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114 results for “Flow structure”
Data from: Landscape genetic structure of Scirpus mariqueter reveals a putatively adaptive differentiation under strong gene flow in estuaries
Estuarine organisms grow in highly heterogeneous habitats and their genetic differentiation are driven by selective and neutral processes as well as population colonization history. However, the relative importance of the processes that underlie genetic structure is still puzzling. Scirpus mariqueter is a perennial grass almost limited in the Changjiang River estuary and it's adjacent Qiantang River estuary. Here, using amplified fragment length polymorphism (AFLP), a moderate-high level of genetic differentiation among populations (range FST: 0.0310-0.3325) was showed despite large ongoing dispersal. FLOCK assigned all individuals to 13 clusters and revealed a complex genetic structure. Some genetic clusters were limited in peripheries compared with very mixing constitution in centre populations, suggesting local adaptation was more likely to occur in peripheral populations. 21 candidate outliers under positive selection were detected, and further, the differentiation patterns correlated with geographic distance, salinity difference and colonization history were analyzed with or without the outliers. Combined results of AMOVA and IBD based on different dataset, it was found that the effects of geographic distance and population colonization history on isolation seemed to be promoted by divergent selection. However, none-liner IBE pattern indicates the effects of salinity were overwhelmed by spatial distance or other ecological process in certain areas, and also suggests that salinity was not the only selective factor driving population differentiation. These results together indicate that geographic distance, salinity difference and colonization history co-contributed in shaping the genetic structure of S. mariqueter, and that their relative importance was correlated with spatial scale and environment gradient.
Data from: Intercontinental genetic structure and gene flow in Dunlin (Calidris alpina), a potential vector of avian influenza
Waterfowl (Anseriformes) and shorebirds (Charadriiformes) are the most common wild vectors of influenza A viruses. Due to their migratory behavior, some may transmit disease over long distances. Migratory connectivity studies can link breeding and nonbreeding grounds while illustrating potential interactions among populations that may spread diseases. We investigated Dunlin (Calidris alpina), a shorebird with a subspecies (C. a. arcticola) that migrates from nonbreeding areas endemic to avian influenza in eastern Asia to breeding grounds in northern Alaska. Using microsatellites and mitochondrial DNA, we illustrate genetic structure among six subspecies: C. a. arcticola, C. a. pacifica, C. a. hudsonia, C. a. sakhalina, C. a. kistchinski, and C. a. actites. We demonstrate that mitochondrial DNA can help distinguish C. a. arcticola on the Asian nonbreeding grounds with >70% accuracy depending on their relative abundance, indicating that genetics can help determine if C. a. arcticola occurs where they may be exposed to highly pathogenic avian influenza (HPAI) during outbreaks. Our data reveal asymmetric intercontinental gene flow, with some C. a. arcticola short-stopping migration to breed with C. a. pacifica in western Alaska. Because C. a. pacifica migrates along the Pacific Coast of North America, interactions between these subspecies and other taxa provides route for transmission of HPAI into other parts of North America.
Data from: Fragmentation can increase spatial genetic structure without decreasing pollen-mediated gene flow in a wind-pollinated tree
Fragmentation reduces population sizes, increases isolation between habitats, and can result in restricted dispersal of pollen and seeds. Given that diploid seed dispersal contributes more to shaping fine-scale spatial genetic structure than haploid pollen flow, we tested whether fine-scale SGS can be sensitive to fragmentation even if extensive pollen dispersal is maintained. Castanopsis sclerophylla (Lindley & Paxton) Schottky (Fagaceae), a wind-pollinated and gravity seed-dispersed tree, was studied in an area of Southeast China where its populations have been fragmented to varying extents by human activity. Using different age classes of trees in areas subject to varying extents of fragmentation, we found no significant difference in genetic diversity between pre- and post-fragmentation C. sclerophylla subpopulations. Genetic differentiation among post-fragmentation subpopulations was also only slightly lower than among post-fragmentation subpopulations. In the most fragmented habitat, selfing rates were significantly higher than zero in pre-fragmentation, but not post-fragmentation, cohorts. These results suggest that fragmentation had not decreased gene flow among these populations and that pollen flow remains extensive. However, significantly greater fine-scale SGS was found in post-fragmentation subpopulations in the most fragmented habitat, but not in less fragmented habitats. This alteration in SGS reflected more restricted seed dispersal, induced by changes in the physical environments and the prevention of secondary seed dispersal by rodents. An increase in SGS can therefore result from more restricted seed dispersal, even in the face of extensive pollen flow, making it a sensitive indicator of the negative consequences of population fragmentation.
Data from: Flow-ecology relationships are spatially structured and differ among flow regimes
1. In streams, hydrology is a predominant driver of ecological structure and function. Providing adequate flows to support aquatic life, or environmental flows, is therefore a top management priority in stream systems. 2. Flow regime classification is a widely accepted approach for establishing environmental flow guidelines. However, it is surprisingly difficult to quantify relationships between hydrology and ecology (flow-ecology relationships) while describing how these relationships vary across classified flow regimes. Developing such relationships is complicated by several sources of spatial bias, such as autocorrelation due to spatial design, flow regime classification, and other environmental or ecological sources of spatial bias. 3. We used mixed moving-average spatial stream network models to develop flow-ecology relationships across classified flow regimes and to assess spatial patterns of these relationships. We compared relationships between fish traits and life-history strategies with hydrologic metrics across flow regimes and assessed whether spatial autocorrelation influenced these relationships. 4. Trait-hydrology relationships varied between flow regimes and across all streams combined. Some relationships between traits and hydrologic metrics fit predictions based on life-history theory, while others exhibited unexpected relationships with hydrology. Spatial factors described a large proportion of variability in fish traits and different patterns of spatial autocorrelation were observed in different flow regimes. Synthesis and Applications. Further work is needed to understand why flow-ecology relationships vary across classified flow regimes and why these relationships may not fit predictions based on life-history theories. Managers determining environmental flow standards need to be aware that different hydrologic metrics are often important drivers of fish trait diversity in different flow-regimes. Flow-ecology relationships may therefore be confounded by spatial structure that is inherent in flow regime classification and much existing biological data. Complex patterns of spatial bias should be considered when managing stream systems within an environmental flows framework.
Data from: Comparative landscape genetics of pond-breeding amphibians in Mediterranean temporal wetlands: the positive role of structural heterogeneity in promoting gene flow
Comparative landscape genetics studies can provide key information to implement cost-effective conservation measures favoring a broad set of taxa. These studies are scarce, particularly in Mediterranean areas, which include diverse but threatened biological communities. Here we focus on Mediterranean wetlands in central Iberia and perform a multi-level, comparative study of two endemic pond-breeding amphibians, a salamander (Pleurodeles waltl) and a toad (Pelobates cultripes). We genotyped 411 salamanders from 20 populations and 306 toads from 16 populations at 18 and 16 microsatellite loci, respectively, and identified major factors associated with population connectivity through the analysis of three sets of variables potentially affecting gene flow at increasingly finer levels of spatial resolution. Topographic, land use/cover, and remotely sensed vegetation/moisture indices were used to derive optimized resistance surfaces for the two species. We found contrasting patterns of genetic structure, with stronger, finer-scale genetic differentiation in Pleurodeles waltl, and notable differences in the role of fine-scale patterns of heterogeneity in vegetation cover and water content in shaping patterns of regional genetic structure in the two species. Overall, our results suggest a positive role of structural heterogeneity in population connectivity in pond-breeding amphibians, with habitat patches of Mediterranean scrubland and open oak woodlands ("dehesas") facilitating gene flow. Our study highlights the usefulness of remotely sensed continuous variables of land cover, vegetation and water content (e.g., NDVI, NDMI) in conservation-oriented studies aimed at identifying major drivers of population connectivity.
Data from: Geographic population structure of the African malaria vector Anopheles gambiae suggests a role for the forest-savannah biome transition as a barrier to gene flow
The primary Afrotropical malaria mosquito vector Anopheles gambiae sensu stricto has a complex population structure. In western Africa, this species is split into two molecular forms and displays local and regional variation in chromosomal arrangements and behaviours. To investigate patterns of macro-geographic population substructure, 25 An. gambiae samples from 12 African countries were genotyped at 13 microsatellite loci. This analysis detected the presence of additional population structuring, with the M-form being subdivided into distinct west, central and southern African genetic clusters. These clusters are coincident with the central African rainforest belt and northern and southern savannah biomes, which suggests restrictions to gene flow associated with the transition between these biomes. By contrast geographically patterned population substructure appears much weaker within the S-form.
Data from: Genetic diversity and structure of Lolium perenne ssp. multiflorum in California vineyards and orchards indicates potential for spread of herbicide resistance via gene flow
Management of agroecosystems with herbicides imposes strong selection pressures on weedy plants leading to the evolution of resistance against those herbicides. Resistance to glyphosate in populations of Lolium perenne L. ssp. multiflorum is increasingly common in California, USA, causing economic losses and the loss of effective management tools. To gain insights into the recent evolution of glyphosate resistance in L. perenne in perennial cropping systems of northwest California and to inform management, we investigated the frequency of glyphosate resistance and the genetic diversity and structure of 14 populations. The sampled populations contained frequencies of resistant plants ranging from 10% to 89%. Analyses of neutral genetic variation using microsatellite markers indicated very high genetic diversity within all populations regardless of resistance frequency. Genetic variation was distributed predominantly among individuals within populations rather than among populations or sampled counties, as would be expected for a wide-ranging outcrossing weed species. Bayesian clustering analysis provided evidence of population structuring with extensive admixture between two genetic clusters or gene pools. High genetic diversity and admixture, and low differentiation between populations, strongly suggests the potential for spread of resistance through gene flow and the need for management that limits seed and pollen dispersal in L. perenne.
Data from: Life-history characteristics and landscape attributes as drivers of genetic variation, gene flow and fine-scale population structure in Northern Dolly Varden (Salvelinus malma malma) in Canada
The Northern Dolly Varden (Salvelinus malma malma) displays variable life-history types and occupies freshwater habitats with varying levels of connectivity. Here, we assayed microsatellite DNA variation in Northern Dolly Varden from the western Canadian Arctic to resolve landscape and life history variables driving variation in genetic diversity and population structure. Overall, genetic variation was highest in anadromous populations and lowest in those isolated above waterfalls with stream-resident forms intermediate between the two. Anadromous and isolated populations were genetically divergent from each other while no genetic differentiation was detectable between sympatric anadromous and stream-resident forms. Population structure was stable over 25 years, hierarchically organized and conformed to an isolation-by-distance pattern, but stream-isolated forms often deviated from these patterns. Gene flow occurred primarily among Yukon North Slope populations and between sympatric anadromous and resident forms. These results were sex-dependent to some extent, but were influenced more by reproductive status and life history. Our study provides novel insights into the life history, population demographic and habitat variables that shape the distribution of genetic variation and population structure in Arctic fluvial habitats while providing a spatial context for management and conservation.
Data from: Fractal characteristics of shale pore structure and its influence on seepage flow
<p>The migration law of shale gas has a significant influence on the seepage characteristics of shale, and the flow of the gas is closely related to the pore structure. To explore the influence of shale pore parameters on permeability in different diffusion zones, the pore structure of the shale in the Niutitang Formation in Guizhou, China, was analyzed based on liquid nitrogen adsorption experiments and nuclear magnetic resonance experiments. The relationship among fractal dimension, organic carbon content (TOC), and BET specific surface area was analyzed based on the fractal dimension of shale pores calculated using the Frenkel‒Halsey‒Hill model. Shale permeability was calculated using the Knudsen number and permeability equation, and the influence of the fractal dimension and porosity in different diffusion zones on shale permeability was analyzed. Previous studies have shown that: (1) the pores of shale in the Niutitang Formation, Guizhou are mainly distributed within 1‒100 nm, with a small total pore volume per unit mass, average pore diameter, large BET specific surface area, and porosity; (2) fractal dimension has a negative correlation with average pore diameter and TOC content and a quadratic relationship with BET specific surface area; (3) permeability has a positive correlation with Kn, porosity, and fractal dimension. In the transitional diffusion zone, fractal dimension and porosity have a significant impact on permeability. In the Knudsen diffusion zone, porosity has no obvious effect on permeability. The methodologies and results presented will enable more accurate characterization of the complexity of pore structures of porous media, and allow further understanding of the seepage law of shale gas.</p>
Next-generation phylogeography of the banded newts (Ommatotriton): A phylogenetic hypothesis for three ancient species with geographically restricted interspecific gene flow and deep intraspecific genetic structure
<p class="MsoNoSpacing">Technological developments now make it possible to employ many markers for many individuals in a phylogeographic setting, even for taxa with large and complex genomes such as salamanders. The banded newt (genus <i>Ommatotriton</i>) from the Near East has been proposed to contain three species (<i>O. nesterovi</i>, <i>O. ophryticus </i>and <i>O. vittatus</i>) with unclear phylogenetic relationships, apparently limited interspecific gene flow and deep intraspecific geographic mtDNA structure. We use parallel tagged amplicon sequencing to obtain 177 nuclear DNA markers for 35 banded newts sampled throughout the range. We determine population structure (with Bayesian clustering and principal component analysis), interspecific gene flow (by determining the distribution of species-diagnostic alleles) and phylogenetic relationships (by maximum likelihood inference of concatenated sequence data and based on a summary-coalescent approach). We confirm that the three proposed species are genetically distinct. A sister relationship between <i>O. nesterovi</i> and <i>O. ophryticus</i> is suggested. We find evidence for introgression between <i>O. nesterovi</i> and <i>O. ophryticus</i>, but this is geographically limited. Intraspecific structuring is extensive, with the only recognized banded newt subspecies, <i>O. vittatus cilicensis</i>, representing the most distinct lineage below the species level. While mtDNA mostly mirrors the pattern observed in nuclear DNA, all banded newt species show mito-nuclear discordance as well.</p>
Supplementary material for the manuscript "Transition to chaos and modal structure of magnetized Taylor–Couette flow"
<p>These data and codes are the supplementary materials for the manuscript "Transition to chaos and modal structure of magnetized Taylor–Couette flow". The description of the data is in the file "DATA_OVERVIEW.txt".</p>
Supplementary material 2 from: Aketarawong N, Isasawin S, Sojikul P, Thanaphum S (2015) Gene flow and genetic structure of Bactrocera carambolae (Diptera, Tephritidae) among geographical differences and sister species, B. dorsalis, inferred from microsatellite DNA data. In: De Meyer M, Clarke AR, Vera MT, Hendrichs J (Eds) Resolution of Cryptic Species Complexes of Tephritid Pests to Enhance SIT Application and Facilitate International Trade. ZooKeys 540: 239-272. https://doi.org/10.3897/zookeys.540.10058
Component data at the four successive thresholds used to illustrate Figure 5: Explanation note: Component data are used to illustrate the structure of the subset of Bactrocera carambolae and Bactrocera dorsalis populations. The highest Betweenness-centrality is highlighted in blue.
Supplementary material 1 from: Aketarawong N, Isasawin S, Sojikul P, Thanaphum S (2015) Gene flow and genetic structure of Bactrocera carambolae (Diptera, Tephritidae) among geographical differences and sister species, B. dorsalis, inferred from microsatellite DNA data. In: De Meyer M, Clarke AR, Vera MT, Hendrichs J (Eds) Resolution of Cryptic Species Complexes of Tephritid Pests to Enhance SIT Application and Facilitate International Trade. ZooKeys 540: 239-272. https://doi.org/10.3897/zookeys.540.10058
Component data at the five successive thresholds used to illustrate Figure 4: Explanation note: Component data are used to illustrate the structure of the subset of Bactrocera carambolae populations. The Highest Betweenness-centrality is highlighted in blue.
Supplementary material 4 from: Aketarawong N, Isasawin S, Sojikul P, Thanaphum S (2015) Gene flow and genetic structure of Bactrocera carambolae (Diptera, Tephritidae) among geographical differences and sister species, B. dorsalis, inferred from microsatellite DNA data. In: De Meyer M, Clarke AR, Vera MT, Hendrichs J (Eds) Resolution of Cryptic Species Complexes of Tephritid Pests to Enhance SIT Application and Facilitate International Trade. ZooKeys 540: 239-272. https://doi.org/10.3897/zookeys.540.10058
Comparisons among three different the individual admixture plots: Explanation note: Comparisons among the individual admixture plots of 289 individuals, for K = 3, considering correlated allele frequency, uncorrelated allele frequency, and missing data as recessive homozygotes for the null alleles, respectively.
Supplementary material 3 from: Aketarawong N, Isasawin S, Sojikul P, Thanaphum S (2015) Gene flow and genetic structure of Bactrocera carambolae (Diptera, Tephritidae) among geographical differences and sister species, B. dorsalis, inferred from microsatellite DNA data. In: De Meyer M, Clarke AR, Vera MT, Hendrichs J (Eds) Resolution of Cryptic Species Complexes of Tephritid Pests to Enhance SIT Application and Facilitate International Trade. ZooKeys 540: 239-272. https://doi.org/10.3897/zookeys.540.10058
Component data at the four successive thresholds used to illustrate Figure 6: Explanation note: Component data are used to illustrate the structure of the subset of the Salaya5 strain and wild populations. The highest Betweenness-centrality is highlighted in blue.
Diffusion rates for GRL manuscript "Red line diffusion-like auroras driven by time domain structures associated with braking magnetotail flow bursts"
<p>This dataset in MATLAB files provide electron bounce-averaged pitch-angle diffusion rates due to scattering by time domain structures and whistler-mode waves, as pertinent to the manuscript submission to the Geophysical Research Letters (doi: 10.1029/2024GL109000), titled "Red line diffusion-like aurora driven by time domain structures associated with braking magnetotail flow bursts". </p> <p>Please cite the original GRL manuscript when using TDS-driven diffusion rates from this dataset for your research.</p>
Data from: Scale-dependent effects of landscape variables on gene flow and population structure in bats
Aim: A common pattern in biogeography is the scale-dependent effect of environmental variables on the spatial distribution of species. We tested the role of climatic and land cover variables in structuring the distribution of genetic variation in the grey long-eared bat, Plecotus austriacus, across spatial scales. Although landscape genetics has been widely used to describe spatial patterns of gene flow in a variety of taxa, volant animals have generally been neglected because of their perceived high dispersal potential.Location: England and Europe. Methods: We used a multiscale integrated approach, combining population genetics with species distribution modelling and geographical information under a causal modelling framework, to identify landscape barriers to gene flow and their effect on population structure and conservation status. Genotyping involved 23 polymorphic microsatellites and 259 samples from across the species' range. Results: We identified distinct population structure shaped by geographical barriers and evidence of population fragmentation at the northern edge of the range. Habitat suitability (as captured by species distribution models, SDMs) was the most important landscape variable affecting genetic connectivity at the broad spatial scale, while at the fine scale, lowland unimproved grasslands, the main foraging habitat of P. austriacus, played a pivotal role in promoting genetic connectivity. Main conclusions: The importance of lowland unimproved grasslands in determining the biogeography and genetic connectivity in P. austriacus highlights the importance of their conservation as part of a wider landscape management for fragmented edge populations. This study illustrates the value of using SDMs in landscape genetics and highlights the need for multiscale approaches when studying genetic connectivity in volant animals or taxa with similar dispersal abilities.
Data from: Contrasting patterns of population structure and gene flow facilitate exploration of connectivity in two widely distributed temperate octocorals
Connectivity is an important component of metapopulation dynamics in marine systems and can influence population persistence, migration rates and conservation decisions associated with Marine Protected Areas (MPAs). In this study, we compared the genetic diversity, gene flow and population structure of two octocoral species, Eunicella verrucosa and Alcyonium digitatum, in the northeast Atlantic (ranging from the northwest of Ireland and the southern North Sea, to southern Portugal), using two panels of 13 and 8 microsatellite loci, respectively. Our results identified regional genetic structure in E. verrucosa partitioned between populations from southern Portugal, northwest Ireland and Britain/France; subsequent hierarchical analysis of population structure also indicated reduced gene flow between southwest Britain and northwest France. However, over a similar geographical area, A. digitatum showed little evidence of population structure, suggesting high gene flow and/or a large effective population size; indeed, the only significant genetic differentiation detected in A. digitatum occurred between North Sea samples and those from the English Channel/northeast Atlantic. In both species the vast majority of gene flow originated from sample sites within regions, with populations in southwest Britain being the predominant source of contemporary exogenous genetic variants for the populations studied. Overall, historical patterns of gene flow appeared more complex, though again southwest Britain appeared to be an important source of genetic variation for both species. Our findings have major conservation implications, particularly for E. verrucosa, a protected species in UK waters and listed by the IUCN as 'Vulnerable', and for the designation and management of European MPAs.
Data from: Landscape genomics of Populus trichocarpa: the role of hybridization, limited gene flow and natural selection in shaping patterns of population structure
Populus trichocarpa is an ecologically important tree across western North America. We used a large population sample of 498 accessions over a wide geographical area genotyped with a 34K Populus SNP array to quantify geographical patterns of genetic variation in this species (landscape genomics). We present evidence that three processes contribute to the observed patterns: (1) introgression from the sister species P. balsamifera (2) isolation-by-distance and (3) natural selection. Introgression was detected only at the margins of the species' distribution. Isolation-by-distance was significant across the sampled area as a whole, but no evidence of restricted gene flow was detected in a core of drainages from southern British Columbia. We identified a large number of FST outliers. GO analyses revealed that FST outliers are overrepresented in genes involved in circadian rhythm and response to red/far-red light when the entire dataset is considered, while in southern British Columbia heat response genes are overrepresented. We also identified strong correlations between geoclimate variables and allele frequencies at FST outlier loci that provide clues regarding the selective pressures acting at these loci.
High-pressure homogenized citrus fiber cellulose dispersions: structural characterization and flow behavior
<p>High-pressure homogenized citrus fiber cellulose dispersions: structural characterization and flow behavior</p>
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