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Io hybrid simulations
<p>Io hybrid global simulations for I0 flyby of Galileo SC.</p> <p>SETUPS:</p> <p>17io3d_g - I0-NC - non-collisional thermal electrons, Io induced dipole</p> <p>17io3d_g_nodip - I0-NC-ND - non-collisional thermal electrons, no Io induced dipole</p> <p>17io3d_g_denseatm - I0-C - I0-NC - collisional thermal electrons, Io induced dipole</p>
Species distribution, hybridization and connectivity in the genus Chionodraco: unveiling unknown icefish diversity in Antarctica
<p><strong>Aim</strong></p> <p>The species of the genus <em>Chionodraco</em> (Notothenioidei) are the most abundant icefish on the continental shelf of the Weddell Sea. While previous studies indicated that only <em>Chionodraco hamatus</em> and <em>Chionodraco myersi</em> inhabit the Weddell Sea, the third <em>Chionodraco</em> species, <em>Chionodraco rastrospinosus</em>, was recently sampled in the area. Since <em>C. rastrospinosus</em> is supposed to be found only at the Antarctic Peninsula and Scotia Arc, this study aimed at confirming the species classification of <em>C. rastrospinosus</em> by molecular methods and identifying its putative source population. Given the documented evidence of introgression among the three species, we tested whether the newly found <em>C. rastrospinosus</em> shared any genetic variability with the other <em>Chionodraco</em> species. To explain the pattern of distribution of the <em>Chionodraco</em> species, we aimed at estimating the hydrodynamic connectivity between the Antarctic Peninsula and the Weddell Sea.</p> <p><strong>Location</strong></p> <p>Antarctic Peninsula, southern Scotia Arc and the south-eastern Weddell Sea</p> <p><strong>Methods</strong></p> <p>We genotyped 19 microsatellites and sequenced the mitochondrial D-loop for 560 <em>Chionodraco</em> individuals. We simulated the dispersal of more than 3 million drifters (Lagrangian model).</p> <p><strong>Results</strong></p> <p>The molecular analyses support the presence of <em>C. rastrospinosus</em> in the Weddell Sea and its homogeneity with <em>C. rastrospinosus</em> from the Antarctic Peninsula. Bayesian clustering identifies three putative hybrids among <em>C. rastrospinosus</em> and the other congenerics. Lagrangian simulations do not support connectivity driven by the oceanographic features of the Antarctic Peninsula and Weddell Sea via passive larval dispersal only.</p> <p><strong>Main conclusions</strong></p> <p>This study documents, for the first time, the presence of <em>C. rastrospinosus</em> in the Weddell Sea unveiling more biodiversity than previously known in this region. The sympatry of the three <em>Chionodraco</em> species explains the occurrence of occasional, ongoing events of hybridization in the genus. Alternative possible hypotheses need to be tested in future studies about the mechanisms maintaining the interspecific connectivity in <em>Chionodraco</em> spp.</p>
Data from: Thermal plasticity in farmed, wild and hybrid Atlantic salmon during early development: has domestication caused divergence in low temperature tolerance?
Background: In the past three decades, millions of domesticated Atlantic salmon Salmo salar L. have escaped from farms into the wild. Their offspring display reduced survival in the natural environment, which demonstrates that gene-flow is likely to have a negative effect on wild populations. However, inter-population differences in introgression of farmed salmon have been observed, and the underlying ecological mechanisms remain enigmatic. We hypothesised that domestication-driven divergence in tolerance to low temperatures during early development may contribute to lower survival of farmed salmon offspring in the wild, which in turn, may influence patterns of introgression among populations exposed to different temperature regimes. We reared the offspring of 35 families of wild, farmed and hybrid origin at three temperatures (3.9, 5.6 and 12 °C) from the onset of exogenous feeding and throughout their first summer. Thermal reaction norms for growth and survival were investigated along the gradient. Results: The main results of this study, which is based upon the analysis of juvenile salmon from five wild strains, two farmed strains and two hybrid strains, can be summarised as; (i) salmon of all origins were able to successfully initiate feeding at all temperatures and similar survival reaction norms were detected in all strains across the temperature gradient; (ii) deviating growth reaction norms were detected between strains, although this result was most likely due to an overall lack of growth in the lower temperature treatments. Conclusions: This study revealed no evidence of domesticated-driven divergence in low temperature tolerance in Atlantic salmon during early development. Although the potential interaction between low temperature and other river-specific factors cannot be excluded, our results indicate that the reduced survival of farmed offspring in the wild is not explained by farmed salmon displaying impaired abilities to initiate feeding at low temperatures. We therefore suggest that the observed inter-population patterns of introgression are not low-temperature driven and that other ecological or biological factors may explain why detection of farmed salmon in wild rivers is not synonymous with introgression. In general, our results support the literature indicating that phenotypic plasticity instead of thermal adaption has been selected for in Atlantic salmon.
Data from: Genetic analyses reveal hybridization but no hybrid swarm in one of the world's rarest birds
Abstract: Hybridization facilitated by human activities has dramatically altered the evolutionary trajectories of threatened taxa around the globe. Whereas introduced mammalian predators and widespread habitat loss and degradation clearly imperil the recovery and survival of the New Zealand endemic black stilt or kakī (Himantopus novaezelandiae), the risk associated with hybridization between this critically endangered endemic and its self-introduced congener, the pied stilt or poaka (H. himantopus leucocephalus) is less clear. Here we combine Bayesian admixture analyses of microsatellite data with mitochondrial DNA sequence data to assess the levels of hybridization and introgression between kakī and poaka. We show that birds classified as hybrids on the basis of adult plumage are indeed of hybrid origin and that hybridisation between kakī and poaka is both extensive and bidirectional. Despite this, we found almost no evidence for introgression from poaka to kakī, thus negating a popular belief that kakī represent a hybrid swarm. To our knowledge, ours represents the first comprehensive study to document a lack of widespread introgression for a species at risk despite a recent history of extensive bidirectional human-induced hybridization. We attribute this rather surprising result, in part, to reduced reproductive success in female hybrids combined with a transient male-biased kakī sex ratio. To maximize the evolutionary potential of kakī, we use these data to recommend conservation management activities aimed to maintain the genetic integrity and to maximize the genetic diversity of this iconic rare bird.
Data from: Differential high-altitude adaptation and restricted gene flow across a mid-elevation hybrid zone in Andean tit-tyrant flycatchers
The tropical Andes are a global hotspot of avian diversity that is characterized by dramatic elevational shifts in community composition and a preponderance of recently evolved species. Bird habitats in the Andes span a nearly two-fold range of atmospheric pressure that poses challenges for respiration, thermoregulation, water balance, and powered flight, but the extent to which physiological constraints limit species' elevational distributions is poorly understood. We report a previously unknown hybrid zone between recently diverged flycatchers (Aves, Tyrannidae) with partially overlapping elevational ranges. The southern Anairetes reguloides has a broad elevational range (0-4200 m), while the northern Anairetes nigrocristatus is restricted to high elevations (>2200 m). We found hybrids in central Peru at elevations between ~3100-3800 m, with A. nigrocristatus above this elevation and A. reguloides below. We analyzed variation in hematology, heart mass, morphometrics, plumage, and one mitochondrial and three nuclear loci across an elevational transect that encompasses the hybrid zone. Phenotypic traits and genetic markers all showed steep clines across the hybrid zone. Hemoglobin concentration, hematocrit, mean cellular hemoglobin concentration, and relative heart mass each increased at altitude more strongly in A. reguloides than in A. nigrocristatus. These findings suggest that A. nigrocristatus is more resistant than A. reguloides to high-altitude hypoxic respiratory stress. Considering that the ancestor of the genus is suggested to have been restricted to high elevations, A. reguloides may be secondarily adapted to low-altitude. We conclude that differential respiratory specialization on atmospheric pressure combined with competitive exclusion maintains replacement along an elevational contour, despite interbreeding.
Data from: Real-time assessment of hybridization between wolves and dogs: combining non-invasive samples with ancestry informative markers
Wolves and dogs provide a paradigmatic example of the ecological and conservation implications of hybridization events between wild and domesticated forms. However, our understanding of such implications has been traditionally hampered by both high genetic similarity and the difficulties in obtaining tissue samples (TS), which limit our ability to assess ongoing hybridization events. To assess the occurrence and extension of hybridization in a pack of wolf-dog hybrids in Northwestern Iberia, we compared the power of 52 nuclear markers implemented on TS with a subset of 13 ancestry informative markers (AIMs) typed in non-invasive samples (NIS). We demonstrate that the 13 AIMs are as accurate as the 52 markers that were chosen without regard to the power to differentiate between wolves and dogs, also having the advantage of being rapidly screened on NIS. The efficiency of AIMs significantly outperformed ten random sets of similar size and an additional commercial set of 18 markers. Bayesian clustering analysis implemented on AIMs and NIS identified nine hybrids, two wolves and two dogs. Four hybrids were unambiguously assigned to F1xWolf backcrosses. Our approach (AIMs + NIS) overcomes previous difficulties related to sample availability and informative power of markers, allowing a quick identification of wolf-dog hybrids in the first phases of hybridization episodes. This provides managers with a reliable tool to evaluate hybridization, and estimate the success of their actions. This approach may be easily adapted for other pairs of wild/domesticated species, thus improving our understanding of the introgression of domestication genes into natural populations.
Data from: Chromosomal rearrangements do not seem to affect the gene flow in hybrid zones between karyotypic races of the common shrew (Sorex araneus)
Chromosomal rearrangements are proposed to promote genetic differentiation between chromosomally differentiated taxa and therefore promote speciation. Due to their remarkable karyotypic polymorphism, the shrews of the Sorex araneus group were used to investigate the impact of chromosomal rearrangements on gene flow. Five intraspecific chromosomal hybrid zones characterized by different levels of karyotypic complexity were studied using 16 microsatellites markers. We observed low levels of genetic differentiation even in the hybrid zones with the highest karyotypic complexity. No evidence of restricted gene flow between differently rearranged chromosomes was observed. Contrary to what was observed at the interspecific level, the effect of chromosomal rearrangements on gene flow was undetectable within the S. araneus species.
Data from: Strong natural selection on juveniles maintains a narrow adult hybrid zone in a broadcast spawner
Natural selection can maintain and help form species across different habitats, even when dispersal is high. Selection against inferior migrants (immigrant inviability) acts when locally adapted populations suffer high mortality on dispersal to unsuitable habitats. Habitat-specific populations undergoing divergent selection via immigrant inviability should thus show (1) a change in the ratio of adapted to nonadapted individuals among age/size classes and (2) a cline (defined by the environmental gradient) as selection counterbalances migration. Here we examine the frequencies of two depth-segregated lineages in juveniles and adults of a Caribbean octocoral, Eunicea flexuosa. Distributions of the two lineages in both shallow and deep environments were more distinct when inferred from adults than juveniles. Despite broad larval dispersal, we also found an extremely narrow hybrid zone (<100 m), with coincident clines for molecular and morphological characters of the host coral and its algal symbiont. Effective dispersal estimates derived from the hybrid zone are remarkably small (<20 m) for a broadcast spawner. The large selection coefficient against mismatched genotypes derived from cohort data is consistent with that from field transplant experiments. Narrow hybrid zones and limited effective dispersal may be a common outcome of long periods of postsettlement, prereproductive selection across steep ecological gradients. Strong diversifying selection provides a mechanism to explain the prevalence of depth-segregated sibling species in the sea.
Data from: Independent homoploid hybrid speciation events in the Macaronesian endemic genus Argyranthemum
Well-characterised examples of homoploid hybrid speciation (HHS) are rare in nature yet they offer the potential to study a number of evolutionary processes. In this study we investigate putative homoploid hybrid species in the genus Argyranthemum (Asteraceae), a group of plants endemic to the Macaronesian archipelagos of the North Atlantic Ocean. We specifically address a number of knowledge gaps surrounding the origin(s) of A. sundingii and A. lemsii, which are thought to be derived from the same parental cross. Comparisons of leaf morphology suggest that A. sundingii and A. lemsii are distinct from their parental progenitors and distinguishable from each other based on leaf area. Ecological niche modelling (ENM) demonstrated that the homoploid hybrid species occupy novel habitats that are intermediate relative to the parental species. Nuclear SSRs and SNP data indicate that the homoploid hybrid species are distinct from the parental taxa, whilst population level sampling of chloroplast SSRs and Approximate Bayesian Computation show that A. sundingii and A. lemsii are independently derived from the same parental cross. As such, Argyranthemum represents an example of independent homoploid hybrid speciation events with evidence of divergence in leaf morphology and adaptation to novel intermediate habitats. On oceanic islands, which are often typified by steep ecological gradients and inhabited by recently derived species with weak reproductive barriers, multiple HHS events from the same parental cross are not only possible but are likely to have played a more important role in oceanic island radiations than we currently think.
Data from: Mitochondrial introgressive hybridization following a demographic expansion in the tomato frogs of Madagascar, genus Dyscophus
Madagascar is a biodiversity hotspot with a unique fauna and flora largely endemic at the species level and highly threatened by habitat destruction. The processes underlying population-level differentiation in Madagascar's biota are poorly understood and have been proposed to be related to Pleistocene climatic cycles, yet the levels of genetic divergence observed are often suggestive of ancient events. We combined molecular markers of different variability to assess the phylogeography of Madagascar's emblematic tomato frogs (Dyscophus guineti and D. antongilii) and interpret the observed pattern as resulting from ancient and recent processes. Our results suggest that the initial divergence between these taxa is probably old as reflected by protein-coding nuclear genes and by a strong mitochondrial differentiation of the southernmost population. Dramatic changes in their demography appear to have been triggered by the end of the last glacial period and possibly by the short return of glacial conditions known as the 8K event. This dramatic change resulted in an approximately 50-fold reduction of the effective population size in various populations of both species. We hypothesize these species' current mitochondrial DNA diversity distribution reflects a swamping of the mitochondrial genetic diversity of D. guineti by that of D. antongilii previous to the populations' bottlenecks during the Holocene, and probably as a consequence of D. antongilii demographic expansion approximately 1 million years ago. Our data support the continued recognition of D. antongilii and D. guineti as separate species and flag D. guineti as the more vulnerable species to past and probably also future environmental changes.
Data from: Hybridization between genetically modified Atlantic salmon and wild brown trout reveals novel ecological interactions
Interspecific hybridization is a route for transgenes from genetically modified (GM) animals to invade wild populations, yet the ecological effects and potential risks that may emerge from such hybridization are unknown. Through experimental crosses, we demonstrate transmission of a growth hormone transgene via hybridization between a candidate for commercial aquaculture production, GM Atlantic salmon (Salmo salar), and closely related wild brown trout (S. trutta). Transgenic hybrids were viable and grew more rapidly than transgenic salmon and other non-transgenic crosses in hatchery-like conditions. In stream mesocosms designed to more closely emulate natural conditions, transgenic hybrids appeared to express competitive dominance and suppressed the growth of transgenic and non-transgenic (wild-type) salmon by 82% and 54%, respectively. To the best of our knowledge, this is the first demonstration of environmental impacts of hybridization between a GM animal and a closely related species. These results provide empirical evidence of the first steps towards introgression of foreign transgenes into the genomes of new species and contribute to the growing evidence that transgenic animals have complex and context-specific interactions with wild populations. We suggest that interspecific hybridization be explicitly considered when assessing the environmental consequences should transgenic animals escape to nature.
Data from: Hybridization, natural selection and evolution of reproductive isolation: a 25-years survey of an artificial sympatric area between two mosquito sibling species of the Aedes mariae complex
Natural selection can act against maladaptive hybridization between co-occurring divergent populations leading to evolution of reproductive isolation among them. A critical unanswered question about this process that provides a basis for the theory of speciation by reinforcement, is whether natural selection can cause hybridization rates to evolve to zero. Here we investigated this issue in two sibling mosquitoes species, Aedes mariae and Ae. zammitii, that show post-mating reproductive isolation (F1 males sterile) and partial pre-mating isolation (different height of mating swarms) that could be reinforced by natural selection against hybridization. In 1986, we created an artificial sympatric area between the two species and sampled about 20,000 individuals over the following 25 years. Between 1986 to 2011, the composition of mating swarms and the hybridization rate between the two species were investigated across time in the sympatric area. Our results showed that Ae. mariae and Ae. zammitii have not completed reproductive isolation since their first contact in the artificial sympatric area. We have discussed the relative role of factors such as time of contact, gene flow, strength of natural selection, and biological mechanisms causing prezygotic isolation to explain the observed results.
Data from: Identifying the African wintering grounds of hybrid flycatchers using a multi–isotope (δ2H, δ13C, δ15N) assignment approach
Migratory routes and wintering grounds can have important fitness consequences, which can lead to divergent selection on populations or taxa differing in their migratory itinerary. Collared (Ficedula albicollis) and pied (F. hypoleuca) flycatchers breeding in Europe and wintering in different sub-Saharan regions have distinct migratory routes on the eastern and western sides of the Sahara desert, respectively. In an earlier paper, we showed that hybrids of the two species did not incur reduced winter survival, which would be expected if their migration strategy had been a mix of the parent species' strategies potentially resulting in an intermediate route crossing the Sahara desert to different wintering grounds. Previously, we compared isotope ratios and found no significant difference in stable-nitrogen isotope ratios (δ15N) in winter-grown feathers between the parental species and hybrids, but stable-carbon isotope ratios (δ13C) in hybrids significantly clustered only with those of pied flycatchers. We followed up on these findings and additionally analyzed the same feathers for stable-hydrogen isotope ratios (δ2H) and conducted spatially explicit multi-isotope assignment analyses. The assignment results overlapped with presumed wintering ranges of the two species, highlighting the efficacy of the method. In contrast to earlier findings, hybrids clustered with both parental species, though most strongly with pied flycatcher.
Data from: Trans-Pacific RAD-Seq population genomics confirms introgressive hybridization in Eastern Pacific Pocillopora corals.
Discrepancies between morphology-based taxonomy and phylogenetic systematics are common in Scleractinian corals. In Pocillopora corals, nine recently identified genetic lineages disagree fundamentally with the 17 recognized Pocillopora species, including 5 major Indo-Pacific reef-builders. Pocillopora corals hybridize in the Tropical Eastern Pacific, so it is possible that some of the disagreement between the genetics and taxonomy may be due to introgressive hybridization. Here we used 6769 genome-wide SNPs from Restriction-site Associated DNA sequencing (RAD-Seq) to conduct phylogenomic comparisons among three common, Indo-Pacific Pocillopora species - P.'damicornis, P. eydouxi and P. elegans - within and between populations in the Tropical Eastern Pacific (TEP) and the Central Pacific. Genome-wide RAD-Seq comparisons of Central and TEP Pocillopora confirm that the morphospecies P.'damicornis, P. eydouxi and P. elegans are not monophyletic, but instead fall into three distinct genetic groups. However, hybrid samples shared fixed alleles with their respective parental species and, even without strict monophyly, P. damicornis share a common set of 33 species- specific alleles across the Pacific. RAD-Seq data confirm the pattern of one-way introgressive hybridization among TEP Pocillopora, suggesting that introgression may play a role in generating shared, polyphyletic lineages among currently recognized Pocillopora species. Levels of population differentiation within genetic lineages indicate significantly higher levels of population differentiation in the Tropical Eastern Pacific than in the Central West Pacific.
Data from: Intermediate habitat associations by hybrids may facilitate genetic introgression in a songbird
Hybridization or the interbreeding of genetically discrete populations or species can occur where ranges of genetically distinct units overlap. Golden-winged warblers Vermivora chrysoptera, a species that has been in steady decline for decades, highlight the potential population-level consequences of hybridization. A major factor implicated in their decline is hybridization with their sister species, the blue-winged warbler Vermivora cyanoptera, which has likely been exacerbated by historic and current land-use practices. We examined habitat associations of golden-winged and blue-winged warblers, phenotypic hybrids, and cryptic hybrids (i.e. mismatch between plumage phenotype and genotype as identified by mitochondrial DNA) in an area of relatively recent range overlap and hybridization in northern New York, USA. To explore the robustness of these results, we then compared the patterns from New York with habitat associations from the central Pennsylvanian Appalachian Mountains where blue-winged warblers either do not occur or are in very low abundance, yet cryptic golden-winged warbler hybrids are present. From 2008 to 2011, we captured 122 birds in New York and 28 in Pennsylvania and collected blood samples, which we used to determine maternal ancestry. For each bird captured, we measured territory-level (50-m radius circles) habitat, and later used remote-sensing data to quantify habitat on the territories and in surrounding areas (100-, 250-, and 500-m radius circles). In New York, golden-winged warblers occupied structurally heterogeneous territories surrounded by homogeneously structured, contiguous deciduous forest, far from urban areas. Blue-winged warblers showed opposite associations, and hybrids' habitat associations were typically intermediate. In Pennsylvania, the habitat associations of golden-winged warblers and their cryptic hybrids were remarkably similar to those in New York. These findings suggest that patterns of habitat occupancy by hybrids may promote contact with golden-winged warblers and thus likely facilitate genetic introgression, even in areas where the parental species are not sympatric.
Data from: Population structure and reticulate evolution of Saccharomyces eubayanus and its lager-brewing hybrids
Reticulate evolution can be a major driver of diversification into new niches, especially in disturbed habitats and at the edges of ranges. Industrial fermentation strains of yeast provide a window into these processes, but progress has been hampered by a limited understanding of the natural diversity and distribution of Saccharomyces species and populations. For example, lager beer is brewed with Saccharomyces pastorianus, an alloploid hybrid of S. cerevisiae and S. eubayanus, a species only recently discovered in Patagonia, Argentina. Here we report that genetically diverse strains of S. eubayanus are readily isolated from Patagonia, demonstrating that the species is well established there. Analyses of multi-locus sequence data strongly suggest that there are two diverse and highly differentiated Patagonian populations. S. eubayanus alleles present among hybrid European brewing strains had strikingly low diversity, suggesting they were drawn from a small subpopulation that is closely related to one of the Patagonian populations. For the first time, we also report the rare isolation of S. eubayanus outside of Patagonia, in Wisconsin, USA. In contrast to the clear population differentiation in Patagonia, the North American strains represent a recent and possibly transient admixture of the two Patagonian populations. These complex and varied reticulation events are not adequately captured by conventional phylogenetic methods and required analyses of Bayesian concordance factors and phylogenetic networks to accurately summarize and interpret. These findings show how genetically diverse eukaryotic microbes can produce rare but economically important hybrids with low genetic diversity when they migrate from their natural ecological context.
Data from: Rapid genetic assimilation of native wall lizard populations (Podarcis muralis) through extensive hybridization with introduced lineages
The Common Wall Lizard (Podarcis muralis) has established more than 150 non-native populations in Central Europe, stemming from eight geographically distinct evolutionary lineages. While the majority of these introduced populations are found outside the native range, some of these populations also exist at the northern range margin in south-western Germany. In order to a) infer the level of hybridization in contact zones of alien and native lineages and b) compare the genetic diversity among purebred introduced, native and hybrid populations we used a combination of maternally inherited markers (mtDNA: cytb) and Mendelian markers (microsatellites). Our results suggest a rapid genetic assimilation of native populations by strong introgression from introduced lineages. Discordant patterns of mtDNA and nDNA variation within hybrid populations may be explained by directed mate choice of females towards males of alien lineages. In contrast to previous studies we found a non-linear relationship between genetic diversity and admixture level. The genetic diversity of hybrid populations was substantially higher than in introduced and native populations belonging to a single lineage, but rapidly reaching a plateau of high genetic diversity at an admixture level of two. However, even introduced populations with low founder sizes and from one source population retained moderate levels of genetic diversity and no evidence for a genetic bottleneck was found. The extent of introgression and the dominance of alien haplotypes in mixed populations indicate that introductions of non-native lineages represent a serious threat to the genetic integrity of native populations due to the rapid creation of hybrid swarms.
Ancient hybridization with an unknown population facilitated high altitude adaptation of canids
<p>Genetic introgression provides material for adaptive evolution, but also confounds our understanding of evolutionary history. This is particularly true for canids, a species complex in which genome sequencing and analysis has revealed a complex history of admixture and introgression. Here, we use newly sequenced genomes of high-altitude Tibetan and Himalayan wolves to explore the evolutionary history and adaptation of this group. We find that Tibetan and Himalayan wolves are closely related to each other, and that approximately 39-49% of their nuclear genome are derived from an as-yet unrecognized wolf-like lineage that is deeply diverged from living Holarctic wolves and dogs. The <i>EPAS1</i> haplotype, which is present at high frequencies in Tibetan dog breeds and wolves and confers an adaptive advantage to animals living at high altitudes, was probably derived from this ancient lineage. Our study suggests the complexity of canid evolution and demonstrates how admixture and introgression shape the evolutionary trajectories and adaptation of species.</p>
Data from: Geographic variation in the structure of oak hybrid zones provides insights into the dynamics of speciation
Studying geographic variation in the rate of hybridization between closely related species could provide a useful window to understand the evolution of reproductive isolation. Reinforcement theory predicts greater prezygotic isolation in areas of prolonged contact between recently diverged species than in areas of recent contact, which implies that old contact zones would be dominated by parental phenotypes with few hybrids (bimodal hybrid zones) whereas recent contact zones would be characterized by hybrid swarms (unimodal hybrid zones). Here we investigate how the hybrid zones of two closely related Chinese oaks, Quercus mongolica and Q. liaotungensis, are structured geographically using both nuclear and chloroplast markers. We found that populations of Q. liaotungensis located around the Changbai Mountains in Northeast China, an inferred glacial refugium, are introgressed by genes from Q. mongolica, suggesting former contact between the two species in this region. Yet, these introgressed populations form sharp bimodal hybrid zones with Q. mongolica. In contrast, populations of Q. liaotungensis located in North China, which show no sign of ancient introgression with Q. mongolica, form unimodal hybrid zones with Q. mongolica. These results are consistent with the hypothesis that selection against hybrids has had sufficient time to reinforce the reproductive barriers between Q. liaotungensis and Q. mongolica in Northeast China but not in North China.
Data from: Molecular evidence for hybridization in Colias (Lepidoptera: Pieridae): are Colias hybrids really hybrids?
Gene flow and hybridization among species dramatically affect our understanding of the species as a biological unit, species relationships, and species adaptations. In North American Colias eurytheme and Colias eriphyle, there has been historical debate over the extent of hybridization occurring and the identity of phenotypically intermediate individuals as genetic hybrids. This study assesses the population structure of these two species to measure the extent of hybridization and the genetic identity of phenotypic intermediates as hybrids. Amplified fragment length polymorphism (AFLP) marker analysis was performed on 378 specimens collected from northern California and Nevada. Population structure was inferred using a Bayesian/Markov chain Monte Carlo method, which probabilistically assigns individuals to genetic clusters. Three genetic clusters provided the best fit for the data. C. eurytheme individuals were primarily assigned to two closely related clusters, and C. eriphyle individuals were mostly assigned to a third, more distantly related cluster. There appeared to be significant hybridization between the two species. Individuals of intermediate phenotype (putative hybrids) were found to be genetically indistinguishable from C. eriphyle, indicating that previous work based on the assumption that these intermediate forms are hybrids may warrant reconsideration.
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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.