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123 results for “Genomic islands”
Data from: Population genomics of Sitka black-tailed deer supports invasive species management and ecological restoration on islands
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Data from: Can AFLP genome scans detect small islands of differentiation? The case of shell sculpture variation in the periwinkle Echinolittorina hawaiiensis
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Data from: Ecological speciation in sympatric palms: 3. genetic map reveals genomic islands underlying species divergence in Howea
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Data from: "Transcriptomic resources for three populations of Conus miliaris (Mollusca: Conidae) from Easter Island, American Samoa and Guam" in Genomic Resources Notes Accepted 1 August 2014-30 September 2014
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Genomic and phenomic analysis of island ant community assembly
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The many population genetic and demographic routes to islands of genomic divergence
<ol> <li>The way that organisms diverge into reproductively isolated species is a major question in biology. The recent accumulation of genomic data provides promising opportunities to understand the genomic landscape of divergence, which describes the distribution of differences across genomes. Genomic areas of unusually high differentiation have been called genomic islands of divergence. Their formation has been attributed to a variety of mechanisms, but a prominent hypothesis is that they result from divergent selection over a small portion of the genome, with surrounding areas homogenised by gene flow. Such islands have often been interpreted as being associated with divergence with gene flow. However other mechanisms related to genomic structure and population history can also contribute to the formation of genomic islands of divergence.</li> <li>We currently lack a quantitative framework to examine the dynamics of genomic landscapes under the complex and nuanced conditions that are found in natural systems. Here, we develop an individual-based simulation to explore the dynamics of diverging genomes under various scenarios of gene flow, selection and genotype-phenotype maps.</li> <li>Our modelling results are consistent with empirical observations demonstrating the formation of genomic islands under genetic isolation. Importantly, we have quantified the range of conditions that produce genomic islands. We demonstrate that the initial level of genetic diversity, drift, time since divergence, linkage disequilibrium, strength of selection and gene flow are all important factors that can influence the formation of genomic islands. Because the accumulation of genomic differentiation over time tends to erode the signal of genomic islands, genomic islands are more likely to be observed in recently divergent taxa, although not all recently diverged taxa will necessarily exhibit islands of genomic divergence. Gene flow primarily slows the swamping of islands of divergence with time.</li> <li>By using this framework, further studies may explore the relative influence of particular suites of events that contribute to the emergence of genomic islands under sympatric, parapatric and allopatric conditions. This approach represents a novel tool to explore quantitative expectations of the speciation process, and should prove useful in elucidating past and projecting future genomic evolution of any taxa.</li> </ol>
Data from: Isolation by environment in white-breasted nuthatches (Sitta carolinensis) of the Madrean Archipelago sky islands: a landscape genomics approach
Understanding landscape processes driving patterns of population genetic differentiation and diversity has been a long-standing focus of ecology and evolutionary biology. Gene flow may be reduced by historical, ecological or geographic factors, resulting in patterns of isolation by distance (IBD) or isolation by environment (IBE). Although IBE has been found in many natural systems, most studies investigating patterns of IBD and IBE in nature have used anonymous neutral genetic markers, precluding inference of selection mechanisms or identification of genes potentially under selection. Using landscape genomics, the simultaneous study of genomic and ecological landscapes, we investigated the processes driving population genetic patterns of White-breasted Nuthatches (Sitta carolinensis) in sky islands (montane forest habitat islands) of the Madrean Archipelago. Using more than 4000 single nucleotide polymorphisms and multiple tests to investigate the relationship between genetic differentiation and geographic or ecological distance, we identified IBE, and a lack of IBD, among sky island populations of S. carolinensis. Using three tests to identify selection, we found 79 loci putatively under selection; of these, seven matched CDS regions in the Zebra Finch. The loci under selection were highly associated with climate extremes (maximum temperature of warmest month and minimum precipitation of driest month). These results provide evidence for IBE – disentangled from IBD – in sky island vertebrates and identify potential adaptive genetic variation.
Data from: Genomic islands of divergence are not affected by geography of speciation in sunflowers.
Genomic studies of speciation often report the presence of highly differentiated genomic regions interspersed within a milieu of weakly diverged loci. The formation of these speciation islands is generally attributed to reduced inter-population gene flow near loci under divergent selection, but few studies have critically evaluated this hypothesis. Here, we report on transcriptome scans among four recently diverged pairs of sunflower (Helianthus) species that vary in the geographical context of speciation. We find that genetic divergence is lower in sympatric and parapatric comparisons, consistent with a role for gene flow in eroding neutral differences. However, genomic islands of divergence are numerous and small in all comparisons, and contrary to expectations, island number and size are not significantly affected by levels of interspecific gene flow. Rather, island formation is strongly associated with reduced recombination rates. Overall, our results indicate that the functional architecture of genomes plays a larger role in shaping genomic divergence than does the geography of speciation.
Data from: Testing models of speciation from genome sequences: divergence and asymmetric admixture in Island Southeast Asian Sus species during the Plio-Pleistocene climatic fluctuations
In many temperate regions, ice ages promoted range contractions into refugia resulting in divergence (and potentially speciation), while warmer periods led to range expansions and hybridization. However, the impact these climatic oscillations had in many parts of the tropics remains elusive. Here, we investigate this issue using genome sequences of three pig (Sus) species, two of which are found on islands of the Sunda-shelf shallow seas in Island Southeast Asia (ISEA). A previous study revealed signatures of inter-specific admixture between these Sus species (Frantz et al. (2013) Genome sequencing reveals fine scale diversification and reticulation history during speciation in Sus. Genome biology, 14, R107). However, the timing, directionality and extent of this admixture remain unknown. Here we use a likelihood based model comparison to more finely resolve this admixture history and test whether it was mediated by humans or occurred naturally. Our analyses suggest that inter-specific admixture between Sunda-shelf species was most likely asymmetric and occurred long before the arrival of humans in the region. More precisely, we show that these species diverged during the late Pliocene but around 23% of their genomes have been affected by admixture during the later Pleistocene climatic transition. In addition, we show that our method provides a significant improvement over D-statistics which are uninformative about the direction of admixture.
Data from: A role for migration-linked genes and genomic islands in divergence of a songbird
Next-generation sequencing has made it possible to begin asking questions about the process of divergence at the level of the genome. For example, recently there has been a debate around the role of "genomic islands of divergence" (i.e. blocks of outlier loci) in facilitating the process of speciation-with-gene-flow. The Swainson's thrush, Catharus ustulatus, is a migratory songbird with two genetically-distinct subspecies that differ in a number of traits known to be involved in reproductive isolation in birds (plumage coloration, song, and migratory behavior), despite contemporary gene flow along a secondary contact zone. Here we use RAD-PE sequencing to test emerging hypotheses about the process of divergence at the level of the genome and identify genes and gene regions involved in differentiation in this migratory songbird. Our analyses revealed distinct genomic islands on 15 of the 23 chromosomes and levels of differentiation that were 2-3 orders of magnitude higher on the sex chromosomes than the autosomes. Further, an analysis of loci linked to pigmentation, song, and migratory behavior showed that genes linked to migration are significantly more differentiated then expected by chance, but that these genes lie primarily outside of the genomic islands. Overall, our analysis supports the idea that genes linked to migration play an important role in divergence in migratory songbirds, but we find no compelling evidence that the observed genomic islands are facilitating adaptive divergence in migratory behavior.
Data from: A genomic island linked to ecotype divergence in Atlantic cod
The genomic architecture underlying ecological divergence and ecological speciation with gene flow is still largely unknown for most organisms. One central question is whether divergence is genome-wide or localized in "genomic mosaics" during early stages when gene flow is still pronounced. Empirical work has so far been limited, and the relative impacts of gene flow and natural selection on genomic patterns have not been fully explored. Here, we use ecotypes of Atlantic cod to investigate genomic patterns of diversity and population differentiation in a natural system characterized by high gene flow and large effective population sizes, properties which theoretically could restrict divergence in local genomic regions. We identify a genomic region of strong population differentiation, extending over approximately 20 cM, between pairs of migratory and stationary ecotypes examined at two different localities. Furthermore, the region is characterized by markedly reduced levels of genetic diversity in migratory ecotype samples. The results highlight the genomic region, or "genomic island", as potentially associated with ecological divergence and suggest a selective sweep involved in ecological divergence. Finally, we also confirm earlier findings of localized genomic differentiation in three other linkage groups associated with divergence among eastern Atlantic populations. Thus, although underlying mechanisms are still unknown, the results suggest that "genomic mosaics" of differentiation may even be found under high levels of gene flow, and that marine fishes may provide insightful model systems for studying and identifying initial targets of selection during ecological divergence.
Data from: Metapopulation dominance and genomic-island acquisition of Bradyrhizobium with superior catabolic capabilities
Root nodule forming rhizobia exhibit a bipartite lifestyle, replicating in soil and also within plant cells where they fix nitrogen for legume hosts. Host control models posit that legume hosts act as a predominant selective force on rhizobia, but few studies have examined rhizobial fitness in natural populations. Here, we genotyped and phenotyped Bradyrhizobium isolates across >800km of the native Acmispon strigosus host range. We sequenced chromosomal genes expressed under free-living conditions and accessory symbiosis loci expressed in planta and encoded on an integrated 'symbiosis island'. We uncovered a massive clonal expansion restricted to the Bradyrhizobium chromosome, with a single chromosomal haplotype dominating populations, ranging >700km, and acquiring 42 divergent symbiosis island haplotypes, none of which were spatially widespread. For focal genotypes we quantified utilization of 190 sole-carbon sources relevant to soil fitness. Chromosomal haplotypes that were both widespread and dominant exhibited superior growth on diverse carbon sources, whereas these patterns were not mirrored among symbiosis island haplotypes. Abundance, spatial range, and catabolic superiority of chromosomal, but not symbiosis genotypes suggests that fitness in the soil environment, rather than symbiosis with hosts, might be the key driver of Bradyrhizobium dominance.
Data from: Reanalysis suggests that genomic islands of speciation are due to reduced diversity, not reduced gene flow
The metaphor of "genomic islands of speciation" was first used to describe heterogeneous differentiation among loci between the genomes of closely related species. The biological model proposed to explain these differences was that the regions showing high levels of differentiation were resistant to gene flow between species, while the remainder of the genome was being homogenized by gene flow and consequently showed lower levels of differentiation. However, the conditions under which such differentiation can occur at multiple unlinked loci are restrictive; additionally, essentially all previous analyses have been carried out using relative measures of divergence, which can be misleading when regions with different levels of recombination are compared. Here we test the model of differential gene flow by asking whether absolute divergence is also higher in the previously identified "islands." Using five species-pairs for which full sequence data is available, we find that absolute measures of divergence are not higher in genomic islands. Instead, in all cases examined we find reduced diversity in these regions, a consequence of which is that relative measures of divergence are abnormally high. These data therefore do not support a model of differential gene flow among loci, though islands of relative divergence may represent loci involved in local adaptation. Simulations using the program IMa2 further suggest that inferences of any gene flow may be incorrect in many comparisons. We instead present an alternative explanation for heterogeneous patterns of differentiation, one in which post-speciation selection generates patterns consistent with multiple aspects of the data.
Data from: Population genomic analysis uncovers African and European admixture in Drosophila melanogaster populations from the southeastern United States and Caribbean Islands
Drosophila melanogaster is postulated to have colonized North America in the past several 100 years in two waves. Flies from Europe colonized the east coast United States while flies from Africa inhabited the Caribbean, which if true, make the south-east US and Caribbean Islands a secondary contact zone for African and European D. melanogaster. This scenario has been proposed based on phenotypes and limited genetic data. In our study, we have sequenced individual whole genomes of flies from populations in the south-east US and Caribbean Islands and examined these populations in conjunction with population sequences from the west coast US, Africa, and Europe. We find that west coast US populations are closely related to the European population, likely reflecting a rapid westward expansion upon first settlements into North America. We also find genomic evidence of African and European admixture in south-east US and Caribbean populations, with a clinal pattern of decreasing proportions of African ancestry with higher latitude. Our genomic analysis of D. melanogaster populations from the south-east US and Caribbean Islands provides more evidence for the Caribbean Islands as the source of previously reported novel African alleles found in other east coast US populations. We also find the border between the south-east US and the Caribbean island to be the admixture hot zone where distinctly African-like Caribbean flies become genomically more similar to European-like south-east US flies. Our findings have important implications for previous studies examining the generation of east coast US clines via selection.
Channel Islands song sparrow (Melospiza melodia) landscape genomics and adaptation to climate with gene flow dataset
<p>Disentangling the effects of neutral and adaptive processes in maintaining phenotypic variation across environmental gradients is challenging in natural populations. <span>Song sparrows (<i>Melospiza melodia</i>) on the California Channel Islands occupy a pronounced east-west climate gradient within a small spatial extent, providing a unique opportunity to examine the interaction of genetic isolation (gene flow) and the environment (selection) in driving variation</span>. We used reduced representation genomic libraries to infer the role of neutral processes (drift and restricted gene flow) and divergent selection in driving variation in thermoregulatory traits with an emphasis on the mechanisms that maintain bill divergence among islands. Analyses of 22,029 neutral SNPs confirm distinct population structure by island with restricted gene flow and relatively large effective population sizes, suggesting bill differences are likely not a product of genetic drift. Instead, we found strong support for local adaptation using 3,294 SNPs in differentiation-based and environmental association analyses coupled with genome-wide association (GWA) tests. Specifically, we identified several putatively adaptive and candidate loci in or near genes involved in bill development pathways (<i>e.g.</i>, <i>BMP</i>, <i>CaM</i>, <i>Wnt</i>), confirming the highly complex and polygenic architecture underlying bill morphology. Furthermore, we found divergence in genes associated with other thermoregulatory traits (i.e., feather structure, plumage color, and physiology). Collectively, these results suggest strong divergent selection across an island archipelago results in genomic changes in a suite of traits associated with thermal adaptation over small spatial scales. Future research should move beyond the study of univariate traits to better understand the multivariate adaptive responses to these complex climate regimes.</p>
Data from: Testing models of speciation from genome sequences: divergence and asymmetric admixture in Island Southeast Asian Sus species during the Plio-Pleistocene climatic fluctuations
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Data from: Population genomic analysis uncovers African and European admixture in Drosophila melanogaster populations from the southeastern United States and Caribbean Islands
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An island-hopping bird reveals how founder events shape genome-wide divergence
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Data from: A role for migration-linked genes and genomic islands in divergence of a songbird
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Data from: Isolation by environment in white-breasted nuthatches (Sitta carolinensis) of the Madrean Archipelago sky islands: a landscape genomics approach
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.