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244 results for “coalescence”
Data from: A coalescent-based estimator of genetic drift, and acoustic divergence in the Pteronotus parnellii species complex
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Data from: ASTRAL: genome-scale coalescent-based species tree estimation
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Supplementary material for: Impact of ghost introgression on coalescent-based species tree inference and estimation of divergence time
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Using a coalescent approach to assess gene flow and effective population size of Acrocomia aculeata (Jacq.) Lodd. Ex Mart. in the Brazilian Atlantic Forest
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Contrasting the depths of divergence between gene-tree and coalescent estimates in the North American Racers (Colubridae: Coluber constrictor)
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Phase resolution of heterozygous sites in diploid genomes is important to phylogenomic analysis under the multispecies coalescent model
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LDhat coalescent likelihood lookup table for 320 sequences with theta = 0.01
<p>The LDhat `complete` tool uses the method of Fearnhead and Donnelly (2001) to calculate coalescent likelihoods (via importance sampling) for all possible two-locus haplotype configurations for a given number of sequences for a grid of recombination rate (rho) values. See the <a href="https://github.com/auton1/LDhat">LDhat documentation</a>. We considered the case of 320 sequences, for which there are 708400 configurations.</p> <p>Generating this table was computationally expensive (approximately 60,000 CPU hours), hence the interest in sharing it for reuse. The included sbatch job script illustrates how the computations were done (with GNU Parallel). The script could be adapted to compute a similar table on Linux clusters that use Slurm for cluster management/job scheduling.</p>
Data from: In the shadows: phylogenomics and coalescent species delimitation unveil cryptic diversity in a Cerrado endemic lizard (Squamata: Tropidurus)
The recognition of cryptic diversity within geographically widespread species is gradually becoming a trend in the highly speciose Neotropical biomes. The statistical methods to recognise such cryptic lineages are rapidly advancing, but have rarely been applied to genomic-scale datasets. Herein, we used phylogenomic data to investigate phylogenetic history and cryptic diversity within Tropidurus itambere, a lizard endemic to the Cerrado biodiversity hotspot. We applied a series of phylogenetic methods to reconstruct evolutionary relationships and a coalescent Bayesian species delimitation approach (BPP) to clarify species limits. The BPP results suggest that the widespread nominal taxon comprises a complex of 5 highly supported and geographically structured cryptic species. We highlight and discuss the different topological patterns recovered by concatenated and coalescent species tree methods for these closely related lineages. Finally, we suggest that the existence of cryptic lineages in the Cerrado is much more common than traditionally thought, highlighting the value of using NGS data and coalescent techniques to investigate patterns of species diversity.
Data from: Pathways of cryptic invasion in a fish parasite traced using coalescent analysis and epidemiological survey
Introduced species have the potential to outperform natives via the introduction of new parasites to which the native ecosystem is vulnerable. Cryptic diversity within an invasive species can obscure invasion patterns and confound proper management measures. The aim of this study is to use coalescent theory based methodology to trace recent routes of invasion in populations of Ligula intestinalis, a globally distributed fish parasite possessing both native and recently introduced populations in North Africa. Molecular analyses of mitochondrial DNA discerned a pronounced genetic divergence between introduced and native populations. Distribution of mitochondrial haplotypes demonstrated common origin of European populations with North African parasites sampled from introduced fish species in Tunisia. To test the suggested pathway of introduction, microsatellite data were examined in a model-based coalescent analysis using the software MIGRATE, where Europe to Tunisia direction of migration was favoured over alternative hypotheses of gene flow. Specificity of Tunisian populations to different host species was assessed in an epidemiologic survey confirming prevailing host-based division between introduced and native parasites in North Africa. This approach combining advanced analysis of molecular markers with host-specificity data allows revealing the evolution of host-parasite interactions following biological invasion and provides basis for devising future management measurements.
Data from: The phylogeny of pikas (Ochotona) inferred from a multilocus coalescent approach
The clarification of the systematics of pikas (genus Ochotona) has been hindered by largely overlapping morphological characters among species and the lack of a comprehensive molecular phylogeny. Here we estimate the first multilocus phylogeny of the genus to date, by analysing 12 nuclear DNA markers (total of 7.5 Kb) in 11 species of pikas from the four classified subgenera (Pika, Ochotona, Lagotona and Conothoa) using a multispecies coalescent-based framework. The species-tree confirmed the subgeneric classification by retrieving as monophyletic the subgenera represented here by more than one species. Contrary to previous phylogenies based on mtDNA alone, Lagotona was found to be sister to Pika. Also, support for the monophyly of the alpina group was not strong, thus caution should be used in future analyses of this group. A relaxed molecular clock calibrated using the Ochotonidae-Leporidae divergence resulted in more recent estimates of divergence times relative to previous studies. Strong concordance with inferences based on fossil records was found, suggesting that the initial diversification of the genus took place by the end of late Miocene. Finally, this work sets up methodologies and gathers molecular markers that can be used to extend the understanding of the evolutionary history of the genus.
Data from: A preliminary framework for DNA barcoding, incorporating the multispecies coalescent
The capacity to identify an unknown organism using the DNA sequence from a single gene has many applications. These include the development of biodiversity inventories (Janzen et al. 2005), forensics (Meiklejohn et al. 2011), biosecurity (Armstrong and Ball 2005), and the identification of cryptic species (Smith et al. 2006). The popularity and widespread use (Teletchea 2010) of the DNA barcoding approach (Hebert et al. 2003), despite broad misgivings (e.g., Smith 2005; Will et al. 2005; Rubinoff et al. 2006), attest to this. However, one major shortcoming to the standard barcoding approach is that it assumes that gene trees and species trees are synonymous, an assumption that is known not to hold in many cases (Pamilo and Nei 1988; Funk and Omland 2003). Biological processes that violate this assumption include incomplete lineage sorting and interspecific hybridization (Funk and Omland 2003). Indeed, simulation studies indicate that the concatenation approach (in which these two processes are ignored) can lead to statistically inconsistent estimation of the species tree (Kubatko and Degnan 2007). However, recent developments make a barcoding approach that utilizes a single locus outdated. The cost of sequencing multiple gene fragments is no longer inhibitory, but more importantly, a range of analytical approaches have been developed that account for incomplete lineage sorting (Degnan and Salter 2005; Edwards et al. 2007; Liu et al. 2008; Kubatko et al. 2009; Heled and Drummond 2010; Yang and Rannala 2010). These approaches incorporate coalescent theory into the analysis of species trees and species delimitation (Fujita et al. 2012) and are conveniently accessible as software programs (e.g., BEST, BPP, *BEAST, MrBayes v. 3.2, STEM, and COAL). Although the general mixed Yule coalescent (GMYC) approach has also been developed for species delimitation (Pons et al. 2006), we do not consider it further here. It operates quite differently to the approaches outlined above (i.e., BEST, BPP, *BEAST, MrBayes v. 3.2, STEM, and COAL). The GMYC approach seeks to identify the shift in the rate of lineage branching that should be evident when interspecific evolutionary processes switch to population-level processes (Pons et al. 2006). Both empirical (Esselstyn et al. 2012) and simulation studies (Esselstyn et al. 2012; Fujisawa and Barraclough 2013) report that it performs poorly when effective population sizes and speciation rates are high, but within biologically relevant ranges. Ideally, a "next-generation" barcoding approach would (1) identify a minimal set of barcoding genes (perhaps specific to certain lineages), (2) generate a large and cladistically divergent database for comparisons, and (3) identify species using species delimitation approaches that incorporate the multispecies coalescent. The first two of these conditions are straightforward and require only discussion (requirement 1) and resources (requirement 2). However, the third requirement is much more problematic. Some of the recently developed approaches for species delimitation could not be used alone; for example, BPP requires a user-specified guide tree (Yang and Rannala 2010). All of the recently developed approaches are computationally intensive (Degnan and Rosenberg 2009), with many having practical limitations on the number of individuals that can be compared. By contrast, the current barcoding approach is able to compare enormous numbers of sequences in a very short time, primarily because the approach is analytically simple; a single sequence is compared with all sequences in the database by calculating all possible pairwise K2P distances. As long as exemplars exist within the database that have K2P distances below some predetermined threshold (usually 4%), the species is considered identified. The speed of analysis is due primarily to the use of distance-based measures. The purpose of this article is to initiate the development of a framework for "next-gen barcoding": one that incorporates the multispecies coalescent, but does so by comparing multiple gene sequences from an unknown taxon with a database of sequences.
Data from: Coalescent and biophysical models of stepping-stone gene flow in Neritid snails
Marine species in the Indo-Pacific have ranges that can span thousands of kilometers, yet studies increasingly suggest that mean larval dispersal distances are less than historically assumed. Gene flow across these ranges must therefore rely to some extent on larval dispersal among intermediate "stepping-stone" populations in combination with long-distance dispersal far beyond the mean of the dispersal kernel. We evaluate the strength of stepping-stone dynamics by employing a spatially explicit biophysical model of larval dispersal in the Tropical Pacific to construct hypotheses for dispersal pathways. We test these hypotheses with coalescent models of gene flow among high-island archipelagos in four Neritid gastropod species. Two of the species live in the marine intertidal, while the other two are amphidromous, living in freshwater but retaining pelagic dispersal. Dispersal pathways predicted by the biophysical model were strongly favored in 16 of 18 tests against alternate hypotheses. In regions where connectivity among high-island archipelagos was predicted as direct, there was no difference in gene flow between marine and amphidromous species. In regions where connectivity was predicted through stepping-stone atolls only accessible to marine species, gene flow estimates between high-island archipelagos were significantly higher in marine species. Moreover, one of the marine species showed a significant pattern of isolation-by-distance consistent with stepping-stone dynamics. While our results support stepping-stone dynamics in Indo-Pacific species, we also see evidence for non-equilibrium processes such as range expansions or rare long-distance dispersal events. This study provides an empirical assessment of a biophysical model that helps to shed light on larval dispersal pathways.
Data from: The effect of gene flow on coalescent-based species-tree inference
Most current methods for inferring species-level phylogenies under the coalescent model assume that no gene flow occurs following speciation. Several studies have examined the impact of gene flow (e.g., Eckert and Carstens (2008); Chung and Ane (2011); Leache et al. (2014); Solis-Lemus et al. (2016)) and of ancestral population structure (DeGeorgio and Rosenberg, 2016) on the performance of species-level phylogenetic inference, and analytic results have been proven for network models of gene flow (e.g., Solis-Lemus et al. (2016); Zhu et al. (2016)). However, there are few analytic results for a continuous model of gene flow following speciation, despite the development of mathematical tools that could facilitate such study (e.g., Hobolth et al. (2011); Andersen et al. (2014); Tian and Kubatko (2016)). In this paper, we consider a three-taxon isolation-with-migration model that allows gene flow between sister taxa for a brief period following speciation, as well as variation in the effective population sizes across the species tree. We derive the probabilities of each of the three gene tree topologies under this model, and show that for certain choices of the gene flow and effective population size parameters, anomalous gene trees (i.e., gene trees that are discordant with the species tree but that have higher probability than the gene tree concor- dant with the species tree) exist. We characterize the region of parameter space producing anomalous trees, and show that the probability of the gene tree that is concordant with the species tree can be arbitrarily small. We then show that there is theoretical support for using SVDQuartets with an outgroup to infer the rooted three-taxon species tree in a model of gene flow between sister taxa. We study the performance of SVDQuartets on simulated data and compare it to three other commonly-used methods for species tree inference, AS- TRAL, MP-EST, and concatenation. The simulations show that ASTRAL, MP-EST, and concatenation can be statistically inconsistent when gene flow is present, while SVDQuartets performs well, though large sample sizes may be required for certain parameter choices.
Data from: Assessing the impacts of positive selection on coalescent-based species tree estimation and species delimitation.
The assumption of strictly neutral evolution is fundamental to the multispecies coalescent model and permits the derivation of gene tree distributions and coalescent times conditioned on a given species tree. In this study, we conduct computer simulations to explore the effects of violating this assumption in the form of species-specific positive selection when estimating species trees, species delimitations, and coalescent parameters under the model. We simulated datasets under an array of evolutionary scenarios that differ in both speciation parameters (i.e., divergence times, strength of selection) and experimental design (i.e., number of loci sampled) and incorporated species-specific positive selection occurring within branches of a species tree to identify the effects of selection on multispecies coalescent inferences. Our results highlight particular evolutionary scenarios and parameter combinations in which inferences may be more, or less, susceptible to the effects of positive selection. In some extreme cases, selection can decrease error in species delimitation and increase error in species tree estimation, yet these inferences appear to be largely robust to the effects of positive selection under many conditions likely to be encountered in empirical datasets.
Data from: Coalescent models characterize sources and demographic history of recent round goby colonization of Great Lakes and inland waters
The establishment and spread of aquatic invasive species is ecologically and economically harmful and a source of conservation concern internationally. Processes of species invasion have traditionally been inferred from observational data of species presence/absence and relative abundance. However, genetic-based approaches can provide valuable sources of inference. Restriction-site associated DNA sequencing was used to identify and genotype single nucleotide polymorphism (SNP) loci for Round Gobies (Neogobius melanostomus) (N=440) from 18 sampling locations in the Great Lakes and in three Michigan, USA drainages (Flint, Au Sable, and Cheboygan River basins). Sampled rivers differed in size, accessibility, and physical characteristics including man-made dispersal barriers. Population levels of genetic diversity and inter-population variance in SNP allele frequency were used in coalescence-based Approximate Bayesian Computation (ABC) to statistically compare models representing competing hypotheses regarding source population, post-colonization dispersal, and demographic history in the Great Lakes and inland waters. Results indicate different patterns of colonization across the three drainages. In the Flint River, models indicate a strong population bottleneck (< 3% of contemporary effective population size) and a single founding event from Saginaw Bay led to the colonization of inland river segments. In the Au Sable River, analyses could not distinguish potential source populations, but supported models indicated multiple introductions from one source population. In the Cheboygan River, supported models indicated that colonization likely proceeded from east (Lake Huron source) to west among inland locales sampled in the system. Despite the recent occupancy of Great Lakes and inland habitats, large numbers of loci analyzed in an ABC framework enable statistically supported identification of source populations and reconstruction of the direction of inland spread and demographic history following establishment. Information from analyses can direct management actions to limit the spread of invasive species from identified sources and most probable vectors into additional inland aquatic habitats.
Data from: Considering gene flow when using coalescent methods to delimit lineages of North American pitvipers of the genus Agkistrodon
Examining species diversity and mechanisms of speciation using coalescent models provides a framework for how regional diversity is accrued, even in well-studied areas such as the Nearctic. It is likely, that gene flow among closely-related species with adjacent distributions may be common. However, the absence of gene flow is a primary assumption of many phylogeographical methods that produce species trees and delimit species using Bayesian or likelihood functions in a coalescent framework. In the present study, we examine delimitation when gene flow between species is present using empirical datasets from two species of North American pitvipers of the genus Agkistrodon. We also use niche modelling to determine whether these young lineages occur in distinct environmental niches. To manage the problem of gene flow between species, we first identify admixed individuals, demonstrate that gene flow has occurred, and then identify the impact of alternative population assignments of admixed individuals on delimitation posterior probabilities. In addition, we examine the influence of mitochondrial genes relative to other loci combined in coalescent analyses that delimit species. Here, we find that the copperheads (Agkistrodon contortrix) and the cottonmouths (Agkistrodon piscivorus) are each composed of two distinct species, with each occupying different niches. Importantly, we find that species can be delimited when the amount of gene flow between lineages is low, although the methods are acutely sensitive to population assignment of individuals.
Data from: Tests of species-specific models reveal the importance of drought in postglacial range shifts of a Mediterranean-climate tree: insights from integrative distributional, demographic and coalescent modelling and ABC model selection
Past climate change has caused shifts in species distributions and undoubtedly impacted patterns of genetic variation, but the biological processes mediating responses to climate change, and their genetic signatures, are often poorly understood. We test six species-specific biologically informed hypotheses about such processes in canyon live oak (Quercus chrysolepis) from the California Floristic Province. These hypotheses encompass the potential roles of climatic niche, niche multidimensionality, physiological trade-offs in functional traits, and local-scale factors (microsites and local adaptation within ecoregions) in structuring genetic variation. Specifically, we use ecological niche models (ENMs) to construct temporally dynamic landscapes where the processes invoked by each hypothesis are reflected by differences in local habitat suitabilities. These landscapes are used to simulate expected patterns of genetic variation under each model and evaluate the fit of empirical data from 13 microsatellite loci genotyped in 226 individuals from across the species range. Using approximate Bayesian computation (ABC), we obtain very strong support for two statistically indistinguishable models: a trade-off model in which growth rate and drought tolerance drive habitat suitability and genetic structure, and a model based on the climatic niche estimated from a generic ENM, in which the variables found to make the most important contribution to the ENM have strong conceptual links to drought stress. The two most probable models for explaining the patterns of genetic variation thus share a common component, highlighting the potential importance of seasonal drought in driving historical range shifts in a temperate tree from a Mediterranean climate where summer drought is common.
Data from: Heterogeneity in genetic diversity among non-coding loci fails to fit neutral coalescent models of population history
Inferring aspects of the population histories of species using coalescent analyses of non-coding nuclear DNA has grown in popularity. These inferences, such as divergence, gene flow, and changes in population size, assume that genetic data reflect simple population histories and neutral evolutionary processes. However, violating model assumptions can result in a poor fit between empirical data and the models. We sampled 22 nuclear intron sequences from at least 19 different chromosomes (a genomic transect) to test for deviations from selective neutrality in the gadwall (Anas strepera), a Holarctic duck. Nucleotide diversity among these loci varied by nearly two orders of magnitude (from 0.0004 to 0.029), and this heterogeneity could not be explained by differences in substitution rates. Using two different coalescent methods to infer models of population history and then simulating neutral genetic diversity under these models, we found that the among-locus heterogeneity in nucleotide diversity was significantly higher than expected for these simple models. Defining more complex models of population history demonstrated that a pre-divergence bottleneck was also unlikely to explain this heterogeneity. However, both selection and interspecific hybridization could account for the heterogeneity observed among loci. Regardless of the cause of the deviation, our results illustrate that violating key assumptions of coalescent models can mislead inferences of population history.
Data from: Assessing species boundaries and the phylogenetic position of the rare Szechwan Ratsnake, Euprepiophis perlacea (Serpentes: Colubridae), using coalescent-based methods
Delimiting species and clarifying phylogenetic relationships are the main goals of systematics. For species with questionable taxonomic status, species delimitation approaches using multi-species coalescent models with multiple loci are recommended if morphological data are unavailable or unhelpful. Moreover, these methods will also reduce subjectivity based on genetic distance or requirement of monophyletic genetic lineages. We determine the validity and phylogenetic position of a rare and long controversial species of Chinese reptile, the Szechwan ratsnake (Euprepiophis perlacea), using multi-locus data from multiple individuals and coalescent-based approaches. Species were first delimited using Bayesian Phylogenetics & Phylogeography (BP&P), Brownie and Bayes Factor model comparison approaches, while relationships among species were estimated using species tree inference in *BEAST. Results indicate that Euprepiophis perlacea is a distinct species sister to Euprepiophis mandarinus. Despite gene tree discrepancy, the coalescent model-based approaches used here demonstrate the taxonomic validity and the phylogenetic position of Euprepiophis perlacea. These approaches objectively test the validity of questionable species diagnoses based on morphological characters and determine their phylogenetic position.
Data from: Para-allopatry in hybridizing fire-bellied toads (Bombina bombina and B. variegata): inference from transcriptome-wide coalescence analyses
Ancient origins, profound ecological divergence, and extensive hybridization make the fire-bellied toads Bombina bombina and B. variegata (Anura: Bombinatoridae) an intriguing test case of ecological speciation. Previous modeling has proposed that the narrow Bombina hybrid zones represent strong barriers to neutral introgression. We test this prediction by inferring the rate of gene exchange between pure populations on either side of the intensively studied Kraków transect. We developed a method to extract high confidence sets of orthologous genes from de novo transcriptome assemblies, fitted a range of divergence models to these data and assessed their relative support with analytic likelihood calculations. There was clear evidence for postdivergence gene flow, but, as expected, no perceptible signal of recent introgression via the nearby hybrid zone. The analysis of two additional Bombina taxa (B. v. scabra and B. orientalis) validated our parameter estimates against a larger set of prior expectations. Despite substantial cumulative introgression over millions of years, adaptive divergence of the hybridizing taxa is essentially unaffected by their lack of reproductive isolation. Extended distribution ranges also buffer them against small-scale environmental perturbations that have been shown to reverse the speciation process in other, more recent ecotypes.
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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.