Enhancer sequence variants and transcription-factor deregulation synergize to construct pathogenic regulatory circuits in B-cell lymphoma.

Most B-cell lymphomas arise in the germinal center (GC), where humoral immune responses evolve from potentially oncogenic cycles of mutation, proliferation, and clonal selection. Although lymphoma gene expression diverges significantly from GC B cells, underlying mechanisms that alter the activities of corresponding regulatory elements (REs) remain elusive. Here we define the complete pathogenic circuitry of human follicular lymphoma (FL), which activates or decommissions REs from normal GC B cells and commandeers enhancers from other lineages. Moreover, independent sets of transcription factors, whose expression was deregulated in FL, targeted commandeered versus decommissioned REs. Our approach revealed two distinct subtypes of low-grade FL, whose pathogenic circuitries resembled GC B or activated B cells. FL-altered enhancers also were enriched for sequence variants, including somatic mutations, which disrupt transcription-factor binding and expression of circuit-linked genes. Thus, the pathogenic regulatory circuitry of FL reveals distinct genetic and epigenetic etiologies for GC B-cell transformation.

Replicate contact zones suggest a limited role of plumage in reproductive isolation among subspecies of the variable seedeater (Sporophila corvina).

After establishing secondary contact, recently diverged populations may remain reproductively isolated or may hybridize to a varying extent depending on factors such as hybrid fitness and the strength of assortative mating. Here, we used genomic and phenotypic data from three independent contact zones between subspecies of the variable seedeater (Sporophila corvina) to examine how coloration and genetic divergence shape patterns of hybridization. We found that differences in plumage coloration are probably maintained by divergent selection across contact zones; however, the degree of plumage differentiation does not match overall patterns of hybridization. Across two parallel contact zones between populations with divergent phenotypes (entirely black vs. pied plumage), populations hybridized extensively across one contact zone but not the other, suggesting that plumage divergence is not sufficient to maintain reproductive isolation. Where subspecies hybridized, hybrid zones were wide and formed by later-generation hybrids, suggesting frequent reproduction and high survivorship for hybrid individuals. Moreover, contemporary gene flow has played an important role in shaping patterns of genetic structure between populations. Replicated contact zones between hybridizing taxa offer a unique opportunity to explore how different factors interact to shape patterns of hybridization. Overall, our results demonstrate that divergence in plumage coloration is important in reducing gene flow but insufficient in maintaining reproductive isolation in this clade, and that other factors such as divergence in song and time since secondary contact may also play an important role in driving patterns of reduced hybridization and gene flow.

Al establecer contacto secundario, las poblaciones que divergieron recientemente pueden permanecer reproductivamente aisladas o pueden hibridarse en distintos grados, dependiendo de factores como la aptitud (fitness) y la fuerza del apareamiento selectivo. Aquí, utilizamos datos genómicos y fenotípicos de tres zonas de contacto independientes entre subespecies del Semillero Variable (Sporophila corvina), para examinar cómo la coloración y la divergencia genética regulan los patrones de hibridación. A través de las zonas de contacto, encontramos que las diferencias en la coloración del plumaje posiblemente se mantienen por selección divergente, pero el grado de diferenciación no coincide con los patrones generales de hibridación. En dos zonas de contacto análogas entre poblaciones con fenotipos divergentes (totalmente negro vs plumaje de varios colores), las poblaciones hibridaron ampliamente en una zona de contacto, pero no en la otra, lo que sugiere que la divergencia del plumaje no es suficiente para mantener el aislamiento reproductivo. Donde las subespecies hibridaron, las zonas híbridas eran amplias y estaban formadas por híbridos de generaciones posteriores, lo que sugiere reproducción frecuente y alta sobrevivencia de los híbridos. Además, el flujo génico ha desempeñado un papel importante en la configuración de patrones de estructura genética entre poblaciones. Las réplicas de zonas de contacto entre taxones que hibridan ofrecen una oportunidad para explorar cómo interactúan diversos factores para dar forma a los patrones de hibridación. En general, nuestros resultados demuestran que la divergencia en la coloración del plumaje es importante para reducir el flujo génico, pero insuficiente para mantener el aislamiento reproductivo en este clado, y que otros factores, como la divergencia en el canto y el tiempo transcurrido desde el contacto secundario, también pueden desempeñar un papel importante en la reducción del flujo génico e hibridación.

Nichima gen. nov. (Alismataceae) based on reproductive structures from the Oligocene-Miocene of Mexico.

PREMISE: Alismataceae, a sub-cosmopolitan family with ca. 17 genera and 113 species, is a large group of aquatic plants. Compression/impressions and bioinclusions of reproductive parts in amber support the documentation of the lineage in low-latitude North America. In Mexico, fossil aquatic plants have been infrequently documented. The new reproductive structures exhibit characteristics of Alismataceae, whose fossil record is mainly documented in the northern hemisphere through of fruits and seeds. METHODS: We described and compared 150 samples of reproductive structures preserved as impressions/compressions from the Oligocene Los Ahuehuetes locality in the state of Puebla, and two bioinclusions from the Miocene amber of Simojovel de Allende in the state of Chiapas, Mexico with extinct and extant taxa. Using a parsimony analysis based on 29 floral characters of 17 extant genera of the Alismataceae, we evaluated the relationship between the fossil material and potential living relatives. RESULTS: We discovered a new genus Nichima based on a perfect, actinomorphic flower with an expanded receptacle, three persistent sepals with multiple vasculatures, delicate and caducous petals, six stamens, and a gynoecium composed of three to more superior carpels, maturing into achenes. These characteristics resemble flowers of Alismataceae. Nichima represents an extinct member of the family, with two new species described here, Nichima magalloniae L. Hern., Cevallos-Ferriz et Hernández-Damián sp. nov. and Nichima gonzalez-medranoi L. Hern., Cevallos-Ferriz et Hernández-Damián, sp. nov. Their phylogenetic position suggests affinity with a clade that includes Baldiella, Echinodorus, and Alisma. CONCLUSIONS: Reproductive structures from the Cenozoic of Mexico support the identification of a new extinct genus, Nichima, evidencing the extensive history of Alismataceae in North America's low latitudes and suggesting a southern extension of the boreotropical flora.

Impact of Drying Process on the Phenolic Profile and Antioxidant Capacity of Raw and Boiled Leaves and Inflorescences of Chenopodium berlandieri ssp. berlandieri.

C. berlandieri ssp. berlandieri (C. berlandieri) is one of the most common members of the group of plants known as quelites, which are dark leafy greens widely consumed in Mexico. This study aimed to evaluate the impact of two drying procedures (oven drying and freeze-drying/lyophilization) on the polyphenolic composition, antioxidant capacity, and proximal chemical analysis of C. berlandieri leaves and inflorescences (raw or boiled). The results indicated that the raw freeze-dried samples had higher amounts (p < 0.05) of total phenolic compounds, total flavonoids, and antioxidant capacity, mainly in the inflorescence. The oven-dried samples showed an increased concentration of polyphenols after boiling, while the lyophilized samples showed a slightly decreased concentration. The drying process was observed to have little impact on the proximal chemical composition. Quantification by UPLC-DAD-ESI-QToF/MS identified up to 23 individual phenolic compounds, with freeze-dried samples showing higher amounts of individual compounds compared with oven-dried. Procyanidin B2 was found exclusively in the inflorescences. The inflorescences have a higher content of phenolic compounds and greater antioxidant capacity than the leaves. Regardless of the drying process, the leaves and inflorescences of C. berlandieri contain an interesting variety of phenolic compounds that may have beneficial effects on health.

Neotropical Birds Respond Innately to Unfamiliar Acoustic Signals.

AbstractMany animals respond to heterospecific signals that indicate the presence of food or predators. Although the benefits of responding are clear, the behavioral and cognitive mechanisms underlying responses are not. Whether responses are learned, innate, or an epiphenomenon created by following other species as they respond to signals remains unknown because most studies have involved respondents that are sympatric with their heterospecific signalers and that have therefore had opportunities to learn their signals. In this study, we tested the mechanisms underlying avian responses to heterospecific chick-a-dee calls. All North American parids produce chick-a-dee calls in response to arousing stimuli, such as food and predators, and diverse species respond by approaching the caller and consuming the food or mobbing the predator. We broadcast chick-a-dee calls plus two control stimuli in Costa Rica, Colombia, and Brazil, where no parids ever occur. We conducted our trials in the winter, when Neotropical migrants that might be familiar with chick-a-dee calls were present, and in the temperate breeding season, when migrants were absent. Across 138 trials, 38 resident species from 14 families and four orders responded to chick-a-dee calls by approaching to within 5 m of the playback speaker. A phylogenetic logistic regression showed that whether a species responded was not significantly associated with the species' mean body mass or the structural similarity between its calls and chick-a-dee calls. Residents were significantly more likely to approach chick-a-dee calls than either control stimulus. This pattern was unaffected by the presence of migrants, thus demonstrating that the observed responses are innate. Our study shows that learning cannot fully explain responses to heterospecific chick-a-dee calls and that structural features distinguishing these calls from other vocalizations are important.

Rapid diversification of the Variable Seedeater superspecies complex despite widespread gene flow.

Disentangling the evolutionary relationships of rapidly radiating clades is often challenging because of low genetic differentiation and potentially high levels of gene flow among diverging taxa. The genus Sporophila consists of small Neotropical birds that show, in general, relatively low genetic divergence, but particularly high speciation rates and pronounced variation in secondary sexual traits (e.g., plumage color), which can be important in generating premating reproductive isolation. In cases like these, the use of genome-wide sequence data can increase the resolution to uncover a clade's evolutionary history. Here, we used a phylogenomic approach to study the evolutionary history and genetic structure of the Variable Seedeater superspecies complex, which includes S. corvina, S. intermedia, and S. americana. Using ∼25,000 genome-wide single nucleotide polymorphisms (SNPs), we confirmed that the Variable Seedeater superspecies complex is monophyletic. However, a phylogenetic reconstruction based on a mitochondrial marker (ND2) resulted in a discordant tree topology, particularly in the position of Wing-barred Seedeater S. americana, which might be due to a mitochondrial capture event. Our results suggest historical gene flow among lineages, particularly between species with conflicting topologies. Among the four phenotypically variable S. corvina subspecies, our structure analyses identified three main distinct genetic groups (K = 3), and that the entirely black subspecies, S. c. corvina, is derived from within a pied-colored clade. Further, we inferred widespread gene flow across the whole species' distribution, including between subspecies. However, gene flow was about 100 times lower at the geographic boundaries of the entirely black and the pied subspecies, suggesting an important role for plumage divergence in limiting gene flow. Overall, our findings suggest that the early diversification of the Sporophila genus occurred rapidly despite historical gene flow between lineages and that divergence in plumage color possibly influences the extent of gene flow among taxa.

Cognitive Enhancement Therapy vs social skills training in schizophrenia: a cluster randomized comparative effectiveness evaluation.

BACKGROUND: Schizophrenia and related disorders are highly disabling and create substantial burdens for families, communities, and health care systems. Although pharmacological treatments can often lessen the psychotic symptoms that are a hallmark of schizophrenia, they do not lessen the social and cognitive deficits that create the greatest impediments to community engagement and functional recovery. This study builds on prior research on psychosocial rehabilitation by comparing the effectiveness of two treatments demonstrated as efficacious in improving social and community functioning, Cognitive Enhancement Therapy (CET) and a version of Social Skills Training (HOPES/SST). METHODS: The study uses a randomized cluster design in which a pair of clinicians at community- and hospital-based mental service centers deliver either CET or HOPES to at least one group of 6-8 eligible clients for 12 months. Clinicians are trained and then supervised weekly, with ongoing process measurement of treatment fidelity, attendance, satisfaction, and retention, and use of other services. Measures administered at baseline and at 6 and 12 months while in treatment, and then at 18 and 24 months after treatment include social adjustment, quality of life, social skills, positive and negative symptoms, and neuro- and social cognition. We hypothesize that CET will be associated with greater improvements than SST in both the primary outcome of community functioning and the secondary outcomes of neuro- and social cognition and social skills. Secondarily, we hypothesize that more cognitive impairment at baseline and younger age will predict more benefit from CET compared to HOPES. DISCUSSION: Resource shortages endemic in mental health services and exacerbated by the pandemic highlight the importance of identifying the most effective approach to improving social and community functioning. We aim to improve understanding of the impact of two efficacious psychosocial treatments and to improve clinicians' ability to refer to both treatments the individuals who are most likely to benefit from them. We expect the result to be programmatic improvements that improve the magnitude and durability of gains in community functioning. TRIAL REGISTRATION: ClinicalTrial.gov NCT04321759 , registered March 25, 2020.

The Dietary Restriction-Like Gene drl-1, Which Encodes a Putative Serine/Threonine Kinase, Is Essential for Orsay Virus Infection in Caenorhabditis elegans.

Orsay virus is the only known natural virus pathogen of Caenorhabditis elegans, and its discovery has enabled virus-host interaction studies in this model organism. Host genes required for viral infection remain understudied. We previously established a forward genetic screen based on a virus-inducible green fluorescent protein transcriptional reporter to identify novel host factors essential for virus infection. Here, we report the essential role in Orsay virus infection of the dietary restriction-like (drl-1) gene, which encodes a serine/threonine kinase similar to the mammalian MEKK3 kinase. Ablation of drl-1 led to a >10,000-fold reduction in Orsay virus RNA levels, which could be rescued by ectopic expression of DRL-1. DRL-1 was dispensable for Orsay replication from an endogenous transgene replicon, suggesting that DRL-1 affects a prereplication stage of the Orsay life cycle. Thus, this study demonstrates the power of C. elegans as a model to identify novel virus-host interactions essential for virus infection.IMPORTANCE The recent discovery of Orsay virus, the only known natural virus of Caenorhabditis elegans, provides a unique opportunity to study virus-host interactions that mediate infection in a genetically tractable multicellular model organism. As viruses remain a global threat to human health, better insights into cellular components that enable virus infection and replication can ultimately lead to the development of new targets for antiviral therapeutics.

Effect of Spathiphyllum blandum on the removal of ibuprofen and conventional pollutants from polluted river water, in fully saturated constructed wetlands at mesocosm level.

In this study, the effect of Spathiphyllum blandum on the removal of ibuprofen (IB) and conventional pollutants such as chemical oxygen demand (COD), total nitrogen (TN), ammonium (NH4 +-N), total phosphorus (TP), and total suspended solids (TSS) is reported; this, through its use as an emergent vegetation in fully saturated (FS) constructed wetlands (CWs) at mesocosm level treating polluted river water. With the exception of TP and COD, it was found that for TN (12%), NH4 +-N (11%), TSS (19%), and IB (23%), the removals in systems with vegetation were superior to systems without vegetation (p < 0.05). These findings demonstrate the importance of the species S. blandum, in particular, for the removal of ibuprofen, which is an anti-inflammatory drug commonly found in effluents of wastewater treatment plants. Thus, the results obtained provide information that can be used for the design of future efficient large-scale systems using a new ornamental species, mainly under tropical climatic conditions.

Stable-isotope analysis reveals sources of organic matter and ontogenic feeding shifts of a mangrove-dependent predator species, New Granada sea catfish, Ariopsis canteri.

To gain a better understanding on the trophic ecology of New Granada sea catfish, Ariopsis canteri, and their linkage to mangroves, nitrogen and stable carbon isotopes (δ15 N and δ13 C), as well as Bayesian mixing models, were used to explore trophic dynamics and potential ontogenic feeding shifts across different size classes: class I (8-20 cm), class II (21-32 cm) and class III (>32 cm). The study area was the estuary of the Atrato River Delta, where information about fish ecology is scarce. The δ13 C of size class I was lower (mean ± s.d. = -24.96 ± 0.69‰) than that of size classes II (-22.20 ± 0.90‰) and III (-22.00 ± 1.96‰). The δ15 N of size class I was lower (mean ± s.d. = 8.50 ± 0.67‰) than that of size classes II (9.77 ± 0.60‰) and III (10.00 ± 0.66‰). Body size was positively and significantly correlated to δ15 N and δ13 C. Individuals with LT > 32 cm presented the highest estimated trophic position (3.8). Five-source mixing models indicated that for class I, the mean estimated contribution of macroalgae was the highest (6%-57% c.i.), and for classes II and III, the mean estimated contribution of macrophytes was the highest (3%-53% c.i. and 4%-53% c.i., respectively). Ontogenetic feeding shifts of A. canteri were confirmed evidencing decreasing intraspecific competition between small and large individuals. Results suggest that mangroves are a nursery and feeding ground habitat for this species and that mangroves support A. canteri mainly due to the substrate/habitat that supports sources in the food webs. These results can be used in ecosystem-based fishery management focused on the protection of extensive mangrove areas in the southern Caribbean Sea.

Influence of a new ornamental species (Spathiphyllum blandum) on the removal of COD, nitrogen, phosphorus and fecal coliforms: a mesocosm wetland study with PET and tezontle substrates.

The objective of this study was to evaluate the influence of a new species of plant (Spathiphyllum blandum) in the elimination of chemical oxygen demand (COD), nitrogen, phosphorus and fecal coliforms (FCs) in mesocosms of wetlands with polyethylene terephthalate (PET) and tezontle substrates under a tropical climate. The experiments were developed at the mesocosm level in 20 experimental units; 10 were planted with Spathiphyllum blandum, five in PET substrates and five in tezontle, and 10 more were used as controls without vegetation, of which five contained tezontle and five contained PET. The systems were fed with contaminated water from the river Sordo, with a hydraulic retention time of 3 days for 12 months; samples were taken in the influent and effluents of the mesocosms every 2 weeks, with the purpose of evaluating the removal of contaminants. The results showed that presence of this species tended to improve or significantly improved the removal of COD, NH4-N, PO4-P, and FCs by 7%, 16%, 29% and 12%, respectively. It was also possible to confirm that the presence of this species reduced the rate of denitrification. These results confirm that in developing countries it is feasible to find new wetland species to be used for wastewater phytoremediation.

Phenolic profile and antioxidant capacity of Pithecellobium dulce (Roxb) Benth: a review.

Pithecellobium dulce (Roxb) Benth (P. dulce), known as "guamúchil", is a tree native to the American continent. Various parts of the tree are used in traditional medicine, primarily for treating gastrointestinal disorders. The phenolic compounds and antioxidant capacity of this plant are largely responsible for the beneficial health effects attributed to it. A number of authors have studied the antioxidant capacity and phenolic compounds of the aril, seed, leaf and root of P. dulce using various methodologies, which can differ considerably in variables such as environmental factors, type of drying, temperature, the way the sample is stored, and the use of different solvents in the various extraction methods. Even methods of quantification by HPLC vary tremendously. This paper summarizes the existing research carried out to date on determining the phenolic profile and antioxidant capacity of P. dulce.

Defect-Enriched Nitrogen Doped-Graphene Quantum Dots Engineered NiCo2 S4 Nanoarray as High-Efficiency Bifunctional Catalyst for Flexible Zn-Air Battery.

Flexible Zn-air batteries have recently emerged as one of the key energy storage systems of wearable/portable electronic devices, drawing enormous attention due to the high theoretical energy density, flat working voltage, low cost, and excellent safety. However, the majority of the previously reported flexible Zn-air batteries encounter problems such as sluggish oxygen reaction kinetics, inferior long-term durability, and poor flexibility induced by the rigid nature of the air cathode, all of which severely hinder their practical applications. Herein, a defect-enriched nitrogen doped-graphene quantum dots (N-GQDs) engineered 3D NiCo2 S4 nanoarray is developed by a facile chemical sulfuration and subsequent electrophoretic deposition process. The as-fabricated N-GQDs/NiCo2 S4 nanoarray grown on carbon cloth as a flexible air cathode exhibits superior electrocatalytic activities toward both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), outstanding cycle stability (200 h at 20 mA cm-2 ), and excellent mechanical flexibility (without observable decay under various bending angles). These impressive enhancements in electrocatalytic performance are mainly attributed to bifunctional active sites within the N-GQDs/NiCo2 S4 catalyst and synergistic coupling effects between N-GQDs and NiCo2 S4 . Density functional theory analysis further reveals that stronger OOH* dissociation adsorption at the interface between N-GQDs and NiCo2 S4 lowers the overpotential of both ORR and OER.

[Effect of traffic-light labeling on nutritional content and on consumption of carbonated beverages in EcuadorEfeito da rotulagem nutricional com modelo de semáforo no consumo de refrigerantes no Equador]. / Efecto del etiquetado de semáforo en el contenido nutricional y el consumo de bebidas gaseosas en Ecuador.

OBJECTIVE: To evaluate the effect of "traffic-light" nutritional labeling on the purchase of soft drinks and on their nutritional content in Ecuador. METHODS: Two databases were used: the first was provided by Ecuador's National Agency for Health Regulation, Control, and Surveillance; the second was obtained from the international market research company Kantar World Panel. A before/after study was conducted of introducing traffic-light labeling, using Student's t-tests to evaluate changes in average nutritional content and the purchase of soft drinks. Multiple linear regression methods were used to evaluate changes in purchases resulting from the introduction of traffic-light labeling. RESULTS: After labeling, average per capita consumption of soft drinks declined by 0.003 L/month--a small change with respect to average per capita consumption of 1.678 L/month. The results of the Student's t-tests indicated that this difference was not statistically significant. Furthermore, the regression analyses found no empirical evidence that traffic-light labeling affected soft drink consumption. With regard to sugar content, an average reduction of 0.93 gm/100 ml of beverage was observed. CONCLUSIONS: No empirical evidence was found that implementation of traffic-light labeling changed soft-drink purchase habits in Ecuador, but there is evidence that it reduced sugar content in carbonated beverages in the country.

OBJETIVO: Avaliar o efeito da rotulagem nutricional com modelo de semáforo na compra e no teor nutricional dos refrigerantes no Equador. MÉTODOS: As informações foram obtidas do banco de dados da Agência Nacional de Regulamentação, Controle e Vigilância Sanitária do Equador e do banco de dados da Kantar World Panel, empresa internacional de pesquisa de mercado. Foi feita uma análise do tipo antes-depois da introdução da rotulagem com modelo de semáforo. Foram usados testes t de Student para avaliar a variação nas médias do teor nutricional e na compra de refrigerantes e métodos de regressão linear multivariada para avaliar a variação na compra com a introdução da rotulagem com modelo de semáforo. RESULTADOS: Foi observada uma redução de 0,003 litro/mês no consumo médio per capita de refrigerantes com a introdução da rotulagem, que representa um valor pequeno em relação ao consumo médio per capita (1,678 litro/mês). Os resultados dos testes t de Student indicaram que esta diferença não foi estatisticamente diferente de zero. As análises de regressão também não forneceram evidências empíricas de que a rotulagem com modelo de semáforo tenha influído no consumo de refrigerantes. Com relação ao teor de açúcar, foi verificada uma redução média de 0,93 g por 100 ml de bebida. CONCLUSÕES: Não foram observadas evidências empíricas de que a implantação da rotulagem nutricional com modelo de semáforo alterou os hábitos de compra de refrigerantes, porém houve uma diminuição no teor de açúcar destas bebidas no Equador.

The biogeographic and evolutionary history of an endemic clade of Middle American sparrows: Melozone and Aimophila (Aves: Passerellidae).

The large number of endemic species in Middle America is frequently attributed to the interplay of geographical barriers and historical climatic changes in the region. This process promotes genetic divergence between populations, and given enough time, may yield new species. Animals that inhabit mid-elevation or highland habitats may be disproportionately affected in this way. Genetic analyses of animals in this region allow us to better understand how historical patterns of isolation have influenced the generation of new species in this biodiversity hotspot. We studied the biogeography and systematics of two closely related genera of sparrows (Passerellidae): Melozone and Aimophila. Collectively, this group is distributed from the southwestern United States and southward as far as central Costa Rica. We sampled 81 individuals of 8 Melozone and 2 Aimophila species, from 19 localities distributed throughout their ranges. We reconstructed phylogenetic relationships and time-calibrated species trees using multilocus sequence data comprised of one mitochondrial gene and five nuclear genes. We conducted an ancestral area reconstruction analysis to determine the probability of ancestral range at each divergent event. Despite analyzing six loci, we were unable to obtain a fully resolved phylogenetic tree. We recovered four main lineages: lineage 1 includes four Melozone species distributed north of Isthmus of Tehuantepec (M. albicollis, M. crissalis, M. aberti, M. fusca); lineage 2 includes three Melozone species distributed south of the Isthmus of Tehuantepec (M. biarcuata, M. cabanisi, M. leucotis); lineage 3 lineage consists of a single species endemic to the Pacific coast of Mexico (M. kieneri); and lineage 4 includes the more widely distributed sparrows in the genus Aimophila. Our analyses suggest that these genera probably originated during the late Miocene in the Madrean Highlands of southern Mexico. We identified dispersal as the prevalent cause of speciation in this clade with most lineages dispersing to their current distributions from southern Mexico either to the north following a developing and expanding Madro-Tertiary flora, or to the south across the Isthmus of Tehuantepec. A similar pattern of dispersal from this biogeographic region has been reported in other taxa including fishes, reptiles, and birds. Our results reveal that the four lineages identified represent geographically coherent and ecologically similar assemblages of taxa. Finally, when our genetic results are considered, along with apparent differences in morphology and song, the allopatric forms M. b. cabanisi and M. l. occipitalis warrant recognition as biological species.

Estimation of genetic variation in closely related cycad species in Ceratozamia (Zamiaceae: Cycadales) using RAPDs markers.

The Ceratozamia norstogii complex from Southern Mexico is made up of four closely related taxa and occurs in similar habitats (Quercus forest). All have linear-lanceolate leaflets with great similarity between them, especially in juvenile stages, but differentiate with age. There has been debate regarding delimitation of species due to character loss in herbarium specimens. The aim of this study was to determine the genetic variation, and to measure genetic similarity between the four taxa. We studied populations in Cintalapa (Chiapas) for C. alvarezii and C. norstogii; the Sierra Atravesada (Oaxaca) for C. chimalapensis, and Villa Flores (Chiapas) for C. mirandae. One population for each taxon was sampled (only one population is known for C. alvarezii) 11-15 randomly chosen adult individuals were sampled. Twenty-eight primers were tested of which five were polymorphic using the RAPD'S technique. The data were analyzed using Bayesian methods. Results revealed low genetic diversity, and a differentiation was found between species, suggesting a recent divergence. A previous morphological and anatomical study on the complex has found the taxa to be distinct. However, the results of this study have shown that the C. norstogii species complex is in a divergence process, probably through genetic drift and founder effects.

The differences in transmission properties of two bird calls show relation to their specific functions.

When vocalizations transmit throughout the environment, attenuation and degradation may change the information of the signal; the loss of information is related to changes in both frequency and duration of vocalizations. The variation in frequency and duration of bird calls is related to the functions of each call type. Using a sound transmission experiment, the authors tested the transmission properties of two call types both produced by white-eared ground-sparrows Melozone leucotis; these calls vary in frequency and duration, suggesting that they may transmit at different distances. The authors broadcasted and re-recorded each call type at four different distances (4, 8, 16, and 32 m) inside ground-sparrow territories. The authors found that calls with a narrow bandwidth and longer duration transmitted at longer distances, and showed a lower attenuation and degradation than the calls with a broad bandwidth and shorter duration. These results support the relationship between the transmission properties of a call and the different functions (short and long distance communication) also evidence how the selection of these calls facilitates the communication over different distances.

Numerical modeling of solid-phase microextraction: binding matrix effect on equilibrium time.

Solid-phase microextraction (SPME) is a well-known sampling and sample preparation technique used for a wide variety of analytical applications. As there are various complex processes taking place at the time of extraction that influence the parameters of optimum extraction, a mathematical model and computational simulation describing the SPME process is required for experimentalists to understand and implement the technique without performing multiple costly and time-consuming experiments in the laboratory. In this study, a mechanistic mathematical model for the processes occurring in SPME extraction of analyte(s) from an aqueous sample medium is presented. The proposed mechanistic model was validated with previously reported experimental data from three different sources. Several key factors that affect the extraction kinetics, such as sample agitation, fiber coating thickness, and presence of a binding matrix component, are discussed. More interestingly, for the first time, shorter or longer equilibrium times in the presence of a binding matrix component were explained with the help of an asymptotic analysis. Parameters that contribute to the variation of the equilibrium times are discussed, with the assumption that one binding matrix component is present in a static sample. Numerical simulation results show that the proposed model captures the phenomena occurring in SPME, leading to a clearer understanding of this process. Therefore, the currently presented model can be used to identify optimum experimental parameters without the need to perform a large number of experiments in the laboratory.

Competing kinetics and he bubble morphology in W.

The growth process of He bubbles in W is investigated using molecular dynamics and parallel replica dynamics for growth rates spanning 6 orders of magnitude. Fast and slow growth regimes are defined relative to typical diffusion hopping times of W interstitials around the He bubble. Slow growth rates allow the diffusion of interstitials around the bubble, favoring the biased growth of the bubble towards the surface. In contrast, at fast growth rates interstitials do not have time to diffuse around the bubble, leading to a more isotropic growth and increasing the surface damage.