Initial Speciation Research Articles

Reconciling Santa Rosalia: Both Reproductive Isolation and Coexistence Constrain Diversification.

AbstractUnderstanding patterns of diversification necessarily requires accounting for both the generation and the persistence of species. Formal models of speciation genetics, however, focus on the generation of new species without explicitly considering the maintenance of biodiversity (e.g., coexistence, the focus of ecological studies of diversity). Consequently, it remains unclear whether and how new species will coexist following a speciation event, a gap limiting our ability to understand the rate-limiting controls of diversification over macroevolutionary timescales. To connect coexistence and speciation theory and assess the relative importance of ecological versus genetic constraints in diversification events, we develop a deterministic, three-locus, population-genetic model that includes a skewed distribution of available resources (to generate variation in fitness differences), frequency-dependent competition, and assortative mating. Both ecology and genetics play vital and interacting roles in shaping initial speciation events and long-term eco-evolutionary outcomes. Ecological constraints are especially important when fitness differences are large and competition remains strong among dissimilar phenotypes. Ephemeral species can occur in our model and are typically lost because of competitive exclusion, a result demonstrating that species persistence may serve as the rate-limiting control of long-term diversification rates. More broadly, our model adds evidence that the unification of ecological and evolutionary (including genetic) perspectives on biodiversity is needed to predict large-scale patterns.

The Multifaceted Role of Boric Acid in Nickel Electrodeposition and Electroforming

This study involved an investigation of the role of boric acid in nickel electroforming from sulfamate electrolytes, especially in relation to its ability to minimise interfacial pH changes during electrodeposition. Initial speciation calculations indicated that buffering by polyborate species and nickel-borate complexes are most likely responsible for this effect. However, the concentration of nickel-borate complexes was too low even at elevated pH to be a significant electroactive species. Polarisation and electrochemical quartz crystal microbalance measurements indicated that, in the absence of boric acid, electrodeposits typically contained Ni(OH)2, while boric acid additions resulted in pure Ni being deposited with a current efficiency approaching unity. Boric acid additions substantially modified the nickel and hydrogen partial currents, and influenced the overall current efficiency. Studies in nickel-free solutions indicated that boric acid adsorbs on the surface which explains the suppression of H2O reduction observed in the electroforming experiments. Collectively, solution buffering due to polyborate and nickel-borate species and inhibition of H2O reduction by adsorbed boric acid minimised interfacial pH changes and prevented the formation of nickel hydroxide.

Phylogenetic climatic niche evolution and diversification of the Neurergus species (Salamandridae) in the Irano-Anatolian biodiversity hotspot.

This study explores how climate variables influenced the evolution and diversification of Neurergus newts within the Irano-Anatolian biodiversity hotspot. We use a dated phylogenetic tree and climatic niche models to analyze their evolutionary history and ecological preferences. Using genetic data from nuclear (KIAA) and mitochondrial (16s and 12s) genes, we estimate divergence times and identify four major Neurergus clades. The initial speciation event occurred approximately 11.3 million years ago, coinciding with the uplift of the Zagros and Anatolian mountains. This geological transformation isolated newt populations, likely triggering the first speciation event. By integrating potential geographic distribution with climate variables, we reconstruct ancestral niche occupancy profiles. This highlights the critical roles of temperature and precipitation in shaping Neurergus habitat preferences and distribution. We observe both phylogenetic niche conservatism and divergence, with niche divergence playing a dominant role in diversification. This research emphasizes the complex interplay of geography, climate, and ecology in speciation and the vulnerability of isolated mountain newt populations to environmental changes.

Multilocus Sequence Analysis of Aspergillus Species from Clinical Samples and the Surge of Cryptic Aspergillosis in Southern India: A Descriptive Cross-sectional Study

Introduction: Aspergillus species cause a broad range of infections, from Allergic Bronchopulmonary Aspergillosis (ABPA) to invasive aspergillosis. Accurate species-level identification is crucial for diagnosis and treatment, especially since some rare Aspergillus species exhibit increased resistance to common antifungal agents. Aim: To identify Aspergillus species at the species complex level and determine the emergence of cryptic Aspergillus species using Multilocus Sequence Analysis (MLSA). Materials and Methods: This descriptive cross-sectional study was conducted over eight months, from January 2023 to August 2023, in three tertiary care centres in Chennai, India. Sixty Aspergillus strains were isolated from various clinical samples. The primary inclusion criteria were patients with suspected aspergillosis, categorised based on the European Organszation for Research and Treatment of Cancer Mycoses Study Group (EORTC-MSG) criteria. Isolates were grown on Oatmeal Agar or Sabouraud Dextrose Agar (SDA) and phenotypically identified using tease mount and slide culture techniques. Genomic fungal Deoxyribonucleic acid (DNA) was extracted and amplified using specific primers for Internal transcribed spacer (ITS), beta-tubulin, hydrophobin, and calmodulin genes, followed by nucleic acid sequencing. Results: Among the 60 Aspergillus isolates, the Aspergillus flavus complex comprised 26 (43.3%), the Aspergillus fumigatus complex 16 (26.7%), the Aspergillus niger complex 12 (20%), and the Aspergillus terreus complex 6 (10%). Initial speciation relied on microscopic and cultural characteristics. Isolates were recovered from various clinical specimens: bronchial wash 6 (10%), Bronchoalveolar lavage (BAL) fluid 10 (16.7%), sputum 3 (5%), ear swab 20 (33.3%), endotracheal aspirate 8 (13.3%), pus and tissue from the nasal cavity and paranasal sinus 11 (18.3%), and tissue from other sites 2 (3.3%). MLSA identified common species such as A. flavus, A. fumigatus, A. terreus, and A. niger, as well as rare species including A. awamori, A. carneus, A. lentulus, A. oryzae, A. tamarii, A. tubingensis, and A. welwitschiae. Sequence identity ranged from 99% to 100%, confirming species diversity. Phylogenetic analysis using ITS, beta-tubulin, hydrophobin, and calmodulin genes supported species identification with robust bootstrap support (1000 replications). Conclusion: Cryptic Aspergillus species are prevalent in clinical samples from the South Indian population, with a notable presence from the section Nigri and the first-time isolation of Aspergillus carneus in clinical samples from India. Molecular identification is essential for determining the invasive potential and guiding appropriate antifungal therapy.

Extensive Phylogenomic Discordance and the Complex Evolutionary History of the Neotropical Cat Genus Leopardus.

Even in the genomics era, the phylogeny of Neotropical small felids comprised in the genus Leopardus remains contentious. We used whole-genome resequencing data to construct a time-calibrated consensus phylogeny of this group, quantify phylogenomic discordance, test for interspecies introgression, and assess patterns of genetic diversity and demographic history. We infer that the Leopardus radiation started in the Early Pliocene as an initial speciation burst, followed by another in its subgenus Oncifelis during the Early Pleistocene. Our findings challenge the long-held notion that ocelot (Leopardus pardalis) and margay (L. wiedii) are sister species and instead indicate that margay is most closely related to the enigmatic Andean cat (L. jacobita), whose whole-genome data are reported here for the first time. In addition, we found that the newly sampled Andean tiger cat (L. tigrinus pardinoides) population from Colombia associates closely with Central American tiger cats (L. tigrinus oncilla). Genealogical discordance was largely attributable to incomplete lineage sorting, yet was augmented by strong gene flow between ocelot and the ancestral branch of Oncifelis, as well as between Geoffroy's cat (L. geoffroyi) and southern tiger cat (L. guttulus). Contrasting demographic trajectories have led to disparate levels of current genomic diversity, with a nearly tenfold difference in heterozygosity between Andean cat and ocelot, spanning the entire range of variability found in extant felids. Our analyses improved our understanding of the speciation history and diversity patterns in this felid radiation, and highlight the benefits to phylogenomic inference of embracing the many heterogeneous signals scattered across the genome.

Expansion processes of two emblematic Luehdorfia butterflies across the Japanese archipelago

AbstractAimAdaptation to local environments has been considered a driving force of ecological speciation. Previous phylogenetic studies at higher taxonomic levels have strongly suggested that herbivore diversification occurs through local adaptation to host plants. However, whether similar mechanisms contribute to within‐species diversification remains poorly understood. We reconstructed species expansion processes using the phylogenetic relationships between two Luehdorfia butterflies and their host plants and tested the local adaptation hypothesis during species diversification.LocationJapanese archipelago.TaxaLuehdorfia japonica and L. puziloi.MethodsWe analysed mitochondrial DNA and single‐nucleotide polymorphisms to trace the expansion processes of two species in the Japanese archipelago. We analysed data collected during trans‐host plant feeding experiments to test for local host plant adaptation in L. japonica.ResultsLuehdorfia japonica differentiated 17.0 million years ago (MYA) from a group of four Luehdorfia species in East Asia, and L. puziloi differentiated 13.3 MYA from the remaining three species. We observed several genetic groups in both species, reflecting geographical differences among populations. Some host plants had detrimental effects on the pupation rates of L. japonica, demonstrating the presence of genetic barriers between populations of this species.Main ConclusionsAlthough these two sibling species were influenced by the geological formation of the Japanese archipelago, their present population structures differ greatly: L. japonica expanded its distribution and adapted to local host plants along at least four expansion routes independent of host plant phylogeny, and L. puziloi exhibited a more isolated population structure and was less strongly influenced by gene flow among populations. These results suggest that both isolation by distance and isolation by adaptation have been important drivers resulting in the present‐day population structure of L. japonica. Unidirectional gene flow through local adaptation to the host plant may have played a role in initial speciation.

Cryptic Diversity in Paramecium multimicronucleatum Revealed with a Polyphasic Approach.

Paramecium (Ciliophora) systematics is well studied, and about twenty morphological species have been described. The morphological species may include several genetic species. However, molecular phylogenetic analyses revealed that the species diversity within Paramecium could be even higher and has raised a problem of cryptic species whose statuses remain uncertain. In the present study, we provide the morphological and molecular characterization of two novel Paramecium species. While Paramecium lynni n. sp., although morphologically similar to P. multimicronucleatum, is phylogenetically well separated from all other Paramecium species, Paramecium fokini n. sp. appears to be a cryptic sister species to P. multimicronucleatum. The latter two species can be distinguished only by molecular methods. The number and structure of micronuclei, traditionally utilized to discriminate species in Paramecium, vary not only between but also within each of the three studied species and, thus, cannot be considered a reliable feature for species identification. The geographic distribution of the P. multimicronucleatum and P. fokini n. sp. strains do not show defined patterns, still leaving space for a role of the geographic factor in initial speciation in Paramecium. Future findings of new Paramecium species can be predicted from the molecular data, while morphological characteristics appear to be unstable and overlapping at least in some species.

Biogeographic Drivers of Evolutionary Radiations

Some lineages radiate spectacularly when colonizing a region, but others do not. Large radiations are often attributed to species’ adaptation into niches, or to other drivers, such as biogeography including dispersal ability and spatial structure of the landscape. Here we aim to disentangle the factors determining radiation size, by modeling simplified scenarios without the complexity of explicit niches. We build a spatially structured neutral model free from niches and incorporating a form of protracted speciation that accounts for gene flow between populations. We find that a wide range of radiation sizes are possible in this model depending on the combination of geographic isolation and species’ dispersal ability. At extremely low rates of dispersal between patches, each patch maintains its own endemic species. Intermediate dispersal rates foster larger radiations as they allow occasional movement between patches whilst sufficiently restricting gene flow to support further speciation in allopatry. As dispersal rates increase further, a critical point is reached at which demographically identical lineages may vary greatly in radiation size due to rare and stochastic dispersal events. At the critical point in dispersal frequency, some lineages remain a single species for a comparatively long time, whilst others with identical characteristics produce the largest radiations of all via a new mechanism for rapid radiation that we term a ‘radiation cascade’. Given a single species covering many patches connected with gene flow, a radiation cascade is triggered when stochastic dispersal is unusually low for a period, leading to an initial speciation event. This speciation means there are fewer individuals per species and thus further reduced gene flow between conspecifics. Reduced gene flow in turn makes it easier for further speciation to occur. During a radiation cascade, dispersal of individuals between patches continues at the same rate as before, but due to the increasing diversity it primarily introduces novel species that will later speciate, rather than adding to gene flow of existing species. Once a radiation cascade begins, it continues rapidly until it is arrested by a new equilibrium between speciation and extinction. We speculate that such radiation cascades may occur more generally and are not only present in neutral models. This process may help to explain rapid radiation, and the extreme radiation sizes of certain lineages with dispersing ancestors. Whilst niches no doubt play a role in community assembly, our findings lead us to question whether diversification and adaptation into niches is sometimes an effect of speciation and rapid radiation, rather than its cause.

Role of microbial dysbiosis in the pathogenesis of esophageal mucosal disease: A paradigm shift from acid to bacteria?

Genomic sequencing, bioinformatics, and initial speciation (e.g., relative abundance) of the commensal microbiome have revolutionized the way we think about the “human” body in health and disease. The interactions between the gut bacteria and the immune system of the host play a key role in the pathogenesis of gastrointestinal diseases, including those impacting the esophagus. Although relatively stable, there are a number of factors that may disrupt the delicate balance between the luminal esophageal microbiome (EM) and the host. These changes are thought to be a product of age, diet, antibiotic and other medication use, oral hygiene, smoking, and/or expression of antibiotic products (bacteriocins) by other flora. These effects may lead to persistent dysbiosis which in turn increases the risk of local inflammation, systemic inflammation, and ultimately disease progression. Research has suggested that the etiology of gastroesophageal reflux disease-related esophagitis includes a cytokine-mediated inflammatory component and is, therefore, not merely the result of esophageal mucosal exposure to corrosives (i.e., acid). Emerging evidence also suggests that the EM plays a major role in the pathogenesis of disease by inciting an immunogenic response which ultimately propagates the inflammatory cascade. Here, we discuss the potential role for manipulating the EM as a therapeutic option for treating the root cause of various esophageal disease rather than just providing symptomatic relief (i.e., acid suppression).

Amphiphilic Thiol Polymer Nanogel Removes Environmentally Relevant Mercury Species from Both Produced Water and Hydrocarbons.

Technologies for removal of mercury from produced water and hydrocarbon phases are desired by oil and gas production facilities, oil refineries, and petrochemical plants. Herein, we synthesize and demonstrate the efficacy of an amphiphilic, thiol-abundant (11.8 wt % S, as thiol) polymer nanogel that can remove environmentally relevant mercury species from both produced water and the liquid hydrocarbon. The nanogel disperses in both aqueous and hydrocarbon phases. It has a high sorption affinity for dissolved Hg(II) complexes and Hg-dissolved organic matter complexes found in produced water and elemental (Hg0) and soluble Hg-alkyl thiol species found in hydrocarbons. X-ray absorption spectroscopy analysis indicates that the sorbed mercury is transformed to a surface-bound Hg(SR)2 species in both water and hydrocarbon regardless of its initial speciation. The nanogel had high affinity to native mercury species present in real produced water (>99.5% removal) and in natural gas condensate (>85% removal) samples, removing majority of the mercury species using only a 50 mg L-1 applied dose. This thiolated amphiphilic polymeric nanogel has significant potential to remove environmentally relevant mercury species from both water and hydrocarbon at low applied doses, outperforming reported sorbents like sulfur-impregnated activated carbons because of the mass of accessible thiol groups in the nanogel.

Biogeographic barriers, Pleistocene refugia, and climatic gradients in the southeastern Nearctic drive diversification in cornsnakes (Pantherophis guttatus complex).

The southeastern Nearctic is a biodiversity hotspot that is also rich in cryptic species. Numerous hypotheses (e.g., vicariance, local adaptation, and Pleistocene speciation in glacial refugia) have been tested in an attempt to explain diversification and the observed pattern of extant biodiversity. However, previous phylogeographic studies have both supported and refuted these hypotheses. Therefore, while data support one or more of these diversification hypotheses, it is likely that taxa are forming within this region in species-specific ways. Here, we generate a genomic data set for the cornsnakes (Pantherophis guttatus complex), which are widespread across this region, spanning both biogeographic barriers and climatic gradients. We use phylogeographic model selection combined with hindcast ecological niche models to determine regions of habitat stability through time. This combined approach suggests that numerous drivers of population differentiation explain the current diversity of this group of snakes. The Mississippi River caused initial speciation in this species complex, with more recent divergence events linked to adaptations to ecological heterogeneity and allopatric Pleistocene refugia. Lastly, we discuss the taxonomy of this group and suggest there may be additional cryptic species in need of formal recognition.

Complexation by cysteine and iron mineral adsorption limit cadmium mobility during metabolic activity of Geobacter sulfurreducens.

Cadmium (Cd) adversely affects human health by entering the food chain via anthropogenic activity. In order to mitigate risk, a better understanding of the biogeochemical mechanisms limiting Cd mobility in the environment is needed. While Cd is not redox-active, Cd speciation varies (i.e., aqueous, complexed, adsorbed), and influences mobility. Here, the cycling of Cd in relation to initial speciation during the growth of Geobacter sulfurreducens was studied. Either fumarate or ferrihydrite (Fh) was provided as an electron acceptor and Cd was present as: (1) an aqueous cation, (2) an aqueous complex with cysteine, which is often present in metal stressed soil environments, or (3) adsorbed to Fh. During microbial Fe(iii) reduction, the removal of Cd was substantial (∼80% removal), despite extensive Fe(ii) production (ratio Fe(ii)total : Fetotal = 0.8). When fumarate was the electron acceptor, there was higher removal from solution when Cd was complexed with cysteine (97-100% removal) compared to aqueous Cd (34-50%) removal. Confocal laser scanning microscopy (CLSM) demonstrated the formation of exopolymeric substances (EPS) in all conditions and that Cd was correlated with EPS in the absence of Fe minerals (r = 0.51-0.56). Most notable is that aqueous Cd was more strongly correlated with Geobacter cells (r = 0.72) compared to Cd-cysteine complexes (r = 0.51). This work demonstrates that Cd interactions with cell surfaces and EPS, and Cd solubility during metabolic activity are dependent upon initial speciation. These processes may be especially important in soil environments where sulfur is limited and Fe and organic carbon are abundant.

Freshwater Perkinsea: diversity, ecology and genomic information

AbstractStudies on freshwater Perkinsea are scarce compared to their marine counterparts; they are therefore not well ecologically characterized. In this study, we investigated the diversity, distribution and ecological role of Perkinsea in freshwater ecosystems. Our approach included (1) the phylogenetic analyses of near full-length SSU and LSU sequences of freshwater Perkinsea, (2) a meta-analysis of public Perkinsea 18S ribosomal RNA gene sequences available from the freshwater environments (25 lakes, 4 rivers), (3) microscopic observations of Perkinsea associated with planktonic communities and (4) single amplified genome analysis. Whereas Perkinsea appear to be rare in river ecosystems (85 reads), they are found in almost all of the lakes studied. However, their diversity does vary considerably between lakes (from 0 to 2 463 Operational Taxonomic Units (OTUs)). Phylogenetic analysis showed that the Parvilucifera/Dinovorax/Snorkelia and Perkinsus/Xcellia/Gadixcellia clades resulted from an initial speciation event. This second clade is further split into well-supported, monophyletic groups, including a clade dominated by freshwater representatives, which is further structured into three distinct subclades: freshwater clade 1, freshwater clade 2 and a freshwater and brackish clade. The Perkinsea Single Amplified Genome (SAG) as well as most of the abundant Operational Taxonomic Units (OTUs) fall into freshwater clade 2. The tyramide signal amplification-fluorescent in situ hybridization method showed an internal association between Perkinsea and the colonial phytoplankton Sphaerocystis. The Single Amplified Genome (SAG) annotation contained 698 genes and gene ontology terms could be assigned to 486 protein-coding genes. Although the number of genes appears to be low (10.6% of the entire gene set assessed by BUSCO), the analysis of the proteome revealed some putative secreted virulence factors. This study showed a large distribution of Perkinsea across lake ecosystems and potential parasitic association with phytoplankton. However, further investigations are needed for a better knowledge on the role of these microorganisms in freshwater ecosystems.

Different diversity-dependent declines in speciation rate unbalances species richness in terrestrial slugs

Two genera of terrestrial slugs (Arion and Geomalacus) display a striking disproportion in species richness in the Iberian Peninsula. While there are 17 Iberian endemic species in Arion, morphological criteria only recognize four species within Geomalacus. Sequence data were used to test whether these differences could result from: (1) cryptic diversity within Geomalacus; (2) an earlier origin for Arion (older clades are expected to accumulate more species); (3) distinct patterns of diversification rates (higher initial speciation rates in Arion), and (4) some combination of the above factors (e.g., an older clade with higher speciation rates). Species delimitation tests based on mitochondrial and nuclear data revealed eight cryptic lineages within Geomalacus that lessened the asymmetry; nevertheless, the disparity required further investigation. No meaningful differences in crown group ages of each recovered clade were found. Regardless the different premises of the two equally plausible diversification models (similar initial speciation rates vs. higher initial speciation rates in Geomalacus), both coincide on diversity-dependent diversification for the two groups but weaker rate declines in Arion best explains the observed asymmetry in species richness. Also, the broader environmental tolerance combined with a faster dispersal and wider distribution may have represented an evolutionary advantage for Arion.

Effect of Initial Speciation of Copper- and Silver-Based Nanoparticles on Their Long-Term Fate and Phytoavailability in Freshwater Wetland Mesocosms.

Ag0- and CuO-engineered nanomaterials (ENMs) or their sulfidized forms are introduced into freshwater wetlands through wastewater effluent and agricultural runoff. Knowledge about the rates of transformations of these ENMs in realistic environments and the impact of the form of the incoming ENM (i.e., sulfidized or pristine) on bioavailability and fate is limited. Here, five freshwater wetland mesocosms were exposed to 3 g of total metal as CuO, CuS, Ag0, or Ag2S ENMs or soluble CuNO3 added weekly for 1 month. Total metal and metal speciation was measured in sediment and plant samples collected 1, 3, 6, and 9 months after addition. The form of the added ENM did not affect the metal distribution, and ENMs distributed similarly to added ionic Cu or Ag. For the dosing condition used, ∼50% of the added Ag or Cu metal mass was found in Egeria densa plant tissue, with the remainder primarily in the surficial sediment. Ag0 and CuO ENMs transformed quickly in sediment, with no evidence of CuO and only ∼4% of silver present as Ag0 ENM 1 week after the last ENM addition. In contrast to sediment, Ag0 and CuO ENMs were persistent in E. densa tissues for up to 9 and 6 months, respectively. The persistence of ENMs in E. densa suggests that chronic exposures, or food web transfers, for both the transformed and the initially added ENMs are possible.

Rapid and recent diversification patterns in Anseriformes birds: Inferred from molecular phylogeny and diversification analyses.

The Anseriformes is a well-known and widely distributed bird order, with more than 150 species in the world. This paper aims to revise the classification, determine the phylogenetic relationships and diversification patterns in Anseriformes by exploring the Cyt b, ND2, COI genes and the complete mitochondrial genomes (mito-genomes). Molecular phylogeny and genetic distance analyses suggest that the Dendrocygna species should be considered as an independent family, Dendrocygnidae, rather than a member of Anatidae. Molecular timescale analyses suggests that the ancestral diversification occurred during the Early Eocene Climatic Optimum (58 ~ 50 Ma). Furthermore, diversification analyses showed that, after a long period of constant diversification, the median initial speciation rate was accelerated three times, and finally increased to approximately 0.3 sp/My. In the present study, both molecular phylogeny and diversification analyses results support that Anseriformes birds underwent rapid and recent diversification in their evolutionary history, especially in modern ducks, which show extreme diversification during the Plio-Pleistocene (~ 5.3 Ma). Therefore, our study support that the Plio-Pleistocene climate fluctuations are likely to have played a significant role in promoting the recent diversification for Anseriformes.

The role of niche divergence and geographic arrangement in the speciation of Eared Pheasants (Crossoptilon, Hodgson 1938)

One of the most contentious theories in current ecology is the ecological niche conservatism, which is defined as conservatism among closely related species; however, the ecological niche can also be shifted, as documented in several cases. Genetic drift and ecological divergent selection may cause ecological niche divergence. The current study aims to test whether the ecological niche is conserved or divergent and to determine the main factor that drives ecological niche divergence or conservation. We analyzed the phylogenetic relationship, ecological niche model (ENM) and demographic history of Eared Pheasants in the genus Crossoptilon (Galliformes: Phasianidae) to test niche conservatism with respect to different geographically distributed patterns. The phylogenetic relationship was reconstructed using ∗BEAST with mitochondrial cytochrome b (cyt b) and 44 unlinked autosomal exonic loci, and ENMs were reconstructed in MAXENT using an average of 41 occurrence sites in each species and 22 bioclimatic variables. A background similarity test was used to detect whether the ecological niche is conserved. Demographic history was estimated using the isolation with migration (IM) model. We found that there was asymmetric gene flow between the allopatric sister species Crossoptilon mantchuricum and C. auritum and the parapatric sister species C. harmani and C. crossoptilon. We found that ecological niches were divergent, not conserved, between C. mantchuricum and C. auritum, which began to diverge at approximately 0.3 million years ago. However, the ecological niches were conserved between C. crossoptilon and C. harmani, which gradually diverged approximately half a million years ago. Ecological niches can be either conserved or divergent, and ecological divergent selection for local adaptation is probably an important factor that promotes and maintains niche divergence in the face of gene flow. This study provides a better understanding of the role that divergent selection has in the initial speciation process. The platform combined demographic processes and ecological niches to offer new insights into the mechanism of biogeography patterns.

Uptake and Distribution of Silver in the Aquatic Plant Landoltia punctata (Duckweed) Exposed to Silver and Silver Sulfide Nanoparticles.

Aquatic ecosystems are expected to receive Ag0 and Ag2S nanoparticles (NPs) through anthropogenic waste streams. The speciation of silver in Ag-NPs affects their fate in ecosystems, but its influence on interactions with aquatic plants is still unclear. Here, the Ag speciation and distribution was measured in an aquatic plant, duckweed (Landoltia punctata), exposed to Ag0 or Ag2S NPs, or to AgNO3. The silver distribution in duckweed roots was visualized using synchrotron-based micro X-ray fluorescence (XRF) mapping and Ag speciation was determined using extended X-ray absorption fine structure (EXAFS) spectroscopy. Duckweed exposed to Ag2S-NPs or Ag0-NPs accumulated similar Ag concentrations despite an order of magnitude smaller dissolved Ag fraction measured in the exposure medium for Ag2S-NPs compared to Ag0-NPs. By 24 h after exposure, all three forms of silver had accumulated on and partially in the roots regardless of the form of Ag exposed to the plants. Once associated with duckweed tissue, Ag0-NPs had transformed primarily into silver sulfide and silver thiol species. This suggests that plant defenses were active within or at the root surface. The Ag2S-NPs remained as Ag2S, while AgNO3 exposure led to Ag0 and sulfur-associated Ag species in plant tissue. Thus, regardless of initial speciation, Ag was readily available to duckweed.

Late Pleistocene climate change promoted divergence between Picea asperata and P.crassifolia on the Qinghai-Tibet Plateau through recent bottlenecks.

Divergence during the early stage of speciation can be driven by a population bottleneck via reduced gene flow and enhanced lineage sorting. In this study, we aimed to examine whether such bottlenecks occurred during the initial speciation of two closely related spruce species Picea asperata and P. crassifolia occurring on the Qinghai–Tibet Plateau (QTP). We analyzed sequences of three chloroplast, two mitochondrial DNA fragments and a further 13 nuclear loci from 216 individuals of the two species. Both species showed a low level of genetic diversity in contrast to other congeners occurring in the QTP and adjacent regions. The estimated population sizes of P. asperata and P. crassifolia are less than the ancestral population size before splitting. These results together with multiple statistical tests (Tajima's D, Fu and Li's D* and F*) suggest that these two species underwent recent bottlenecks. Based on approximate Bayesian computation (ABC), we also determined that the period of the population shrinkage was consistent with the interspecific divergence during the late Pleistocene. The reduced population sizes and the divergent selection may together have triggered the initial divergence under high gene flow between these two species. Our results therefore highlight the importance of climatic oscillations during the late Pleistocene in promoting speciation through changing demographic sizes of the ancestral species on the QTP and in adjacent regions.

Stability of Tl(III) in the context of speciation analysis of thallium in plants.

The paper presents both "good" and "bad" results obtained during speciation analysis of thallium in plant tissues of a hyperaccumulator of this metal. The object was white mustard - Sinapis alba L. In this plant there were found traces of trivalent thallium. The crucial point of this study (especially in the case of so unstable thallium form as Tl(III)) was to prove that the presence of Tl(III) was not caused by the procedure of sample preparation itself, and that the whole analytical method provides reliable results. Choice of the method for conservation of the initial speciation, extraction with the highest efficiency and proving the correctness of the obtained data were the most difficult parts of the presented study. It was found that: both freezing and drying cause significant changes in the speciation of thallium; quantitative analysis could be performed only with fresh tissues of mustard plants; only short-term storage of an extract from fresh plant tissues is possible; the methodology is not the source of thallium (III); only the presence of DTPA can greatly limit the reduction of TI(III) to TI(I) (up to 1-3%); the UV irradiation results in disintegration of TI(III)DTPA in the presence of plant matrix (reduction up to 90%).