Genomic Displacement and Shift of the Hybrid Zone in the Japanese Fire-Bellied Newt
13
Citation
66
Reference
10
Related Paper
Citation Trend
Abstract:
Hybridizations on a secondary contact zone between 2 diverged lineages can have various evolutionary consequences, including the genetic replacement of one lineage by another. We detected such a case between 2 lineages (the Central and Western lineages) of the Japanese fire-bellied newt, Cynops pyrrhogaster in the Chugoku district of western Japan. We genotyped 269 individuals from 30 localities using the mitochondrial cytochrome b gene and 11 microsatellite loci. The mitochondrial DNA (mtDNA) analysis revealed that the 2 lineages were mostly distributed parapatrically to each other but co-occurred around the contact zone, whereas the microsatellite analyses indicated the presence of a hybrid zone. Geographic cline analysis revealed that the cline width of mtDNA is wider than the width of the microsatellite loci. The migration rate estimation and the NewHybrids analysis revealed that the Central lineage has expanded their range into the range of the hybrid zone, suggesting the possibility of range displacement of the 2 lineages as a consequence of the shift of their hybrid zone. We explored the process of asymmetric gene flow associated with the invasion of the Central lineage to explain this pattern.Keywords:
Cline (biology)
Hybrid zone
Lineage (genetic)
Abstract This study points out the evidence of a hybrid zone between two groups of genetically differentiated populations of chestnut (Castanea sativa Mill.) in Turkey. Genetic structure, gene flow and introgression levels, based on 16 allozyme loci, were investigated on 34 population samples spanning the entire C. sativa distribution area in this country. The occurrence of the hybrid zone, located in the Bithynian region, was inferred in a group of populations showing the following genetic characteristics: (i) enhanced genetic variability and intermediate allelic frequencies between those of the Western and Eastern groups of populations; (ii) sharp and concordant changes in allele frequencies; (iii) decreased gene flow with the Western and Eastern populations. Starting from the cline width estimated to be 324 km, strength of selection was evaluated from the gene flow distance, as indicated from the degree of genetic structuring outside the hybrid zone. Evolutionary processes shaping the observed genetic differentiation and introgression are discussed on the basis of palynological data, palaeoclimatic events and evidence of hybridization found in other plant and animal species in the same region.
Cline (biology)
Introgression
Hybrid zone
Gene pool
Genetic Variability
Population Genetics
Cite
Citations (53)
Abstract 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.
Hybrid zone
Cline (biology)
Contact zone
Divergence (linguistics)
Cite
Citations (0)
The shape and position of clines can provide crucial insights into the evolutionary forces at work in hybrid zones. In this issue, Del-Rio and colleagues applied cline theory to a hybrid zone between two antbird species in Amazonia. A narrow and displaced mitochondrial cline suggests that the selected genetic marker failed to track the northward movement of this hybrid zone, possibly due to reduced fitness of female hybrids.
Cline (biology)
Hybrid zone
Cite
Citations (0)
Abstract Asymmetrical gene flow is an important, but rarely examined genetic parameter. Here, we develop a new method for detecting departures from symmetrical migration between two populations using microsatellite data that are based on the difference in the proportion of private alleles. Application of this approach to data collected from wild-caught Drosophila melanogaster along a latitudinal body-size cline in eastern Australia revealed that asymmetrical gene flow could be detected, but was uncommon, nonlocalized, and occurred in both directions. We also show that, in contrast to the findings of a previous study, there is good evidence to suggest that the cline experiences significant levels of gene flow between populations.
Cline (biology)
Melanogaster
Cite
Citations (64)
This study characterizes a hybrid zone that spans a migratory divide between subspecies of the Swainson's thrush (Catharus ustulatus), a long distance migratory songbird, in the Coast Mountains of British Columbia. To assess the potential for a barrier to gene flow between the subspecies, I: (1) analyzed the shape and width of genetic and morphological clines relative to estimates of dispersal distance, (2) assessed the ratio of parental to hybrid genotypes across the hybrid zone, (3) estimated population density across the hybrid zone, and (4) compared the spatial relationship between the hybrid zone and an existing environmental gradient. The results indicate that the hybrid zone is characterized by mostly concordant character clines that are narrow relative to dispersal, the absence of a hybrid swarm, and low population density at the center of the zone. This hybrid zone and additional regions of contact between these subspecies are found on the border between coastal and interior climatic regions throughout the Pacific Northwest. An identified shift in the location, but not the width, of the mtDNA cline relative to the nuclear clines is consistent with asymmetrical hybridization. Neutral diffusion of populations following secondary contact and hybrid superiority within an ecotone are insufficient explanations for the observed patterns. The hypothesis that best fits the data is that the Swainson's thrush hybrid zone is a tension zone maintained by dispersal and ecologically mediated barriers to gene flow.
Hybrid zone
Cline (biology)
Subspecies
Songbird
Geographical distance
Cite
Citations (118)
Hybrid zone
Cline (biology)
House mouse
Subspecies
Contact zone
Assortative mating
House mice
Reproductive isolation
Cite
Citations (49)
The common shrew (Sorex araneus) is subdivided into several karyotypic races in Britain. Two of these races meet near Oxford o form the "Oxford-Hermitage" hybrid zone. We present a model which describes this system a; a "tension zone," i.e., a set of clines maintained by a balance between dispersal and selection against chromosomal heterozygotes. The Oxford and Hermitage races differ by Robertsonian fusions with monobrachial homology (kq, no versus ko), and so Fl hybrids between them would have low fertility. However, the acrocentric karyotype is found at high frequency within the hybrid zone, so that complex Robertsonian heterozygotes (kg no/q ko n) are replaced by more fertile combinations, such as (kg no/k q n o). This suggests that the hybrid zone has been modified so as to increase hybrid fitness. Mathematical analysis and simulation show that, if selection against complex heterozygotes is sufficiently strong relative to selection against simple heterozygotes, acrocentrics increase, and displace the clines for kg and no from the cline for ko. Superimposed on this separation is a tendency for the hybrid zone to move in favor of the Oxford (kg no) race. We compare the model with estimates of linkage disequilibrium and cline shape made from field data.
Hybrid zone
Sorex
Cline (biology)
Araneus
Shrew
Insectivora
Cite
Citations (64)
Abstract 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.
Hybrid zone
Cline (biology)
Bufo
Introgression
Genetic drift
Cite
Citations (28)
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.
Hybrid zone
Cline (biology)
Contact zone
Divergence (linguistics)
Cite
Citations (25)
The genetic structure of a hybrid zone can provide insights into the relative roles of the various factors that maintain the zone. Here, we use a multilocus approach to characterize a hybrid zone between two subspecies of killifish (Fundulus heteroclitus, Walbaum 1792) found along the Atlantic coast of North America. We first analysed clinal variation along the Atlantic coast using a single-nucleotide polymorphism in the mitochondrial DNA (mtDNA) displacement loop (D-loop) and a panel of nine nuclear microsatellite markers. A model constraining all clines to the same width and centre was not significantly different from a model in which the clines were allowed to vary independently. Locus-by-locus analysis indicated that the majority of nuclear clines shared the same centre as the mtDNA cline, and the widths of these clines were also narrower than that predicted by a neutral model, suggesting that selection is operating to maintain the hybrid zone. However, two of the nuclear clines had widths greater than the neutral prediction and had centres that were displaced relative to the mtDNA cline centre. We also found that a marsh located near the centre of the mtDNA cline demonstrated a bimodal distribution of nuclear hybrid index values, suggesting a deficit of first-generation hybrids and backcrossed genotypes. Thus, selection against hybrid genotypes may be playing a role in maintaining this hybrid zone and the associated steep nuclear and mtDNA clines.
Hybrid zone
Cline (biology)
Subspecies
Introgression
Fundulus
Cite
Citations (14)