Hybrid zone formation and contrasting outcomes of secondary contact over transects in common toads

Abstract The study investigates the genetic differentiation among two subspecies of Allium ursinum L., namely A. ursinum subsp. ursinum and subsp. ucrainicum as well as their putative hybrid that is represented by individuals with intermediate morphology. Inter-Simple Sequence Repeats (ISSR) were applied to determine the status of intermediate morphotypes in terms of their genetic pattern and to assess the level of genetic variability within and between various populations of A. ursinum. The study comprises 144 specimens from nine populations along the east-west transect in Poland, which includes localities of both subspecies and their putative hybrid. Among the examined populations, 48 bands were amplified, of which 45 were found to be polymorphic. The principal coordinate analysis (PCoA), the neighbour-net analysis and Mantel test showed a strong correlation between genetic variability and geographic distance. Analysis of molecular variance (AMOVA) revealed that a greater proportion of total genetic variation resided within populations rather than among them. The Structure Bayesian clustering analysis revealed the presence of three distinct genetic groups within studied populations, where ‘eastern’ genotypes correspond to A. ursinum subsp. ucrainicum, and ‘western’ to subsp. ursinum; whereas the third genetic group has the largest share in the individuals occurring at the border of the distribution ranges of both subspecies. The emergence of the third genetic group is probably an effect of hybridization events occurring within the secondary contact zone. Typical morphologically intermediate populations occur only in a relatively narrow geographical zone, but the hybrid zone revealed by molecular markers is actually much wider than it is suggested by the morphological pattern of individuals. The current distribution pattern of both subspecies of A. ursinum and their hybrid zone is related to the two main directions of postglacial migration of Fagus sylvatica to the area of Poland. The hybrid zone arose as an effect of the secondary contact of two divergent lineages of A. ursinum.

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Extensive hybridization between two Andean warbler species with shallow divergence in mtDNA

The Auk ◽

10.1093/ornithology/ukaa065 ◽

2021 ◽

Vol 138 (1) ◽

Cited By ~ 1

Author(s):

Laura N Céspedes-Arias ◽

Andrés M Cuervo ◽

Elisa Bonaccorso ◽

Marialejandra Castro-Farias ◽

Alejandro Mendoza-Santacruz ◽

...

Keyword(s):

Genetic Structure ◽

Contact Zone ◽

Hybrid Zone ◽

Secondary Contact ◽

Tropical Andes ◽

Phenotypic Data ◽

Geographic Ranges ◽

Intermediate Phenotypes ◽

Ecological Barriers

Abstract Studying processes acting on differentiated populations upon secondary contact, such as hybridization, is important to comprehensively understand how species are formed and maintained over time. However, avian speciation studies in the tropical Andes have largely focused on the role of topographic and ecological barriers promoting divergence in allopatry, seldom examining hybridization and introgression. We describe a hybrid zone involving 2 closely related Andean warblers (Parulidae), the Golden-fronted Redstart (Myioborus ornatus), and the Spectacled Redstart (Myioborus melanocephalus). Geographic ranges of these species abut near the Colombia-Ecuador border and many specimens from the region exhibit intermediate phenotypes, but a formal description of phenotypic variation in the contact zone was heretofore lacking. We collected specimens across a transect encompassing the area where ranges abut and areas where only “pure” parental phenotypes of M. ornatus chrysops and M. melanocephalus ruficoronatus occur. We described variation in plumage traits including patterns of head and ventral coloration and tail markings based on 321 specimens. To describe genetic variation in the contact zone and over a broader phylogeographic context, we used sequences of the mitochondrial ND2 gene for 219 individuals across the transect and the entire range of both species, including all subspecies, from Venezuela to Bolivia. We documented a hybrid zone ~200 km wide based on head coloration, where intermediate plumage phenotypes are most common and “pure” forms do not overlap geographically, consistent with extensive hybridization. Across the range of the M. ornatus–M. melanocephalus complex, mitochondrial genetic structure was shallow, with genetic breaks only coinciding clearly with one topographic feature. Such a low genetic structure is striking given the high diversity in plumage phenotypes and the current taxonomy of the group. Our phenotypic data suggest that barriers to hybridization are not strong, and allow us to postulate hypotheses to be tested using forthcoming genomic data.

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Incomplete reproductive isolation may promote hybrid zone formation between Ligularia tongolensis and L. cymbulifera

10.22541/au.159586597.72114750 ◽

2020 ◽

Author(s):

Rui Yang ◽

Li Hu ◽

Guoqian Yang ◽

Guiling Sun ◽

Xun Gong

Keyword(s):

Reproductive Isolation ◽

Hybrid Zone ◽

Zone Formation ◽

Incomplete Reproductive Isolation

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How often do they do it? An in-depth analysis of the hybrid zone of two grass snake species (Natrix astreptophora and Natrix helvetica)

Biological Journal of the Linnean Society ◽

10.1093/biolinnean/blaa152 ◽

2020 ◽

Vol 131 (4) ◽

pp. 756-773

Author(s):

Marika Asztalos ◽

Nadine Schultze ◽

Flora Ihlow ◽

Philippe Geniez ◽

Matthieu Berroneau ◽

...

Keyword(s):

Contact Zone ◽

Hybrid Zone ◽

Climatic Conditions ◽

Secondary Contact ◽

Distribution Models ◽

Long Distance ◽

Depth Analysis ◽

Grass Snake ◽

Genetic Signatures ◽

Cline Width

Abstract We examined the contact zone of two parapatric species of grass snake (Natrix astreptophora and Natrix helvetica) in southern France. To this end, we used comprehensive sampling, analysed mtDNA sequences and microsatellite loci, and built Species Distribution Models for current and past climatic conditions. The contact zone had established by the mid-Holocene during range expansions from glacial refuges in the Iberian Peninsula (N. astreptophora) and southern or western France (N. helvetica). The contact zone represents a narrow bimodal hybrid zone, with steep genetic transition from one taxon to the other and rare hybridization, supporting species status for N. astreptophora and N. helvetica. Our results suggest that the steepness of the clines is a more robust tool for species delimitation than cline width. In addition, we discovered in western France, beyond the hybrid zone, a remote population of N. helvetica with genetic signatures of hybridization with N. astreptophora, most likely the result of human-mediated long-distance dispersal. For N. helvetica, we identified a southern and a northern population cluster, connected by broad-scale gene flow in a unimodal hybrid zone running across France. This pattern either reflects genetic divergence caused by allopatry in two microrefuges and subsequent secondary contact or introgression of foreign alleles into the southern cluster.

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Secondary contact between Lycaeides idas and L. melissa in the Rocky Mountains: extensive admixture and a patchy hybrid zone

Molecular Ecology ◽

10.1111/j.1365-294x.2010.04727.x ◽

2010 ◽

Vol 19 (15) ◽

pp. 3171-3192 ◽

Cited By ~ 72

Author(s):

Zachariah Gompert ◽

Lauren K. Lucas ◽

James A. Fordyce ◽

Matthew L. Forister ◽

Chris C. Nice

Keyword(s):

Hybrid Zone ◽

Rocky Mountains ◽

Secondary Contact

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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 ◽

10.1098/rspb.2013.2733 ◽

2014 ◽

Vol 281 (1776) ◽

pp. 20132733 ◽

Cited By ~ 21

Author(s):

Yasmin Latour ◽

Marco Perriat-Sanguinet ◽

Pierre Caminade ◽

Pierre Boursot ◽

Carole M. Smadja ◽

...

Keyword(s):

Sexual Selection ◽

Gene Flow ◽

Hybrid Zone ◽

Mus Musculus ◽

Character Displacement ◽

Secondary Contact ◽

Lower Hybrid ◽

Mus Musculus Domesticus ◽

Hybrid Fitness ◽

Signal Perception

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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Ancestral chloroplast polymorphism and historical secondary contact in a broad hybrid zone of Aesculus (Sapindaceae)

American Journal of Botany ◽

10.3732/ajb.93.3.377 ◽

2006 ◽

Vol 93 (3) ◽

pp. 377-388 ◽

Cited By ~ 8

Author(s):

J. L Modliszewski ◽

D. T Thomas ◽

C. Fan ◽

D. J Crawford ◽

C. W dePamphilis ◽

...

Keyword(s):

Hybrid Zone ◽

Secondary Contact

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Asymmetric Reproductive Barriers and Gene Flow Promote the Rise of a Stable Hybrid Zone in the Mediterranean High Mountain

Frontiers in Plant Science ◽

10.3389/fpls.2021.687094 ◽

2021 ◽

Vol 12 ◽

Author(s):

Mohamed Abdelaziz ◽

A. Jesús Muñoz-Pajares ◽

Modesto Berbel ◽

Ana García-Muñoz ◽

José M. Gómez ◽

...

Keyword(s):

Gene Flow ◽

Reproductive Isolation ◽

Sierra Nevada ◽

Hybrid Zone ◽

High Elevation ◽

Secondary Contact ◽

High Mountain ◽

Hybrid Zones ◽

Reproductive Barriers ◽

Sierra Nevada Mountains

Hybrid zones have the potential to shed light on evolutionary processes driving adaptation and speciation. Secondary contact hybrid zones are particularly powerful natural systems for studying the interaction between divergent genomes to understand the mode and rate at which reproductive isolation accumulates during speciation. We have studied a total of 720 plants belonging to five populations from two Erysimum (Brassicaceae) species presenting a contact zone in the Sierra Nevada mountains (SE Spain). The plants were phenotyped in 2007 and 2017, and most of them were genotyped the first year using 10 microsatellite markers. Plants coming from natural populations were grown in a common garden to evaluate the reproductive barriers between both species by means of controlled crosses. All the plants used for the field and greenhouse study were characterized by measuring traits related to plant size and flower size. We estimated the genetic molecular variances, the genetic differentiation, and the genetic structure by means of the F-statistic and Bayesian inference. We also estimated the amount of recent gene flow between populations. We found a narrow unimodal hybrid zone where the hybrid genotypes appear to have been maintained by significant levels of a unidirectional gene flow coming from parental populations and from weak reproductive isolation between them. Hybrid plants exhibited intermediate or vigorous phenotypes depending on the analyzed trait. The phenotypic differences between the hybrid and the parental plants were highly coherent between the field and controlled cross experiments and through time. The highly coherent results obtained by combining field, experimental, and genetic data demonstrate the existence of a stable and narrow unimodal hybrid zone between Erysimum mediohispanicum and Erysimum nevadense at the high elevation of the Sierra Nevada mountains.

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Spatial variation in introgression along a toad hybrid zone in France

10.1101/746073 ◽

2019 ◽

Author(s):

I. van Riemsdijk ◽

J.W. Arntzen ◽

G. Bucciarelli ◽

E. McCartney-Melstad ◽

M. Rafajlović ◽

...

Keyword(s):

Gene Flow ◽

Reproductive Isolation ◽

Hybrid Zone ◽

Restriction Site ◽

Bufo Bufo ◽

Secondary Contact ◽

Barrier Effect ◽

Sequencing Data ◽

Asymmetric Introgression ◽

Stable Hybrid

AbstractThe barrier effect is a restriction of gene flow between diverged populations by barrier genes. Restriction of gene flow and asymmetric introgression over multiple transects indicates species wide (genetic) adaptations, whereas transect-specific barrier loci may indicate local adaptation to gene flow. Asymmetric introgression can be caused by selection, hybrid zone movement, asymmetric reproductive isolation, or a combination of these. We study two widely separated transects (northwest and southeast France) for the 900 km long hybrid zone between Bufo bufo and B. spinosus toads, using ~1200 markers from restriction-site associated DNA (RAD) sequencing data. Genomic and geographic clines were used to identify outlier markers which show restricted or elevated introgression. Twenty-six barrier markers are shared between transects (the union of 56 and 123 barrier markers identified in each transect), which is more than would be expected by chance. However, the number of barrier markers is twice as high in the southeast transect. In the northwest transect a high amount of (asymmetric) introgression from B. spinosus into B. bufo is consistent with hybrid zone movement or asymmetric reproductive isolation. In the southeast transect, introgression is symmetric and consistent with a stable hybrid zone. Differences between transects may be related to genetic sub-structure within B. bufo. A longer period of secondary contact in southeast France appears to result in a relatively stronger barrier effect than in the northwest. The Bufo hybrid zone provides an excellent opportunity to separate a general barrier to gene flow from local reductions in gene flow.

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Origin and cross-century dynamics of an avian hybrid zone

10.1101/012856 ◽

2014 ◽

Author(s):

Andrea Morales-Rozo ◽

Elkin A. Tenorio ◽

Matthew D. Carling ◽

Carlos Daniel Cadena

Keyword(s):

Hybrid Zone ◽

Secondary Contact ◽

Population Divergence ◽

Climatic Data ◽

Hybrid Zones ◽

Spatial Analyses ◽

Demographic Expansion ◽

Phenotypic Characters ◽

Genetic Signatures ◽

Phenotypic Cline

AbstractBackgroundCharacterizations 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.ResultsModels 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.ConclusionsOur 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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