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180 results for “contact zone”
Fig. 4 in Hybridization Among Western Whiptail Lizards (Cnemidophorus Tigris) In Southwestern New Mexico: Population Genetics, Morphology, And Ecology In Three Contact Zones
Fig. 4. The northern hybrid zone, with collecting sites numbered (enlarged from fig. 3). Transect sites are numbers within squares (1–7), but the midpoint (50:50 point of gene exchange) is within a diamond (site 3). Associated sites are numbers in circles (table 2; appendix 1).
Fig. 9 in Hybridization Among Western Whiptail Lizards (Cnemidophorus Tigris) In Southwestern New Mexico: Population Genetics, Morphology, And Ecology In Three Contact Zones
Fig. 9. Habitats at collecting sites in the northern transect and near an associated site, Animas Valley north of Lordsburg (tables 2, 3; figs. 3, 4; appendix 1), 22 August 1990. Top. Site 7, looking W from NM Hwy 464. Bottom. Abrupt ecotone of mesquite grassland and creosote desertscrub (in near background), 5.8 km (by road) W of site 3, looking NW. Site 8 is 0.3 km off the left side of the photo.
Implications of headwater contact zones for the riverine barrier hypothesis: a case study of the Blue-capped Manakin (Lepidothrix coronata)
<p>Rivers frequently delimit the geographic ranges of species in the Amazon Basin. These rivers also define the boundaries between genetic clusters within many species, yet river boundaries have been documented to break down in headwater regions where rivers are narrower. To explore the evolutionary implications of headwater contact zones in Amazonia, we examined genetic variation in the Blue-capped Manakin (<em>Lepidothrix coronata</em>), a species previously shown to contain several genetically and phenotypically distinct populations across the western Amazon Basin. We collected restriction site-associated DNA sequence data (RADcap) for 706 individuals and found that spatial patterns of genetic structure indicate rivers, particularly the Amazon and Ucayali, are major dispersal barriers for <em>L. coronata</em> along a distance of more than 3000 km. We also found evidence that genetic connectivity is elevated across several headwater regions, highlighting the importance of headwater gene flow for models of Amazonian diversification. The headwaters of the Ucayali River provide a notable exception to findings of headwater gene flow by harboring non-admixed populations of <em>L. coronata</em> on opposite sides of a <1 km-wide river channel with a known dynamic history, potentially suggesting that additional prezygotic barriers are limiting gene flow in this region. </p>
Implications of headwater contact zones for the riverine barrier hypothesis: a case study of the Blue-capped Manakin (Lepidothrix coronata)
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Data from: Contact zones reveal restricted introgression despite frequent hybridization across a recent lizard radiation
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SNP datasets obtained with ddRADseq from four contact zones between Podarcis carbonelli and four other Podarcis species
<p><span><span><span>We used double digestion restriction site associated DNA (ddRAD) sequencing to discover SNPs in samples from four contact zones between <i>Podarcis carbonelli</i> and four other <em>Podarcis</em> species</span></span>. We obtained a panel of SNPs for each for each contact zone and reference populations and a dataset of diagnostic SNPs between reference populations for each contact zone but excluding private alleles from references, i.e. excluding alleles that are not present in the populations of contact. The final datasets (complete and diagnostic) were obtained after removing loci with depth coverage <8, missing data >20% and removing individuals with more than 35% of missing data. Across complete and diagnostic datasets, mean coverage by individuals ranged from 28 to 47 and by loci from 28 to 44<span><span>. The analysis of replicate samples (about 6% of samples were replicated, i.e. were amplified and sequenced in independent libraries and SNP calling was performed independently) showed high levels (>99%) of multilocus genotype replicability.</span></span></span></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>
Fig. 1 in Morphological Patterns Of A Nightingale Population In A Contact Zone Of Luscinia Megarhynchos And L. Luscinia
Fig. 1. Locationofthestudyareasbasedonthestudiedpopulations (1: Bódva, 2: Tisza-
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.
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>
Is there hybridisation between diploid and tetraploid Euphrasia in a secondary contact zone?
<p>• Premise of the study: Hybridisation between species with contrasting ploidy is usually considered rare in nature due to strong ploidy related postzygotic reproductive isolating barriers. However, genomic sequencing has revealed previously overlooked examples of natural cross-ploidy hybridisation, suggesting this phenomenon may be more common than once thought. Here, we investigate potential cross-ploidy hybridisation in British eyebrights (Euphrasia, Orobanchaceae), a group where thirteen putative cross-ploidy hybrid combinations have been reported based on morphology. • Methods: We analysed a contact zone between diploid E. rostkoviana and tetraploid E. arctica in Wales. We sequenced part of the internal transcribed spacer of nuclear ribosomal DNA (ITS1) and used Genotyping by Sequencing (GBS) to look for evidence of cross-ploidy hybridisation and introgression. • Key results: All variant sites in the ITS1 region were fixed between diploids and tetraploids, indicating a strong barrier to hybridisation. Clustering analyses of 356 SNPs generated using GBS clearly separated samples by ploidy and revealed strong genetic structure (FST = 0.44). However, the FST distribution across all SNPs was bimodal, indicating potential differential selection on loci between diploids and tetraploids. Demographic inference with dadI suggested potential gene flow – with this limited to around one or fewer migrants per generation. • Conclusions: Our results suggest recent cross-ploidy hybridisation is rare or absent in a site of secondary contact in Euphrasia. While a strong ploidy barrier prevents hybridisation over ecological time-scales, such hybrids may form in stable populations over evolutionary time-scales and may allow for cross-ploidy introgression to take place.</p>
Interspecific introgression of MHC genes in Triturus newts: Evidence from multiple contact zones
<p>The major histocompatibility complex (MHC) genes are central to the adaptive immune response in vertebrates. Selection generally maintains high MHC variation because the spectrum of recognised pathogens depends on MHC polymorphism. Novel alleles favoured by selection originate by interallelic recombination or <em>de</em> <em>novo</em> mutations but may also be acquired by introgression from related species. However, the extent and prevalence of MHC introgression remain an open question. In this study, we tested for MHC introgression in six hybrid zones formed by six <em>Triturus</em> newt species. We sequenced and genotyped the polymorphic second exons of the MHC class I and II genes and compared their interspecific similarity at various distances from the centre of the hybrid zone. We found evidence for introgression of both MHC classes in the majority of examined hybrid zones, with support for a more substantial class I introgression. Furthermore, the overall MHC allele sharing outside of hybrid zones was elevated between pairs of <em>Triturus</em> species with abutting ranges, regardless of the phylogenetic distance between them. No effect of past hybrid zone movement on MHC allele sharing was found. Finally, using previously published genome-wide data, we demonstrated that MHC introgression was more extensive than genome-wide introgression, supporting its adaptive potential. Our study thus provides evidence for the prevalence of MHC introgression across multiple <em>Triturus</em> hybrid zones, indicating that MHC introgression between divergent hybridising species may be widespread and adaptive.</p>
Data from: Replicate contact zones suggest a limited role of plumage in reproductive isolation among subspecies of the Variable Seedeater (Sporophila corvina)
<p>After establishing secondary contact, recently diverged populations may remain reproductively isolated or may hybridize to a varying extent depending on factors such as hybrid fitness and the strength of assortative mating. Here, we used genomic and phenotypic data from three independent contact zones between subspecies of the Variable Seedeater (<em>Sporophila corvina</em>) to examine how coloration and genetic divergence shape patterns of hybridization. We found that differences in plumage coloration are likely maintained by divergent selection across contact zones; however, the degree of plumage differentiation does not match overall patterns of hybridization. Across two parallel contact zones between populations with divergent phenotypes (entirely black vs. pied plumage), populations hybridized extensively across one contact zone but not the other, suggesting that plumage divergence is not sufficient to maintain reproductive isolation. Where subspecies hybridized, hybrid zones were wide and formed by later-generation hybrids, suggesting frequent reproduction and high survivorship for hybrid individuals. Moreover, contemporary gene flow has played an important role in shaping patterns of genetic structure between populations. Replicated contact zones between hybridizing taxa offer a unique opportunity to explore how different factors interact to shape patterns of hybridization. Overall, our results demonstrate that divergence in plumage coloration is important in reducing gene flow but insufficient in maintaining reproductive isolation in this clade, and that other factors such as divergence in song and time since secondary contact may also play an important role in driving patterns of reduced hybridization and gene flow.</p>
Supplementary data from: Introgression across narrow contact zones shapes the genomic landscape of phylogenetic variation in an African bird clade
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Contrasting levels of hybridization across the two contact zones between two hedgehog species revealed by genome-wide SNP data
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Is there hybridisation between diploid and tetraploid Euphrasia in a secondary contact zone?
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Data for: Tracking hybrid viability across life-stages in a natural avian contact zone
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Data from: Replicate contact zones suggest a limited role of plumage in reproductive isolation among subspecies of the Variable Seedeater (Sporophila corvina)
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SNP datasets obtained with ddRADseq from four contact zones between Podarcis carbonelli and four other Podarcis species
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International Brain Laboratory public data
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OpenNeuro
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