pegmatites are very similar to those of the coexisting aplites. The obtained data using aplites as a proxy for their host pegmatites precludes a unique line of melt descent at the origin of the SPP aplites and unzoned pegmatites and thus strongly support an anatectic origin from different sources.

Characterization of the Complete Mitochondrial Genome of the Central Highland Grey-Shanked Douc Langur (Pygathrix cinerea), a Critically Endangered Species Endemic to Vietnam (Mammalia: Primates).

The grey-shanked douc langur (Pygathrix cinerea) is a recently described, critically endangered primate, endemic to Vietnam. In this study, we describe the Central Highland species' complete mitochondrial genome (mitogenome-mtDNA). It is a circular molecule with a length of 16,541 base pairs (bp). The genome consists of 37 genes, consistent with those found in most other vertebrates, including 13 protein coding genes, 22 transfer RNAs, and two ribosomal RNAs. A comparison with the mitogenomes of more than 50 primates showed that the mitogenome of Vietnamese Central Highland Pygathrix cinerea has a conservative gene order. We identified 43 nucleotide differences when comparing this genome with a previously published mitogenome of Pygathrix cinerea. It is evident that there are distinct differences between the Pygathrix cinerea we are currently studying and other Pygathrix cinerea specimens. These differences are unlikely to be solely the result of sequencing errors, as the mitogenomes were generated using high-quality methods. The genetic divergence observed between the two Pygathrix cinerea mitogenomes implies the potential existence of at least two distinct lineages or forms of this primate species within its native range in Vietnam.

Anas platyrhynchos (Mallard) has been replacing Anas rubripes (American Black Duck) in human-altered landscapes in Ontario, 1996 to 2019

Abstract Anas rubripes (American Black Duck) has received much attention over the years as a popular game bird species that experienced historical declines on its wintering grounds. Declines may be due to changes in the quality and quantity of breeding habitat, competition with A. platyrhynchos (Mallard), or both. Although the A. rubripes population has stabilized, spatial variation in regional population trends of A. rubripes on their breeding grounds can provide insight into the relative importance of these alternative hypotheses at provincial and local scales. We analyzed indicated breeding pairs count data collected in Ontario between 1996 and 2019 through the Eastern Waterfowl Survey to evaluate the correlation in breeding densities and trends of the 5 most abundant waterfowl species. We also tested whether habitat and anthropogenic disturbance variables could explain the distribution of those species. Overall, A. platyrhynchos breeding pair densities increased across the survey area, whereas A. rubripes breeding pair densities decreased in the southern and northern part of the survey area but remained stable in the central part. Densities of breeding pairs of A. rubripes and A. platyrhynchos were negatively correlated across survey plots but the trends in breeding densities were not correlated. Densities of A. platyrhynchos breeding pairs increased in human altered landscapes, whereas the density of A. rubripes breeding pairs was negatively correlated with agriculture. Our results suggest that A. platyrhynchos did not competitively exclude A. rubripes on the breeding grounds, but instead, A. rubripes were replaced by A. platyrhynchos following encroachment of agriculture into A. rubripes breeding habitat. Habitat management plans focused on breeding A. rubripes should emphasize reduction in the expansion of anthropogenic perturbations and increases in habitat conservation efforts in the central area of the breeding range in Ontario.

Meta-Analysis and MaxEnt Model Prediction of the Distribution of Phenacoccus solenopsis Tinsley in China under the Context of Climate Change.

Phenacoccus solenopsis Tinsley is a pest that poses a significant threat to agricultural crops, especially cotton, and is now widely distributed across many regions worldwide. In this study, we performed a meta-analysis on the collected experimental data and found that within the suitable temperature range, the survival rate of P. solenopsis increases with rising temperatures, indicating that climate plays a decisive role in its distribution. Using the MaxEnt model this study predicted that under three future climate scenarios (SSP1-2.6, SSP3-7.0, and SSP5-8.5), the distribution of P. solenopsis will expand and move towards higher latitudes. Climate change is the primary factor influencing changes in pest distribution. We conducted a meta-analysis of P. solenopsis, including seven independent studies covering 221 observation results, and examined the impact of temperature ranging from 18 °C to 39 °C on the developmental cycle of P. solenopsis. As the temperature rises, the development cycle of P. solenopsis gradually decreases. Additionally, by combining the MaxEnt model, we predicted the current and potential future distribution range of P. solenopsis. The results show that under future climate warming, the distribution area of P. solenopsis in China will expand. This research provides a theoretical basis for early monitoring and control of this pest's occurrence and spread. Therefore, the predictive results of this study will provide important information for managers in monitoring P. solenopsis and help them formulate relevant control strategies.

A Sister Species for the Blue Crab, Callinectes sapidus? A Tale Revealed by Mitochondrial DNA.

The Atlantic blue crab, Callinectes sapidus, is acknowledged as one of the worst invasive alien species in the Mediterranean, impacting biodiversity and human activities. Native to the western Atlantic, it has expanded to European coastal waters since the early 1900s. Despite its ecological and commercial importance, genetic research on this species is limited. Here we show a comprehensive investigation of the genetic variation and evolutionary history in Callinectes sapidus using 667 mitochondrial COI gene sequences. Our dataset encompasses 36 newly generated sequences from previously understudied Mediterranean sites and 631 from worldwide locations obtained from the GenBank public database. Our findings reveal two distinct, but closely related, genetic groups within the species' distribution range, suggesting the occurrence of a potential species complex. Furthermore, in the Mediterranean, low levels of genetic variability were observed except for substantial haplotypic differentiation in Turkish samples. This study depicts the global genetic diversity and evolutionary patterns of Callinectes sapidus, offering new insights into the taxonomic status of the species.

Decline in the West Greenland population of a zooplanktivorous seabird, the little auk Alle alle

The warming of the Arctic had lead to a diverse range of impacts on local biota, including northward shifts of some species range. Here, we report past and present distribution and abundance of an Arctic zooplanktivorous seabird, the little auk Alle alle in West Greenland south of 74° N, and examine the changes in sea surface temperature (SST) and sea ice concentration (SIC) in the birds foraging areas in 1850–2007. We estimated the little auk population in the studied region to be 5,200 pairs in the 1930s, 6,000–6,500 pairs in the 1940-1970s and 70–80 pairs by the 2000s. We found that periods with increased SST and reduced SIC, especially in the last few decades, coincided with little auk population declines. Besides, years with little auk presence in breeding sites were characterized by either low SST and low to moderate SIC or higher SST but moderate to high SIC. Observed contraction of the breeding range and a decrease in abundance of the little auk may be attributed to more complex climate-driven changes in the marine ecosystem at finer spatial and temporal scales and/or cannot be easily detected given the coarseness of data used. It is possible that the population in this region has never been very numerous being subjected to local impacts such as disease, bycatch, predation, etc. The climate warming that is currently being observed, along with corresponding shifts in zooplankton communities, may lead to extirpation of the studied little auk populations.

The Origin of the Problem: Characterization of Paraguayan Septoria steviae, Causal Agent of Septoria Leaf Spot of Stevia, Based on Multilocus Sequence Analysis.

Septoria leaf spot is a significant disease affecting cultivated stevia, potentially reducing yields by > 50%. The disease is caused by Septoria steviae, first identified in 1978 in Japan as a new pathogen of stevia. Understanding the origin of S. steviae could clarify how it spread to new production areas. To investigate this, 12 isolates of Septoria sp. were obtained from stevia's native range in the Amambay forests and field plantings in Paraguay from 2018 to 2020. These isolates underwent colony morphology and molecular characterization of Actin, β-Tubulin, Calmodulin, ITS, LSU, RPB2, and TEF1α loci. GenBank sequences from S. steviae isolates collected in France, Japan, and the United States were included. Multilocus sequence phylogenetic analysis generated a maximum likelihood (ML) tree. The morphological characteristics of Paraguayan isolates were similar to those of previously reported S. steviae type cultures from Japan. The ML analysis showed that Paraguayan isolates formed a monophyletic group with S. steviae isolates from France, Japan, and the United States. During blotter tests, pycnidia and cirri of S. steviae were observed on multiple stevia seed surfaces from different sources. Further characterization confirmed viable pathogenic conidia of S. steviae. This observation suggests that S. steviae could be associated with stevia seed, possibly spreading from the center of origin to other countries. This research is the first to genetically characterize S. steviae from Paraguay and propose its potential spread mechanism from the center of origin to the rest of the world.

Microstructure Evolution and Tensile Properties of Medium Manganese Steel Heat Treated by Two-Step Annealing

In this paper, the nucleation and growth of austenite are controlled through a two-step annealing process to achieve multi-scale distribution and content increase of retained austenite in low manganese series medium-Mn steel. Combining SEM, EBSD, AES, and other experimental equipment, the evolution rules of the microstructure, properties, and element distribution behavior of the test steel during the annealing process are studied. Compared with one-step annealing, the two-step annealing significantly broadens the size distribution range of retained austenite. In the first step, after annealing at a higher intercritical temperature (760 °C), the ferrite and the M/A island are obtained, completing the initial partition of Mn and the refinement of microstructures. During the second step of annealing (720 °C), the primary Mn-rich martensite region provides higher nucleation driving force and finer dispersed nucleation sites, promoting the nucleation and growth of reverse transformation austenite. At the same time, the metastable-retained austenite formed after the first step of annealing continues to grow through interface movement. Furthermore, a high proportion (23.4%) of retained austenite with multi-scale distribution is formed in the final microstructure, and the product of strength and elongation increased from 21.8 GPa·% by the one-step annealing process to 30.1 GPa·%.