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402 results for “hybrid zone”
Data from: Climate-mediated hybrid zone movement revealed with genomics, museum collection and simulation modeling
Climate-mediated changes in hybridization will dramatically alter the genetic diversity, adaptive capacity and evolutionary trajectory of interbreeding species. Our ability to predict the consequences of such changes will be key to future conservation and management decisions. Here we tested through simulations how recent warming (over a 32-year period) is affecting the geographic extent of a climate-mediated developmental threshold implicated in maintaining a butterfly hybrid zone (Papilio glaucus and Papilio canadensis; Lepidoptera: Papilionidae). These simulations predict a 68 km shift of this hybrid zone. To empirically test this prediction, we assessed genetic and phenotypic changes using contemporary and museum collections and document a 40 km northward shift of this hybrid zone. Interactions between the two species appear relatively unchanged during hybrid zone movement. We found no change in the frequency of hybridization and regions of the genome that experience little to no introgression moved largely in concert with the shifting hybrid zone. Model predictions based on climate scenarios predict this hybrid zone will continue to move northward, but with substantial spatial heterogeneity in the velocity (55-144 km/1°C), shape, and contiguity of movement. Our findings suggest that the presence of non-climatic barriers (e.g., genetic incompatibilities) and/or non-linear responses to climatic gradients may preserve species boundaries as the species shift. Further, we show that variation in the "geography" of hybrid zone movement could result in evolutionary responses that differ for geographically distinct populations spanning hybrid zones and thus have implications for the conservation and management of genetic diversity.
Data from: Patterns of divergence across the geographic and genomic landscape of a butterfly hybrid zone associated with a climatic gradient
Hybrid zones are a valuable tool for studying the process of speciation and for identifying the genomic regions undergoing divergence and the ecological (extrinsic) and non-ecological (intrinsic) factors involved. Here, we explored the genomic and geographic landscape of divergence in a hybrid zone between Papilio glaucus and Papilio canadensis. Using a genome scan of 28,417 ddRAD SNPs, we identified genomic regions under possible selection and examined their distribution in the context of previously identified candidate genes for ecological adaptations. We showed that differentiation was genome-wide, including multiple candidate genes for ecological adaptations, particularly those involved in seasonal adaptation and host plant detoxification. The Z-chromosome and four autosomes showed a disproportionate amount of differentiation, suggesting genes on these chromosomes play a potential role in reproductive isolation. Cline analyses of significantly differentiated genomic SNPs, and of species diagnostic genetic markers, showed a high degree of geographic coincidence (81%) and concordance (80%) and were associated with the geographic distribution of a climate-mediated developmental threshold (length of the growing season). A relatively large proportion (1.3%) of the outliers for divergent selection were not associated with candidate genes for ecological adaptations and may reflect the presence of previously unrecognized intrinsic barriers between these species. These results suggest that exogenous (climate-mediated) and endogenous (unknown) clines may have become coupled and act together to reinforce reproductive isolation. This approach of assessing divergence across both the genomic and geographic landscape can provide insight about the interplay between the genetic architecture of reproductive isolation and endogenous and exogenous selection.
Assortative mating in hybrid zones is remarkably ineffective in promoting speciation
<p>Partial prezygotic isolation is often viewed as more important than partial postzygotic isolation (low fitness of hybrids) early in the process of speciation. I simulate secondary contact between two populations ('species') to examine effects of assortative mating and low hybrid fitness in preventing blending. A small reduction in hybrid fitness (e.g., by 10%) produces a narrower hybrid zone than a strong but imperfect mating preference (e.g., 10x stronger preference for conspecific over heterospecific mates). In the latter case, rare F1 hybrids find each other attractive (due to assortative mating), leading to the buildup of a continuum of intermediates. The weakness of assortative mating compared to reduced fitness of hybrids in preventing blending is robust to varying genetic bases of these traits. Assortative mating is most powerful in limiting blending when it is encoded by a single locus, is essentially complete, or when there is a large mate search cost. In these cases assortative mating is likely to cause hybrids to have low fitness, due to frequency-dependent mating disadvantage of individuals of rare mating types. These results prompt a questioning of the concept of partial prezygotic isolation, since it is not very isolating unless there is also postzygotic isolation.</p>
Data for: Tracking hybrid viability across life-stages in a natural avian contact zone
<p><span>Hybrid inviability is an important post-zygotic reproductive barrier between species, but emerging signs of reduced viability can be difficult to study across the lifespan of natural hybrids.</span><span> We use a combination of long-term monitoring, extra-pair paternity and mitochondrial DNA identification in a natural hybrid zone of <em>Ficedula </em>flycatchers to detect emerging signs of intrinsic hybrid inviability across their entire lifespan. We evaluate possible evidence of Darwin's corollary to Haldane's rule, predicting asymmetries in inviability between hybrids resulting from reciprocal crosses, due to incompatible genetic factors with sex-specific inheritance patterns. We found higher hatching failure among mixed-species pairs, possibly indicating early developmental impairments associated with specific parental genetic combinations. Adult hybrids had a higher basal mortality rate than both parental species, and different age-specific mortality trajectories. There were signs of differences in age-independent mortality rates between the reciprocal hybrid crosses: hybrids with a pied flycatcher mother experienced slightly increased mortality later in life. Using an exceptional dataset with many natural hybrids tracked across life stages, we provide evidence for several emerging signs of reduced hybrid viability. Incompatibilities between alleles located on autosomes and uniparentally inherited factors such Z-linked and/or mitochondrial genes are strong candidates underlying intrinsic hybrid dysfunction in this system.</span></p>
High sexual display trait diversity without measured genetic divergence in a montane hybrid zone involving young species (Habronattus americanus subgroup, Araneae, Salticidae)
<p>Genetic introgression, allele exchange across species boundaries, is a commonly recognized feature of animal evolution. Under such a paradigm contemporary contact zones provide first-hand and complementary insight into the geographic, phenotypic, and genetic details of introgression. Also, when mate choice phenotypes are conspicuous and variable in hybrids, contact zones provide potential insight into how sexual selection interacts with species boundary maintenance, particularly when postzygotic reproductive isolation is weak. The <em>Habronattus</em> <em>americanus</em> subgroup includes several recently evolved jumping spider species, with an estimated age of about 200,000 years, and substantial evidence for hybridization and introgression. We explored a contact zone involving <em>H. americanus</em> (Keyserling, 1885) and <em>H. kubai</em> (Griswold, 1979) on Mount Shasta, California, in alpine habitats that would have been unavailable (under ice) at the Last Glacial Maximum. We characterized morphological diversity within the contact zone, including the fine-scale geographic distribution of hybrid and parental individuals, and assessed genetic variation using ddRADseq data. Combined results indicate a lack of measured genomic differentiation between specimens with distinct morphologies, including individuals with phenotypes of the parental species. We identified a diverse array of hybrid morphologies, with phenotypic evidence for backcrossing, essentially forming a phenotypic bridge between parental taxa. The study area is characterized by more hybrid than parental individuals, with a significantly larger number of red-palped morphologies than white and/or yellow-palped morphologies; the novel, white-palped phenotype is perhaps transgressive. Overall, these results contribute to a better understanding of the expected ebb and flow of lineage interactions during the early stages of speciation.</p>
Extensive introgression at late stages of species formation: Insights from grasshopper hybrid zones
<p><span class="TextRun SCXW104780834 BCX0"><span class="NormalTextRun SCXW104780834 BCX0">The</span><span class="NormalTextRun SCXW104780834 BCX0"> process of species formation is </span><span class="NormalTextRun SCXW104780834 BCX0">characterised by the accumulation</span><span class="NormalTextRun SCXW104780834 BCX0"> of </span><span class="NormalTextRun SCXW104780834 BCX0">multiple reproductive barriers. The evolution</span><span class="NormalTextRun SCXW104780834 BCX0"> of </span><span class="NormalTextRun SCXW104780834 BCX0">hybrid male sterility, or Haldane's rule, typically characterises later stages of species formation, when total </span><span class="NormalTextRun SCXW104780834 BCX0">reproductive isolation is </span><span class="NormalTextRun SCXW104780834 BCX0">strongest.</span><span class="NormalTextRun SCXW104780834 BCX0"> Yet, understanding how </span><span class="NormalTextRun SCXW104780834 BCX0">quickly reproductive barriers evolve and their consequences for maintaining genetic boundaries between emerging species </span><span class="NormalTextRun SCXW104780834 BCX0">remains a challenging task because </span><span class="NormalTextRun SCXW104780834 BCX0">it requires studying</span><span class="NormalTextRun SCXW104780834 BCX0"> taxa that hybridise in nature. Here, we address these questions using the meadow grasshopper </span></span><span class="TextRun SCXW104780834 BCX0"><span class="NormalTextRun SCXW104780834 BCX0">Pseudochorthippus parallelus</span></span><span class="TextRun SCXW104780834 BCX0"><span class="NormalTextRun SCXW104780834 BCX0">,</span><span class="NormalTextRun SCXW104780834 BCX0"> where populations that </span><span class="NormalTextRun SCXW104780834 BCX0">show multiple reproductive barriers, including hybrid male sterility,</span><span class="NormalTextRun SCXW104780834 BCX0"> hybridise in two natural hybrid zones</span><span class="NormalTextRun SCXW104780834 BCX0">.</span><span class="NormalTextRun SCXW104780834 BCX0"> </span><span class="NormalTextRun SCXW104780834 BCX0">Using mitochondrial data, we infer that such populations have diverged some 100,000 years ago, </span></span><span class="TextRun SCXW104780834 BCX0"><span class="NormalTextRun SCXW104780834 BCX0">at the beginning of the last </span><span class="NormalTextRun SCXW104780834 BCX0">glacial </span><span class="NormalTextRun SCXW104780834 BCX0">cycle in Europe</span></span><span class="TextRun SCXW104780834 BCX0"><span class="NormalTextRun SCXW104780834 BCX0">.</span><span class="NormalTextRun SCXW104780834 BCX0"> </span><span class="NormalTextRun SCXW104780834 BCX0">Nuclear data shows that </span><span class="NormalTextRun SCXW104780834 BCX0">contraction</span><span class="NormalTextRun SCXW104780834 BCX0">s</span><span class="NormalTextRun SCXW104780834 BCX0"> at multiple glacial refugia, and post-glacial expansions have facilitated genetic differentiation between lineages that today interact in hybrid zones. We find </span><span class="NormalTextRun SCXW104780834 BCX0">extensive introgression throughout the </span><span class="NormalTextRun SCXW104780834 BCX0">sampled </span><span class="NormalTextRun SCXW104780834 BCX0">species range, </span><span class="NormalTextRun SCXW104780834 BCX0">irrespective of current strength of reproductive isolation. Populations</span><span class="NormalTextRun SCXW104780834 BCX0"> exhibiting hybrid male sterility</span><span class="NormalTextRun SCXW104780834 BCX0"> in two hybrid zones show </span><span class="NormalTextRun SCXW104780834 BCX0">repeatable patterns of genomic differentiation</span><span class="NormalTextRun SCXW104780834 BCX0">,</span><span class="NormalTextRun SCXW104780834 BCX0"> consistent with shared genomic constraints </span><span class="NormalTextRun SCXW104780834 BCX0">affecting ancestral divergence or with the </span><span class="NormalTextRun SCXW104780834 BCX0">role </span><span class="NormalTextRun SCXW104780834 BCX0">of those regions </span><span class="NormalTextRun SCXW104780834 BCX0">in reproductive isolation. Together, our results suggest that </span><span class="NormalTextRun SCXW104780834 BCX0">reproductive barriers that characterise late stages of species formation</span><span class="NormalTextRun SCXW104780834 BCX0"> can evolve relatively quickly within species, particularly when associated </span><span class="NormalTextRun SCXW104780834 BCX0">with</span><span class="NormalTextRun SCXW104780834 BCX0"> strong demographic changes. </span><span class="NormalTextRun SCXW104780834 BCX0">Moreover, we show that such barriers persist in the face of</span><span class="NormalTextRun SCXW104780834 BCX0"> extensive gene flow, allowing future studies to identify </span><span class="NormalTextRun SCXW104780834 BCX0">associated </span><span class="NormalTextRun SCXW104780834 BCX0">genomic regions.</span></span><span class="EOP SCXW104780834 BCX0"> </span></p>
Candidate-species delimitation in Desmognathus salamanders reveals gene flow across lineage boundaries, confounding phylogenetic estimation and clarifying hybrid zones
Dusky Salamanders (genus Desmognathus) currently comprise only 22 described, extant species. However, recent mitochondrial and nuclear estimates indicate the presence of up to 49 candidate species based on ecogeographic sampling. Previous studies also suggest a complex history of hybridization between these lineages. Studies in other groups suggest that disregarding admixture may affect both phylogenetic inference and clustering-based species-delimitation. With a dataset comprising 233 Anchored Hybrid Enrichment (AHE) loci sequenced for 896 Desmognathus specimens from all 49 candidate species, we test three hypotheses regarding i) species-level diversity, ii) hybridization and admixture, and iii) misleading phylogenetic inference. Using phylogenetic and population-clustering analyses considering gene flow, we find support for at least 47 candidate species in the phylogenomic dataset, some of which are newly characterized here while others represent combinations of previously named lineages that are collapsed in the current dataset. Within these, we observe significant phylogeographic structure, with up to 64 total geographic genetic lineages, many of which hybridize either narrowly at contact zones or extensively across ecological gradients. We find strong support for both recent admixture between terminal lineages and ancient hybridization across internal branches. This signal appears to distort concatenated phylogenetic inference, wherein more heavily admixed terminal specimens occupy apparently artifactual early diverging topological positions, occasionally to the extent of forming false clades of intermediate hybrids. Additional geographic and genetic sampling and more robust computational approaches will be needed to clarify taxonomy, and to reconstruct a network topology to display evolutionary relationships in a manner that is consistent with their complex history of reticulation. --
Morphometric data of two tree frog species and their hybrids from a hybrid zone in Poland
<p><span><span><span><span>Under incomplete reproductive isolation, secondary contact of diverged allopatric lineages may form hybrid zones that allow to study recombinants over several generations as excellent systems of genomic interactions, resulting from the evolutionary forces, acting on certain genes and phenotypes. Hybrid phenotypes are expected to either exhibit intermediacy or, alternatively, transgressive traits, which exceed the extremes of their parents due to epistasis and segregation of complementary alleles. While transgressive morphotypes have been examined in fish, reptiles, birds, and mammals, studies in amphibians are rare. Here, we associate microsatellite-based genotypes and morphometrics-based morphotypes of two European tree frog species of the <em>Hyla arborea</em> group, sampled across a hybrid zone in Poland, to understand whether the genetically differentiated parental species also differ in morphology between each other and their hybrids, and whether secondary contact leads to the evolution of intermediate or transgressive morphotypes. Using univariate approaches, explorative multivariate methods (Principal Component Analyses) as well as techniques with prior grouping (Discriminant Function Analyses), we find that morphotypes of both parental species and hybrids differ from each other. Importantly, hybrid morphotypes are neither intermediate nor transgressive but found to be more similar to <em>H. orientalis</em> than to <em>H. arborea</em>. Our study presents one of the rare datasets, in which genotypes along with morphotypes examined the occurrence or absence of transgressive morphologies in wild amphibians.</span></span></span></span></p>
Demographic history shapes genomic ancestry in hybrid zones
<p>Demographic factors such as migration rate and population size can impede or facilitate speciation. In hybrid zones, reproductive boundaries between species are tested and demography mediates the opportunity for admixture between lineages that are partially isolated. Genomic ancestry is a powerful tool for revealing the history of admixed populations, but models and methods based on local ancestry are rarely applied to structured hybrid zones. To understand the effects of demography on ancestry in hybrids zones, we performed individual-based simulations under a stepping-stone model, treating migration rate, deme size, and hybrid zone age as parameters. We find that the number of ancestry junctions (the transition points between genomic regions with different ancestries), as well as heterogenicity (the genomic proportion heterozygous for ancestry), are often closely connected to demographic history. Reducing deme size reduces junction number and heterogenicity. Elevating migration increases heterogenicity, but migration affects junction number in more complex ways. We highlight the junction frequency spectrum as a novel and informative summary of ancestry that responds to demographic history. A substantial proportion of junctions are expected to fix when migration is limited or deme size is small, changing the shape of the spectrum. Our findings suggest that genomic patterns of ancestry could be used to infer demographic history in hybrid zones.</p>
Population genomics of an emergent tri-species hybrid zone
<p>Isolating barriers that drive speciation are commonly studied in the context of two-species hybrid zones. There is however evidence that more complex introgressive relationships are common in nature. Here, we use field observations and genomic analysis, including the sequencing and assembly of a novel reference genome, to study an emergent hybrid zone involving two colliding hybrid zones of three woodpecker species: red-breasted, red-naped, and yellow-bellied sapsuckers (<em>Sphyrapicus ruber</em>, <em>S. nuchalis</em>, and <em>S. varius</em>). Surveys of the area surrounding Prince George, British Columbia, Canada, show that all three species are sympatric, and Genotyping-by-Sequencing identifies hybrids from each species pair and birds with ancestry from all three species. Observations of phenotypes and genotypes of mated pairs provide evidence for assortative mating, though there is some heterospecific pairing. Hybridization is more extensive in this tri-species hybrid zone than in two di-species hybrid zones. However, there is no evidence of a hybrid swarm, and admixture is constrained to contact zones, so we classify this region as a tension zone and invoke selection against hybrids as a likely mechanism maintaining species boundaries. Analysis of sapsucker age classes does not show disadvantages in hybrid survival to adulthood, so we speculate the selection upholding the tension zone may involve hybrid fecundity. Gene flow among all sapsuckers in di-species hybrid zones suggests introgression likely occurred before the formation of this tri-species hybrid zone and might result from bridge hybridization, vagrancies, or other three-species interactions. </p>
A Novel Hybrid Finite Element-Spectral Boundary Integral Scheme for Modeling Earthquake Cycles: Application to Rate and State Faults with Low-Velocity Zones
<p>We present a novel hybrid finite element (FE) - spectral boundary integral (SBI) scheme that enables efficient simulation of earthquake cycles. This combined FE-SBI approach captures the benefits of finite elements in modelling problems with nonlinearities, as well as the computational superiority of SBI. The domain truncation enabled by this scheme allows us to utilize high-resolution finite elements discretization to capture inhomogeneities or complexities that may exist in a narrow region surrounding the fault. Combined with an adaptive time stepping algorithm, this framework opens new opportunities for modeling earthquake cycles with high-resolution fault zone physics. In this initial study, we consider a two dimensional (2-D) anti-plane model with a vertical strike-slip fault governed by rate and state friction in the quasi-dynamic limit under the radiation damping approximation. The proposed approach is first verified using the benchmark problem BP-1 from the Southern California Earthquake Center (SCEC) sequence of earthquake and aseismic slip (SEAS) community verification effort. The computational framework is then utilized to model the earthquake sequence and aseismic slip of a fault embedded within a low-velocity fault zone (LVFZ) with different widths and compliance levels. Our results indicate that sufficiently compliant LVFZs contribute to the emergence of sub-surface events that fail to penetrate to the free surface and may experience earthquake clusters with nonuniform inter-seismic time. Furthermore, the LVFZ leads to slip rate amplification relative to the homogeneous elastic case. We discuss the implications of our results for understanding earthquake complexity as an interplay of fault friction and bulk heterogeneities. The complete work consists of all files listed below. </p>
Data from: Integrating Bayesian genomic cline analyses and association mapping of morphological and ecological traits to dissect reproductive isolation and introgression in a Louisiana Iris hybrid zone
Hybrid zones provide unique opportunities to examine reproductive isolation and introgression in nature. We utilized 45,384 Single Nucleotide Polymorphism (SNP) loci to perform association mapping of 14 floral, vegetative, and ecological traits that differ between Iris hexagona and Iris fulva, and to investigate, using a Bayesian Genomic Cline (BGC) framework, patterns of genomic introgression in a large and phenotypically diverse hybrid zone in southern Louisiana. Many loci of small effect-size were consistently found to be associated with phenotypic variation across all traits, and several individual loci were revealed to influence phenotypic variation across multiple traits. Patterns of genomic introgression were quite heterogeneous throughout the Louisiana Iris genome, with I. hexagona alleles tending to be favored over those of I. fulva. Loci that were found to have exceptional patterns of introgression were also found to be significantly associated with phenotypic variation in a small number of morphological traits. However, this was the exception rather than the rule, as most loci that were associated with morphological trait variation were not significantly associated with excess ancestry. These findings provide insights into the complexity of the genomic architecture of phenotypic differences and are a first step towards identifying loci that are associated with both trait variation and reproductive isolation in nature.
Fig. 35 in Hybridization Among Western Whiptail Lizards (Cnemidophorus Tigris) In Southwestern New Mexico: Population Genetics, Morphology, And Ecology In Three Contact Zones
Fig. 35. Ventral views of the same lizards arranged in the same sequence as in figure 34.
Fig. 3. The contact region. Numbers designate collecting sites. Compare with figure 49 in Hybridization Among Western Whiptail Lizards (Cnemidophorus Tigris) In Southwestern New Mexico: Population Genetics, Morphology, And Ecology In Three Contact Zones
Fig. 3. The contact region. Numbers designate collecting sites. Compare with figure 49.
Real-time geographic settling of a hybrid zone between the invasive winter moth (Operophtera brumata L.) and the native Bruce spanworm (O. bruceata Hulst)
<p>Hybridization plays an important and underappreciated role in shaping the evolutionary trajectories of species. Following the introduction of a non-native organism to a novel habitat, hybridization with a native congener may affect the probability of establishment of the introduced species. In most documented cases of hybridization between a native and a non-native species, a mosaic hybrid zone is formed, with hybridization occurring heterogeneously across the landscape. In contrast, most naturally occurring hybrid zones are clinal in structure. Here we report on a long-term microsatellite dataset that monitored hybridization between the invasive winter moth, <i>Operophtera brumata </i>(Lepidoptera: Geometridae), and the native Bruce spanworm, <i>O. bruceata, </i>over a 12-year period. Our results document one of the first examples of the real-time formation and geographic settling of a clinal hybrid zone. In addition, by comparing one transect in Massachusetts where extreme winter cold temperatures have been hypothesized to restrict the distribution of winter moth, and one in coastal Connecticut, where winter temperatures are moderated by Long Island Sound, we<i> </i>find that the location of the hybrid zone appears to be independent of environmental variables and maintained under a tension model wherein the stability of the hybrid zone is constrained by population density, reduced hybrid fitness, and low dispersal rates. Documenting the formation of a contemporary clinal hybrid zone may provide important insights into the factors that shaped other well-established hybrid zones.</p>
Contrasting levels of hybridization across the two contact zones between two hedgehog species revealed by genome-wide SNP data
<p>Hybridization and introgression have played important roles in the history of various species, including lineage diversification and the evolution of adaptive traits. Hybridization can accelerate the development of reproductive isolation between diverging species, and thus valuable insight into the evolution of reproductive barrier formation may be gained by studying secondary contact zones. Hedgehogs of the genus <em>Erinaceus</em>, which are insectivores sensitive to changes in climate, are a pioneer model in Pleistocene phylogeography. The present study provides the first genome-wide SNP data regarding the <em>Erinaceus</em> hedgehogs species complex, offering a unique comparison of two secondary contact zones between <em>Erinaceus</em> <em>europaeus</em> and <em>E</em>. <em>roumanicus</em>. Results confirmed diversification of the genus during the Pleistocene period and detected a new refugial lineage of <em>E</em>. <em>roumanicus</em> outside the Mediterranean region, most likely in the Ponto-Caspian region. In the Central European zone, the level of hybridization was low, whereas in the Russian-Baltic zone, both species hybridise extensively. Asymmetrical gene flow from <em>E</em>. <em>europaeus</em> to <em>E</em>. <em>roumanicus</em> suggests that reproductive isolation varies according to the direction of the crosses in the hybrid zones. However, no loci with significantly different patterns of introgression were detected. Markedly different pre- and post-zygotic barriers, and thus diverse modes of species boundary maintenance in the two contact zones, likely exist. This pattern is probably a consequence of the different ages and thus of the different stages of evolution of reproductive isolating mechanisms in each hybrid zone.</p>
Tension zone trapped by exogenous cline: analysis of a narrow hybrid zone between two parapatric Oxytropis species (Fabaceae)
<p>Hybrid zones have been widely highlighted for their interest in understanding evolutionary processes. It is generally accepted that hybrid zones can be maintained in a balance between dispersal and selection. However, the selective forces can either be endogenous (i.e., genetic incompatibilities between parental taxa) or exogenous (i.e., parental taxa are adapted to different environments).</p> <p>In this study, we evaluated these alternatives and determined the maintenance of a narrow hybrid zone between parapatric distributed <em>Oxytropis diversifolia</em> and <em>O. leptophylla</em> in Nei Mongol, China. For 507 individuals sampled from two populations in the hybrid zone, 12 <em>O. diversifolia</em> populations and five <em>O. leptophylla</em> populations, we measured leaf-morphological characteristics, quantified genetic structure using 11 nuclear microsatellite loci and five chloroplast DNA intergenic regions, collected micro- and macrohabitat data, and conducted geographical cline analysis.</p> <p>We found that the two species differed in leaf morphology, and putative hybrids showed either intermediacy or a bias to <em>O. diversifolia</em>. Parental taxa formed two genetically distinct clusters, while populations in the hybrid zone consisted of both parental forms and various admixed individuals, exhibiting a bimodal pattern. The hybrid zone was coupled to ecological transitions of both microhabitat (i.e., the slope) and macroclimatic conditions. However, the genetic clines were significantly narrower than the environmental cline.</p> <p>Our results indicate that endogenous selection can be primarily responsible for maintaining the hybrid zone, while local adaptation accounts for the position of the zone. We further suggest the probable outcome of hybridization could be introgression.</p>
Asymmetric allelic introgression across a hybrid zone of the coal tit (Periparus ater) in the central Himalayas
<p>In the Himalayas, a number of secondary contact zones have been described for vicariant vertebrate taxa. However, analyses of genetic divergence and admixture are missing for most of these examples. In this study, we provide a population genetic analysis for the coal tit (<i>Periparus ater</i>) hybrid zone in Nepal. Intermediate phenotypes between the distinctive western 'spot-winged tit' (<i>P. a. melanolophus</i>) and e<span class="msoDel">E</span>astern Himalayan coal tits (<i>P. a. aemodius</i>) occur across a narrow range of less than 100 km in western Nepal. As a peculiarity, another distinctive cinnamon-bellied form is known from a single population so far. Genetic admixture of western and eastern mitochondrial lineages was restricted to the narrow zone of phenotypically intermediate populations. The cline width was estimated 46 km only with a center close to the population of the cinnamon-bellied phenotype. In contrast, allelic introgression of microsatellite loci was asymmetrical from eastern <i>P. a. aemodius</i> into far western populations of phenotypic <i>P. a. melanolophus</i> but not vice versa. Accordingly, the microsatellite cline was about 3.7 times wider than the mitochondrial one.</p>
Integrating top-down and bottom-up approaches to understand the genetic architecture of speciation across a monkeyflower hybrid zone
<p><span>Understanding the phenotypic and genetic architecture of reproductive isolation is a longstanding goal of speciation research. In several systems, large-effect loci contributing to barrier phenotypes have been characterized, but such causal connections are rarely known for more complex genetic architectures. In this study, we combine 'top-down' and 'bottom-up' approaches with demographic modeling toward an integrated understanding of speciation across a monkeyflower hybrid zone. Previous work suggests that pollinator visitation acts as a primary barrier to gene flow between two divergent red- and yellow-flowered ecotypes of <em>Mimulus</em> <em>aurantiacus</em>. Several candidate isolating traits and anonymous SNP loci under divergent selection have been identified, but their genomic positions remain unknown. Here, we report findings from demographic analyses that indicate this hybrid zone formed by secondary contact, but that subsequent gene flow was restricted by widespread barrier loci across the genome. Using a novel, geographic cline-based genome scan, we demonstrate that candidate barrier loci are broadly distributed across the genome, rather than mapping to one or a few 'islands of speciation.' Quantitative trait locus (QTL) mapping reveals that most floral traits are polygenic, with little evidence that QTL co-localize, indicating that most traits are genetically independent. Finally, we find little evidence that QTL and candidate barrier loci overlap, suggesting that some loci contribute to other forms of reproductive isolation. Our findings highlight the challenges of understanding the genetic architecture of reproductive isolation and reveal that barriers to gene flow aside from pollinator isolation may play an important role in this system.</span></p>
Podarcis bocagei vs P. carbonelli hybrid zone SNP datasets from ddRADseq
<p>We used double digestion restriction site associated DNA (ddRAD) sequencing to discover SNPs in samples across a transect including a hybrid zone between <em>Podarcis carbonelli</em> and <em>Podarcis carbonelli</em>. <span>We used <em>P. bocagei</em> and <em>P. carbonelli</em> samples from the locations at the extremes of the transect as references. We obtained a SNP dataset including all SNPs after removing loci with depth coverage <8, missing data >20%, removing loci containing more than five SNPs, and with more than 70% heterozygosity (complete dataset; 6905 SNPs, 329 individuals). Additionally, we obtained</span> from the complete dataset two other datasets, prior to apply a missing data filter. One dataset contained loci with allele frequencies higher than 0.8 in the reference population containing only parental individuals of one species and lower than 0.2 in the reference population of the other species ("80/20" dataset; 2300 SNPs, 329 individuals); the other dataset comprised diagnostic SNPs between reference populations (diagnostic dataset; 1241 SNPs, 236 individuals) but excluding private alleles from references, i.e. excluding alleles that are not present in the populations of contact. Individuals with missing data >35% were removed from all datasets (the number of individuals reported for each dataset is after applying this filter, but note that the 80/20 and the diagnostic datasets were obtained before applying this filter to the complete dataset). Across datasets, average depth of coverage by individuals was 28 (median = 26.8, min = 12.5, max = 85.8) and by loci was 29 (median = 28.8; min = 15.6; max = 48.6). The analysis of replicate samples (four samples were replicated twice, i.e. were amplified and sequenced in independent libraries and SNP calling was performed independently) showed high levels (99.87%) of multilocus genotype replicability.</p>
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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
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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
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