Drift Events Research Articles

Genomic analysis of bovine herpesvirus type 4 (BoHV-4) from Argentina: High genetic variability and novel phylogenetic groups

Bovine herpesvirus 4 (BoHV-4) is a γ-herpesvirus that has been isolated both from apparently healthy animals and from cattle with a variety of clinical signs, including post-partum endometritis and abortion. BoHV-4 causes either a persistent or a latent infection in cells of the monocyte/macrophage lineage. Two groups of BoVH-4 strains have been defined based on their restriction patterns: the Movar-like strains (European prototype) and the DN 599-like strains (American prototype). The purpose of the present study was to genetically characterize wild type BoHV-4 strains isolated from vaginal discharges of aborted cows in Argentina. The virus was identified by isolation and nested PCR in all vaginal discharge samples from aborted cows, either as a sole agent or in association with other pathogens. Restriction enzyme profiling and phylogenetic analysis demonstrated that there is a high genetic variability among the studied field isolates. The existence of three groups of strains, which were designated as genotypes 1, 2 and 3, is described. Genotypes 1 and 2 possibly correspond to the Movar-like and DN 599-like groups, respectively, whereas Genotype 3 corresponds to a novel group. Two viral strains did not cluster into any of these three groups, indicating that other genotypes could be circulating in Argentina. These results suggest a complex epidemiological background for the Argentinean BoHV-4 strains, probably influenced by independent events of genetic drift. This hypothesis cannot be rejected based on the available data. However, there is no direct evidence supporting this possibility. Thus, it seems speculative to suggest that interspecific jumps are responsible for the observed phylogenetic grouping. On the other hand, our analyses suggest a geographical structure for the observed viral genotypes, since genotypes 1 and 2 included the European (Movar-like) and American (DN599-like) reference strains, respectively. Geographic dispersion is known to be a driver of herpes viruses diversification, and independent evolution in geographical isolated places ensures the emergence of particular mutations in each location due to genetic drift (Compans, 2007; Zong et al., 1999). Therefore, at this point, the genetic drift hypothesis is the one that requires less ad-hoc considerations and thus, to our understanding, is the one that fits to the findings from this study. The involvement of this genetic variability in the detection and pathogenesis of BoHV-4 remains to be investigated.

Submarine slide initiation and evolution offshore Pointe Odden, Gabon — Analysis from annual bathymetric data (2004–2009)

Time serial bathymetric data acquired between 2004 and 2009 are used to evaluate the morphological evolution of the coastal area offshore Pointe Odden, located on the Mandji Island (Gabon). Data analysis highlights the alternation between fast sedimentation periods at shallow water depth related to intense longshore drift and catastrophic erosional events. Because of sediment overloading and slope oversteepening, small-scale instabilities are generated (successive slide scars, channel formation and growth by retrogressive erosion). However, when critical stability conditions are reached, large failures occur (2005 submarine slide). Geotechnical measurements and sedimentological analyses on the study area suggest that flow liquefaction would be the triggering mechanism of the 2005 event. Moreover, our analysis shows that the associated slide scar is rapidly filled by compensation and that failure morphology could disappear from the seafloor in about 15–20years.

Signs of Selective Pressure on Genetic Variants Affecting Human Height

Many decades of scientific investigation have proved the role of selective pressure in Homo Sapiens at least at the level of individual genes or loci. Nevertheless, there are examples of polygenic traits that are bound to be under selection, but studies devoted to apply population genetics methods to unveil such occurrence are still lacking. Stature provides a relevant example of well-studied polygenic trait for which is now available a genome-wide association study which has identified the genes involved in this trait, and which is known to be under selection. We studied the behavior of FST in a simulated toy model to detect population differentiation on a generic polygenic phenotype under selection. The simulations showed that the set of alleles involved in the trait has a higher mean FST value than those undergoing genetic drift only. In view of this we looked for an increase in the mean FST value of the 180 variants associated to human height. For this set of alleles we found FST to be significantly higher than the genomic background (p = 0.0356). On the basis of a statistical analysis we excluded that the increase was just due to the presence of outliers. We also proved as marginal the role played by local adaptation phenomena, even on different phenotypes in linkage disequilibrium with genetic variants involved in height. The increase of FST for the set of alleles involved in a polygenic trait seems to provide an example of symmetry breaking phenomenon concerning the population differentiation. The splitting in the allele frequencies would be driven by the initial conditions in the population dynamics which are stochastically modified by events like drift, bottlenecks, etc, and other stochastic events like the born of new mutations.

Gradual changes in the age distribution of excess deaths in the years following the 1918 influenza pandemic in Copenhagen: Using epidemiological evidence to detect antigenic drift

Background The 1918 influenza pandemic was associated with an unusual age pattern of mortality, with most deaths occurring among young adults. Few studies have addressed changes in the age distribution for influenza-related mortality in the pre-pandemic and post-pandemic period, which has implications for pandemic preparedness. In the present paper, we analyse the age patterns of influenza-related excess mortality in the decades before and after the 1918 pandemic, using detailed historic surveillance data from Copenhagen. Methods Weekly age-specific rates of respiratory mortality and influenza-like-illnesses were compiled for 1904–1937. Seasonal excess rates of morbidity and mortality attributable to influenza were calculated using a seasonal regression approach. To characterize the age patterns of influenza-related deaths in individual seasons, we used two rate ratio (RR) measures representing ratios of excess mortality rates between age groups and influenza seasons. Results Individuals aged 15–64 years experienced sharply elevated excess respiratory mortality rates in the 1918–1919 and 1919–1920 pandemic periods, compared to pre-pandemic seasons (RR for excess mortality in the fall of 1918 = 67 relative to inter-pandemic seasons). Of all excess respiratory deaths occurring during 1918–1919, 84% were reported in individuals 15–64 years. By contrast, seniors over 65 years of age experienced no measurable excess mortality during 1918–1919 and moderate excess mortality in the recrudescent pandemic wave of 1919–1920. The first post-pandemic season associated with high excess mortality rates in individuals over 65 years was 1928–1929, with 73% of excess deaths occurring among seniors. We estimate that the age patterns of influenza-related mortality returned to pre-pandemic levels after 1925, based on trends in the rate ratio of excess respiratory mortality in people under and over 65 years. Conclusions The unusual elevation of excess respiratory mortality rates in young and middle-aged adults was confined to the first three years of A/H1N1 virus circulation 1918–1920; the rapid return to “epidemic” mortality pattern in this age group was probably due to high attack rates and build-up of immunity. In contrast, seniors were completely spared from pandemic mortality during 1918–1919, likely due to childhood exposure to an A/H1-like influenza virus. The rise in excess mortality rates in seniors in the recrudescent pandemic wave of 1919–1920 may suggest the emergence of an early influenza A/H1N1 drift variant. Subsequent drift events may have been associated with the particularly severe 1928–1929 epidemic in Denmark and elsewhere.

Genetic variation in farmed populations of the gilthead sea bream Sparus aurata in Greece using microsatellite DNA markers

Genetic variation in seven reared stocks of gilthead sea bream Sparus aurata, originating from Greek commercial farms, was assessed using five polymorphic microsatellite markers and was compared with that of two natural populations from the Ionian and the Adriatic Seas. The total number of alleles per marker ranged from 11 to 19 alleles, and hatchery samples showed the same levels of observed heterozygosity with samples from the wild but substantially smaller allelic diversity and expected heterozygosity. The global genetic differentiation for the cultivated samples was significant as indicated by Fst analysis, which might indicate random genetic drift and inbreeding events operating in the hatcheries. On the contrary, no significant difference was found between the two wild populations. Population pairwise tests between farmed and wild stocks were also significant, with the exception of one hatchery sample, the Central Greece 1, which was not significantly different from the two wild samples perhaps due to its recent use in aquaculture from wild-caught animals. The UPGMA tree topology grouped the wild samples together with the Central Greece 1 stock, and showed a clear division between wild and farmed sample sets for the six remaining hatchery samples. Knowledge of the genetic variation in S. aurata cultured populations compared with that in the wild ones is essential for setting up appropriate guidelines for the proper monitoring and management of the stocks either under traditional practices or for the implementation of selective breeding programmes.

Understanding snow-transport processes shaping the mountain snow-cover

Abstract. Mountain snow-cover is normally heterogeneously distributed due to wind and precipitation interacting with the snow cover on various scales. The aim of this study was to investigate snow deposition and wind-induced snow-transport processes on different scales and to analyze some major drift events caused by north-west storms during two consecutive accumulation periods. In particular, we distinguish between the individual processes that cause specific drifts using a physically based model approach. Very high resolution wind fields (5 m) were computed with the atmospheric model Advanced Regional Prediction System (ARPS) and used as input for a model of snow-surface processes (Alpine3D) to calculate saltation, suspension and preferential deposition of precipitation. Several flow features during north-west storms were identified with input from a high-density network of permanent and mobile weather stations and indirect estimations of wind directions from snow-surface structures, such as snow dunes and sastrugis. We also used Terrestrial and Airborne Laser Scanning measurements to investigate snow-deposition patterns and to validate the model. The model results suggest that the in-slope deposition patterns, particularly two huge cross-slope cornice-like drifts, developed only when the prevailing wind direction was northwesterly and were formed mainly due to snow redistribution processes (saltation-driven). In contrast, more homogeneous deposition patterns on a ridge scale were formed during the same periods mainly due to preferential deposition of precipitation. The numerical analysis showed that snow-transport processes were sensitive to the changing topography due to the smoothing effect of the snow cover.

A computational framework for influenza antigenic cartography.

Influenza viruses have been responsible for large losses of lives around the world and continue to present a great public health challenge. Antigenic characterization based on hemagglutination inhibition (HI) assay is one of the routine procedures for influenza vaccine strain selection. However, HI assay is only a crude experiment reflecting the antigenic correlations among testing antigens (viruses) and reference antisera (antibodies). Moreover, antigenic characterization is usually based on more than one HI dataset. The combination of multiple datasets results in an incomplete HI matrix with many unobserved entries. This paper proposes a new computational framework for constructing an influenza antigenic cartography from this incomplete matrix, which we refer to as Matrix Completion-Multidimensional Scaling (MC-MDS). In this approach, we first reconstruct the HI matrices with viruses and antibodies using low-rank matrix completion, and then generate the two-dimensional antigenic cartography using multidimensional scaling. Moreover, for influenza HI tables with herd immunity effect (such as those from Human influenza viruses), we propose a temporal model to reduce the inherent temporal bias of HI tables caused by herd immunity. By applying our method in HI datasets containing H3N2 influenza A viruses isolated from 1968 to 2003, we identified eleven clusters of antigenic variants, representing all major antigenic drift events in these 36 years. Our results showed that both the completed HI matrix and the antigenic cartography obtained via MC-MDS are useful in identifying influenza antigenic variants and thus can be used to facilitate influenza vaccine strain selection. The webserver is available at http://sysbio.cvm.msstate.edu/AntigenMap.

Explanation for Anomalous Readings during Monitoring of a Best Management Practice

The USEPA’s Urban Watershed Management Branch (UWMB) has monitored storm-water drainage and best management practices (BMPs) as part of its overall research program. As part of this effort, continuous monitoring equipment was deployed to measure both storm events and periods between storms in a BMP. Of particular concern were electrodes used to measure ammonium ( NH 4+ ) concentrations. During the third deployment of the electrode there were readings of concern for NH 4+ which exceeded expectations for drift or storm event response. The electrode indicated concentrations of NH 4+ exceeded 2 mg/L, with a sustained maximum concentration of 8 mg/L recorded. These observations occurred between December 5, 2003 and December 10, 2003 after snow events. This period was marked by increased measures of conductivity measured which were contrary to typically low conductivity readings especially after precipitation events. Deicers (sodium chloride) spread on the roadway most likely caused increased NH 4+ readings, as...

Is There a Genetic Basis for Health Disparities in Human Immunodeficiency Virus Disease?

The highest global prevalence rates for human immunodeficiency virus and acquired immune deficiency syndrome have been recorded in southern Africa; in the United States, individuals of African descent are disproportionately affected by human immunodeficiency virus infection. Human immunodeficiency virus-infected individuals with African ancestry are also estimated to have a 17-fold or greater risk for developing human immunodeficiency virus-associated nephropathy in comparison with their counterparts of non-African descent. Several recent studies have implicated genetic alleles that are more frequent in populations of African descent and increase the risk of human immunodeficiency virus infection and the risk of human immunodeficiency virus-associated neuropathy (HIVAN). The supposition that persons of African descent are more susceptible to human immunodeficiency virus infection because of an underlying genetic predisposition is not supported by available evidence. However, strong, replicated data show that the increased risk for human immunodeficiency virus-associated nephropathy, as well as other major forms of kidney disease in individuals of African descent, is due in part to MYH9 (myosin, heavy chain 9, non-muscle) renal disease susceptibility alleles that are very frequent throughout sub-Saharan Africa but are infrequent or absent in non-Africans. Selection, drift, and demographic events shape the allelic architecture of the human genome: it is expected that these events will be reflected in geographic-specific differentiation in allele frequencies for a small subset of alleles that may be associated with either increased or reduced risk for complex and infectious diseases.

Island biology and morphological divergence of the Skyros wall lizard Podarcis gaigeae: a combined role for local selection and genetic drift on color morph frequency divergence?

BackgroundPatterns of spatial variation in discrete phenotypic traits can be used to draw inferences about the adaptive significance of traits and evolutionary processes, especially when compared to patterns of neutral genetic variation. Population divergence in adaptive traits such as color morphs can be influenced by both local ecology and stochastic factors such as genetic drift or founder events. Here, we use quantitative color measurements of males and females of Skyros wall lizard, Podarcis gaigeae, to demonstrate that this species is polymorphic with respect to throat color, and the morphs form discrete phenotypic clusters with limited overlap between categories. We use divergence in throat color morph frequencies and compare that to neutral genetic variation to infer the evolutionary processes acting on islet- and mainland populations.ResultsGeographically close islet- and mainland populations of the Skyros wall lizard exhibit strong divergence in throat color morph frequencies. Population variation in throat color morph frequencies between islets was higher than that between mainland populations, and the effective population sizes on the islets were small (Ne:s < 100). Population divergence (FST) for throat color morph frequencies fell within the neutral FST-distribution estimated from microsatellite markers, and genetic drift could thus not be rejected as an explanation for the pattern. Moreover, for both comparisons among mainland-mainland population pairs and between mainland-islet population pairs, morph frequency divergence was significantly correlated with neutral divergence, further pointing to some role for genetic drift in divergence also at the phenotypic level of throat color morphs.ConclusionsGenetic drift could not be rejected as an explanation for the pattern of population divergence in morph frequencies. In spite of an expected stabilising selection, throat color frequencies diverged in the islet populations. These results suggest that there is an interaction between selection and genetic drift causing divergence even at a phenotypic level in these small, subdivided populations.

Phylogenetic analysis of 3C protease (3Cpro) coding region of Foot-and-mouth disease virus type A

Nucleotide sequence analysis of the 3C protease (3C(pro)) region of Foot-and-mouth disease virus type A (FMDV-A) isolates from India has revealed incongruous phylogenetic grouping between 3C(pro) and VP1 region possibly due to the genetic recombination or independent evolution of non-structural and structural protein coding regions. Similar to the VP1 region, the emerging VP3(59)-deletion group maintained its genetic distinctiveness at 3C(pro) region and was found to be diverging with time. Two lineage specific signature aa residues were detected for the deletion group in proof of lineage specific drift or selection events. 3C(pro) region exhibited high degree of conservation as evident from low dN/dS ratio (0.036) and percentage of variable aa positions (20%). A transmembrane domain from aa 27 to 44 could be predicted that possibly anchors 3C to intracellular membranes for better interaction with RNA replication complex. On the basis of sequence conservation, the likelihood that the region aa 121-150 was carrying a vaccine exploitable T-cell epitope was very high.

Predicting Pesticide Environmental Risk in Intensive Agricultural Areas. I: Screening Level Risk Assessment of Individual Chemicals in Surface Waters

A GIS-based procedure for assessing and mapping pesticide ecotoxicological risk for surface waters was applied to all active ingredients used in a catchment characterized by intensive agriculture. Chemical concentrations in riverwaterwere calculated for 54 chemicals in 25 drift and 21 runoff events that occurred during the growing season, from March to September. Screening level risk for the aquatic community was estimated using a risk index. The different role of drift and runoff processes, as well as the temporal trends of exposure and risk, were compared for the three classes of pesticides (herbicides, fungicides, and insecticides). High levels of risk are usually associated with runoff events for herbicides and to drift events for insecticides and fungicides. The described approach may serve as a powerful tool for a comparative evaluation of site-specific pesticide risk for surface water. However, for large-scale risk mapping, getting information on pesticide use with sufficient detail would be the major problem.

Simulations of Antigenic Variability in Influenza A

AbstractComputational models of the immune system (IS) and pathogenic agents have several applications, such as theory testing and validation, or as a complement to first stages of drug trials. One possible application is the prediction of the lethality of new Influenza A strains, which are constantly created due to antigenic drift and shift. Here, we present several simulations of antigenic variability in Influenza A using an agent-based approach, where low level molecular antigen-antibody interactions are explicitly described. Antigenic drift and shift events are analyzed regarding the virulence of emergent strains against the IS. Results are discussed from a qualitative point of view taking into account recent and generally recognized immunology and influenza literature.

Is the growth stimulation by low doses of glyphosate sustained over time?

The herbicide, glyphosate, has been shown to stimulate growth in a range of species when applied at doses of 5-60 g a.e.ha(-1), corresponding to realistic spray drift events. This study investigates growth of shoot parameters over time to detect whether the glyphosate induced growth increase was sustained and had a final effect on reproduction. The results showed that an actual biomass growth rate increase took place within the first week after spraying with glyphosate doses <60 g a.e.ha(-1). This initial growth boost kept treated plants larger than untreated plants for up to six weeks, but at harvest there was no significant difference between control plants and treated plants. Possible effects of glyphosate hormesis on the competitive ability of spray drift affected plants are discussed.

Study of a semi-rigid steel braced building damaged in the Bam earthquake

A steel frame building with an X-bracing system, infill panels in both directions and “Khorjini” connections damaged in the Bam earthquake was studied using nonlinear dynamic analysis. To model the nonlinear force–deformation characteristics of columns, infill panels and braces, the specifications given in FEMA-356 were used, whereas for the Khorjini connections experimental results demonstrated these specifications. The comparison criterion for damage was life safety performance. The results show good correspondence of the building’s overall behavior in a story drift event. The extent of damage to columns and infill panels is in excellent correlation with the real damaged structure. It was also shown that most of the energy was absorbed by the infill panels, and for this complex system the infill panels played a crucial role in preventing the structure from collapse.

Combination effects of herbicides on plants and algae: do species and test systems matter?

Risk assessment of herbicides towards non-target plants in Europe is currently based solely on tests on algae and floating aquatic plants of Lemna sp. Effects on terrestrial non-target species is not systematically addressed. The purpose of the present study was to compare combination effects of herbicide mixtures across aquatic and terrestrial test systems, and to test whether results obtained in the traditional aquatic test systems can be extrapolated to the terrestrial environment. This was done by evaluating ten binary mixtures of nine herbicides representing the seven most commonly used molecular target sites for controlling broadleaved weeds. Data were evaluated statistically in relation to the concentration addition model, and for selected concentrations to the independent action model. The mixtures were tested on the terrestrial species Tripleurospermum inodorum (L.) Schultz-Bip. (Scentless Mayweed) and Stellaria media (L.) Vill. (Common Chickweed), and on the aquatic species Lemna minor L. (Lesser duckweed) and the alga Pseudokirchneriella subcapitata (Korschikov) Hindak. For the two mixtures of herbicides with the same molecular site of action, the joint effect was additive. For the eight mixtures of herbicides with different sites of action, two of the mixtures were consistently antagonistic across species, while for the remaining six mixtures the joint effect depended on the species tested. This dependence was, however, not systematic, in the sense that none of the species or test systems (terrestrial versus aquatic) had a significantly higher probability of showing synergistic or antagonistic joint effects than others. Synergistic interactions were not observed, but approximately 70% of the mixtures of herbicides with different sites of action showed significant antagonism. Hence, the concentration addition model can be used to estimate worst-case effects of mixtures of herbicides on both terrestrial and aquatic species. Comparing the sensitivity of the species to a 10% spray drift event showed that the terrestrial species were more vulnerable to all herbicides compared with the aquatic species, emphasising the importance of including terrestrial non-target plants in herbicide risk assessment.

Shikimate Accumulation in Sunflower, Wheat, and Proso Millet after Glyphosate Application

Experiments were conducted to examine the utility of a spectrophometric leaf disc assay for detecting shikimate accumulation after glyphosate application in sunflower, proso millet, and wheat. The assay was conducted on both greenhouse- and field-grown plants. Glyphosate was applied at five rates ranging from 840 to 53 g ae ha−1. Shikimate accumulation data were generated at 1, 4, 7, and 14 d after application (DAA). Sunflower accumulated shikimate more rapidly and at lower glyphosate rates than the other two species. At 14 DAA, glyphosate at the two highest rates remained detectable in all three species. Plants receiving lower glyphosate doses (210, 105, and 53 g ae ha−1) had begun to grow out of the injury, or at least the shikimate levels in the plants were no longer significantly different than that present in the untreated controls. This spectrophotometric assay is both rapid and simple, with respect to other means of detecting shikimate, and it can be used to detect glyphosate drift. For it to be used by crop managers, samples from potentially drift-affected crops should be taken as soon as possible after the suspected drift event or immediately after the appearance of glyphosate injury.

The role of wind and splash erosion in inland drift-sand areas in the Netherlands

European drift-sand areas reached their maximum size in the 19th century. From the late 19th until the mid-20th century most drift-sand areas in Europe were successfully reforested. Today drift-sand formation can still be studied in the Netherlands. However, due to change in land-use, their limited size, eutrophication and colonisation by invasive exotics, the area occupied by active drift sand is rapidly declining and with it its unique fauna and vegetation. Between 2001 and 2005, experiments and observations were carried out at the inland drift-sand area Kootwijkerzand (central Netherlands) to know more about the extent, the intensity and the role of wind and splash erosion in a drift-sand ecosystem. Measurements were carried out on the horizontal sediment flux, the vertical accumulation flux, the raising and lowering of the surface, the organic matter content of the topsoil, the saltation activity and the weather conditions. An attempt was also made to evaluate the effect of various measures to re-activate erosion. Without sufficient erosion the scattered drift-sand vegetation will rapidly change into closed, grass-dominated vegetation. The role of erosion in the drift-sand ecosystem is therefore crucial: erosion slows down the succession rate because it causes the regular deposition of nutrient-poor sediment, and facilitates the regular renewal of the vegetation by creating new locations with extremely poor conditions for colonisation (blow-outs). On bare deflation plains wind erosion is the dominant process. Here the transport generated by splash drift can be of the same magnitude as during a moderate wind erosion event, but splash drift events are less frequent and also shorter than wind erosion events. They normally represent less than 10% of the total sediment transport. In the scattered drift-sand vegetation areas, on the other hand, splash erosion and splash drift dominate. Here the organic matter content of the transported (and later deposited) sediment is equal to the organic matter content of the parent soil, showing that splash (drift) has been the main transport mechanism. Biological crusts developed in these areas may later reduce the influence of splash. High transport rates are needed to reactivate wind erosion in vegetated areas. Under the present conditions the erosion activity in most drift-sand areas is small. Heavy wind erosion is only observed during extreme storms.

Genome-wide linkage scan of schizophrenia: A cross-isolate study

Genetic isolates are exceptional resources for the detection of susceptibility genes for complex diseases because of the potential reduction in genetic and clinical heterogeneity. However, the outcome of these mapping efforts is dependent upon the demographic history of a given isolated population, with the most significant factors being a constant population size, the number of generations since founding, and the pathogenic loci and their allele frequencies among founders. Here we employed a cross-isolate genome-wide multipoint linkage study design using uniform genetic and clinical methods in four Daghestan ethnically and demographically diverse isolates with an aggregation of schizophrenia. Our previous population-genetics study showed that Daghestan has an extremely high genetic diversity between ethnic populations and a low genetic diversity within them. The isolates selected for this study include some with more than 200 and some with fewer than 100 generations of demographical history since their founding. Updated clinical data using DSM-IV criteria showed between-isolate differences in aggregation of distinct types of schizophrenia: one of the isolates had a predominant aggregation of disorganized schizophrenia, while the other three had predominantly paranoid schizophrenia. The summarized cross-isolate results indicated prominent within and between-isolate differences in clinical and genetic heterogeneity: the most ancient isolates have roughly twofold fewer incidences of distinct clinical phenotypes and fewer linked genomic regions compared to the demographically younger isolates, which exhibit higher clinical and genetic heterogeneity. Affected individuals in the demographically ancient isolate of ethnic Dargins (No. 6022) who suffered from disorganized schizophrenia showed the highest linkage evidence at 17p11–p12 (LOD = 3.73), while isolates with a predominant aggregation of paranoid schizophrenia (Nos. 6005, 6011, and 6034) showed the highest linkage evidence at 22q11 (LOD = 3.0 and 4.4). The unified clinical, genomic, and statistical design we used enabled us to separate the linked and unlinked pedigrees in an unbiased fashion for each genomic location. Overall maximized heterogeneity lod scores for the combined pedigrees ranging from 3.5 to 8.7 were found at 2p24, 10q26, 11q23, 12q24, 17p11–p12, 22q11, and 22q13. The cross-isolate homogeneity in linkage patterns may be ascribed to an identical-by-descent “metahaplotype” block with pathogenic loci derived from the Daghestan ethnic groups’ common ancestral metapopulation, while the cross-isolate differences may reflect differences in gene drift and recombination events in the history of local isolates. The results obtained support the notion that mapping genes of any complex disease (e.g., schizophrenia) in demographically older genetic isolates may be more time and cost effective in comparison with demographically younger isolates, especially in genetically heterogeneous outbred populations, due to higher clinical and genetic homogeneity of the primary isolates. A study at higher genotyping density across the regions of interest and fluorescence in situ hybridization analyses are currently underway.

Silk filaments enhance the settlement of stream insect larvae

Many aquatic organisms need to settle in suitable benthic habitats while being transported via water currents. Such settlement is especially challenging for organisms that encounter complex benthic topography and lack the ability to move easily from the water column to the bed (e.g., via swimming). We conducted flume studies to examine whether the settlement of drifting stream insects is facilitated by adhesive filaments that extend from their bodies. Using a new tripwire visualization technique, we found that neonatal black flies (Simulium tribulatum) drifted with silk threads averaging six times their body length. These threads allowed larvae to contact or snag the bed from a greater height than would be possible through direct body-to-bed contact alone, and instantly arrested their downstream movement. Thus, silk increased their probability of settlement. We then performed an experiment to examine how settlement varied with bed topography and velocity. We tested whether settlement rate differed between a flat bed and an irregular bed that mimicked key aspects of their natural cobble-bed habitat. Velocities were similar for both bed treatments. Settlement on the irregular bed was 40 times greater than on the flat bed due to silk use. Settlement rate also exhibited a marginally significant decline with increasingly velocity on the flat bed, but not on the irregular bed. Silk threads should greatly increase the settlement rate of these nonswimming larvae on coarse-grained stream beds. Thus, silk snagging can potentially reduce the downstream distance that individuals are transported during a drift event, although the effects of silk on other phases of larval dispersal may differ.