Speciation Model Research Articles

Assessing Potential Health Impacts of Cyanide-Contaminated Seepage in Paddy Field Near a Gold Mine in Thailand: Cyanide Speciation and Vapor Intrusion Modeling

Assessing Potential Health Impacts of Cyanide-Contaminated Seepage in Paddy Field Near a Gold Mine in Thailand: Cyanide Speciation and Vapor Intrusion Modeling

The influence of redox conditions on aqueous-solid partitioning of arsenic and selenium in a closed coal ash impoundment

A closed coal ash impoundment case study characterized the effects of field redox conditions on arsenic and selenium partitioning through monitoring of porewater and subsurface gas in conjunction with geochemical speciation modeling. When disposed coal ash materials and porewater were recovered for testing, oxidation led to lower arsenic and higher selenium concentrations in leaching test extracts compared to porewater measurements. Multiple lines of evidence suggest multiple mechanisms of arsenic retention are plausible and the concurrent presence of several redox processes and conditions (e.g., methanogenesis, sulfate reduction, and Fe(III)-reduction) controlled by spatial gradients and dis-equilibrium. Geochemical speciation modeling indicated that, under reducing field conditions, selenium was immobilized through the formation of insoluble precipitates Se(0) or FeSe while arsenic partitioning was affected by a progression of reactions including changes in arsenic speciation, reduction in adsorption due to dissolution and recrystallization of hydrous ferric oxides, and precipitation of arsenic sulfide minerals.

Lifestyle Evolution Analysis by Binary-State Speciation and Extinction (BiSSE) Model.

Phylogenetic comparative methods (PCMs) combine statistics and evolutionary models to infer the dynamics of trait evolution and diversification that underlie the observed phylogeny. While PCMs have been used to study macro-evolutionary processes and evolutionary transitions of macroorganisms, their application to microbes is still limited. With the abundance of publicly available genomic and trait character data for diverse microbes nowadays, applications of PCMs on these data can provide insights into the fundamental principles that govern microbial evolution. Here, we introduce the Binary-State Speciation and Extinction (BiSSE) model, which is a relatively simple yet powerful approach for analyzing trait evolution. We begin by explaining the theoretical background and intuition behind the BiSSE model. Then, R commands for running the BiSSE model are presented. Finally, we introduce a case study that successfully applied the BiSSE model to investigate generalist and specialist microbial lifestyle evolution.

Species-range-size distributions: Integrating the effects of speciation, transformation, and extinction.

The species‐range size distribution is a product of speciation, transformation of range‐sizes, and extinction. Previous empirical studies showed that it has a left‐skewed lognormal‐like distribution. We developed a new mathematical framework to study species‐range‐size distributions, one in which allopatric speciation, transformation of range size, and the extinction process are explicitly integrated. The approach, which we call the gain‐loss‐allopatric speciation model, allows us to explore the effects of various speciation scenarios. Our model captures key dynamics thought to lead to known range‐size distributions. We also fitted the model to empirical range‐size distributions of birds, mammals, and beetles. Since geographic range dynamics are linked to speciation and extinction, our model provides predictions for the dynamics of species richness. When a species‐range‐size distribution initially evolves away from the range sizes at which the likelihood of speciation is low, it tends to cause diversification slowdown even in the absence of (bio)diversity dependence in speciation rate. Using the mathematical model developed here, we give a potential explanation for how observed range‐size distributions emerge from range‐size dynamics. Although the framework presented is minimalistic, it provides a starting point for examining hypotheses based on more complex mechanisms.

POSSMs: a parsimonious speciation model for metals in soils

Environmental context Predicting the chemistry of metals is important for understanding their movement and impacts in the environment. Metal chemistry models are generally complex and difficult to apply, but a simpler model, which does not need large amounts of input data, can also provide good results. A simpler model can be more easily included in large-scale models of metal transport and impacts in the environment. Abstract Mechanistic geochemical models are useful for detailed study of the speciation of metals in well-characterised soils, but can be challenging to apply when driving soil compositional data are sparse, for example, at large scales. Empirical models, using minimal driving data, have been developed either for prediction of solid–solution partitioning or for the computation of the free metal ion from the total or geochemically active metal. This work presents an empirical speciation model, POSSMs (ParsimOniouS Speciation of Metals in soils), which predicts the free, solution-bound and sorbed metal in a soil in a single calculation, using a minimal set of soil parameters. The model has been parameterised for Ni, Cu, Zn, Cd and Pb using datasets of geochemically active soil metal and solution phase composition. The parameterised model can also be used to compute the free metal ion from the solution metal. The model was tested by applying it to literature datasets on the speciation of metals in soil solutions and extracts, and on the metal solid–solution partitioning. The performance of the model was comparable to other empirical models of similar complexity. Some test datasets produced biased predictions, particularly in the underestimation of measured free ion at circumneutral and alkaline pH, where the model predicted low free ion concentrations. The model is not a replacement for mechanistic geochemical models, but is a useful tool for soil metal speciation where comprehensive driving data are not available.

Prediction of Cadmium Bioavailability in the Rice-Soil System on a County Scale Based on the Multi-Surface Speciation Model

Prediction of Cadmium Bioavailability in the Rice-Soil System on a County Scale Based on the Multi-Surface Speciation Model

Corrigendum

Journal of BiogeographyVolume 49, Issue 1 p. 236-236 CORRIGENDUMFree Access Corrigendum This article corrects the following: A topoclimate model for Quaternary insular speciation Víctor García-Olivares, Jairo Patiño, Isaac Overcast, Antonia Salces-Castellano, Unai López de Heredia, Fernando Mora-Márquez, Antonio Machado, Michael J. Hickerson, Brent C. Emerson, Volume 46Issue 12Journal of Biogeography pages: 2769-2786 First Published online: October 20, 2019 First published: 31 December 2021 https://doi.org/10.1111/jbi.14287AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL In the article by García-Olivares et al., after additional genotyping of new individuals to further investigate evidence for admixture within the genotype of L061Laposo_C04, the unique individual comprising group G2 (Figure 4), the authors have become aware that the published genotype is artefactual. The apparent admixed nature of the genotype arose from two unfortunate errors. First, during laboratory processing, DNA from L061Laposo_C04 was at some point contaminated with a sample from the island of Tenerife. Second, accurate filtering of loci with more than two alleles during consensus sequence calling (ipyrad step 5) was not functional in the ipyrad version used for assembly. This issue does not affect the remaining 12 admixed individuals, pertaining to groups G5 and G6 (Figure 4), thus the central results of our manuscript are not compromised. The issue within ipyrad has now been corrected in version 0.9.81. We apologise for our genotype error, and encourage users of ipyrad to move to version 0.9.81 or greater. Reference García-Olivares, V., Patiño, J., Overcast, I., Salces-Castellano, A., López de Heredia, U., Mora-Márquez, F., Machado, A., Hickerson, M. J., & Emerson, B. C. (2019). A topoclimate model for Quaternary insular speciation. Journal of Biogeography, 46(12), 2769– 2786. https://doi.org/10.1111/jbi.13689 Volume49, Issue1January 2022Pages 236-236 ReferencesRelatedInformation

Транзитивні таксономічні системи (TTS) та видоутворення в процесі динаміки ареалів

The system of views on the structure of geographic ranges of species (superspecies) and their dynamics as one of the key features of species and the basis of taxonomic differentiation and evolution is considered. The mechanisms leading to the formation of new taxa in several ways are analysed, including (1) the formation of transitive taxonomic systems (TTS), in which spatial differentiation leads to the formation of geographically differentiated races as ‘small’ species; (2) the formation of new geographical races in relation to the maternal species (plesions), distributed within the primary ranges; (3) the formation of sibling species as a result of dispersal of one ‘small’ species into the range of the sister species. All such groups of ‘small’ species coexist in time and illustrate models that correspond to E. E. Reclus’s view of ‘geography is history in space.’ A number of illustrative cases discovered in the analysis of the taxonomic heterogeneity of different groups of mammals of the European fauna or the Palaearctic as a whole are considered. In particular, there were analysed the features of spatial-taxonomic differentiation in allospecies complexes that fall under the definition of TTS, in which the distribution of allospecies reflects the patterns of spatial differentiation of the ‘large’ species over time (phylogeographic patterns). Similar complexes have been demonstrated on the example of ground squirrels, birch mice, and wood mice. The formation of TTS, as well as new forms as a result of invasions into new ranges (or dispersal to ranges of adjacent forms) is considered within the amplificative species concept (ASCo), according to which specialization occurs not as a result of reduction of both the range and variability (classic models with founder effect or bottleneck), but in the phase of flourishing of the species, in particular when new populations emerge outside the initial natural ranges due to expansions or invasions. The invasive model of speciation was formed based on this idea, and a partial example of it is the formation of sympatric pairs of sibling species formed as a result of secondary sympatry, i.e. expansion. Examples from other groups, in particular regarding the formation of compilospecies and other variants of hybridogenic taxa provoked by introductions or invasions, are considered. All this is viewed through the prism of the concept of speciesness as the level of achievement of evolutionary separateness.

Improving inference and avoiding overinterpretation of hidden‐state diversification models: Specialized plant breeding has no effect on diversification in frogs

The hidden-state speciation and extinction (HiSSE) model helps avoid spurious results when testing whether a character affects diversification rates. However, care must be taken to optimally analyze models and interpret results. Recently, Tonini etal. (TEA hereafter) studied anuran (frog and toad) diversification with HiSSE methods. They concluded that their focal state, breeding in phytotelmata, increases net diversification rates. Yet this conclusion is counterintuitive, because the state that purportedly increases net diversification rates is 14 times rarer among species than the alternative. Herein, I revisit TEA's analyses and demonstrate problems with inferring model likelihoods, conducting post hoc tests, and interpreting results. I also reevaluate their top models and find that diverse strategies are necessary to reach the parameter values that maximize each model's likelihood. In contrast to TEA, I find no support for an effect of phytotelm breeding on net diversification rates in Neotropical anurans. In particular, even though the most highly supported models include the focal character, averaging parameter estimates over hidden states shows that the focal character does not influence diversification rates. Finally, I suggest ways to better analyze and interpret complex diversification models-both state-dependent and beyond-for future studies in other organisms.

The Effect of Metal Cations on the Aqueous Behavior of Dopamine. Thermodynamic Investigation of the Binary and Ternary Interactions with Cd2+, Cu2+ and UO22+ in NaCl at Different Ionic Strengths and Temperatures.

The interactions of dopamine [2-(3,4-Dihydroxyphenyl)ethylamine, (Dop−)] with cadmium(II), copper(II) and uranyl(VI) were studied in NaCl(aq) at different ionic strengths (0 ≤ I/mol dm−3 ≤ 1.0) and temperatures (288.15 ≤ T/K ≤ 318.15). From the elaboration of the experimental data, it was found that the speciation models are featured by species of different stoichiometry and stability. In particular for cadmium, the formation of only MLH, ML and ML2 (M = Cd2+; L = dopamine) species was obtained. For uranyl(VI) (UO22+), the speciation scheme is influenced by the use of UO2(acetate)2 salt as a chemical; in this case, the formation of ML2, MLOH and the ternary MLAc (Ac = acetate) species in a wide pH range was observed. The most complex speciation model was obtained for the interaction of Cu2+ with dopamine; in this case we observed the formation of the following species: ML2, M2L, M2L2, M2L2(OH)2, M2LOH and ML2OH. These speciation models were determined at each ionic strength and temperature investigated. As a further contribution to this kind of investigation, the ternary interactions of dopamine with UO22+/Cd2+ and UO22+/Cu2+ were investigated at I = 0.15 mol dm−3 and T = 298.15K. These systems have different speciation models, with the MM’L and M2M’L2OH [M = UO22+; M’ = Cd2+ or Cu2+, L = dopamine] common species; the species of the mixed Cd2+ containing system have a higher stability with respect the Cu2+ containing one. The dependence on the ionic strength of complex formation constants was modelled by using both an extended Debye–Hückel equation that included the Van’t Hoff term for the calculation of the formation enthalpy change values and the Specific Ion Interaction Theory (SIT). The results highlighted that, in general, the entropy is the driving force of the process. The quantification of the effective sequestering ability of dopamine towards the studied cations was evaluated by using a Boltzmann-type equation and the calculation of pL0.5 parameter. The sequestering ability was quantified at different ionic strengths, temperatures and pHs, and this resulted, in general, that the pL0.5 trend was always: UO22+ > Cu2+ > Cd2+.

Chemical Characterization and Biological Evaluation of New Cobalt(II) Complexes with Bioactive Ligands, 2-Picolinehydroxamic Acid and Reduced Schiff Base N-(2-Hydroxybenzyl)alanine, in Terms of DNA Binding and Antimicrobial Activity.

Five new heteroligand cobalt(II) complexes with 2-picolinehydroxamic acid and reduced Schiff base, N-(2-hydroxybenzyl)alanine, were formed in an aqueous solution over a wide pH range. The coordination properties of ligands towards the metal ion were determined using a pH-metric method, and then the speciation model was confirmed by UV–Vis studies. A stacking interaction between the Schiff base phenol ring and the 2-picolinehydroxamic acid pyridine ring was found to improve the stability of the heteroligand species, indicating more effective coordination in mixed-ligand complexes than in their respective binary systems. The antimicrobial properties of heteroligand complexes were determined against Gram-negative and Gram-positive bacteria, as well as fungal strains. The formulation demonstrated the highest bacteriostatic and bactericidal activity (3.65 mM) against two strains of Gram-negative Helicobacter pylori bacteria and towards Candida albicans and Candida glabrata; this is important due to the potential co-existence of these microorganisms in the gastric milieu and their role in the development of gastritis. The binary complexes in the cobalt(II)—2-picolinehydroxamic acid system and 2-picolinehydroxamic acid were not cytotoxic against L929 mouse fibroblasts, neither freshly prepared solutions or after two weeks’ storage. By comparison, the heteroligand complexes within the range 0.91–3.65 mM diminished the metabolic activity of L929 cells, which was correlated with increased damage to cell nuclei. The concentration of the heteroligand species increased over time; therefore, the complexes stored for two weeks exhibited stronger anticellular toxicity than the freshly prepared samples. The complexes formed in an aqueous solution under physiological pH effectively bound to calf thymus DNA in an intercalative manner. This DNA-binding ability may underpin the antimicrobial/antifungal activity of the heteroligand complexes and their ability to downregulate the growth of eukaryotic cells.

Estimation of the strength of mate preference from mated pairs observed in the wild.

A number of key processes in evolution are driven by individuals preferring mates with particular phenotypes. However, despite long‐standing interest, it is difficult to quantify the strength of mate preference from phenotypic observations in nature in a way that connects directly to key parameters in theoretical models. To bridge the gap between mathematical models and empirical data, we develop a novel maximum likelihood‐based method to estimate the strength and form of mate preference, where preference depends on traits expressed in both males and females. Using simulated data, we demonstrate that our method accurately infers model parameters, including the strength of mate preference and the optimal offset match between trait values in mated pairs when model assumptions are satisfied. Applying our method to two previous studies of assortative mating in marine gastropods and the European common frog, we support previous findings, but also give additional insight into the role of mate preference in each system. Our method can be generalized to a variety of plant and animal taxa that exhibit mating preferences to facilitate the testing of evolutionary hypotheses and link empirical data to theoretical models of assortative mating, sexual selection, and speciation.

Electrochemical Modeling of Iodide Oxidation in Metal-Halide Molten Salts

The oxidation of iodide in NaI-AlBr3, NaI-AlCl3, and NaI-GaCl3 molten salts was analyzed using simulation software to extract relevant kinetic parameters. The experimental oxidation potentials were ordered AlCl3 < AlBr3 < GaCl3, with higher oxidation potentials correlating with softer Lewis acidity of the metal halide. An iodide oxidation and metal halide speciation model was developed and simulated to fit the electrochemical response, enabling determination of electrochemical charge transfer parameters and chemical equilibrium constants. NaI-AlBr3 displayed the fastest electron transfer rates yet showed the lowest current densities. All salts revealed smaller than expected current densities, explained by equilibrium between various species, where some are not electrochemically active at the studied potentials. These equilibrium reactions are due to the various metal halide species, controlling the reactant concentration of iodide and the resultant current. We hypothesize the electrochemically active iodide species, present as a metal halide monomer (MX3I−), is decreased dramatically from the expected concentration, sequestered as a more stable metal halide dimer species (M2X6I−) with a higher oxidation potential. Traditional Tafel analysis of the experimental data supports the validity of the simulations. These results increase understanding of iodide oxidation in low-temperature Lewis acidic molten salts and inform task-specific molten salt design.

5S‐IGS rDNA in wind‐pollinated trees (Fagus L.) encapsulates 55 million years of reticulate evolution and hybrid origins of modern species

SUMMARYStandard models of plant speciation assume strictly dichotomous genealogies in which a species, the ancestor, is replaced by two offspring species. The reality in wind‐pollinated trees with long evolutionary histories is more complex: species evolve from other species through isolation when genetic drift exceeds gene flow; lineage mixing can give rise to new species (hybrid taxa such as nothospecies and allopolyploids). The multi‐copy, potentially multi‐locus 5S rDNA is one of few gene regions conserving signal from dichotomous and reticulate evolutionary processes down to the level of intra‐genomic recombination. Therefore, it can provide unique insights into the dynamic speciation processes of lineages that diversified tens of millions of years ago. Here, we provide the first high‐throughput sequencing (HTS) of the 5S intergenic spacers (5S‐IGS) for a lineage of wind‐pollinated subtropical to temperate trees, the Fagus crenata – F. sylvatica s.l. lineage, and its distant relative F. japonica. The observed 4963 unique 5S‐IGS variants reflect a complex history of hybrid origins, lineage sorting, mixing via secondary gene flow, and intra‐genomic competition between two or more paralogous‐homoeologous 5S rDNA lineages. We show that modern species are genetic mosaics and represent a striking case of ongoing reticulate evolution during the past 55 million years.

The Complex History of Genome Duplication and Hybridization in North American Gray Treefrogs.

Polyploid speciation has played an important role in evolutionary history across the tree of life, yet there remain large gaps in our understanding of how polyploid species form and persist. Although systematic studies have been conducted in numerous polyploid complexes, recent advances in sequencing technology have demonstrated that conclusions from data-limited studies may be spurious and misleading. The North American gray treefrog complex, consisting of the diploid Hyla chrysoscelis and the tetraploid H. versicolor, has long been used as a model system in a variety of biological fields, yet all taxonomic studies to date were conducted with only a few loci from nuclear and mitochondrial genomes. Here, we utilized anchored hybrid enrichment and high-throughput sequencing to capture hundreds of loci along with whole mitochondrial genomes to investigate the evolutionary history of this complex. We used several phylogenetic and population genetic methods, including coalescent simulations and testing of polyploid speciation models with approximate Bayesian computation, to determine that H. versicolor was most likely formed via autopolyploidization from a now extinct lineage of H. chrysoscelis. We also uncovered evidence of significant hybridization between diploids and tetraploids where they co-occur, and show that historical hybridization between these groups led to the re-formation of distinct polyploid lineages following the initial whole-genome duplication event. Our study indicates that a wide variety of methods and explicit model testing of polyploid histories can greatly facilitate efforts to uncover the evolutionary history of polyploid complexes.

Cuticular hydrocarbon variation among Rhagoletis fruit flies (Diptera: Tephritidae): implications for premating reproductive isolation and ecological speciation

1. Fruit flies in the genus Rhagoletis are a model for ecological speciation via sympatric host plant shifting. Rhagoletis mate on or near the fruit of their respective host plants, generating premating reproductive isolation between taxa specialised on different hosts. However, non‐host‐related premating isolation has been observed between some Rhagoletis species associated with morphological differences in body colour and wing patterns.2. Here, the extent of epicuticular hydrocarbon (CHC) variation as a possible, additional determinant of mate choice in adults of six Rhagoletis taxa, including the apple and hawthorn‐infesting host races of R. pomonella is investigated.3. Gas‐chromatography‐mass‐spectrometry revealed 36 repeatable and quantifiable hydrocarbon components present on the epicuticles of all six fly taxa, comprised of at least 53 different CHC compounds, with chain lengths varying from 27 to 34 carbon atoms, consisting of n‐alkanes, mono‐, dimethyl‐, and trimethyl‐alkanes, alkenes, and alkadienes. There were significant differences in the relative proportions of CHCs between adult R. cingulata, R. cornivora, R. zephyria, R. mendax, and R. pomonella, as well as between the apple‐ and hawthorn‐infesting host races of R. pomonella. Furthermore, within the R. pomonella host races and R. mendax, significant CHC differences were observed between the sexes and across collecting sites.4. The results are consistent with variation in CHCs potentially contributing to observed patterns of premating isolation between Rhagoletis taxa, possibly due to combination of sexual and host‐related selection, which will necessitate further, in depth chemical analyses and future mating trials to substantiate.

A speciation model linking the fate of carbon and hydrogen during core – magma ocean equilibration

The core – mantle differentiation in the magma ocean constitutes a major planetary event that involved two elements that are essential to life: carbon (C) and hydrogen (H). These two elements are conventionally classified as volatiles (i.e. atmophile), but they can also evolve into being siderophile and lithophile at the extreme conditions found in planetary magma oceans. We report here a model for H and C species dissolved in silicate melts in equilibrium with iron-rich alloys under variable pressure, temperature and redox conditions. This speciation model is able to reconcile and reproduce a large body of experimental data on metal–silicate partitioning for H and C at carbon-saturation and in C-undersaturated systems. At low pressure, we conclude that the prevailing species in a silicate magma ocean are CO2, CO, H2O, H2, whereas CH4 appears to dominate at high pressure. These speciation changes explain recent experimental observations that (i) C evolves from being strongly siderophile at low pressure to moderately siderophile at high pressure, and (ii) H is not siderophile at low pressure but becomes increasingly so as pressure rises. Moreover, it shows that H becomes increasingly siderophile as the total H content of the silicate melt and C-activity are lowered. Despite it offers a promising reconciliation of a large set of experimental and molecular dynamics observations, this model still suffers from large uncertainties when extrapolated to high pressure. In particular, endmember and mixing properties in both the silicate melt and the molten metal must be independently deciphered.The enhanced CH4 stability in the silicate melt at high pressure couples the fate of C and H in deep magma oceans. In such cases, the solubility of C in the basal ocean depends on the H-content and is higher than C-solubility at low pressure. This implies an increase in C activity as the ascending convective cells of the magma ocean, which may cause C saturation as graphite or diamond unless Fe-metal droplets, having a great C-solubility, are present in the shallow magma ocean. Under certain conditions, enhanced siderophile behaviour for H can lead via a runaway process to the desiccation of the magma ocean.

Phylogeny of the damselfishes (Pomacentridae) and patterns of asymmetrical diversification in body size and feeding ecology.

The damselfishes (family Pomacentridae) inhabit near-shore communities in tropical and temperature oceans as one of the major lineages in coral reef fish assemblages. Our understanding of their evolutionary ecology, morphology and function has often been advanced by increasingly detailed and accurate molecular phylogenies. Here we present the next stage of multi-locus, molecular phylogenetics for the group based on analysis of 12 nuclear and mitochondrial gene sequences from 345 of the 422 damselfishes. The resulting well-resolved phylogeny helps to address several important questions about higher-level damselfish relationships, their evolutionary history and patterns of divergence. A time-calibrated phylogenetic tree yields a root age for the family of 55.5 mya, refines the age of origin for a number of diverse genera, and shows that ecological changes during the Eocene-Oligocene transition provided opportunities for damselfish diversification. We explored the idea that body size extremes have evolved repeatedly among the Pomacentridae, and demonstrate that large and small body sizes have evolved independently at least 40 times and with asymmetric rates of transition among size classes. We tested the hypothesis that transitions among dietary ecotypes (benthic herbivory, pelagic planktivory and intermediate omnivory) are asymmetric, with higher transition rates from intermediate omnivory to either planktivory or herbivory. Using multistate hidden-state speciation and extinction models, we found that both body size and dietary ecotype are significantly associated with patterns of diversification across the damselfishes, and that the highest rates of net diversification are associated with medium body size and pelagic planktivory. We also conclude that the pattern of evolutionary diversification in feeding ecology, with frequent and asymmetrical transitions between feeding ecotypes, is largely restricted to the subfamily Pomacentrinae in the Indo-West Pacific. Trait diversification patterns for damselfishes across a fully resolved phylogeny challenge many recent general conclusions about the evolution of reef fishes.

Molecular species delimitation of shrub frogs of the genus Pseudophilautus (Anura, Rhacophoridae).

Sri Lanka is an amphibian hotspot of global significance. Its anuran fauna is dominated by the shrub frogs of the genus Pseudophilautus. Except for one small clade of four species in Peninsular India, these cool-wet adapted frogs, numbering some 59 extant species, are distributed mainly across the montane and lowland rain forests of the island. With species described primarily by morphological means, the diversification has never yet been subjected to a molecular species delimitation analysis, a procedure now routinely applied in taxonomy. Here we test the species boundaries of Pseudophilautus in the context of the phylogenetic species concept (PSC). We use all the putative species for which credible molecular data are available (nDNA–Rag-1; mt-DNA– 12S rRNA, 16S rRNA) to build a well resolved phylogeny, which is subjected to species delimitation analyses. The ABGD, bPTP, mPTP and bGMYC species delimitation methods applied to the 16S rRNA frog barcoding gene (for all species), 12S rRNA and Rag-1 nDNA grouped P. procax and P. abundus; P. hallidayi and P. fergusonianus; P. reticulatus and P. pappilosus; P. pleurotaenia and P. hoipolloi; P. hoffmani and P. asankai; P. silvaticus and P. limbus; P. dilmah and P. hankeni; P. fulvus and P. silus.. Surprisingly, all analyses recovered 14 unidentified potential new species as well. The geophylogeny affirms a distribution across the island’s aseasonal ‘wet zone’ and its three principal hill ranges, suggestive of allopatric speciation playing a dominant role, especially between mountain masses. Among the species that are merged by the delimitation analyses, a pattern leading towards a model of parapatric speciation emerges–ongoing speciation in the presence of gene flow. This delimitation analysis reinforces the species hypotheses, paving the way to a reasonable understanding of Sri Lankan Pseudophilautus, enabling both deeper analyses and conservation efforts of this remarkable diversification. http://zoobank.org/urn:lsid:zoobank.org:pub:DA869B6B-870A-4ED3-BF5D-5AA3F69DDD27.

Equilibrium calculations of iron speciation and apparent iron solubility in the Celtic Sea at ambient seawater pH using the NICA-Donnan model

We used a combined ion pairing - organic matter speciation model (NICA-Donnan) to predict the organic complexation of iron (Fe) at ambient pH and temperature in the Celtic Sea. We optimized our model by direct comparison with Fe speciation determined by Adsorptive Cathodic Stripping Voltammetry using the added Fe-binding ligand 1-nitroso-2-naphthol (HNN) in the presence and absence of natural organic matter. We compared determined Fe speciation with simulated titrations obtained via application of the NICA-Donnan model with four different NICA parameter sets representing a range of binding site strengths and heterogeneities. We tested the assumption that binding sites scale to dissolved organic carbon (DOC) concentrations in marine waters. We found that a constant low DOC concentration resulted in an improved fit of our titration data to the simulated titrations, suggesting that inputs of autochthonous marine DOM may not increase the heterogeneity or concentrations of Fe binding sites. Using the optimal parameter set, we calculated pFe(III)´ (−log(∑Fe(OH)i3−i)) and apparent Fe(III) solubility (SFe(III)app) at ambient pH and temperature in the water column of the Celtic Sea. SFe(III)app was defined as the sum of aqueous inorganic Fe(III) species and Fe(III) bound to DOM formed at a free Fe (Fe3+) concentration equal to the limiting solubility of Fe hydroxide (Fe(OH)3(s)). SFe(III)app was within range of the determined dissolved Fe concentrations observed after winter mixing on the shelf and in waters >1500 m depth at our most offshore stations. Our study supports the hypothesis that the ocean dissolved Fe inventory is controlled by the interplay between Fe solubility and Fe binding by organic matter, although the overall number of metal binding sites in the marine environment may not be directly scalable to DOC concentrations.