Species Complex Research Articles

Performance of the VITEK® MS system for the identification of filamentous fungi in a microbiological laboratory in Chile

Filamentous fungi are an emergent cause of severe infections in immunocompromised patients. Timely and accurate identification is crucial to initiate appropriate therapy. Traditional identification methods are time-consuming, labor-intensive, and operator-dependent. Matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometry is a rapid and easy-to-perform identification method. The effectiveness of a commercial MALDI-TOF MS platform to identify filamentous fungi in a clinical laboratory was evaluated. The study included 67 fungal isolates from 35 species/species complexes, which were identified and confirmed in mycology reference laboratories; 32 derived from clinical samples, 34 from strain collections and one was an ATCC strain. The study used the VITEK® MS system (v3.2.0 database), after sample extraction by VITEK® MS Mould Kit. Results were classified as “correct species”, “correct species complex”, “correct genus”and “no identification”. VITEK® MS correctly identified 91.0% of isolates (58.2% to species, 29.9% to species complex, and 1.5% to genus level only). In 82%, the result matched the species/species complex identified by reference methods. No misidentifications were observed. The kit was rapid and easy to use. In conclusion, the VITEK® MS system showed a high capability to accurately identify filamentous fungi in a clinical laboratory.

Shedding Light into the Confusing History of <i>Pelodiscus axenaria</i> (Zhou, Zhang et Fang, 1991), Clarifying and Correcting Its Taxonomic Position within the <i>P. axenaria</i> Complex with the Description of Yet Another <i>Pelodiscus</i> Species

The softshell turtle genus Pelodiscus has a long and complex taxonomic history. It was long believed that no specimens of the original description of Pelodiscus axenaria exist and as such, a detailed description and molecular phylogenetic analysis of P. axenaria from its type specimen locality Taoyuan, Hunan, China, were not possible. Recent studies revealed that P. axenaria belongs to a species complex comprising at least four morphologically challenging but genetically divergent lineages. In this study, we redescribe the original type specimen series (4 males and 6 females) of P. axenaria from Yuanjiang area of Taoyuan based on morphological and molecular evidence. Our molecular phylogenetic analysis provided evidence that Pelodiscus shipian and Pelodiscus jiangxiensis clearly cluster within our P. axenaria clade and as such should be regarded as junior synonyms of Pelodiscus axenaria. The specimens that Gong et al. (2022) regarded as P. axenaria in their studies, clearly represent a new and herein newly described species. The proposed neotype of P. axenaria by Gong et al. (2022), which represents this new species, is designated as the holotype of this new species, Pelodiscus huike sp. nov.

Species diversity in the new lamprey genus Occidentis, formerly classified as western North American ‘Lampetra’

Accurate taxonomy is fundamental to the study and conservation of biodiversity. Because of their morphological similarities, most brook and river lampreys in western North America have been placed in the genus Lampetra along with lampreys from Eurasia and eastern North America. However, molecular-based phylogenetic studies dating back several decades indicate that lampreys from Pacific drainages are genetically distinct from Atlantic Lampetra. Reviewing previous phylogenetic analysis of two mitochondrial and two nuclear genes for Northern Hemisphere lampreys, we assign these western North American brook and river lampreys to a new genus, Occidentis. To assess species diversity within Occidentis, we performed a species delimitation analysis using all publicly available cytochrome b sequences of the genus. Similar to previous studies, O. ayresii and O. richardsoni were not reciprocally monophyletic and are best categorized as life history variants of a single species. In addition to O. pacifica, O. hubbsi, and the diverse O. ayresii species complex, as many as seven undescribed candidate species from Oregon and California were identified, supporting results from previous studies with more geographically limited datasets. One specimen from Paynes Creek, California, was identified as a candidate species, although this single individual showed minimal interspecific divergence (1.34%) with O. hubbsi. Further genetic assessment along with information on morphology and phylogeography is needed to determine whether the variation observed between groups of candidate species represents distinct species or divergent lineages within a species complex. Additional sampling will inform whether there are additional species not currently represented in this dataset. Thus, the number of species formally recognized under Occidentis is subject to change with new information. Systematic assessment of the distribution and phylogenetic complexity within Occidentis will enhance our understanding of its evolutionary history and taxonomic diversity, which will guide efforts to conserve the biodiversity of lampreys.

Multiple old differentiation centres around the Alps and complex range expansion patterns in a semi-aquatic insect: the phylogeny and biogeography of the Wormaldia occipitalis species complex (Trichoptera)

The understanding of cryptic species complexes with their often highly interesting biogeographical patterns is still a crucial aspect in evolutionary biology and related disciplines. Trichoptera are a group of insects particularly rich in unresolved groups. One example is the Wormaldia occipitalis species complex in which morphological studies suggest remarkable patterns of differentiation. In order to determine genetic differentiation and phylogenetic structure, one mitochondrial (COI) and two nuclear markers (CAD, wingless) were analysed for the W. occipitalis species complex around the Alps and northwards to Germany. The morphology-defined differentiation pattern was also observed at the genetic level. The morphologically well distinguishable groups W. occipitalis and W. subterranea were identified as two genetically distant monophyletic groups with about 10 % genetic divergence of the mitochondrial marker. These two taxa likely split during the Mio-Pliocene transition. Genetic analyses revealed four subgroups within W. occipitalis and three within W. subterranea. Several possible postglacial dispersal and differentiation processes are proposed. Thereby, W. occipitalis from the western Alps and individuals of W. subterranea from the eastern Alps spread towards Central Europe after the Last Glacial Maximum. Today, both species groups are sympatric and partly syntopic in the recolonised area in western Germany but apparently allopatric in their centres of origin around the Alps. The high genetic differentiation, lack of detectable genetic evidence for hybridisation, their syntopic distribution and the morphological distinctness indicate that W. occipitalis and W. subterranea are two distinct species. The genetically determined subgroups might represent subspecies.

Identification and Characterization of Endophytic Fungus DJE2023 Isolated from Banana (Musa sp. cv. Dajiao) with Potential for Biocontrol of Banana Fusarium Wilt

This study characterized an endophytic fungus, DJE2023, isolated from healthy banana sucker of the cultivar (cv.) Dajiao. Its potential as a biocontrol agent against banana Fusarium wilt was assessed, aiming to provide a novel candidate strain for the biological control of the devastating disease. The fungus was isolated using standard plant tissue separation techniques and fungal culture methods, followed by identification through morphological comparisons, multi-gene phylogenetic analyses, and molecular detection targeting Fusarium oxysporum f. sp. cubense (Foc) race 1 and race 4. Furthermore, assessments of its characteristics and antagonistic effects were conducted through pathogenicity tests, biological trait investigations, and dual-culture experiments. The results confirmed isolate DJE2023 to be a member of the Fusarium oxysporum species complex but distinct from Foc race 1 or race 4, exhibiting no pathogenicity to banana plantlets of cv. Fenza No.1 or tomato seedlings cv. money maker. Only minute and brown necrotic spots were observed at the rhizomes of banana plantlets of ‘Dajiao’ and ‘Baxijiao’ upon inoculation, contrasting markedly with the extensive necrosis induced by Foc tropical race 4 strain XJZ2 at those of banana cv Baxijiao. Notably, co-inoculation with DJE2023 and XJZ2 revealed a significantly reduced disease severity compared to inoculation with XJZ2 alone. An in vitro plate confrontation assay showed no significant antagonistic effects against Foc, indicating a suppressive effect rather than direct antagonism of DJE2023. Research on the biological characteristics of DJE2023 indicated lactose as the optimal carbon source for its growth, while maltose favored sporulation. The optimal growth temperature for this strain is 28 °C, and its spores can germinate effectively within the range of 25–45 °C and pH 4–10, demonstrating a strong alkali tolerance. Collectively, our findings suggest that DJE2023 exhibits weak or non-pathogenic properties and lacks direct antagonism against Foc, yet imparts a degree of resistance against banana Fusarium wilt. The detailed information provides valuable insight into the potential role of DJE2023 in integrated banana disease control, presenting a promising candidate for biocontrol against banana Fusarium wilt.

A Genetic Polymorphism Underlying Alternative Reproductive Tactics in Eurycea Salamanders.

Alternative reproductive tactics are discrete, intrasexual differences in reproductive behaviour within a population. In some cases, these complex phenotypes are determined by autosomal supergenes or sex chromosomes-both of which exhibit reduced recombination and thus enable the linked inheritance of co-adapted alleles from multiple loci. Most alternative reproductive tactics in amphibians are plastic (and reversible), environmentally determined and lacking morphological differentiation, but a striking exception is found in the two-lined salamander (Eurycea bislineata) species complex. In some populations, two distinct male phenotypes coexist: 'searching' males have mental glands, protruding premaxillary teeth and elongate cirri used in terrestrial courtship, while 'guarding' males lack these traits and instead have hypertrophied jaw musculature used in mate guarding at aquatic nesting sites. These tactics differ in many morphological and behavioural phenotypes, but their proximate cause has not yet been described. Here, we generated genome-wide SNP data from > 130 Eurycea cf. wilderae collected from Highlands Biological Station. We provide evidence for an XY sex determination and for a Y-linked polymorphism underlying alternative reproductive tactics in this population. We then develop and validate a PCR-based genotyping assay and apply it to characterise the sex ratio and relative frequency of male tactics from a sample of larvae. Our results add to the growing body of literature exploring the importance of supergenes and sex chromosomes in complex intraspecific polymorphisms, and we highlight opportunities for future work to continue exploring the genomic architecture of these traits.

Redescription and validity of Formosania gilberti Oshima, 1919 (Cypriniformes: Balitoridae), an endemic hillstream loach from Taiwan

For over a century, only one species of Formosania has been recognised in Taiwanese waters. However, through the use of mitogenomic analyses and the identification of morphological differences, an endemic balitorid loach was revalidated and redescribed based on specimens herein of northern Taiwan. Formosania gilberti Oshima, 1919 was previously mistreated as a junior synonym of F. lacustris (Steindachner, 1908), but the two can be clearly differentiated by their vertebral counts (26+11 vs. 26+12) and body marking patterns (intensely mottled with vermicular markings vs. cloud-like blotches or brown and blotchless). Furthermore, mitogenomic analyses also showed high intra-specific diversity among Formosania loaches in Taiwan, which not only supports F. gilberti as a valid species but also hints the presence of a species complex distributed in western Taiwan.

Description of a new uniformly brown estuarine moray eel (Anguilliformes, Muraenidae) from the Central Indo-Pacific Ocean.

A new estuarine moray eel, Uropterygiushades sp. nov., is described based on 14 specimens from Japan, Taiwan, the Philippines, southern Indonesia, and Fiji. It is a small-bodied, slender, uniformly dark-brown moray separated from congeners within the U.concolor species complex. The new species can be distinguished from congeners by the anteriorly positioned small eyes (5.0-7.2% of head length), absence of branchial pores, and extended inner rows of teeth which reach the posterior end of the jaws. Uropterygiushades sp. nov. represents a rare species of moray eel that inhabits turbid estuarine environments, preferring soft, muddy substrates, and burrowing and hiding among rocks or in fallen mangrove leaves. Additionally, Uropterygiusmactanensis Huang, Balisco, Evacitas & Liao, another species recently separated from the U.concolor species complex, is reported for the first time from Iriomote Island in the Ryukyu Archipelago based on two specimens; this new record expands the geographic range of U.mactanensis from the central Philippines to southern Japan.

Ralstonia solanacearum Species Complex in Australia.

The Ralstonia solanacearum species complex (RSSC) causes vascular wilt of many crops and is considered one of the most destructive plant pathogenic bacteria worldwide. The species complex was recently resolved into a stable taxonomy of three species aligning with the previously determined phylotypes, namely R. solanacearum (phylotype II), R. pseudosolanacearum (phylotype I and III), and R. syzygii (phylotype IV). Knowing which Ralstonia species and subspecies are established in Australia is important to Australia's biosecurity and market access. The goal of this study was to analyze Australia's Ralstonia culture collections and to assign the isolates to the modern taxonomic groups. The results shed light on the identity, distribution, and pathogenicity of the Ralstonia strains in Australia. Ralstonia solanacearum, R. pseudosolanacearum phylotype I, and R. syzygii phylotype IV-11 are present in Australia but have limited geographic ranges. We identified two aberrant RSSC strains that have genetic similarity to R. syzygii based on sequevar analysis, but do not yield a phylotype IV multiplex PCR band, similar to the known aberrant strain ACH732. The aberrant strains may represent a novel species. Three new sequevars were determined, 72, 73, and 74. Several Ralstonia lineages remain undetected in Australia, providing evidence that they are absent. These include R. pseudosolanacearum phylotype III and the phylotype I mulberry infecting strains; R. solanacearum strains IIC and the Moko causing strains; and R. syzygii subsp. celebesensis, and R. syzygii subsp. syzygii. This study fulfilled Koch's postulates for the Australian strains, R. solanacearum wilted potato plants, and R. pseudosolanacearum wilted blueberry plants, the hosts from which they were initially isolated. The data supports the hypothesis that Australia has native and introduced strains of Ralstonia.

Phylogeny and Taxonomy of the Naematelia aurantialba Complex in Southwestern China

Naematelia aurantialba and its allies are important edible and medicinal mushrooms in China. They are usually called Jiner (金耳) and have been cultivated on a commercial scale. However, due to the lack of DNA sequences from the holotype of Naematelia aurantialba, the taxonomic issues of the species complex are unresolved. In this study, the authors successfully generated DNA sequences from the holotype of N. aurantialba by a genome skimming approach and additional allied species by Sanger sequencing. Based on morphological characteristics, molecular phylogenetic data, and geographic distribution patterns, four species, including three new ones, in the complex in southwestern China were uncovered. Naematelia aurantialba occurs at high altitudes (over 3000 m above sea level), with subalpine dead plants as its substrates, and has larger basidiospores, while the commonly cultivated species, described as N. sinensis in this work, is distributed in subtropical areas at altitudes between 1800 m and 2600 m on the dead wood of subtropical plants and has smaller basidiospores. The third species, namely N. nodulosa, has habitats similar to those of N. sinensis but differs from the latter in its basidiomata with an uneven nodulose surface, a loose context with small internal cavities, and numerous conidia. The fourth species, N. pedicellata, is easily distinguished from the others by its basidia, with long basal stalks and broadly ellipsoid basidiospores measuring 10.5–12.5 × 8.0–10.0 μm. All these species are parasitic on Stereum species. This study provides a solid basis for future guidance for the selection of new strains and cultivation practices of these valuable fungi.

Genetic variation within the arctic-alpine Calamagrostis stricta (Poaceae) species complex in Europe

The Calamagrostis stricta (Poaceae) species complex is a circumpolar, boreo-arctic and montane taxon that includes numerous subspecies and varieties. The recent discovery of Calamagrostis lonana in the Alps calls for a thorough assessment of relationships within C. stricta. The main aim of our study was to elucidate the phylogenetic position, genetic structure and ploidy level of C. lonana, as compared to the other members of the C. stricta species complex from Central Europe to the Arctic. Fifteen populations of the C. stricta species complex were sampled across Central and Northern Europe, and their ploidy level was estimated using flow cytometry. Genetic variation was characterized using double digest RAD sequencing reads (ddRAD-seq) on a total of 115 individuals genotyped at 1157 single-nucleotide polymorphisms. Based on flow cytometric measurements, tetraploidy was observed in Arctic populations from Northern Europe and C. lonana in the Alps, in contrast to other populations exhibiting higher ploidy levels. Calamagrostis lonana was genetically closely related to the arctic C. stricta subsp. groenlandica, while C. stricta subsp. stricta formed a second genetic cluster across Central Europe. A third, very distinct genetic cluster was observed in the northern Svalbard archipelago. Despite lacking evidence of sexual reproduction, substantially more genetic diversity than expected under asexual reproduction was detected within populations in C. lonana and other taxa. The distribution and genetic structure of the C. stricta species complex has been shaped by major post-glacial environmental changes having affected cold regions and specifically highlights C. lonana as a valuable relict taxon for the Alps.

Composition and antimicrobial activity of hydroalcoholic extracts of Pleurotus eryngii var. ferulae and P. eryngii var. elaeoselini.

The basidiomycetes Pleurotus eryngii var. ferulae Lanzi and P. eryngii var. elaeoselini Venturella et al. belong to the P. eryngii species complex, acting as facultative biotrophs in association with members of Apiaceae family, i.e., Ferula communis L. and Elaeoselinum asclepium L., respectively. The consumption of these fungi has rapidly increased in recent decades, not only thanks to their nutritional properties and pleasant flavor, but also for their bioactive and medicinal properties. A quantitative study of their hydroalcoholic extracts was carried out by liquid chromatography-mass spectrometry. The potential antimicrobial activity of the extracts was also tested against some phytopathogenic bacteria [Clavibacter michiganensis and Bacillus megaterium (Gram-positive), Pseudomonas viridiflava, Xanthomonas campestris, and Escherichia coli (Gram-negative)] and fungi (Aspergillus fumigatus, Penicillium italicum, Monilinia laxa, Botrytis cinerea, Cadophora sp., and Sclerotinia sclerotiorum). The chemical analysis allowed the identification of secondary metabolites belonging to different classes, as flavonoids, organic acids, amino acids, carbohydrates, vitamins, nucleic acids, fatty acids, and triterpenoids. Both extracts demonstrated antimicrobial activity against of the most tested microorganisms. The results can broaden the knowledge on the possible use of these fungal species in the agricultural sector.

Molecular Identification of Mosquitoes (Diptera: Culicidae) Using COI Barcode and D2 Expansion of 28S Gene

The purpose of this study is to improve the identification of Culicidae species from the Vale Ribeira region, São Paulo state, Brazil. Adults were collected in the municipalities of Cananeia and Pariquera-Açu and morphologically identified. Molecular analyses were performed on sequences of COI barcode and a fragment of the D2 expansion of the 28S ribosomal RNA gene generated from field collected mosquitoes. The analyses included species delimitation, phylogeny, and interspecific genetic distances using the Kimura 2-parameter model. Species included in the analyses were Aedes perventor, Aedes scapularis, Aedes serratus/Aedes nubilus, Aedes serratus s.s., Aedes terrens, Haemagogus capricornii, Haemagogus leucocelaenus, Haemagogus janthinomys, Kerteszia bellatrix, Kerteszia cruzii, Psorophora ferox, Psorophora forceps, Sabethes conditus, and Wyeomyia confusa. COI sequences from specimens collected at other localities were included in the analysis for comparison. Results of barcode RESL analysis showed that specimens of Ps. ferox and Hg. janthinomys split into three clusters for each species. Similarly, sequences of Ke. bellatrix and Ke. cruzii were recovered in two groups for each species. Distinct from other species included in analyses, Ps. ferox and Ps. forceps shared 100% similarity in the D2 fragment sequenced. Overall, the analysis of COI barcode sequences revealed the following key findings: (1) the presence of subclades within Hg. janthinomys, with its division into three groups suggests that this species may represent a species complex; (2) Ke. bellatrix from the Atlantic tropical rainforest shares 95.59% sequence similarity with a specimen from the type locality, indicating that specimens from Southeastern Brazil may belong to an unidentified species within the Ke. bellatrix complex; (3) Ke. cruzii also represents a species complex; and (4) D2 sequences successfully identified most species studied, apart from Ps. forceps and Ps. ferox.

A Comparative Analysis of Mitogenomes in Species of the Tapinoma nigerrimum Complex and Other Species of the Genus Tapinoma (Formicidae, Dolichoderinae)

Using next-generation sequencing data, the complete mitogenomes of six species from the genus Tapinoma were assembled. This study explores the mitochondrial genomes of Tapinoma species, among them the five species from the Tapinoma nigerrimum complex, comparing them with each other and with other species from Dolichoderinae subfamily to understand their evolutionary relationships and evolution. Tapinoma mitochondrial genomes contain the typical set of 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNAs, and the A + T-rich control region. A phylogenetic analysis using the protein-coding gene sequences from available Dolichoderinae mitogenomes supports the monophyletic nature of the genus Tapinoma, with the T. nigerrimum complex forming a well-supported clade. Key findings include genetic traits unique to the T. nigerrimum complex, such as a start codon in the atp8 gene and a complete stop codon in cox1, distinguishing them from other Tapinoma species. Additionally, a gene rearrangement involving tRNA-Trp, tRNA-Cys, and tRNA-Tyr was found exclusively in the Tapinoma species, suggesting a potential phylogenetic marker for the genus.

Lavandula angustifolia oil induces oxidative stress, stiffening of membranes, and cell wall in Cryptococcus spp.

The Cryptococcus neoformans and Cryptococcus gattii species complexes are the etiological agents of cryptococcosis, a disease responsible for 181 000 deaths annually worldwide due to late diagnosis and limited treatment options. Studies focusing on the identification of new substances with antifungal activity, such as essential oils (EOs), are urgently needed. While the antifungal effects of EO have already been suggested, their mechanism of action at the molecular level still requires evaluation. In this work, we assessed the molecular changes induced by the exposure of Cryptococus neoformans (H99) and Cryptococcus deuterogatti (R265) to lavender essential oil (LEO) using a morphological and proteomics approach. The identified proteins were categorized by Gene Ontology according to biological processes and molecular functions, and Kyoto Encyclopedia of Genes and Genomes pathway analysis was also conducted. Our findings indicate that LEO creates a stressful environment in both strains; however, the response to this stimulus differs between the two species. In C. neoformans, changes were observed in energy metabolism and pathways related to alternative sources of energy and oxidative stress response. In C. deuterogatti, changes were identified in pathways related to cellular architecture, implying that the cell underwent morphological changes such as membrane and cell wall stiffening.

Bromeliad rosettes as shelters for hylid treefrogs during a heat wave in the Brazilian Pantanal

During a heat wave in November 2023, we assessed the use of bromeliad rosettes as shelters for hylid treefrogs in the Brazilian Pantanal (area of Nhecolândia). During the day time, four hylid species (genera Boana, Scinax, Trachycephalus) were detected sheltering in 40 rosettes of the terrestrial bromeliad Bromelia balansae; this was a different species complex from when observations were made in October 2019 when the temperature conditions corresponded to long-term averages. The internal and external day time temperature of each shelter was measured. The mean daytime temperature inside the shelters was 36.1 °C (range 24.0–43.5 °C), this varied depending on the microhabitat conditions, and was 1.1 °C lower than the mean temperature of the leaves of the upper part of the rosettes; the difference was statistically significant. We suggest that during this very dry and hot period the main advantage provided by the bromeliad shelters was to enable frogs to have behavioural control of overheating so that they could avoid excessive evaporative water loss.

Mycological and Genomic Characterization of Fusarium vorosii, a Potentially Pathogenic Fungus, Isolated from Field Crops and Weeds in Korea.

Fusarium vorosii (Fv) is one of the least studied species of the Fusarium graminearum species complex, a major plant pathogen causing Fusarium head blight (FHB) in a variety of crops. In this study, we isolated 12 strains of Fv from cereal samples with FHB symptoms and gramineous weeds. Trichothecene genotyping of Fv strains showed that 10 strains were nivalenol (NIV) type and 2 strains were 15-acetyldeoxynivalenol (15ADON) type. Fv strains have similar mycological characteristics to Fusarium asiaticum, a major FHB pathogen of rice in Asia, however, asexual sporulation was at least 100 to 1,000 times higher in Fv. In comparison of pathogenicity, the Fv-15ADON type was more pathogenic than the NIV type in both rice and wheat, and had a similar level of pathogenicity as the F. asiaticum-NIV type. Among the 12 Fv strains, two representative ones, Fv-NIV type RN1 and Fv-15ADON type W15A1, were selected and their whole genomes were sequenced and analyzed. Complete genome sequences of two Fv strains, RN1 and W15A1, were assembled at the chromosome level with high quality compared to known Fv genomes. The genome data of the two Fv strains were compared with the reference strains already known. As a result of comparative genome analysis, it was found that they are phylogenetically related according to the trichothecene biosynthetic gene cluster, that is, toxin chemotype. Through this study, we provided important information about Fv species that can be potential pathogens in domestic crops about biological and genomic characteristics.

The type III effector RipBB from Ralstonia pseudosolanacearum inhibits plant immunity responses and contributes to virulence on peanut

AbstractRalstonia solanacearum species complex (RSSC) is a serious soilborne phytopathogen affecting over 310 plant species. R. pseudosolanacearum is one clade of RSSC, which infects the important oil crop peanut. A variety of virulence factors are employed by RSSC to promote disease, among which type III effectors (T3Es) are prominent. How T3Es manipulate the interaction between R. pseudosolanacearum and peanut is unclear. A T3E RipBB was previously found specifically in a more virulent peanut R. pseudosolanacearum PeaFJ1 strain. In the present study, the function of RipBB was analysed. Loss of RipBB from PeaFJ1 strain resulted in attenuated pathogenicity to peanut, and complementation with RipBB recovered the virulence of the mutant strain. Transient expression of RipBB induced cell death and inhibited flg22‐triggered reactive oxygen species (ROS) burst in the leaves of Nicotiana benthamiana. The expression of pattern‐triggered immunity (PTI)‐related genes were also suppressed by RipBB transient expression. Among the available sequenced 639 RSSC strains, RipBB is an infrequent T3E that is only present in eight strains. Two ankyrin (ANK) repeats were identified in RipBB, which play an important role in localizing the protein to the cytomembrane and nucleus. Altogether, we verified that RipBB contributes to infecting peanut by acting as a virulence T3E, and causes cell death and suppresses immunity in N. benthamiana. These results enhance the study of ANK‐containing effectors. Further elucidation of the molecular mechanisms underlying RipBB effect on immunity may reveal ANK‐containing effector functions in host cells, helping to understanding the mechanism of R. pseudosolanacearum–peanut interaction.

A core genome MLST scheme for Borrelia burgdorferi sensu lato improves insights into the evolutionary history of the species complex.

Multi-locus sequence typing (MLST) based on eight genes has become the method of choice for Borrelia typing and is extensively used for population studies. Whole-genome sequencing enables studies to scale up to genomic levels but necessitates extended schemes. We have developed a 639-loci core genome MLST (cgMLST) scheme for Borrelia burgdorferi sensu lato (s.l.) that enables unambiguous genotyping and improves the robustness of phylogenies and lineage resolution within species. Notably, all inner nodes of the cgMLST phylogenies had consistently high statistical support. Analyses of the genetically homogeneous European B.bavariensis population support the notion that cgMLST provides high discriminatory power even for closely related isolates. While isolates differed maximally in one MLST locus, there were up to 179 cgMLST loci differences. Thus, the developed cgMLST scheme for B.burgdorferi s.l. resolves lineages at a finer resolution than MLST and improves insights into the evolutionary history of the species complex.

Unraveling enigmatic disjunctions: Population genetic analysis points to independent origins of rare rhododendrons in the Rhododendron keiskei complex (Ericaceae)

AbstractUnraveling species boundaries is pivotal for evolutionary biology and conservation endeavors. However, it proves challenging in instances where recent speciation is intertwined with complex demographic histories and natural selection processes. The Rhododendron keiskei complex, an evergreen rhododendron distributed in East Asia, consists of a widespread variety (R. keiskei var. keiskei) and a more restricted R. keiskei var. hypoglaucum. Intriguingly, the latter is exceptionally rare yet displays a disjunction that spans approximately 1100 km. This study aimed to elucidate the evolutionary backgrounds of the enigmatic disjunctions of R. keiskei var. hypoglaucum and to propose species delimitation within the species complex. An integrative approach, combining genomic data (MIG‐seq and GBS‐derived SNPs) with Scanning Electron Microscopy analysis of leaf microstructures was adopted in this study. Phylogenetic analyses revealed significant divergence among the studied rhododendrons. Genetic demographic analyses favored the population models that assumed non‐monophyly of two disjunct populations of R. keiskei var. hypoglaucum indicating their independent origins. Recent gene flow between the widespread R. keiskei var. keiskei and “var. hypoglaucum” populations were limited due to geographic and habitat isolation factors, even in areas where their distributions overlap. Detailed morphological assessments detected distinctions between morphologically similar “var. hypoglaucum” populations based on leaf microstructures and flowering habits. Our study has shown that the apparent disjunctions of rare rhododendrons are more likely attributed to morphological convergence, possibly due to similar environmental selections in unrelated taxa. The finding highlights the importance of an integrative approach for resolving taxonomic challenges in plant species complexes.