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675 results for “Introgression”
Data from: Genome-wide single nucleotide polymorphism analysis reveals recent genetic introgression from domestic pigs into Northwest European wild boar populations
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Data from: Widespread hybridization and bidirectional introgression in sympatric species of coral reef fish
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Data from: Introgressive hybridization and natural selection in Darwin's finches
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Data from: Directional mitochondrial introgression and character displacement due to reproductive interference in two closely related Pterostichus ground beetle species
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Population structure of Rosa spinosissima L. on the Frisian Islands and introgression from cultivated material
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Integrative taxonomy of two thrush complexes (Aves: Turdidae) reveals introgression across sister species
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Maintaining genetic integrity with high promiscuity: Frequent hybridization with low introgression in multiple hybrid zones of Melocactus(Cactaceae)
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Ancient introgression between distantly related white oaks (Quercus sect Quercus) shows evidence of climate-associated asymmetric gene exchange
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Introgression across evolutionary scales suggests reticulation contributes to Amazonian tree diversity
<p>Hybridisation has the potential to generate or homogenize biodiversity and is a particularly common phenomenon in plants, with an estimated 25% of plant species undergoing inter-specific gene flow. However, hybridisation in Amazonia's megadiverse tree flora was assumed to be extremely rare despite extensive sympatry between closely related species, and its role in diversification remains enigmatic because it has not yet been examined empirically. Using members of a dominant Amazonian tree family (<i>Brownea</i>, Fabaceae) as a model to address this knowledge gap, our study recovered extensive evidence of hybridisation among multiple lineages across phylogenetic scales. More specifically, using targeted sequence capture our results uncovered several historical introgression events between <i>Brownea </i>lineages and indicated that gene tree incongruence in <i>Brownea</i> is best explained by reticulation, rather than solely by incomplete lineage sorting. Furthermore, investigation of recent hybridisation using ~19,000 ddRAD loci recovered a high degree of shared variation between two <i>Brownea </i>species that co-occur in the Ecuadorian Amazon.</p> <p>Our analyses also showed that these sympatric lineages exhibit homogeneous rates of introgression among loci relative to the genome-wide average, implying a lack of selection against hybrid genotypes and persistent hybridisation. Our results demonstrate that gene flow between multiple Amazonian tree species has occurred across temporal scales, and contrasts with the prevailing view of hybridisation's rarity in Amazonia. Overall, our results provide novel evidence that reticulate evolution influenced diversification in part of the Amazonian tree flora, which is the most diverse on Earth.</p>
Phylogenomic data reveal widespred introgression across the range of an alpine and arctic specialist
<p>Understanding how gene flow affects population divergence and speciation remains challenging. Differentiating one evolutionary process from another can be difficult because multiple processes can produce similar patterns, and more than one process can occur simultaneously. While simple population models produce predictable results, how these processes balance in taxa with patchy distributions and complicated natural histories is less certain. These types of populations might be highly connected through migration (gene flow), but can experience stronger effects of genetic drift and inbreeding, or localized selection. While different signals can be difficult to separate, the application of high throughput sequence data can provide the resolution necessary to distinguish many of these processes. We present whole genome sequence data for an avian species group with an alpine and arctic tundra distribution to examine the role that different population genetic processes have played in their evolutionary history. Rosy-finches inhabit high elevation mountaintop sky islands and high-latitude island and continental tundra. They exhibit extensive plumage variation coupled with low levels of genetic variation. Additionally, the number of species within the complex is debated, making them excellent for studying the forces involved in the process of diversification, as well as an important species group in which to investigate species boundaries. Total genomic variation suggests a broadly continuous pattern of allele frequency changes across the mainland taxa of this group in North America. However, phylogenomic analyses recover multiple distinct, well supported, groups that coincide with previously described morphological variation and current species-level taxonomy. Tests of introgression using D-statistics and approximate Bayesian computation reveal significant levels of introgression between multiple North American taxa. These results provide insight into the balance between divergent and homogenizing population genetic processes, and highlight remaining challenges in interpreting conflict between different types of analytical approaches with whole genome sequence data.</p>
Data from: Spontaneous hybridization and introgression between walleye (Sander vitreus) and sauger (S. canadensis) in two large reservoirs: insights from genotyping-by-sequencing
<p>Anthropogenic activities may facilitate undesirable hybridization and genomic introgression between fish species. Walleye (<i>Sander vitreus</i>) and sauger (<i>Sander canadensis</i>) are economically valuable freshwater species that can spontaneously hybridize in areas of sympatry. Levels of genomic introgression between walleye and sauger may be increased by modifications to waterbodies (e.g., reservoir development) and inadvertent propagation of hybrids in stocking programs. We used genotyping by sequencing (GBS) to examine 217 fish from two large reservoirs with mixed populations of walleye and sauger in Saskatchewan, Canada (Lake Diefenbaker, Tobin Lake). Analyses with 20,038 (r90) and 478 (r100) SNPs clearly resolved walleye and sauger, and classified hybrids with high confidence. F<sub>1</sub>, F<sub>2</sub>, and multi-generation hybrids were detected in Lake Diefenbaker, indicating potentially high levels of genomic introgression. In contrast, only F<sub>1</sub> hybrids were detected in Tobin Lake. Field classification of fish was unreliable; 7% of fish were misidentified based on broad species categories. Important for activities such as brood stock selection, 12/173 (7%) fish field-identified as pure walleye, and 1/24 (4%) identified as pure sauger were actually hybrids. In addition, 2/15 (13%) field-identified hybrids were actually pure walleye or sauger. We conclude that hybridization and introgression are occurring in Saskatchewan reservoirs, and that caution is warranted when using these populations in stocking programs. GBS offers a powerful and flexible tool for examining hybridization without pre-identification of informative loci, eliminating some of the key challenges associated with other marker types.</p>
Data from: Evaluating the use of ABBA-BABA statistics to locate introgressed loci
Several methods have been proposed to test for introgression across genomes. One method tests for a genome-wide excess of shared derived alleles between taxa using Patterson's D statistic, but does not establish which loci show such an excess or whether the excess is due to introgression or ancestral population structure. Several recent studies have extended the use of D by applying the statistic to small genomic regions, rather than genome-wide. Here, we use simulations and whole genome data from Heliconius butterflies to investigate the behavior of D in small genomic regions. We find that D is unreliable in this situation as it gives inflated values when effective population size is low, causing D outliers to cluster in genomic regions of reduced diversity. As an alternative, we propose a related statistic f̂d, a modified version of a statistic originally developed to estimate the genome-wide fraction of admixture. f̂d is not subject to the same biases as D, and is better at identifying introgressed loci. Finally, we show that both D and f̂d outliers tend to cluster in regions of low absolute divergence (dXY), which can confound a recently proposed test for differentiating introgression from shared ancestral variation at individual loci.
Data from: Detection and polarization of introgression in a five-taxon phylogeny
When multiple speciation events occur rapidly in succession, discordant genealogies due to incomplete lineage sorting (ILS) can complicate the detection of introgression. A variety of methods, including the D-statistic (a.k.a. the "ABBA–BABA test"), have been proposed to infer introgression in the presence of ILS for a four-taxon clade. However, no integrated method exists to detect introgression using allelic patterns for more complex phylogenies. Here we explore the issues associated with previous systems of applying D-statistics to a larger tree topology, and propose new DFOIL tests as an integrated framework to infer both the taxa involved in and the direction of introgression for a symmetric five-taxon phylogeny. Using theory and simulations, we show that the DFOIL statistics correctly identify the introgression donor and recipient lineages, even at low rates of introgression. DFOIL is also shown to have extremely low false-positive rates. The DFOIL tests are computationally inexpensive to calculate and can easily be applied to phylogenomic data sets, both genome-wide and in windows of the genome. In addition, we explore both the principles and problems of introgression detection in even more complex phylogenies.
Data from: Differential introgression and the maintenance of species boundaries in an advanced generation avian hybrid zone
Background: Evolutionary processes, including selection and differential fitness, shape the introgression of genetic material across a hybrid zone, resulting in the exchange of some genes but not others. Differential introgression of molecular or phenotypic markers can thus provide insight into factors contributing to reproductive isolation. We characterized patterns of genetic variation across a hybrid zone between two tidal marsh birds, Saltmarsh (Ammodramus caudacutus) and Nelson's (A. nelsoni) sparrows (n = 286), and compared patterns of introgression among multiple genetic markers and phenotypic traits. Results: Geographic and genomic cline analyses revealed variable patterns of introgression among marker types. Most markers exhibited gradual clines and indicated that introgression exceeds the spatial extent of the previously documented hybrid zone. We found steeper clines, indicating strong selection for loci associated with traits related to tidal marsh adaptations, including for a marker linked to a gene region associated with metabolic functions, including an osmotic regulatory pathway, as well as for a marker related to melanin-based pigmentation, supporting an adaptive role of darker plumage (salt marsh melanism) in tidal marshes. Narrow clines at mitochondrial and sex-linked markers also offer support for Haldane's rule. We detected patterns of asymmetrical introgression toward A. caudacutus, which may be driven by differences in mating strategy or differences in population density between the two species. Conclusions: Our findings offer insight into the dynamics of a hybrid zone traversing a unique environmental gradient and provide evidence for a role of ecological divergence in the maintenance of pure species boundaries despite ongoing gene flow.
Data from: Distinguishing migration from isolation using genes with intragenic recombination: detecting introgression in the Drosophila simulans species complex
Background: Determining the presence or absence of gene flow between populations is the target of some statistical methods in population genetics. Until recently, these methods either avoided the use of recombining genes, or treated recombination as a nuisance parameter. However, genes with recombination contribute additional information for the detection of gene flow (i.e. through linkage disequilibrium). Methods: We present three summary statistics based on the spatial arrangement of fixed differences, and shared and exclusive polymorphisms that are sensitive to the presence and direction of gene flow. Power and false positive rate for tests based on these statistics are studied by simulation. Results: The application of these tests to populations from the Drosophila simulans species complex yielded results consistent with migration between D. simulans and its two endemic sister species D. mauritiana and D. sechellia, and between populations D. mauritiana on the islands of the Mauritius and Rodrigues. Conclusions: We demonstrate the sensitivity of the developed statistics to the presence and direction of gene flow, and characterize their power as a function of differentiation level and recombination rate. The properties of these statistics make them especially suitable for analyzing high-throughput sequencing data or for their integration within the approximate Bayesian computation framework.
Data from: Uncovering the genomic signature of ancient introgression between white oak lineages (Quercus)
• Botanists have long recognized interspecific gene flow as a common occurrence within white oaks (Quercus section Quercus). Historical allele exchange, however, has not been fully characterized, and the complex genomic signals resulting from the combination of vertical and horizontal gene transmission may confound phylogenetic inference and obscure our ability to accurately infer the deep evolutionary history of oaks. • Using anchored enrichment, we obtained a phylogenomic dataset consisting of hundreds of single-copy nuclear loci. Concatenation, species tree, and network analyses were carried out in an attempt to uncover the genomic signal of ancient introgression and infer the divergent phylogenetic topology for the white oak clade. Locus and site-level likelihood comparisons were then conducted to further explore the introgressed signal within our dataset. • Historical, intersectional gene flow is suggested to have occurred between (1) an ancestor of the Eurasian Roburoid lineage and Quercus pontica and (2) North American Dumosae and Prinoideae lineages. • Despite extensive time past, our approach proved successful in detecting the genomic signature of ancient introgression. Our results, however, highlight the importance of sampling and the use of a plurality of analytical tools and methods to sufficiently explore genomic datasets, uncover this signal, and accurately infer evolutionary history.
Data from: Reticulate evolutionary history and extensive introgression in mosquito species revealed by phylogenetic network analysis
The role of hybridization and subsequent introgression has been demonstrated in an increasing number of species. Recently, Fontaine et al. (Science, 347, 2015, 1258524) conducted a phylogenomic analysis of six members of the Anopheles gambiae species complex. Their analysis revealed a reticulate evolutionary history and pointed to extensive introgression on all four autosomal arms. The study further highlighted the complex evolutionary signals that the co-occurrence of incomplete lineage sorting (ILS) and introgression can give rise to in phylogenomic analyses. While tree-based methodologies were used in the study, phylogenetic networks provide a more natural model to capture reticulate evolutionary histories. In this work, we reanalyse the Anopheles data using a recently devised framework that combines the multispecies coalescent with phylogenetic networks. This framework allows us to capture ILS and introgression simultaneously, and forms the basis for statistical methods for inferring reticulate evolutionary histories. The new analysis reveals a phylogenetic network with multiple hybridization events, some of which differ from those reported in the original study. To elucidate the extent and patterns of introgression across the genome, we devise a new method that quantifies the use of reticulation branches in the phylogenetic network by each genomic region. Applying the method to the mosquito data set reveals the evolutionary history of all the chromosomes. This study highlights the utility of 'network thinking' and the new insights it can uncover, in particular in phylogenomic analyses of large data sets with extensive gene tree incongruence.
Data from: Adaptive divergence in wine yeasts and their wild relatives suggests a prominent role for introgressions and rapid evolution at non coding sites
In Saccharomyces cerevisiae, the main yeast in wine fermentation, the opportunity to examine divergence at the molecular level between a domesticated lineage and its wild counterpart arose recently due to the identification of the closest relatives of wine strains, a wild population associated with Mediterranean oaks. Since genomic data is available for a considerable number of representatives belonging to both groups, we used population genomics to estimate the degree and distribution of nucleotide variation between wine yeasts and their closest wild relatives. We found widespread genome-wide divergence, particularly at non-coding sites, which, together with above average divergence in trans-acting DNA binding proteins, may suggest an important role for divergence at the level of transcriptional regulation. Nine outlier regions putatively under strong divergent selection were highlighted by a genome wide scan under stringent conditions. Several cases of introgressions originating in the sibling species S. paradoxus, were also identified in the Mediterranean oak population. FFZ1 and SSU1, mostly known for conferring sulphite resistance in wine yeasts, were among the introgressed genes, although not fixed. Because the introgressions detected in our study are not found in wine strains, we hypothesise that ongoing divergent ecological selection segregates the two forms between the different niches. Together, our results provide a first insight into the extent and kind of divergence between wine yeasts and their closest wild relatives.
Data from: A new method to scan genomes for introgression in a secondary contact model
Secondary contact between divergent populations or incipient species may result in the exchange and introgression of genomic material. We develop a simple DNA sequence measure, called Gmin, which is designed to identify genomic regions experiencing introgression in a secondary contact model. Gmin is defined as the ratio of the minimum between-population number of nucleotide differences in a genomic window to the average number of between-population differences. Although it is conceptually simple, one advantage of Gmin is that it is computationally inexpensive relative to model-based methods for detecting gene flow and it scales easily to the level of whole-genome analysis. We compare the sensitivity and specificity of Gmin to those of the widely used index of population differentiation, FST, and suggest a simple statistical test for identifying genomic outliers. Extensive computer simulations demonstrate that Gmin has both greater sensitivity and specificity for detecting recent introgression than does FST. Furthermore, we find that the sensitivity of Gmin is robust with respect to both the population mutation and recombination rates. Finally, a scan of Gmin across the X chromosome of Drosophila melanogaster identifies candidate regions of introgression between sub-Saharan African and cosmopolitan populations that were previously missed by other methods. These results show that Gmin is a biologically straightforward, yet powerful, alternative to FST, as well as to more computationally intensive model-based methods for detecting gene flow.
Data from: Local inter-species introgression is the main cause of extreme levels of intra-specific differentiation in mussels
Structured populations, and replicated zones of contact between species, are an ideal opportunity to study regions of the genome with unusual levels of differentiation; and these can illuminate the genomic architecture of species isolation, and the spread of adaptive alleles across species ranges. Here, we investigated the effects of gene flow on divergence and adaptation in the Mytilus complex of species, including replicated parental populations in quite distant geographical locations. We used target enrichment sequencing of 1269 contigs of a few Kb each, including some genes of known function, to infer gene genealogies at a small chromosomal scale. We show that geography is an important determinant of the genome-wide patterns of introgression in Mytilus, and that gene flow between different species, with contiguous ranges, explained up to half of the intra-specific outliers. This suggests that local introgression is both widespread and tends to affect larger chromosomal regions than purely intraspecific processes. We argue that this situation might be common, and this implies that genome scans should always consider the possibility of introgression from sister species, unsampled differentiated backgrounds, or even extinct relatives, e.g. Neanderthals in humans. The hypothesis that reticulate evolution over long periods of time contributes widely to adaptation, and to the spatial and genomic reorganisation of genetic backgrounds, needs to be more widely considered in order to make better sense of genome scans.
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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)
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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.