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Jan W. Arntzen - One of the best experts on this subject based on the ideXlab platform.
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Environmental correlates of the European common toad Hybrid Zone
Contributions to Zoology, 2020Co-Authors: Jan W. Arntzen, Daniele Canestrelli, Íñigo Martínez-solanoAbstract:The interplay between intrinsic (development, physiology, behavior) and extrinsic (landscape features, climate) factors determines the outcome of admixture processes in Hybrid Zones, in a continuum from complete genetic merger to full reproductive isolation. Here we assess the role of environmental correlates in shaping admixture patterns in the long Hybrid Zone formed by the toads Bufo bufo and B. spinosus in western Europe. We used species-specific diagnostic SNP markers to genotype 6584 individuals from 514 localities to describe the contact Zone and tested for association with topographic, bioclimatic and land use variables. Variables related to temperature and precipitation contributed to accurately predict the distribution of pure populations of each species, but the models did not perform well in areas where genetically admixed populations occur. A sliding window approach proved useful to identify different sets of variables that are important in different sections of this long and heterogeneous Hybrid Zone, and offers good potential to predict the fate of moving contact Zones in global change scenarios.
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An amphibian species pushed out of Britain by a moving Hybrid Zone.
Molecular ecology, 2019Co-Authors: Jan W. ArntzenAbstract:Classical theory states that Hybrid Zones will be stable in troughs of low population density where dispersal is hampered. Yet, evidence for moving Hybrid Zones is mounting. One possible reason that moving Zones have been underappreciated is that they may drive themselves into oblivion and with just the superseding species remaining, morphological and genetic signals of past species replacement may be difficult to appreciate. Using genetic data (32 diagnostic single nucleotide polymorphisms) from a clinal Hybrid Zone of the common toad (Bufo bufo) and the spined toad (Bufo spinosus) in France for comparison, alleles of the latter species were documented in common toads in the south of Great Britain, at frequencies in excess of 10%. Because long distance dispersal across the Channel is unlikely, the conclusion reached was that the continental toad Hybrid Zone which previously extended into Britain, moved southwards and extirpated B. spinosus. Species distribution models for the mid-Holocene and the present support that climate has locally changed in favour of B. bufo. The system bears resemblance with the demise of Homo neanderthalensis and the rise of Homo sapiens and provides an example that some paleoanthropologists demanded in support of a hominin "leaky replacement" scenario. The toad example is informative just because surviving pure B. spinosus and an extant slowly moving interspecific Hybrid Zone are available for comparison.
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Molecular Ecology - Testing an hypothesis of Hybrid Zone movement for toads in France.
Molecular ecology, 2019Co-Authors: Isolde Van Riemsdijk, Ben Wielstra, Roger K. Butlin, Jan W. ArntzenAbstract:Hybrid Zone movement may result in substantial unidirectional introgression of selectively neutral material from the local to the advancing species, leaving a genetic footprint. This genetic footprint is represented by a trail of asymmetric tails and displaced cline centres in the wake of the moving Hybrid Zone. A peak of admixture linkage disequilibrium is predicted to exist ahead of the centre of the moving Hybrid Zone. We test these predictions of the movement hypothesis in a Hybrid Zone between common (Bufo bufo) and spined toads (B. spinosus), using 31 nuclear and one mtDNA SNPs along a transect in the northwest of France. Average effective selection in Bufo Hybrids is low and clines vary in shape and centre. A weak pattern of asymmetric introgression is inferred from cline discordance of seven nuclear markers. The dominant direction of gene flow is from B. spinosus to B. bufo and is in support of southward movement of the Hybrid Zone. Conversely, a peak of admixture linkage disequilibrium north of the Hybrid Zone suggests northward movement. These contrasting results can be explained by reproductive isolation of the B. spinosus and B. bufo gene pools at the southern (B. spinosus) side of the Hybrid Zone. The joint occurrence of asymmetric introgression and admixture linkage disequilibrium can also be explained by the combination of low dispersal and random genetic drift due to low effective population sizes.
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A common toad Hybrid Zone that runs from the Atlantic to the Mediterranean
Amphibia-Reptilia, 2018Co-Authors: Jan W. Arntzen, Jacob Mcatear, Roland Butôt, Íñigo Martínez-solanoAbstract:We document the distribution of the common toad Bufo bufo and the spined toad B. spinosus at their contact Zone across France with data from a mitochondrial DNA RFLP assay, complementing similar work including nuclear markers in the northwest and southeast of France and in Italy. We also reconstruct geographical clines across the species’ contact Zone in central France. Bufo bufo is found in the north-eastern half of France. Bufo spinosus is found in the south-western complement. The contact Zone they form runs from the Atlantic coast near Caen, France, to the Mediterranean coast near Savona, Italy, and has a length of over 900 km. In central France B. bufo and B. spinosus engage in a Hybrid Zone with a unimodal genetic signature. Hybrid Zone width is ca. 10 km at mitochondrial DNA and averages at 61 km for four nuclear loci. The Hybrid Zone is distinctly asymmetric with a signature of B. spinosus in B. bufo and not the other way round. We attribute this observation to B. bufo moving southwards at the expense of B. spinosus , with introgression in the direction of the advancing species. We noted substantial geographic variation in characters for species identification. Morphological species identification performs well in France, but breaks down in Italy. Mitochondrial DNA is inconclusive in south-eastern France and Italy. The nuclear genetic markers perform consistently well but have not yet been applied to the Zone in full. Possible, but surely heterogeneous ecological correlates for the position of the Hybrid Zone are mountains and rivers.
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A genomic footprint of Hybrid Zone movement in crested newts
Evolution letters, 2017Co-Authors: Ben Wielstra, Roger K. Butlin, Terry Burke, Aziz Avci, Nazan Üzüm, Emin Bozkurt, Kurtuluş Olgun, Jan W. ArntzenAbstract:Speciation typically involves a stage in which species can still exchange genetic material. Interspecific gene flow is facilitated by the Hybrid Zones that such species establish upon secondary contact. If one member of a Hybridizing species pair displaces the other, their Hybrid Zone would move across the landscape. Although theory predicts that moving Hybrid Zones quickly stagnate, Hybrid Zones tracked over one or a few decades do not always follow such a limitation. This suggests that Hybrid Zones have the potential to traverse considerable distances over extended periods of time. When Hybrid Zones move, introgression is predicted to result in biased gene flow of selectively neutral alleles, from the receding species into the advancing species. We test for such a genomic footprint of Hybrid Zone movement in a pair of crested newt species (genus Triturus) for which we have a priori support for westward Hybrid Zone movement. We perform a multilocus phylogeographical survey and conduct Bayesian clustering analysis, estimation of ancestry and heterozygosity, and geographical cline analysis. In a 600 km wide area east of the present day Hybrid Zone a genomic footprint constitutes empirical evidence consistent with westward Hybrid Zone movement. The crested newt case suggests that Hybrid Zone movement can occur over an extensive span of time and space. Inferring Hybrid Zone movement provides fundamental insight into historical biogeography and the speciation process, and we anticipate that Hybrid Zones will prove to be far more mobile than currently appreciated.
Darren E. Irwin - One of the best experts on this subject based on the ideXlab platform.
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cross decades stability of an avian Hybrid Zone
Journal of Evolutionary Biology, 2019Co-Authors: Silu Wang, Kira E. Delmore, Sievert Rohwer, Darren E. IrwinAbstract:Hybrid Zones are particularly valuable for understanding the evolution of partial reproductive isolation between differentiated populations. An increasing number of Hybrid Zones have been inferred to move over time, but in most such cases Zone movement has not been tested with long-term genomic data. The Hybrid Zone between Townsend's Warblers (Setophaga townsendi) and Hermit Warblers (S. occidentalis) in the Washington Cascades was previously inferred to be moving from northern S. townsendi southwards towards S. occidentalis, based on plumage and behavioural patterns as well as a 2000-km genetic wake of hermit mitochondrial DNA (mtDNA) in coastal Townsend's Warblers. We directly tested whether Hybrid Zone position has changed over 2-3 decades by tracking plumage, mtDNA and nuclear genomic variation across the Hybrid Zone over two sampling periods (1987-94 and 2015-16). Surprisingly, there was no significant movement in genomic or plumage cline centres between the two time periods. Plumage cline widths were narrower than expected by neutral diffusion, consistent with a 'tension Zone' model, in which selection against Hybrids is balanced by movement of parental forms into the Zone. Our results indicate that this Hybrid Zone is either stable in its location or moving at a rate that is not detectable over 2-3 decades. Despite considerable gene flow, the stable clines in multiple phenotypic and genotypic characters over decades suggest evolutionary stability of this young pair of sister species, allowing divergence to continue. We propose a novel biogeographic scenario to explain these patterns: rather than the Hybrid Zone having moved thousands of kilometres to its current position, inland Townsend's met coastal Hermit Warbler populations along a broad front of the British Columbia and Alaska coast and Hybridization led to replacement of the Hermit Warbler plumage with Townsend's Warbler plumage patterns along this coastline. Hence, Hybrid Zones along British Columbia and Alaska moved only a short distance from the inland to the coast, whereas the Hermit Warbler phenotype appears stable in Washington and further south. This case provides an example of the complex biogeographic processes that have led to the distribution of current phenotypes within and among closely related species.
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Cross‐decades stability of an avian Hybrid Zone
Journal of evolutionary biology, 2019Co-Authors: Silu Wang, Kira E. Delmore, Sievert Rohwer, Darren E. IrwinAbstract:Hybrid Zones are particularly valuable for understanding the evolution of partial reproductive isolation between differentiated populations. An increasing number of Hybrid Zones have been inferred to move over time, but in most such cases Zone movement has not been tested with long-term genomic data. The Hybrid Zone between Townsend's Warblers (Setophaga townsendi) and Hermit Warblers (S. occidentalis) in the Washington Cascades was previously inferred to be moving from northern S. townsendi southwards towards S. occidentalis, based on plumage and behavioural patterns as well as a 2000-km genetic wake of hermit mitochondrial DNA (mtDNA) in coastal Townsend's Warblers. We directly tested whether Hybrid Zone position has changed over 2-3 decades by tracking plumage, mtDNA and nuclear genomic variation across the Hybrid Zone over two sampling periods (1987-94 and 2015-16). Surprisingly, there was no significant movement in genomic or plumage cline centres between the two time periods. Plumage cline widths were narrower than expected by neutral diffusion, consistent with a 'tension Zone' model, in which selection against Hybrids is balanced by movement of parental forms into the Zone. Our results indicate that this Hybrid Zone is either stable in its location or moving at a rate that is not detectable over 2-3 decades. Despite considerable gene flow, the stable clines in multiple phenotypic and genotypic characters over decades suggest evolutionary stability of this young pair of sister species, allowing divergence to continue. We propose a novel biogeographic scenario to explain these patterns: rather than the Hybrid Zone having moved thousands of kilometres to its current position, inland Townsend's met coastal Hermit Warbler populations along a broad front of the British Columbia and Alaska coast and Hybridization led to replacement of the Hermit Warbler plumage with Townsend's Warbler plumage patterns along this coastline. Hence, Hybrid Zones along British Columbia and Alaska moved only a short distance from the inland to the coast, whereas the Hermit Warbler phenotype appears stable in Washington and further south. This case provides an example of the complex biogeographic processes that have led to the distribution of current phenotypes within and among closely related species.
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Migratory orientation in a narrow avian Hybrid Zone.
PeerJ, 2017Co-Authors: David P. L. Toews, Kira E. Delmore, Matthew M. Osmond, Philip D. Taylor, Darren E. IrwinAbstract:BACKGROUND Zones of contact between closely related taxa with divergent migratory routes, termed migratory divides, have been suggested as areas where Hybrid offspring may have intermediate and inferior migratory routes, resulting in low fitness of Hybrids and thereby promoting speciation. In the Rocky Mountains of Canada there is a narrow Hybrid Zone between Audubon's and myrtle warblers that is likely maintained by selection against Hybrids. Band recoveries and isotopic studies indicate that this Hybrid Zone broadly corresponds to the location of a possible migratory divide, with Audubon's warblers migrating south-southwest and myrtle warblers migrating southeast. We tested a key prediction of the migratory divide hypothesis: that genetic background would be predictive of migratory orientation among warblers in the center of the Hybrid Zone. METHODS We recorded fall migratory orientation of wild-caught migrating warblers in the center of the Hybrid Zone as measured by video-based monitoring of migratory restlessness in circular orientation chambers. We then tested whether there was a relationship between migratory orientation and genetic background, as measured using a set of species-specific diagnostic genetic markers. RESULTS We did not detect a significant association between orientation and genetic background. There was large variation among individuals in orientation direction. Mean orientation was towards the NE, surprising for birds on fall migration, but aligned with the mountain valley in which the study took place. CONCLUSIONS Only one other study has directly analyzed migratory orientation among naturally-produced Hybrids in a migratory divide. While the other study showed an association between genetic background and orientation, we did not observe such an association in yellow-rumped warblers. We discuss possible reasons, including the possibility of a lack of a strong migratory divide in this Hybrid Zone and/or methodological limitations that may have prevented accurate measurements of long-distance migratory orientation.
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Cultural isolation is greater than genetic isolation across an avian Hybrid Zone.
Journal of evolutionary biology, 2016Co-Authors: Haley L. Kenyon, Miguel Alcaide, David P. L. Toews, Darren E. IrwinAbstract:Elucidating the relationship between genetic and cultural evolution is important in understanding speciation, as learned premating barriers might be involved in maintaining species differences. Here, we test this relationship by examining a widely recognized premating barrier, bird song, in a Hybrid Zone between black-throated green (Setophaga virens) and Townsend's warblers (S. townsendi). We use song analysis, genomic techniques and playback experiments to characterize the cultural and genetic backgrounds of individuals in this region, expecting that if song is an important reproductive barrier between these species, there should be a strong relationship between song and genotype. We show that songs in the Hybrid Zone correspond to the distinctly different songs found in allopatry but that song and genotype are not tightly coupled in sympatry. Allopatric individuals responded only to local songs, indicating that individuals may have learned to respond to songs they commonly hear. We observed discordance between song and genotype clines; a narrower cline suggests that cultural selection on song is stronger than natural selection on genotype. These findings indicate that song is unlikely to play a role in reproductive isolation between these species, and we suggest that spatial variation in song may nonetheless be maintained by frequency-dependent cultural selection. This decoupling of genes and culture may contribute to Hybridization in this region.
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Isotopic variation across the Audubon's-myrtle warbler Hybrid Zone.
Journal of evolutionary biology, 2014Co-Authors: David P. L. Toews, Alan Brelsford, Darren E. IrwinAbstract:Differences in seasonal migratory behaviours are thought to be an important component of reproductive isolation in many organisms. Stable isotopes have been used with success in estimating the location and qualities of disjunct breeding and wintering areas. However, few studies have used isotopic data to estimate the movements of Hybrid offspring in species that form Hybrid Zones. Here, we use stable hydrogen to estimate the wintering locations and migratory patterns of two common and widespread migratory birds, Audubon's (Setophaga auduboni) and myrtle (S. coronata) warblers, as well as their Hybrids. These two species form a narrow Hybrid Zone with extensive interbreeding in the Rocky Mountains of British Columbia and Alberta, Canada, which has been studied for over four decades. Isotopes in feathers grown on the wintering grounds or early on migration reveal three important patterns: (1) Audubon's and myrtle warblers from allopatric breeding populations winter in isotopically different environments, consistent with band recovery data and suggesting that there is a narrow migratory transition between the two species, (2) most Hybrids appear to overwinter in the south-eastern USA, similar to where myrtle warblers are known to winter, and (3) some Hybrid individuals, particularly those along the western edge of the Hybrid Zone, show Audubon's-like isotopic patterns. These data suggest there is a migratory divide between these two species, but that it is not directly coincident with the centre of the Hybrid Zone in the breeding range. We interpret these findings and discuss them within the context of previous research on Hybrid Zones, speciation and migratory divides.
Guila Ganem - One of the best experts on this subject based on the ideXlab platform.
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Sexual selection against natural Hybrids may contribute to reinforcement in a house mouse Hybrid Zone
Proceedings of the Royal Society B: Biological Sciences, 2014Co-Authors: Yasmin Latour, Marco Perriat-sanguinet, Pierre Caminade, Pierre Boursot, Carole Smadja, Guila GanemAbstract:Sexual selection may hinder gene flow across contact Zones when Hybrid recognition signals are discriminated against. We tested this hypothesis in a unimodal Hybrid Zone between Mus musculus musculus and Mus musculus domesticus where a pattern of reinforcement was described and lower Hybrid fitness documented. We presented mice from the border of the Hybrid Zone with a choice between opposite sex urine from the same subspecies versus Hybrids sampled in different locations across the Zone. While no preference was evidenced in domesticus mice, musculus males discriminated in favour of musculus signals and against Hybrid signals. Remarkably, the pattern of Hybrid unattractiveness did not vary across the Hybrid Zone. Moreover, allopatric populations tested in the same conditions did not discriminate against Hybrid signals, indicating character displacement for signal perception or preference. Finally, habituation-discrimination tests assessing similarities between signals pointed out that Hybrid signals differed from the parental ones. Overall, our results suggest that perception of Hybrids as unattractive has evolved in border populations of musculus after the secondary contact with domesticus. We discuss the mechanisms involved in Hybrid unattractiveness, and the potential impact of asymmetric sexual selection on the Hybrid Zone dynamics and gene flow between the two subspecies.
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Variation in mate preference across a house mouse Hybrid Zone.
Heredity, 2008Co-Authors: Guila Ganem, C Litel, Thomas LenormandAbstract:Reproductive character displacement is known to occur at the borders of a secondary contact Zone between the two European subspecies of the house mouse (in Jutland, Denmark), where selection against Hybridization occurs. This study assessed patterns of mate preference in naturally occurring Hybrids of the two subspecies. Mate odour choice was investigated in male and female mice sampled across the Hybrid Zone. Odour samples comprised urine (from the opposite sex to the test animal) obtained from populations geographically distant from the Hybrid Zone. Urine is known to carry subspecies recognition signals. The behavioural results changed across the Hybrid Zone, and were analysed by a model of clinal variation. This behavioural cline was compared with the allozyme cline across the same Hybrid Zone. Males on both sides of the Hybrid Zone showed an assortative preference, which shifted significantly and abruptly ∼10 km from the genetic centre of the Hybrid Zone on the Mus musculus musculus side. Directional preference was not detected in females, which could relate to variation in sexual receptivity. Our model indicates that the peculiar pattern of male preference could involve several genes and be characterized by mild to strong epistasis favouring the expression of M. m. domesticus-like preference over a large portion of the Hybrid Zone. This study may provide the first picture of the genetic determination of mate preference in a mammal.
J W Arntzen - One of the best experts on this subject based on the ideXlab platform.
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testing an hypothesis of Hybrid Zone movement for toads in france
Molecular Ecology, 2019Co-Authors: Roger K. Butlin, Ben Wielstra, Isolde Van Riemsdijk, J W ArntzenAbstract:Hybrid Zone movement may result in substantial unidirectional introgression of selectively neutral material from the local to the advancing species, leaving a genetic footprint. This genetic footprint is represented by a trail of asymmetric tails and displaced cline centres in the wake of the moving Hybrid Zone. A peak of admixture linkage disequilibrium is predicted to exist ahead of the centre of the moving Hybrid Zone. We test these predictions of the movement hypothesis in a Hybrid Zone between common (Bufo bufo) and spined toads (B. spinosus), using 31 nuclear and one mtDNA SNPs along a transect in the northwest of France. Average effective selection in Bufo Hybrids is low and clines vary in shape and centre. A weak pattern of asymmetric introgression is inferred from cline discordance of seven nuclear markers. The dominant direction of gene flow is from B. spinosus to B. bufo and is in support of southward movement of the Hybrid Zone. Conversely, a peak of admixture linkage disequilibrium north of the Hybrid Zone suggests northward movement. These contrasting results can be explained by reproductive isolation of the B. spinosus and B. bufo gene pools at the southern (B. spinosus) side of the Hybrid Zone. The joint occurrence of asymmetric introgression and admixture linkage disequilibrium can also be explained by the combination of low dispersal and random genetic drift due to low effective population sizes.
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Hybrid Zone formation and contrasting outcomes of secondary contact over transects in common toads
Molecular Ecology, 2017Co-Authors: J W Arntzen, Daniele Canestrelli, Wouter De Vries, Inigo MartinezsolanoAbstract:Much progress in speciation research stems from documenting patterns of morphological and genetic variation in Hybrid Zones. Contrasting patterns of marker introgression in different sections of the contact can provide valuable insights on the relative importance of various evolutionary mechanisms maintaining species differences in the face of Hybridization and gene flow and on Hybrid Zone temporal and spatial dynamics. We studied species interactions in the common toads Bufo bufo and B. spinosus in France and northwestern Italy using morphological and molecular data from the mitochondrial and nuclear genomes in an extensive survey, including two independent transects west and east of the Alps. At both, we found sharp, coincident and concordant nuclear genetic transitions. However, morphological clines were wider or absent and mtDNA introgression was asymmetric. We discuss alternative, nonexclusive hypotheses about evolutionary processes generating these patterns, including drift, selection, long-distance dispersal and spatial shifts in Hybrid Zone location and structure. The distribution of intraspecific mtDNA lineages supports a scenario in which B. bufo held a local refugium during the last glacial maximum. Present-day genetic profiles are best explained by an advance of B. spinosus from a nearby Iberian refugium, largely superseding the local B. bufo population, followed by an advance of B. bufo from the Balkans, with prongs north and south of the Alps, driving B. spinosus southwards. A pendulum moving Hybrid Zone, first northwards and then southwards, explains the wide areas of introgression at either side of the current position of the contact Zones.
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restricted gene flow in a moving Hybrid Zone of the newts triturus cristatus and t marmoratus in western france
Evolution, 1991Co-Authors: J W Arntzen, Graham P WallisAbstract:Two Hybridizing species of newts, Triturus cristatus and T. marmoratus, with overlapping distributions show a parapatric distribution when surveyed in detail. The factors that govern the distribution of cristatus vs. marmoratus in the departement (province) of Mayenne in western France are identified as forestation and relief. The parapatric Hybrid Zone running through Mayenne is narrow but widens to approximately 20 km in an area with mixed habitat. In this area most breeding sites are shared and F1 Hybrids form about 4% of the total population. Analysis of survey data collected about 30 years previously also shows an essentially parapatric distribution. Comparison of past and present distribution maps reveals that cristatus has superseded marmoratus over large areas in the south of Mayenne. An area where marmoratus replaced cristatus also exists, but it is more limited in size. Gene flow between cristatus and marmoratus is analyzed using 10 diagnostic genetic markers [9 protein loci and mitochondrial (mt) DNA]. In syntopic populations nuclear gene flow is bidirectional with a mean frequency of introgressed alleles (f) of 0.3%. In allotopic populations of cristatus and marmoratus gene flow is present in areas of species replacement (f = 0.3%), while gene flow appears to be absent in those areas that have been continuously occupied by a single species. At the biogeographic level, the presence or absence of introgression is paralleled by the persistence or absence, respectively, of pockets of cristatus-marmoratus syntopy. All F1 Hybrids possess the cristatus type mtDNA. This may be due to asymmetric interspecific mate choice and would explain the observed absence of introgression of the maternally inherited mtDNA genome in areas where cristatus replaced marmoratus. The cristatus-marmoratus Hybrid Zone bears characteristics of both the clinal (parapatric) Hybrid Zone model and the mosaic Hybrid Zone model. Such a mixed model-for which we propose the term "reticulate Hybrid Zone"-can be appreciated only if studied over a two-dimensional geographic area and also through time.
Matthew D Carling - One of the best experts on this subject based on the ideXlab platform.
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phenotypic and genetic introgression across a moving woodpecker Hybrid Zone
Molecular Ecology, 2019Co-Authors: Shawn M Billerman, Carla Cicero, Rauri C K Bowie, Matthew D CarlingAbstract:In Hybrid Zones in which two divergent taxa come into secondary contact and interbreed, selection can maintain phenotypic diversity despite widespread genetic introgression. Red-breasted (Sphyrapicus ruber) and red-naped (S. nuchalis) sapsuckers meet and Hybridize along a narrow contact Zone that stretches from northern California to southern British Columbia. We found strong evidence for changes in the structure of this Hybrid Zone across time, with significant temporal shifts in allele frequencies and in the proportions of parental phenotypes across the landscape. In addition to these shifts, we found that differences in plumage predict genetic differences (R2 = 0.80), suggesting that plumage is a useful proxy for assessing ancestry. We also found a significant bimodal distribution of Hybrids across the contact Zone, suggesting that premating barriers may be driving reproductive isolation, perhaps as a result of assortative mating based on plumage differences. However, despite evidence of selection and strong patterns of population structure between parental samples, we found only weak patterns of genetic divergence. Using museum specimens and genomic data, this study of sapsuckers provides insight into the ways in which phenotypic and genetic structure have changed over a 40-year period, as well as insight into the mechanisms that may contribute to the maintenance of the Hybrid Zone over time.
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Origin and cross-century dynamics of an avian Hybrid Zone
BMC evolutionary biology, 2017Co-Authors: Andrea Morales-rozo, Matthew D Carling, Elkin A. Tenorio, Carlos Daniel CadenaAbstract:Characterizations of the dynamics of Hybrid Zones in space and time can give insights about traits and processes important in population divergence and speciation. We characterized a Hybrid Zone between tanagers in the genus Ramphocelus (Aves, Thraupidae) located in southwestern Colombia. We evaluated whether this Hybrid Zone originated as a result of secondary contact or of primary differentiation, and described its dynamics across time using spatial analyses of molecular, morphological, and coloration data in combination with paleodistribution modeling. Models of potential historical distributions based on climatic data and genetic signatures of demographic expansion suggested that the Hybrid Zone likely originated following secondary contact between populations that expanded their ranges out of isolated areas in the Quaternary. Concordant patterns of variation in phenotypic characters across the Hybrid Zone and its narrow extent are suggestive of a tension Zone, maintained by a balance between dispersal and selection against Hybrids. Estimates of phenotypic cline parameters obtained using specimens collected over nearly a century revealed that, in recent decades, the Zone appears to have moved to the east and to higher elevations, and may have become narrower. Genetic variation was not clearly structured along the Hybrid Zone, but comparisons between historical and contemporary specimens suggested that temporal changes in its genetic makeup may also have occurred. Our data suggest that the Hybrid Zone likey resulted from secondary contact between populations. The observed changes in the Hybrid Zone may be a result of sexual selection, asymmetric gene flow, or environmental change.
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Differences in aggressive responses do not contribute to shifts in a sapsucker Hybrid Zone
The Auk, 2017Co-Authors: Shawn M Billerman, Matthew D CarlingAbstract:ABSTRACT Interspecific interactions, such as aggressive territorial behaviors, can be important in establishing range boundaries, especially in Hybrid Zones where 2 divergent taxa meet and interbreed. Further, differences in the aggressive responses among Hybridizing taxa can be important in moving Hybrid Zones, especially when there are strong asymmetries in their aggressive interactions. To determine how between-taxon interactions may be contributing to Hybrid Zone movement between 2 species of sapsucker, we studied an aspect of territory maintenance: aggression toward a territory intruder between species. Using a series of field experiments involving playback and taxidermic mounts, we tested whether Red-naped (Sphyrapicus nuchalis) and Red-breasted (S. ruber) sapsucker differ in their levels of aggressive behavior, thereby influencing the dynamic nature of the Hybrid Zone between these species. We found that 2 of the 3 aggressive response variables we measured differed between the 2 species. Red-naped ...
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Origin and cross-century dynamics of an avian Hybrid Zone
2014Co-Authors: Andrea Morales-rozo, Matthew D Carling, Elkin A. Tenorio, Carlos Daniel CadenaAbstract:Background: Characterizations of the dynamics of Hybrid Zones in space and time can give insights about traits and processes important in population divergence and speciation. We characterized a Hybrid Zone between tanagers in the genus Ramphocelus (Aves, Thraupidae) located in southwestern Colombia. We tested whether this Hybrid Zone originated as a result of secondary contact or of primary differentiation, and described its dynamics across time using spatial analyses of molecular, morphological, and coloration data in combination with paleodistribution modeling. Results: Models of potential historical distributions based on climatic data and genetic signatures of demographic expansion suggested that the Hybrid Zone likely originated following secondary contact between populations that expanded their ranges out of isolated areas in the Quaternary. Concordant patterns of variation in phenotypic characters across the Hybrid Zone and its narrow extent are suggestive of a tension Zone, maintained by a balance between dispersal and selection against Hybrids. Estimates of phenotypic cline parameters obtained using specimens collected over nearly a century revealed that, in recent decades, the Zone appears to have moved to the east and to higher elevations, and has apparently become narrower. Genetic variation was not clearly structured along the Hybrid Zone, but comparisons between historical and contemporary specimens suggested that temporal changes in its genetic makeup may also have occurred. Conclusions: Our data suggest that the Hybrid Zone likey resulted from secondary contact between populations. The observed changes in the Hybrid Zone may be a result of sexual selection, asymmetric gene flow, or environmental change.
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Spatio-temporal changes in the genetic structure of the Passerina bunting Hybrid Zone
Molecular Ecology, 2011Co-Authors: Matthew D Carling, Benjamin ZuckerbergAbstract:Although theoretical models predict that the structure of a Hybrid Zone can change under a variety of scenarios, only a few empirical studies of Hybrid Zones have unequivocally demonstrated Zone movement. These studies are rare because few data sets exist that include repeated, temporally spaced, samples of the same Hybrid Zone. We analysed mitochondrial DNA haplotype data from samples separated by 40-45 years from across the Passerina amoena (Lazuli Bunting) and Passerina cyanea (Indigo Bunting) Hybrid Zone to investigate whether the genetic structure of this Zone has changed during that interval. Both cline and generalized linear mixed modelling analyses uncovered a significant narrowing and a substantial westward shift of the Passerina bunting Hybrid Zone, clearly illustrating Hybrid Zone movement. The cause of the change may be due to a combination of ecological, demographic and behavioural factors. Our results predict that the width of the Hybrid Zone will continue to narrow over time, a finding consistent with reinforcement theory.
