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J. Ebersbach - One of the best experts on this subject based on the ideXlab platform.
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The Role of Hybridisation in the Making of the Species-Rich Arctic-Alpine Genus Saxifraga (Saxifragaceae)
Diversity, 2020Co-Authors: J. Ebersbach, Natalia Tkach, Martin Röser, Adrien FavreAbstract:Evolutionary processes fuelling rapid species diversification are not yet fully understood, although their major contribution to overall patterns of plant biodiversity is well established. Hybridisation is among the least understood of these processes, despite its multifaceted role in speciation processes being widely accepted. Species of the large arctic-alpine genus Saxifraga are notorious for their ability to hybridise; however, the overall role of hybridisation and polyploidisation for the diversification of this genus remains unknown. Here, we provide a comprehensive genus-wide review of hybridisation accounts and ploidy levels. We find that the sections of Saxifraga vary greatly in their propensity to hybridise. The majority of natural hybridisation accounts are from recent localised events (n = 71). Hybridisation hotspots were located in the Pyrenees and the European Alps, thus contrasting with the overall distribution of species richness in the genus. Hybrids or hybrid populations are often short-lived in Saxifraga due to a multitude of reproductive barriers, most commonly low F1 hybrid fertility. However, these barriers are not always fully effective, allowing for backcrossing and the formation of hybrid swarms. In addition, we find that the incidence of polyploidy varies widely across different sections of Saxifraga, with species-rich sections Porphyrion and Saxifraga showing divergent polyploidy proportions. Overall, we show that hybridisation and polyploidisation played differential roles in the diversification of this large genus. Nevertheless, a significant proportion of species are yet to be scrutinised, particularly among the Asian Saxifraga species, illustrating the need for systematic further study to fully unravel the role of hybridisation during the evolution of Saxifraga.
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Evolutionary radiations in the species-rich mountain genus Saxifraga L.
BMC Evolutionary Biology, 2017Co-Authors: J. Ebersbach, Adrien Favre, J. Schnitzler, Alexandra N. Muellner-riehlAbstract:A large number of taxa have undergone evolutionary radiations in mountainous areas, rendering alpine systems particularly suitable to study the extrinsic and intrinsic factors that have shaped diversification patterns in plants. The species-rich genus Saxifraga L. is widely distributed throughout the Northern Hemisphere, with high species numbers in the regions adjacent to the Qinghai-Tibet Plateau (QTP) in particular the Hengduan Mountains and the Himalayas. Using a dataset of 297 taxa (representing at least 60% of extant Saxifraga species), we explored the variation of infrageneric diversification rates. In addition, we used state-dependent speciation and extinction models to test the effects of geographic distribution in the Hengduan Mountains and the entire QTP region as well as of two morphological traits (cushion habit and specialized lime-secreting glands, so-called hydathodes) on the diversification of this genus. We detected two to three rate shifts across the Saxifraga phylogeny and two of these shifts led to radiations within two large subclades of Saxifraga, sect. Ciliatae Haworth subsect. Hirculoideae Engl. & Irmsch. and sect. Porphyrion Tausch subsect. Kabschia Engl. GEOSSE analyses showed that presence in the Hengduan Mountains had a positive effect on diversification across Saxifraga. Influence of these mountains was strongest in Saxifraga sect. Ciliatae subsect. Hirculoideae given its pronounced distribution there, and thus the radiation in this group can be classified at least partially as geographic. In contrast, the evolution of the cushion life form and lime-secreting hydathodes had positive effects on diversification only in selected Saxifraga sections, including sect. Porphyrion subsect. Kabschia. We therefore argue that radiation in this group was likely adaptive. Our study underlines the complexity of processes and factors underpinning plant radiations: Even in closely related lineages occupying the same life zone, shifts in diversification are not necessarily governed by similar factors. In conclusion, alpine plant radiations result from a complex interaction among geographical settings and/or climatic modifications providing key opportunities for diversification as well as the evolution of key innovations.
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Additional file 5: of Evolutionary radiations in the species-rich mountain genus Saxifraga L.
2017Co-Authors: J. Ebersbach, J. Schnitzler, A. Favre, A.n. Muellner-riehlAbstract:1. Best scoring GEOSSE models for state-dependent diversification of Saxifraga in QTP region. 2. Parameter estimates for best scoring GEOSSE model for state-dependent diversification of Saxifraga in QTP region (DOCX 35Â kb
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Evolutionary radiations in the species-rich mountain genus Saxifraga L.
BMC, 2017Co-Authors: J. Ebersbach, J. Schnitzler, A. Favre, A.n. Muellner-riehlAbstract:Abstract Background A large number of taxa have undergone evolutionary radiations in mountainous areas, rendering alpine systems particularly suitable to study the extrinsic and intrinsic factors that have shaped diversification patterns in plants. The species-rich genus Saxifraga L. is widely distributed throughout the Northern Hemisphere, with high species numbers in the regions adjacent to the Qinghai-Tibet Plateau (QTP) in particular the Hengduan Mountains and the Himalayas. Using a dataset of 297 taxa (representing at least 60% of extant Saxifraga species), we explored the variation of infrageneric diversification rates. In addition, we used state-dependent speciation and extinction models to test the effects of geographic distribution in the Hengduan Mountains and the entire QTP region as well as of two morphological traits (cushion habit and specialized lime-secreting glands, so-called hydathodes) on the diversification of this genus. Results We detected two to three rate shifts across the Saxifraga phylogeny and two of these shifts led to radiations within two large subclades of Saxifraga, sect. Ciliatae Haworth subsect. Hirculoideae Engl. & Irmsch. and sect. Porphyrion Tausch subsect. Kabschia Engl. GEOSSE analyses showed that presence in the Hengduan Mountains had a positive effect on diversification across Saxifraga. Influence of these mountains was strongest in Saxifraga sect. Ciliatae subsect. Hirculoideae given its pronounced distribution there, and thus the radiation in this group can be classified at least partially as geographic. In contrast, the evolution of the cushion life form and lime-secreting hydathodes had positive effects on diversification only in selected Saxifraga sections, including sect. Porphyrion subsect. Kabschia. We therefore argue that radiation in this group was likely adaptive. Conclusions Our study underlines the complexity of processes and factors underpinning plant radiations: Even in closely related lineages occupying the same life zone, shifts in diversification are not necessarily governed by similar factors. In conclusion, alpine plant radiations result from a complex interaction among geographical settings and/or climatic modifications providing key opportunities for diversification as well as the evolution of key innovations
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Additional file 4: of Evolutionary radiations in the species-rich mountain genus Saxifraga L.
2017Co-Authors: J. Ebersbach, J. Schnitzler, A. Favre, A.n. Muellner-riehlAbstract:Results for model fitting of simulated traits in Saxifraga (PDF 416Â kb
Adrien Favre - One of the best experts on this subject based on the ideXlab platform.
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The Role of Hybridisation in the Making of the Species-Rich Arctic-Alpine Genus Saxifraga (Saxifragaceae)
Diversity, 2020Co-Authors: J. Ebersbach, Natalia Tkach, Martin Röser, Adrien FavreAbstract:Evolutionary processes fuelling rapid species diversification are not yet fully understood, although their major contribution to overall patterns of plant biodiversity is well established. Hybridisation is among the least understood of these processes, despite its multifaceted role in speciation processes being widely accepted. Species of the large arctic-alpine genus Saxifraga are notorious for their ability to hybridise; however, the overall role of hybridisation and polyploidisation for the diversification of this genus remains unknown. Here, we provide a comprehensive genus-wide review of hybridisation accounts and ploidy levels. We find that the sections of Saxifraga vary greatly in their propensity to hybridise. The majority of natural hybridisation accounts are from recent localised events (n = 71). Hybridisation hotspots were located in the Pyrenees and the European Alps, thus contrasting with the overall distribution of species richness in the genus. Hybrids or hybrid populations are often short-lived in Saxifraga due to a multitude of reproductive barriers, most commonly low F1 hybrid fertility. However, these barriers are not always fully effective, allowing for backcrossing and the formation of hybrid swarms. In addition, we find that the incidence of polyploidy varies widely across different sections of Saxifraga, with species-rich sections Porphyrion and Saxifraga showing divergent polyploidy proportions. Overall, we show that hybridisation and polyploidisation played differential roles in the diversification of this large genus. Nevertheless, a significant proportion of species are yet to be scrutinised, particularly among the Asian Saxifraga species, illustrating the need for systematic further study to fully unravel the role of hybridisation during the evolution of Saxifraga.
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Saxifraga scardica (Saxifragaceae) – a new record for the Bulgarian flora
Phytologia Balcanica: International Journal of Balkan Flora and Vegetation, 2019Co-Authors: Zheko Naychov, Natalia Tkach, Adrien Favre, Ekaterina KozuharovaAbstract:Saxifraga scardica is an endemic plant occurring in the mountains of the Balkan Peninsula, between Montenegro and Southern Continental Greece. Morphologically, it is most similar to S. marginata, one of the 23 reported Bulgarian Saxifraga species. In Bulgaria, S. marginata is reported as growing on limestone, in the Forebalkan (Western) and Balkan Range (Central) floristic regions. Saxifraga scardica is reported for the first time for the Bulgarian flora. It was found in the Zemen Gorge of River Struma, in the Znepole floristic region. This location is the easternmost part of its distribution range. Under IUCN criteria, the species is classified as ‘Endangered’.
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Evolutionary radiations in the species-rich mountain genus Saxifraga L.
BMC Evolutionary Biology, 2017Co-Authors: J. Ebersbach, Adrien Favre, J. Schnitzler, Alexandra N. Muellner-riehlAbstract:A large number of taxa have undergone evolutionary radiations in mountainous areas, rendering alpine systems particularly suitable to study the extrinsic and intrinsic factors that have shaped diversification patterns in plants. The species-rich genus Saxifraga L. is widely distributed throughout the Northern Hemisphere, with high species numbers in the regions adjacent to the Qinghai-Tibet Plateau (QTP) in particular the Hengduan Mountains and the Himalayas. Using a dataset of 297 taxa (representing at least 60% of extant Saxifraga species), we explored the variation of infrageneric diversification rates. In addition, we used state-dependent speciation and extinction models to test the effects of geographic distribution in the Hengduan Mountains and the entire QTP region as well as of two morphological traits (cushion habit and specialized lime-secreting glands, so-called hydathodes) on the diversification of this genus. We detected two to three rate shifts across the Saxifraga phylogeny and two of these shifts led to radiations within two large subclades of Saxifraga, sect. Ciliatae Haworth subsect. Hirculoideae Engl. & Irmsch. and sect. Porphyrion Tausch subsect. Kabschia Engl. GEOSSE analyses showed that presence in the Hengduan Mountains had a positive effect on diversification across Saxifraga. Influence of these mountains was strongest in Saxifraga sect. Ciliatae subsect. Hirculoideae given its pronounced distribution there, and thus the radiation in this group can be classified at least partially as geographic. In contrast, the evolution of the cushion life form and lime-secreting hydathodes had positive effects on diversification only in selected Saxifraga sections, including sect. Porphyrion subsect. Kabschia. We therefore argue that radiation in this group was likely adaptive. Our study underlines the complexity of processes and factors underpinning plant radiations: Even in closely related lineages occupying the same life zone, shifts in diversification are not necessarily governed by similar factors. In conclusion, alpine plant radiations result from a complex interaction among geographical settings and/or climatic modifications providing key opportunities for diversification as well as the evolution of key innovations.
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In and out of the Qinghai-Tibet Plateau: divergence time estimation and historical biogeography of the large arctic-alpine genus Saxifraga L.
Journal of Biogeography, 2016Co-Authors: J. Ebersbach, Natalia Tkach, Martin Röser, Alexandra N. Muellner-riehl, Ingo Michalak, Matthias H. Hoffmann, Hang Sun, Adrien FavreAbstract:Aim Geologically dynamic areas often harbour remarkable levels of biodiversity. Among other factors, mountain building is assumed to be a precondition for species radiation, and yet, the potential role of immigration as a source of biodiversity prior to radiation is often neglected. Here, we studied the biogeographical history of the large genus Saxifraga to unravel the role played by the Qinghai-Tibet Plateau (QTP) for the diversification of this genus and to understand factors that have led to the establishment of high biodiversity in and around this region. Location QTP and surrounding mountain ranges and worldwide distribution range of Saxifraga. Methods Using a total of 420 taxa (321 ingroup taxa) comprising more than 60% of extant Saxifraga species, we studied the evolutionary history of Saxifraga by performing phylogenetic analyses (maximum likelihood and Bayesian inference on nuclear ITS and plastid trnL–trnF, matK sequences), divergence time estimation (using uncorrelated log-normal clock models and four fossil constraints in beast) and ancestral range estimation (using BioGeoBEARS). Results Saxifraga originated in North America around 74 (64–83) Ma, dispersed to South America and northern Asia during its early diversification and colonized Europe and the QTP region by the Late Eocene. The QTP region was colonized several times independently, followed in some lineages by rapid radiations, temporally coinciding with recent uplifts of the Hengduan Mountains at the southeastern fringe of the QTP. Subsequently, several lineages dispersed out of Tibet. Main conclusions Immigration, recent rapid radiation and lineage persistence were all important processes for the establishment of a rich species stock of Saxifraga in the QTP region. Because floristic exchanges between the neighbouring areas and the QTP region were bi-directional, the spatio-temporal evolution of Saxifraga contrasts with the ‘out of QTP’ pattern, which has often been assumed for northern temperate plants.
Natalia Tkach - One of the best experts on this subject based on the ideXlab platform.
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The Role of Hybridisation in the Making of the Species-Rich Arctic-Alpine Genus Saxifraga (Saxifragaceae)
Diversity, 2020Co-Authors: J. Ebersbach, Natalia Tkach, Martin Röser, Adrien FavreAbstract:Evolutionary processes fuelling rapid species diversification are not yet fully understood, although their major contribution to overall patterns of plant biodiversity is well established. Hybridisation is among the least understood of these processes, despite its multifaceted role in speciation processes being widely accepted. Species of the large arctic-alpine genus Saxifraga are notorious for their ability to hybridise; however, the overall role of hybridisation and polyploidisation for the diversification of this genus remains unknown. Here, we provide a comprehensive genus-wide review of hybridisation accounts and ploidy levels. We find that the sections of Saxifraga vary greatly in their propensity to hybridise. The majority of natural hybridisation accounts are from recent localised events (n = 71). Hybridisation hotspots were located in the Pyrenees and the European Alps, thus contrasting with the overall distribution of species richness in the genus. Hybrids or hybrid populations are often short-lived in Saxifraga due to a multitude of reproductive barriers, most commonly low F1 hybrid fertility. However, these barriers are not always fully effective, allowing for backcrossing and the formation of hybrid swarms. In addition, we find that the incidence of polyploidy varies widely across different sections of Saxifraga, with species-rich sections Porphyrion and Saxifraga showing divergent polyploidy proportions. Overall, we show that hybridisation and polyploidisation played differential roles in the diversification of this large genus. Nevertheless, a significant proportion of species are yet to be scrutinised, particularly among the Asian Saxifraga species, illustrating the need for systematic further study to fully unravel the role of hybridisation during the evolution of Saxifraga.
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Saxifraga scardica (Saxifragaceae) – a new record for the Bulgarian flora
Phytologia Balcanica: International Journal of Balkan Flora and Vegetation, 2019Co-Authors: Zheko Naychov, Natalia Tkach, Adrien Favre, Ekaterina KozuharovaAbstract:Saxifraga scardica is an endemic plant occurring in the mountains of the Balkan Peninsula, between Montenegro and Southern Continental Greece. Morphologically, it is most similar to S. marginata, one of the 23 reported Bulgarian Saxifraga species. In Bulgaria, S. marginata is reported as growing on limestone, in the Forebalkan (Western) and Balkan Range (Central) floristic regions. Saxifraga scardica is reported for the first time for the Bulgarian flora. It was found in the Zemen Gorge of River Struma, in the Znepole floristic region. This location is the easternmost part of its distribution range. Under IUCN criteria, the species is classified as ‘Endangered’.
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Additional file 4: of Contrasting evolutionary origins of two mountain endemics: Saxifraga wahlenbergii (Western Carpathians) and S. styriaca (Eastern Alps)
2019Co-Authors: Natalia Tkach, Martin Röser, Tomasz Suchan, Elżbieta Cieślak, Peter Schönswetter, Michał RonikierAbstract:Figure S2. Maximum likelihood phylogram of Saxifraga (arrow) and representative genera of Saxifragaceae based on plastid trnL–trnF and rpl32–trnL Sanger sequence data. Pterostemon rotundifolius and Itea virginica (Iteaceae) were chosen as outgroups. Maximum likelihood and maximum parsimony bootstrap support values as well posterior probabilities of Bayesian inference ≥50% are indicated on the branches. The sections of Saxifraga are labelled on the right-hand side. (PDF 793 kb
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Additional file 3: of Contrasting evolutionary origins of two mountain endemics: Saxifraga wahlenbergii (Western Carpathians) and S. styriaca (Eastern Alps)
2019Co-Authors: Natalia Tkach, Martin Röser, Tomasz Suchan, Elżbieta Cieślak, Peter Schönswetter, Michał RonikierAbstract:Figure S1. Maximum likelihood phylogram of Saxifraga (arrow) and representative genera of Saxifragaceae based on nuclear ribosomal ITS DNA Sanger sequence data. Pterostemon rotundifolius and Itea virginica (Iteaceae) were chosen as outgroups. Maximum likelihood and maximum parsimony bootstrap support values as well as posterior probabilities of Bayesian inference ≥50% are indicated on the branches. The sections of Saxifraga are labelled on the right-hand side. (PDF 2680 kb
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In and out of the Qinghai-Tibet Plateau: divergence time estimation and historical biogeography of the large arctic-alpine genus Saxifraga L.
Journal of Biogeography, 2016Co-Authors: J. Ebersbach, Natalia Tkach, Martin Röser, Alexandra N. Muellner-riehl, Ingo Michalak, Matthias H. Hoffmann, Hang Sun, Adrien FavreAbstract:Aim Geologically dynamic areas often harbour remarkable levels of biodiversity. Among other factors, mountain building is assumed to be a precondition for species radiation, and yet, the potential role of immigration as a source of biodiversity prior to radiation is often neglected. Here, we studied the biogeographical history of the large genus Saxifraga to unravel the role played by the Qinghai-Tibet Plateau (QTP) for the diversification of this genus and to understand factors that have led to the establishment of high biodiversity in and around this region. Location QTP and surrounding mountain ranges and worldwide distribution range of Saxifraga. Methods Using a total of 420 taxa (321 ingroup taxa) comprising more than 60% of extant Saxifraga species, we studied the evolutionary history of Saxifraga by performing phylogenetic analyses (maximum likelihood and Bayesian inference on nuclear ITS and plastid trnL–trnF, matK sequences), divergence time estimation (using uncorrelated log-normal clock models and four fossil constraints in beast) and ancestral range estimation (using BioGeoBEARS). Results Saxifraga originated in North America around 74 (64–83) Ma, dispersed to South America and northern Asia during its early diversification and colonized Europe and the QTP region by the Late Eocene. The QTP region was colonized several times independently, followed in some lineages by rapid radiations, temporally coinciding with recent uplifts of the Hengduan Mountains at the southeastern fringe of the QTP. Subsequently, several lineages dispersed out of Tibet. Main conclusions Immigration, recent rapid radiation and lineage persistence were all important processes for the establishment of a rich species stock of Saxifraga in the QTP region. Because floristic exchanges between the neighbouring areas and the QTP region were bi-directional, the spatio-temporal evolution of Saxifraga contrasts with the ‘out of QTP’ pattern, which has often been assumed for northern temperate plants.
Peter Schönswetter - One of the best experts on this subject based on the ideXlab platform.
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Additional file 4: of Contrasting evolutionary origins of two mountain endemics: Saxifraga wahlenbergii (Western Carpathians) and S. styriaca (Eastern Alps)
2019Co-Authors: Natalia Tkach, Martin Röser, Tomasz Suchan, Elżbieta Cieślak, Peter Schönswetter, Michał RonikierAbstract:Figure S2. Maximum likelihood phylogram of Saxifraga (arrow) and representative genera of Saxifragaceae based on plastid trnL–trnF and rpl32–trnL Sanger sequence data. Pterostemon rotundifolius and Itea virginica (Iteaceae) were chosen as outgroups. Maximum likelihood and maximum parsimony bootstrap support values as well posterior probabilities of Bayesian inference ≥50% are indicated on the branches. The sections of Saxifraga are labelled on the right-hand side. (PDF 793 kb
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Additional file 3: of Contrasting evolutionary origins of two mountain endemics: Saxifraga wahlenbergii (Western Carpathians) and S. styriaca (Eastern Alps)
2019Co-Authors: Natalia Tkach, Martin Röser, Tomasz Suchan, Elżbieta Cieślak, Peter Schönswetter, Michał RonikierAbstract:Figure S1. Maximum likelihood phylogram of Saxifraga (arrow) and representative genera of Saxifragaceae based on nuclear ribosomal ITS DNA Sanger sequence data. Pterostemon rotundifolius and Itea virginica (Iteaceae) were chosen as outgroups. Maximum likelihood and maximum parsimony bootstrap support values as well as posterior probabilities of Bayesian inference ≥50% are indicated on the branches. The sections of Saxifraga are labelled on the right-hand side. (PDF 2680 kb
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tales of the unexpected phylogeography of the arctic alpine model plant Saxifraga oppositifolia Saxifragaceae revisited
Molecular Ecology, 2012Co-Authors: Manuela Winkler, Rolf Holderegger, R Abbott, Felix Gugerli, Andreas Tribsch, Gerald M Schneeweiss, Sabine Brodbeck, Peter SchönswetterAbstract:Arctic-alpine biota occupy enormous areas in the Arctic and the northern hemisphere mountain ranges and have undergone major range shifts during their comparatively short history. The origins of individual arctic-alpine species remain largely unknown. In the case of the Purple saxifrage, Saxifraga oppositifolia, an important model for arcticalpine plants, phylogeographic studies have remained inconclusive about early stages of the species’ spatiotemporal diversification but have provided evidence for long-range colonization out of a presumed Beringian origin to cover today’s circumpolar range. We re-evaluated the species’ large-scale range dynamics based on a geographically extended sampling including crucial areas such as Central Asia and the (south-)eastern European mountain ranges and employing up-to-date phylogeographic analyses of a plastid sequence data set and a more restricted AFLP data set. In accordance with previous studies, we detected two major plastid DNA lineages also reflected in AFLP divergence, suggesting a long and independent vicariant history. Although we were unable to determine the species’ area of origin, our results point to Europe (probably the Alps) and Central Asia, respectively, as the likely ancestral areas of the two main lineages. AFLP data suggested that contact areas between the two clades in the Carpathians, Northern Siberia and western Greenland were secondary. In marked contrast to high levels of diversity revealed in previous studies, populations from the major arctic refugium Beringia did not exhibit any plastid sequence polymorphism. Our study shows that adequate sampling of the southern, refugial populations is crucial for understanding the range dynamics of arctic-alpine species.
Alexandra N. Muellner-riehl - One of the best experts on this subject based on the ideXlab platform.
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Evolutionary radiations in the species-rich mountain genus Saxifraga L.
BMC Evolutionary Biology, 2017Co-Authors: J. Ebersbach, Adrien Favre, J. Schnitzler, Alexandra N. Muellner-riehlAbstract:A large number of taxa have undergone evolutionary radiations in mountainous areas, rendering alpine systems particularly suitable to study the extrinsic and intrinsic factors that have shaped diversification patterns in plants. The species-rich genus Saxifraga L. is widely distributed throughout the Northern Hemisphere, with high species numbers in the regions adjacent to the Qinghai-Tibet Plateau (QTP) in particular the Hengduan Mountains and the Himalayas. Using a dataset of 297 taxa (representing at least 60% of extant Saxifraga species), we explored the variation of infrageneric diversification rates. In addition, we used state-dependent speciation and extinction models to test the effects of geographic distribution in the Hengduan Mountains and the entire QTP region as well as of two morphological traits (cushion habit and specialized lime-secreting glands, so-called hydathodes) on the diversification of this genus. We detected two to three rate shifts across the Saxifraga phylogeny and two of these shifts led to radiations within two large subclades of Saxifraga, sect. Ciliatae Haworth subsect. Hirculoideae Engl. & Irmsch. and sect. Porphyrion Tausch subsect. Kabschia Engl. GEOSSE analyses showed that presence in the Hengduan Mountains had a positive effect on diversification across Saxifraga. Influence of these mountains was strongest in Saxifraga sect. Ciliatae subsect. Hirculoideae given its pronounced distribution there, and thus the radiation in this group can be classified at least partially as geographic. In contrast, the evolution of the cushion life form and lime-secreting hydathodes had positive effects on diversification only in selected Saxifraga sections, including sect. Porphyrion subsect. Kabschia. We therefore argue that radiation in this group was likely adaptive. Our study underlines the complexity of processes and factors underpinning plant radiations: Even in closely related lineages occupying the same life zone, shifts in diversification are not necessarily governed by similar factors. In conclusion, alpine plant radiations result from a complex interaction among geographical settings and/or climatic modifications providing key opportunities for diversification as well as the evolution of key innovations.
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In and out of the Qinghai-Tibet Plateau: divergence time estimation and historical biogeography of the large arctic-alpine genus Saxifraga L.
Journal of Biogeography, 2016Co-Authors: J. Ebersbach, Natalia Tkach, Martin Röser, Alexandra N. Muellner-riehl, Ingo Michalak, Matthias H. Hoffmann, Hang Sun, Adrien FavreAbstract:Aim Geologically dynamic areas often harbour remarkable levels of biodiversity. Among other factors, mountain building is assumed to be a precondition for species radiation, and yet, the potential role of immigration as a source of biodiversity prior to radiation is often neglected. Here, we studied the biogeographical history of the large genus Saxifraga to unravel the role played by the Qinghai-Tibet Plateau (QTP) for the diversification of this genus and to understand factors that have led to the establishment of high biodiversity in and around this region. Location QTP and surrounding mountain ranges and worldwide distribution range of Saxifraga. Methods Using a total of 420 taxa (321 ingroup taxa) comprising more than 60% of extant Saxifraga species, we studied the evolutionary history of Saxifraga by performing phylogenetic analyses (maximum likelihood and Bayesian inference on nuclear ITS and plastid trnL–trnF, matK sequences), divergence time estimation (using uncorrelated log-normal clock models and four fossil constraints in beast) and ancestral range estimation (using BioGeoBEARS). Results Saxifraga originated in North America around 74 (64–83) Ma, dispersed to South America and northern Asia during its early diversification and colonized Europe and the QTP region by the Late Eocene. The QTP region was colonized several times independently, followed in some lineages by rapid radiations, temporally coinciding with recent uplifts of the Hengduan Mountains at the southeastern fringe of the QTP. Subsequently, several lineages dispersed out of Tibet. Main conclusions Immigration, recent rapid radiation and lineage persistence were all important processes for the establishment of a rich species stock of Saxifraga in the QTP region. Because floristic exchanges between the neighbouring areas and the QTP region were bi-directional, the spatio-temporal evolution of Saxifraga contrasts with the ‘out of QTP’ pattern, which has often been assumed for northern temperate plants.
