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Jan 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: Ben Wielstra, Roger K. Butlin, Isolde Van Riemsdijk, 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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hybrid zone formation and contrasting outcomes of secondary contact over transects in common toads
Molecular Ecology, 2017Co-Authors: Jan W. Arntzen, Inigo Martinezsolano, Daniele Canestrelli, Wouter De VriesAbstract: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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A common toad hybrid zone that runs from the Atlantic to the Mediterranean. Supplementary Material
2017Co-Authors: Jan W. Arntzen, Roland Butot, Jacob Mcatear, 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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morphological and molecular data to describe a hybrid population of the common toad Bufo Bufo and the spined toad Bufo spinosus in western france
Contributions to Zoology, 2017Co-Authors: Tania Trujillo, Jorge Gutierrezrodriguez, Jan W. Arntzen, Inigo MartinezsolanoAbstract:The use of hyper-variable markers across species is often hindered by low cross-species amplification success, a reduced level of polymorphism or a high frequency of null alleles. However, optimizing sets of reliable and informative markers that can be consistently amplified and scored across taxa is key to address questions about patterns of genetic diversity and structure, hybridization and speciation. Here we present 14 newly developed microsatellite markers in the Spined toad (Bufo spinosus), assess their polymorphism in two Iberian populations and test for cross-species amplification in the closely related Common toad (Bufo Bufo). We then use the 12 loci co-amplifying in both species to the study of a morphologically intermediate population (Moyaux) from the contact zone in northwest France as well as reference populations of the two species from both sides of the contact zone. Individuals from Moyaux had mtDNA haplotypes of the two species and were identified as hybrids in analyses with software NewHybrids. These results provide solid evidence for ongoing hybridization between B. Bufo and B. spinosus, with no apparent restrictions to gene flow.
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how complex is the Bufo Bufo species group
Various articles, 2013Co-Authors: Jan W. Arntzen, Daniele Canestrelli, Ernesto Recuero, Inigo MartinezsolanoAbstract:Species delineation remains one of the most challenging tasks in the study of biodiversity, mostly owing to the application of different species concepts, which results in contrasting taxonomic arrangements. This has important practical consequences, since species are basic units in fields like ecology and conservation biology. We here review molecular genetic evidence relevant to the systematics of toads in the Bufo Bufo species group (Anura, Bufonidae). Two studies recently published in this journal (Recuero et al., MPE 62: 71–86 and Garci´a-Porta et al., MPE 63: 113–130) addressed this issue but reached opposing conclusions on the taxonomy of the group (four versus two species). In particular, allozyme data in the latter paper were interpreted as evidence for hybridization across species (between B. Bufo–B. spinosus and B. Bufo–B. verrucosissimus). We tested claims for hybridization through re-analysis of allozyme data for individuals instead of populations, to be able to distinguish between sympatry with and without admixture, and found no evidence of hybridization across taxa. We propose alternative explanations for the observed patterns that Garci´a-Porta et al. (2012) failed to consider. In the absence of unequivocal evidence for hybridization and introgression, we reject the proposal to downgrade Bufo spinosus and Bufo verrucosissimus to the subspecies level.
Inigo Martinezsolano - One of the best experts on this subject based on the ideXlab platform.
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hybrid zone formation and contrasting outcomes of secondary contact over transects in common toads
Molecular Ecology, 2017Co-Authors: Jan W. Arntzen, Inigo Martinezsolano, Daniele Canestrelli, Wouter De VriesAbstract: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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morphological and molecular data to describe a hybrid population of the common toad Bufo Bufo and the spined toad Bufo spinosus in western france
Contributions to Zoology, 2017Co-Authors: Tania Trujillo, Jorge Gutierrezrodriguez, Jan W. Arntzen, Inigo MartinezsolanoAbstract:The use of hyper-variable markers across species is often hindered by low cross-species amplification success, a reduced level of polymorphism or a high frequency of null alleles. However, optimizing sets of reliable and informative markers that can be consistently amplified and scored across taxa is key to address questions about patterns of genetic diversity and structure, hybridization and speciation. Here we present 14 newly developed microsatellite markers in the Spined toad (Bufo spinosus), assess their polymorphism in two Iberian populations and test for cross-species amplification in the closely related Common toad (Bufo Bufo). We then use the 12 loci co-amplifying in both species to the study of a morphologically intermediate population (Moyaux) from the contact zone in northwest France as well as reference populations of the two species from both sides of the contact zone. Individuals from Moyaux had mtDNA haplotypes of the two species and were identified as hybrids in analyses with software NewHybrids. These results provide solid evidence for ongoing hybridization between B. Bufo and B. spinosus, with no apparent restrictions to gene flow.
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how complex is the Bufo Bufo species group
Various articles, 2013Co-Authors: Jan W. Arntzen, Daniele Canestrelli, Ernesto Recuero, Inigo MartinezsolanoAbstract:Species delineation remains one of the most challenging tasks in the study of biodiversity, mostly owing to the application of different species concepts, which results in contrasting taxonomic arrangements. This has important practical consequences, since species are basic units in fields like ecology and conservation biology. We here review molecular genetic evidence relevant to the systematics of toads in the Bufo Bufo species group (Anura, Bufonidae). Two studies recently published in this journal (Recuero et al., MPE 62: 71–86 and Garci´a-Porta et al., MPE 63: 113–130) addressed this issue but reached opposing conclusions on the taxonomy of the group (four versus two species). In particular, allozyme data in the latter paper were interpreted as evidence for hybridization across species (between B. Bufo–B. spinosus and B. Bufo–B. verrucosissimus). We tested claims for hybridization through re-analysis of allozyme data for individuals instead of populations, to be able to distinguish between sympatry with and without admixture, and found no evidence of hybridization across taxa. We propose alternative explanations for the observed patterns that Garci´a-Porta et al. (2012) failed to consider. In the absence of unequivocal evidence for hybridization and introgression, we reject the proposal to downgrade Bufo spinosus and Bufo verrucosissimus to the subspecies level.
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morphological and genetic differentiation of Bufo toads two cryptic species in western europe anura Bufonidae
Contributions to Zoology, 2013Co-Authors: Jan W. Arntzen, Jacob Mcatear, Ernesto Recuero, Janine M Ziermann, A Ohler, J Van Alphen, Inigo MartinezsolanoAbstract:The Common toad Bufo Bufo sensu lato is a widespread, morphologically conserved taxon. Recent studies have uncovered deep genetic differentiation between population groups, highlighting the need to revise the current taxonomy of the group and recognize additional species. Here we investigate patterns of variation in molecular (a mitochondrial DNA restriction enzyme assay and sequence data for two nuclear DNA fragments totalling 979 bp) and 17 morphological variables in Northern France where two of these groups meet (B. Bufo sensu stricto and B. spinosus), in order to delineate their contact zone and uncover characters that would allow discrimination of the two taxa. Mitochondrial DNA data show an abrupt transition from areas where B. Bufo is present to those inhabited by B. spinosus, with a narrow area of overlap east of the city of Caen. Morphometric characters, particularly those related to the positioning of the parotoid glands and metatarsal tubercle shape and size, proved useful in discriminating between species (AUC ≥ 0.97, kappa ≥ 0.79). We then used the differentiating character states to allocate over 300 museum specimens from Western Europe to either species with consistent results, including comparable values of AUC and kappa of the identification models, indicating that models could successfully be applied across datasets. We summarize available evidence relevant to the delineation of the distribution of B. Bufo and B. spinosus in France and discuss the characters differentiating both species in an evolutionary context. In view of the observed morphological and genetic differentiation and the absence of unequivocal evidence for widespread hybridization we support the view that B. Bufo and B. spinosus are best considered different species. Finally, we propose that ‘parotoids in parallel position’ and a thin and smooth skin are derived character states for B. Bufo over the northern part of its range.
Minoru Uchiyama - One of the best experts on this subject based on the ideXlab platform.
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arginine vasotocin promotes urea permeability through urea transporter expressed in the toad urinary bladder cells
General and Comparative Endocrinology, 2007Co-Authors: Norifumi Konno, Susumu Hyodo, Kouhei Matsuda, Minoru UchiyamaAbstract:Abstract We previously isolated a cDNA of a urea transporter ( Bufo UT) from the kidney of the marine toad, Bufo marinus , and demonstrated that the Bufo UT was specifically localized on the epithelial membrane of the early distal tubules in the kidney and urinary bladder. In the present study, the function of Bufo UT was investigated using a Xenopus oocytes expression system. Further, we examined the effects of arginine vasotocin (AVT) on urea transport in isolated cells from the toad urinary bladder. When expressed in Xenopus oocytes Bufo UT induced more than a 10-fold increase in [ 14 C]urea uptake compared with water-injected control oocytes. Phloretin, a urea transport inhibitor, fully blocked the increase of urea uptake. In epithelial cells isolated from the toad urinary bladder, addition of AVT to the medium increased the urea uptake in a concentration-dependent manner (10 −12 –10 −8 M). To examine the relationship between the Bufo UT protein expression and an increase of urea transportability, we analyzed the time course of the Bufo UT expression levels and urea uptake in the cells treated with 10 −8 M AVT. Treatment of 10 −8 M AVT increased the urea uptake in the cells after 24 and 48 h incubation, but not after 12 h. According to the immunoblot analysis, UT protein expression was coincident with the results of urea uptake in the AVT-treated cells. These results suggest that Bufo UT isolated from the kidney, functions as an AVT-mediated urea transporter in the urinary bladder of the toad.
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effect of osmotic stress on expression of a putative facilitative urea transporter in the kidney and urinary bladder of the marine toad Bufo marinus
The Journal of Experimental Biology, 2006Co-Authors: Norifumi Konno, Susumu Hyodo, Kouhei Matsuda, Minoru UchiyamaAbstract:Anuran amphibians accumulate a large amount of urea in their extracellular fluids to avoid a severe dehydration under dry and hyper-saline environments. To clarify the mechanisms of urea retention, we examined structure and distribution of the urea transporter (UT) in the kidney of the marine toad (Bufo marinus), and its expression in the kidney and urinary bladder following exposure to dry and hyper-saline conditions by means of cDNA cloning, semiquantitative RT-PCR, immunoblot analysis and immunohistochemistry. The Bufo UT cDNA cloned from the kidney encodes a 390-amino-acid residue protein, which is 80% identical to Rana esculenta UT with the functional characteristics of a urea transporter. The Bufo UT mRNA was abundantly expressed in the kidney and urinary bladder, but not in the skin. In immunoblot analysis using a specific antibody raised against the Bufo UT, a 52·kDa protein similar to the glycosylated forms of mammalian UT-A2 (~55·kDa) was detected in extracts from plasma membrane fractions of the kidney and urinary bladder. When toads were acclimated to dry and hyper-saline environments for 7·days, UT mRNA expression was upregulated in the kidney and urinary bladder and there was an elevated plasma urea concentration and osmolality. Immunohistochemistry showed that the UT was specifically localized on the apical membrane of the early distal tubule, known to be the diluting segment, in the kidney and the epithelial cells of urinary bladder. Immunoreactive cells were not detected along the late distal tubule, the connecting tubule or the collecting duct in the kidney. The present findings suggest that the Bufo UT probably contributes to urea transport in the kidney and urinary bladder in response to hyperosmotic stresses such as body fluid hypertonicity and dehydration. Summary
Norifumi Konno - One of the best experts on this subject based on the ideXlab platform.
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arginine vasotocin promotes urea permeability through urea transporter expressed in the toad urinary bladder cells
General and Comparative Endocrinology, 2007Co-Authors: Norifumi Konno, Susumu Hyodo, Kouhei Matsuda, Minoru UchiyamaAbstract:Abstract We previously isolated a cDNA of a urea transporter ( Bufo UT) from the kidney of the marine toad, Bufo marinus , and demonstrated that the Bufo UT was specifically localized on the epithelial membrane of the early distal tubules in the kidney and urinary bladder. In the present study, the function of Bufo UT was investigated using a Xenopus oocytes expression system. Further, we examined the effects of arginine vasotocin (AVT) on urea transport in isolated cells from the toad urinary bladder. When expressed in Xenopus oocytes Bufo UT induced more than a 10-fold increase in [ 14 C]urea uptake compared with water-injected control oocytes. Phloretin, a urea transport inhibitor, fully blocked the increase of urea uptake. In epithelial cells isolated from the toad urinary bladder, addition of AVT to the medium increased the urea uptake in a concentration-dependent manner (10 −12 –10 −8 M). To examine the relationship between the Bufo UT protein expression and an increase of urea transportability, we analyzed the time course of the Bufo UT expression levels and urea uptake in the cells treated with 10 −8 M AVT. Treatment of 10 −8 M AVT increased the urea uptake in the cells after 24 and 48 h incubation, but not after 12 h. According to the immunoblot analysis, UT protein expression was coincident with the results of urea uptake in the AVT-treated cells. These results suggest that Bufo UT isolated from the kidney, functions as an AVT-mediated urea transporter in the urinary bladder of the toad.
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effect of osmotic stress on expression of a putative facilitative urea transporter in the kidney and urinary bladder of the marine toad Bufo marinus
The Journal of Experimental Biology, 2006Co-Authors: Norifumi Konno, Susumu Hyodo, Kouhei Matsuda, Minoru UchiyamaAbstract:Anuran amphibians accumulate a large amount of urea in their extracellular fluids to avoid a severe dehydration under dry and hyper-saline environments. To clarify the mechanisms of urea retention, we examined structure and distribution of the urea transporter (UT) in the kidney of the marine toad (Bufo marinus), and its expression in the kidney and urinary bladder following exposure to dry and hyper-saline conditions by means of cDNA cloning, semiquantitative RT-PCR, immunoblot analysis and immunohistochemistry. The Bufo UT cDNA cloned from the kidney encodes a 390-amino-acid residue protein, which is 80% identical to Rana esculenta UT with the functional characteristics of a urea transporter. The Bufo UT mRNA was abundantly expressed in the kidney and urinary bladder, but not in the skin. In immunoblot analysis using a specific antibody raised against the Bufo UT, a 52·kDa protein similar to the glycosylated forms of mammalian UT-A2 (~55·kDa) was detected in extracts from plasma membrane fractions of the kidney and urinary bladder. When toads were acclimated to dry and hyper-saline environments for 7·days, UT mRNA expression was upregulated in the kidney and urinary bladder and there was an elevated plasma urea concentration and osmolality. Immunohistochemistry showed that the UT was specifically localized on the apical membrane of the early distal tubule, known to be the diluting segment, in the kidney and the epithelial cells of urinary bladder. Immunoreactive cells were not detected along the late distal tubule, the connecting tubule or the collecting duct in the kidney. The present findings suggest that the Bufo UT probably contributes to urea transport in the kidney and urinary bladder in response to hyperosmotic stresses such as body fluid hypertonicity and dehydration. Summary
Isolde Van Riemsdijk - 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: Ben Wielstra, Roger K. Butlin, Isolde Van Riemsdijk, 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.
