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Andrea D Schreier - One of the best experts on this subject based on the ideXlab platform.
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mechanical shock during egg de adhesion and post ovulatory ageing contribute to spontaneous Autopolyploidy in white sturgeon culture acipenser transmontanus
Aquaculture, 2020Co-Authors: Joel P Van Eenennaam, Aviva J Fiske, Michaiah J Leal, Chessie Cooleyrieders, Anne E Todgham, Fred S Conte, Andrea D SchreierAbstract:Abstract Spontaneous Autopolyploidy, a 1.5x increase in genome size resulting from second polar body retention after fertilization, has been documented in cultured sturgeons, with the proportion of spontaneous autopolyploid progeny ranging widely among maternal families. Sturgeon farms wish to reduce the number of spontaneous autopolyploids because their progeny, when crossed with a normal ploidy parent, exhibit intermediate ploidies, resulting in reproductive abnormalities. However, there is limited knowledge of the causes of the second polar body retention in sturgeon culture. In this study, we report the results of experiments performed from 2015 to 2019 aimed at identifying the sources of spontaneous Autopolyploidy in white sturgeon (Acipenser transmontanus) culture. In collaboration with several sturgeon farms, we tested whether post-ovulatory ageing, mechanical shock during egg de-adhesion, and the combined effects of both factors increased spontaneous Autopolyploidy. To test the effect of post-ovulatory ageing, eggs were collected from females and either fertilized at the industry normative time (2–5 h post-oviposition) or stored in ovarian fluid at 15 °C for 6–8 h before fertilization. To test the effect of mechanical shock, eggs were collected, fertilized 2–5 h post-oviposition and exposed to either gentle or vigorous mixing during the 60 min de-adhesion treatment. Results from this work reveal that post-ovulatory ageing does increase the incidence of spontaneous Autopolyploidy in some females, but overall the proportions produced were low (range 0–15%). Proportions of spontaneous autopolyploids in eggs exposed to vigorous mixing were also variable (1–92%) but significantly higher in 75% of the females when compared to their respective controls or gentle mixing treatments, indicating that mechanical shock during egg de-adhesion is likely the primary cause of spontaneous Autopolyploidy. To our knowledge this is the first study to document mechanical shock to eggs during de-adhesion as a cause of abnormal ploidy in cultured fishes. We observed high variability in egg quality among females and a significant relationship between embryo mortality and the incidence of spontaneous Autopolyploidy when eggs were exposed to mechanical shock. Repeated spawning of a female that produced a high proportion of spontaneous autopolyploids provided preliminary evidence that genetic background may influence the likelihood that a female's eggs will be prone to second polar body retention when subjected to mechanical shock. Although spontaneous Autopolyploidy in sturgeon culture will likely never be eliminated entirely, we provide practical recommendations to sturgeon producers to reduce its incidence in a production setting.
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evidence for a maternal origin of spontaneous Autopolyploidy in cultured white sturgeon acipenser transmontanus
Aquaculture, 2015Co-Authors: Daphne A Gille, Thomas R Famula, Andrea D SchreierAbstract:Abstract Sturgeons (order Acipenseriformes) are members of an ancient evolutionary lineage that has experienced multiple rounds of whole-genome duplication. As a result, most extant species are polyploid and possess more than two complete sets of chromosomes. While interspecific variation in ploidy and overall genome size is common within this order, recent studies have also documented intraspecific variation in some captive bred sturgeon species, most notably in white sturgeon ( Acipenser transmontanus ). The unintentional duplication of one or more complete sets of chromosomes in a single species in the absence of hybridization is known as spontaneous autopolyploidization. The mechanism and the effects on viability and reproductive development of spontaneous Autopolyploidy, however, are poorly understood. Sturgeons are valuable aquacultural species for production of boneless meat and caviar, and incidence of spontaneous Autopolyploidy could have negative economic implications. In this study, we wished to determine whether there was a maternal or paternal origin of spontaneous Autopolyploidy. We used flow cytometry to identify spontaneous autopolyploids and microsatellite genotyping to track the transfer of unique maternal and paternal alleles from broodstock to offspring across multiple full-sibling families in two populations of cultured white sturgeon. In all families, we found that the probability of transfer success of unique maternal alleles was greater than that of unique paternal alleles in spontaneous autopolyploid white sturgeon, indicating a maternal origin of spontaneous Autopolyploidy. Secondly, as no spontaneous autopolyploid progeny shared all the same microsatellite alleles as the respective dam as would be expected with premeiotic endomitosis or apomixis, we believe that failure to extrude the second polar body in meiosis II is the most likely cause of spontaneous Autopolyploidy in cultured white sturgeon.
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incidence of spontaneous Autopolyploidy in cultured populations of white sturgeon acipenser transmontanus
Aquaculture, 2013Co-Authors: Andrea D Schreier, Daphne A GilleAbstract:Many fish of aquacultural importance including sturgeon and paddlefish have a history of polyploidy in their evolutionary lineages. Spontaneous autopolyploids have been detected in several sturgeon species in culture despite the fact that the induction of triploidy is not a management tool in farming sturgeon for meat and caviar. In 2010, we discovered two female spontaneous autopolyploid white sturgeon (Acipenser transmontanus) on a commercial caviar farm that had successfully produced offspring of intermediate ploidy in crosses with normal males. Here we use flow cytometry and microsatellite genotyping to screen a second aquaculture program for the presence of spontaneous autopolyploids. Flow cytometry of female parents and their progeny in the 2011 year class created by the Kootenai River white sturgeon conservation aquaculture program revealed that wild caught females used as dams possessed normal ploidy (8N). Five of ten families sampled from the 2011 year class contained spontaneous autopolyploids possessing DNA content consistent with dodecaploidy (12N). The percent of autopolyploid individuals sampled ranged from 0 to 33% per family, and the total number of spontaneous autopolyploids in the 2011 year class was 12/150 (8%). Microsatellites were not useful in detecting spontaneous autopolyploids in the conservation aquaculture program due to low levels of genetic diversity in the endangered Kootenai River population. The two families with the highest incidence of spontaneous autopolyploids (33% and 26% of offspring sampled) were sired by a single male, suggesting a paternal effect on the generation of spontaneous autopolyploids in white sturgeon.
Daphne A Gille - One of the best experts on this subject based on the ideXlab platform.
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evidence for a maternal origin of spontaneous Autopolyploidy in cultured white sturgeon acipenser transmontanus
Aquaculture, 2015Co-Authors: Daphne A Gille, Thomas R Famula, Andrea D SchreierAbstract:Abstract Sturgeons (order Acipenseriformes) are members of an ancient evolutionary lineage that has experienced multiple rounds of whole-genome duplication. As a result, most extant species are polyploid and possess more than two complete sets of chromosomes. While interspecific variation in ploidy and overall genome size is common within this order, recent studies have also documented intraspecific variation in some captive bred sturgeon species, most notably in white sturgeon ( Acipenser transmontanus ). The unintentional duplication of one or more complete sets of chromosomes in a single species in the absence of hybridization is known as spontaneous autopolyploidization. The mechanism and the effects on viability and reproductive development of spontaneous Autopolyploidy, however, are poorly understood. Sturgeons are valuable aquacultural species for production of boneless meat and caviar, and incidence of spontaneous Autopolyploidy could have negative economic implications. In this study, we wished to determine whether there was a maternal or paternal origin of spontaneous Autopolyploidy. We used flow cytometry to identify spontaneous autopolyploids and microsatellite genotyping to track the transfer of unique maternal and paternal alleles from broodstock to offspring across multiple full-sibling families in two populations of cultured white sturgeon. In all families, we found that the probability of transfer success of unique maternal alleles was greater than that of unique paternal alleles in spontaneous autopolyploid white sturgeon, indicating a maternal origin of spontaneous Autopolyploidy. Secondly, as no spontaneous autopolyploid progeny shared all the same microsatellite alleles as the respective dam as would be expected with premeiotic endomitosis or apomixis, we believe that failure to extrude the second polar body in meiosis II is the most likely cause of spontaneous Autopolyploidy in cultured white sturgeon.
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incidence of spontaneous Autopolyploidy in cultured populations of white sturgeon acipenser transmontanus
Aquaculture, 2013Co-Authors: Andrea D Schreier, Daphne A GilleAbstract:Many fish of aquacultural importance including sturgeon and paddlefish have a history of polyploidy in their evolutionary lineages. Spontaneous autopolyploids have been detected in several sturgeon species in culture despite the fact that the induction of triploidy is not a management tool in farming sturgeon for meat and caviar. In 2010, we discovered two female spontaneous autopolyploid white sturgeon (Acipenser transmontanus) on a commercial caviar farm that had successfully produced offspring of intermediate ploidy in crosses with normal males. Here we use flow cytometry and microsatellite genotyping to screen a second aquaculture program for the presence of spontaneous autopolyploids. Flow cytometry of female parents and their progeny in the 2011 year class created by the Kootenai River white sturgeon conservation aquaculture program revealed that wild caught females used as dams possessed normal ploidy (8N). Five of ten families sampled from the 2011 year class contained spontaneous autopolyploids possessing DNA content consistent with dodecaploidy (12N). The percent of autopolyploid individuals sampled ranged from 0 to 33% per family, and the total number of spontaneous autopolyploids in the 2011 year class was 12/150 (8%). Microsatellites were not useful in detecting spontaneous autopolyploids in the conservation aquaculture program due to low levels of genetic diversity in the endangered Kootenai River population. The two families with the highest incidence of spontaneous autopolyploids (33% and 26% of offspring sampled) were sired by a single male, suggesting a paternal effect on the generation of spontaneous autopolyploids in white sturgeon.
Douglas E. Soltis - One of the best experts on this subject based on the ideXlab platform.
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Pure polyploidy: Closing the gaps in autopolyploid research
Journal of Systematics and Evolution, 2017Co-Authors: Jonathan P. Spoelhof, Pamela S. Soltis, Douglas E. SoltisAbstract:Polyploidy (whole-genome duplication, WGD) is an integral feature of eukaryotic evolution with two main forms typically recognized, Autopolyploidy and allopolyploidy. In plants, a growing body of research contradicts historical assumptions that Autopolyploidy is both infrequent and inconsequential in comparison to allopolyploidy. However, the legacy of these assumptions still persists through a lack of research on central facets of autopolyploid evolution. This review highlights recent research that has significantly increased scientific understanding of Autopolyploidy. Key advances include: 1) unreduced female gametes contribute disproportionally to polyploidization through the formation of triploids, 2) niche divergence in autopolyploids can occur immediately or gradually after WGD through a diverse set of mechanisms, but broad niche overlap is also common between diploids and autopolyploids, and 3) the degree of genomic and transcriptomic changes following WGD is lower in autopolyploids than allopolyploids, but is highly variable both within and between species in both types of polyploids. We discuss the implications of these and other recent findings, present promising systems for future research, and advocate for expanded research in diverse areas of autopolyploid evolution.
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Niche divergence between diploid and autotetraploid Tolmiea
American Journal of Botany, 2016Co-Authors: Clayton J Visger, Pamela S. Soltis, Charlotte C. Germain-aubrey, Maya Patel, Emily B. Sessa, Douglas E. SoltisAbstract:Polyploidy is common in eukaryotes and is of major evolutionary importance over both short and long time-scales. Compared to allopolyploids, autopolyploids remain understudied; they are often morphologically cryptic and frequently remain taxonomically unrecognized, although there is increasing recognition of the high frequency of Autopolyploidy in angiosperms. While Autopolyploidy can serve as an instant speciation mechanism, little is known about the ecological consequences of this process. We describe the ecological divergence of a diploid-autotetraploid species pair in Tolmiea. We investigated whether abiotic niche divergence has shaped the current allopatric distribution of diploid T. diplomenziesii and its autotetraploid derivative, T. menziesii, in the Pacific Northwest of North America. We employed field measures of light availability, as well as niche modeling and a principal component analysis of environmental space. Within a common garden, we also investigated physiological responses to changes in soil moisture. Diploid and autotetraploid Tolmiea inhabit significantly different climatic niche spaces. The climatic niche divergence between these two species is best explained by a shift in precipitation availability, and we found evidence of differing physiological response to water availability between these species. We found that spatial segregation of T. diplomenziesii and T. menziesii was accompanied by adaptation to changes in climatic regime. Tolmiea menziesii is not a nascent autotetraploid, having persisted long enough to be established throughout the Pacific Northwest, and therefore both polyploidization and subsequent evolution have contributed to the observed differences between T. menziesii and T. diplomenziesii. © 2016 Botanical Society of America.
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population genetic variation geographic structure and multiple origins of Autopolyploidy in galax urceolata
American Journal of Botany, 2015Co-Authors: Stein V Servick, Pamela S. Soltis, Clayton J Visger, Matthew A Gitzendanner, Douglas E. SoltisAbstract:PREMISE OF THE STUDY: Whereas population genetic studies have examined allopolyploids, comparable studies of naturally occurring autopolyploids remain rare. To address fundamental questions regarding Autopolyploidy, we undertook a detailed population genetic study of one of the classic examples of Autopolyploidy, Galax urceolata (Diapensiaceae), which comprises diploid, triploid, and autotetraploid cytotypes. Galax is endemic to the Appalachian Mountains, the adjacent piedmont, sandhills, and coastal plain and represents perhaps the most widely known example of Autopolyploidy in nature. METHODS: Flow cytometry was used to diagnose ploidal level of ∼1000 individuals across 71 populations. We used 10 microsatellite markers to examine genetic variation across the geographic range of Galax and assessed multiple origins though comparisons of diploid, triploid, and tetraploid accessions using multiple analytical approaches. KEY RESULTS: Tetraploids had higher levels of heterozygosity than diploids did. Genetic variation in diploid and tetraploid Galax is geographically structured among the ecoregions of the southeastern United States. Autotetraploidy in Galax urceolata has occurred independently at least 46 times, with triploidy having occurred a minimum of 31 times. CONCLUSIONS: Genetic differentiation among ecoregions suggests historical patterns of local adaptation. The numerous independent origins of tetraploid Galax reported here are among the highest frequencies of independent polyploidizations ever reported for any polyploid (auto- or allopolyploid).
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Population genetic variation, geographic structure, and multiple origins of Autopolyploidy in Galax urceolata
American Journal of Botany, 2015Co-Authors: Stein V Servick, Pamela S. Soltis, Clayton J Visger, Matthew A Gitzendanner, Douglas E. SoltisAbstract:Whereas population genetic studies have examined allopolyploids, comparable studies of naturally occurring autopolyploids remain rare. To address fundamental questions regarding Autopolyploidy, we undertook a detailed population genetic study of one of the classic examples of Autopolyploidy, Galax urceolata (Diapensiaceae), which comprises diploid, triploid, and autotetraploid cytotypes. Galax is endemic to the Appalachian Mountains, the adjacent piedmont, sandhills, and coastal plain and represents perhaps the most widely known example of Autopolyploidy in nature. Flow cytometry was used to diagnose ploidal level of ∼1000 individuals across 71 populations. We used 10 microsatellite markers to examine genetic variation across the geographic range of Galax and assessed multiple origins though comparisons of diploid, triploid, and tetraploid accessions using multiple analytical approaches. Tetraploids had higher levels of heterozygosity than diploids did. Genetic variation in diploid and tetraploid Galax is geographically structured among the ecoregions of the southeastern United States. Autotetraploidy in Galax urceolata has occurred independently at least 46 times, with triploidy having occurred a minimum of 31 times. Genetic differentiation among ecoregions suggests historical patterns of local adaptation. The numerous independent origins of tetraploid Galax reported here are among the highest frequencies of independent polyploidizations ever reported for any polyploid (auto- or allopolyploid). © 2015 Botanical Society of America, Inc.
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Autopolyploidy in angiosperms have we grossly underestimated the number of species
Taxon, 2007Co-Authors: Douglas E. Soltis, Pamela S. Soltis, Douglas W Schemske, James F Hancock, John N Thompson, Brian C Husband, Walter S JuddAbstract:Many species comprise multiple cytotypes that represent autopolyploids, or presumed autopolyploids, of the basic diploid cytotype. However, rarely has an autopolyploid been formally named and considered to represent a species distinct from its diploid progenitor (Zea diploperennis and Z. perennis represent a rare example). The major reasons why autopolyploids have not been named as distinct species are: (1) tradition of including multiple cytotypes in a single named species; and (2) tradition and convenience of adhering to a broad morphology-based taxonomic (or phenetic) species concept. As a result, plant biologists have underrepresented the distinct biological entities that actually exist in nature. Although it may seem "practical" to include morphologically highly similar cytotypes in one species, this practice obscures insights into evolution and speciation and hinders conservation. However, we do not suggest that all cytotypes should be named; each case must be carefully considered. A number of species comprising multiple cytotypes have been thoroughly investigated. Drawing on the literature, as well as our own experience with several autopolyploids (Tolmiea menziesii, Galax urceolata, Chamerion angustifolium, Heuchera grossulariifolia, Vaccinium corymbosum), we reassess the traditional view of plant autopolyploids as mere cytotypes. When considered carefully, many "unnamed" autopolyploids fulfill the requirements of multiple species concepts, including the biological, taxonomic, diagnosability, apomorphic, and evolutionary species concepts. Compared to the diploid parent, the autopolyploids noted above possess distinct geographic ranges, can be distinguished morphologically, and are largely reproductively isolated (via a diversity of mechanisms including reproductive and ecological isolation). These five autopolyploids (and probably many others) represent distinct evolutionary lineages; we therefore suggest that they be considered distinct species and also provide a system for naming them.
Christoph Dobeš - One of the best experts on this subject based on the ideXlab platform.
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The morphometrics of Autopolyploidy: insignificant differentiation among sexual–apomictic cytotypes
Aob Plants, 2019Co-Authors: Karin Bigl, Juraj Paule, Christoph DobešAbstract:Polyploidization of the plant genome affects the phenotype of individuals including their morphology, i.e. size and form. In autopolyploids, we expect mainly nucleotypic effects, from a number of monoploid genomes (i.e. chromosome sets) or genome size, seen from an increase in size or dimension of the polyploids compared with the diploids (or lower ploids). To identify nucleotypic effects, confounding effects of hybridity (observed in allopolyploids), postpolyploidization processes or environmental effects need to be considered. We morphometrically analysed five ploidy cytotypes of the sexual-apomictic species Potentilla puberula cultivated ex situ under the same experimental conditions. Sexuals are mainly tetraploid, while higher ploidy (penta- to octoploidy) is typically associated with the expression of apomixis. The cytotypes likely arose via autopolyploidization although historic involvement of another species in the origin of apomicts cannot be fully ruled out, suggested by a slight molecular differentiation among reproductive modes. We (i) revisited molecular differentiation using amplified fragment length polymorphisms and performed a morphometric analysis to test (ii) if cytotypes are morphologically differentiated from each other and (iii) if the size of individuals is related to their ploidy. Weak molecular differentiation of sexual versus apomictic individuals was confirmed. Cytotypes and reproductive modes were also morphologically poorly differentiated from each other, i.e. apomicts largely resampled the variation of the sexuals and did not exhibit a unique morphology. Overall size of individuals increased moderately but significantly with ploidy (ca. 14 % in the comparison of octo- with tetraploids). The results support an autopolyploid origin of the P. puberula apomicts and suggest a nucleotypic effect on overall plant size. We discuss taxonomic consequences of the results in the context of data on reproductive relationships among cytotypes and their ecological preferences and evolutionary origin, and conclude that cytotypes are best treated as intraspecific variants within a single species.
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the morphometrics of Autopolyploidy insignificant differentiation among sexual apomictic cytotypes
Aob Plants, 2019Co-Authors: Karin Bigl, Juraj Paule, Christoph DobešAbstract:: Polyploidization of the plant genome affects the phenotype of individuals including their morphology, i.e. size and form. In autopolyploids, we expect mainly nucleotypic effects, from a number of monoploid genomes (i.e. chromosome sets) or genome size, seen from an increase in size or dimension of the polyploids compared with the diploids (or lower ploids). To identify nucleotypic effects, confounding effects of hybridity (observed in allopolyploids), postpolyploidization processes or environmental effects need to be considered. We morphometrically analysed five ploidy cytotypes of the sexual-apomictic species Potentilla puberula cultivated ex situ under the same experimental conditions. Sexuals are mainly tetraploid, while higher ploidy (penta- to octoploidy) is typically associated with the expression of apomixis. The cytotypes likely arose via autopolyploidization although historic involvement of another species in the origin of apomicts cannot be fully ruled out, suggested by a slight molecular differentiation among reproductive modes. We (i) revisited molecular differentiation using amplified fragment length polymorphisms and performed a morphometric analysis to test (ii) if cytotypes are morphologically differentiated from each other and (iii) if the size of individuals is related to their ploidy. Weak molecular differentiation of sexual versus apomictic individuals was confirmed. Cytotypes and reproductive modes were also morphologically poorly differentiated from each other, i.e. apomicts largely resampled the variation of the sexuals and did not exhibit a unique morphology. Overall size of individuals increased moderately but significantly with ploidy (ca. 14 % in the comparison of octo- with tetraploids). The results support an autopolyploid origin of the P. puberula apomicts and suggest a nucleotypic effect on overall plant size. We discuss taxonomic consequences of the results in the context of data on reproductive relationships among cytotypes and their ecological preferences and evolutionary origin, and conclude that cytotypes are best treated as intraspecific variants within a single species.
Pamela S. Soltis - One of the best experts on this subject based on the ideXlab platform.
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Pure polyploidy: Closing the gaps in autopolyploid research
Journal of Systematics and Evolution, 2017Co-Authors: Jonathan P. Spoelhof, Pamela S. Soltis, Douglas E. SoltisAbstract:Polyploidy (whole-genome duplication, WGD) is an integral feature of eukaryotic evolution with two main forms typically recognized, Autopolyploidy and allopolyploidy. In plants, a growing body of research contradicts historical assumptions that Autopolyploidy is both infrequent and inconsequential in comparison to allopolyploidy. However, the legacy of these assumptions still persists through a lack of research on central facets of autopolyploid evolution. This review highlights recent research that has significantly increased scientific understanding of Autopolyploidy. Key advances include: 1) unreduced female gametes contribute disproportionally to polyploidization through the formation of triploids, 2) niche divergence in autopolyploids can occur immediately or gradually after WGD through a diverse set of mechanisms, but broad niche overlap is also common between diploids and autopolyploids, and 3) the degree of genomic and transcriptomic changes following WGD is lower in autopolyploids than allopolyploids, but is highly variable both within and between species in both types of polyploids. We discuss the implications of these and other recent findings, present promising systems for future research, and advocate for expanded research in diverse areas of autopolyploid evolution.
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Niche divergence between diploid and autotetraploid Tolmiea
American Journal of Botany, 2016Co-Authors: Clayton J Visger, Pamela S. Soltis, Charlotte C. Germain-aubrey, Maya Patel, Emily B. Sessa, Douglas E. SoltisAbstract:Polyploidy is common in eukaryotes and is of major evolutionary importance over both short and long time-scales. Compared to allopolyploids, autopolyploids remain understudied; they are often morphologically cryptic and frequently remain taxonomically unrecognized, although there is increasing recognition of the high frequency of Autopolyploidy in angiosperms. While Autopolyploidy can serve as an instant speciation mechanism, little is known about the ecological consequences of this process. We describe the ecological divergence of a diploid-autotetraploid species pair in Tolmiea. We investigated whether abiotic niche divergence has shaped the current allopatric distribution of diploid T. diplomenziesii and its autotetraploid derivative, T. menziesii, in the Pacific Northwest of North America. We employed field measures of light availability, as well as niche modeling and a principal component analysis of environmental space. Within a common garden, we also investigated physiological responses to changes in soil moisture. Diploid and autotetraploid Tolmiea inhabit significantly different climatic niche spaces. The climatic niche divergence between these two species is best explained by a shift in precipitation availability, and we found evidence of differing physiological response to water availability between these species. We found that spatial segregation of T. diplomenziesii and T. menziesii was accompanied by adaptation to changes in climatic regime. Tolmiea menziesii is not a nascent autotetraploid, having persisted long enough to be established throughout the Pacific Northwest, and therefore both polyploidization and subsequent evolution have contributed to the observed differences between T. menziesii and T. diplomenziesii. © 2016 Botanical Society of America.
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population genetic variation geographic structure and multiple origins of Autopolyploidy in galax urceolata
American Journal of Botany, 2015Co-Authors: Stein V Servick, Pamela S. Soltis, Clayton J Visger, Matthew A Gitzendanner, Douglas E. SoltisAbstract:PREMISE OF THE STUDY: Whereas population genetic studies have examined allopolyploids, comparable studies of naturally occurring autopolyploids remain rare. To address fundamental questions regarding Autopolyploidy, we undertook a detailed population genetic study of one of the classic examples of Autopolyploidy, Galax urceolata (Diapensiaceae), which comprises diploid, triploid, and autotetraploid cytotypes. Galax is endemic to the Appalachian Mountains, the adjacent piedmont, sandhills, and coastal plain and represents perhaps the most widely known example of Autopolyploidy in nature. METHODS: Flow cytometry was used to diagnose ploidal level of ∼1000 individuals across 71 populations. We used 10 microsatellite markers to examine genetic variation across the geographic range of Galax and assessed multiple origins though comparisons of diploid, triploid, and tetraploid accessions using multiple analytical approaches. KEY RESULTS: Tetraploids had higher levels of heterozygosity than diploids did. Genetic variation in diploid and tetraploid Galax is geographically structured among the ecoregions of the southeastern United States. Autotetraploidy in Galax urceolata has occurred independently at least 46 times, with triploidy having occurred a minimum of 31 times. CONCLUSIONS: Genetic differentiation among ecoregions suggests historical patterns of local adaptation. The numerous independent origins of tetraploid Galax reported here are among the highest frequencies of independent polyploidizations ever reported for any polyploid (auto- or allopolyploid).
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Population genetic variation, geographic structure, and multiple origins of Autopolyploidy in Galax urceolata
American Journal of Botany, 2015Co-Authors: Stein V Servick, Pamela S. Soltis, Clayton J Visger, Matthew A Gitzendanner, Douglas E. SoltisAbstract:Whereas population genetic studies have examined allopolyploids, comparable studies of naturally occurring autopolyploids remain rare. To address fundamental questions regarding Autopolyploidy, we undertook a detailed population genetic study of one of the classic examples of Autopolyploidy, Galax urceolata (Diapensiaceae), which comprises diploid, triploid, and autotetraploid cytotypes. Galax is endemic to the Appalachian Mountains, the adjacent piedmont, sandhills, and coastal plain and represents perhaps the most widely known example of Autopolyploidy in nature. Flow cytometry was used to diagnose ploidal level of ∼1000 individuals across 71 populations. We used 10 microsatellite markers to examine genetic variation across the geographic range of Galax and assessed multiple origins though comparisons of diploid, triploid, and tetraploid accessions using multiple analytical approaches. Tetraploids had higher levels of heterozygosity than diploids did. Genetic variation in diploid and tetraploid Galax is geographically structured among the ecoregions of the southeastern United States. Autotetraploidy in Galax urceolata has occurred independently at least 46 times, with triploidy having occurred a minimum of 31 times. Genetic differentiation among ecoregions suggests historical patterns of local adaptation. The numerous independent origins of tetraploid Galax reported here are among the highest frequencies of independent polyploidizations ever reported for any polyploid (auto- or allopolyploid). © 2015 Botanical Society of America, Inc.
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Autopolyploidy in angiosperms have we grossly underestimated the number of species
Taxon, 2007Co-Authors: Douglas E. Soltis, Pamela S. Soltis, Douglas W Schemske, James F Hancock, John N Thompson, Brian C Husband, Walter S JuddAbstract:Many species comprise multiple cytotypes that represent autopolyploids, or presumed autopolyploids, of the basic diploid cytotype. However, rarely has an autopolyploid been formally named and considered to represent a species distinct from its diploid progenitor (Zea diploperennis and Z. perennis represent a rare example). The major reasons why autopolyploids have not been named as distinct species are: (1) tradition of including multiple cytotypes in a single named species; and (2) tradition and convenience of adhering to a broad morphology-based taxonomic (or phenetic) species concept. As a result, plant biologists have underrepresented the distinct biological entities that actually exist in nature. Although it may seem "practical" to include morphologically highly similar cytotypes in one species, this practice obscures insights into evolution and speciation and hinders conservation. However, we do not suggest that all cytotypes should be named; each case must be carefully considered. A number of species comprising multiple cytotypes have been thoroughly investigated. Drawing on the literature, as well as our own experience with several autopolyploids (Tolmiea menziesii, Galax urceolata, Chamerion angustifolium, Heuchera grossulariifolia, Vaccinium corymbosum), we reassess the traditional view of plant autopolyploids as mere cytotypes. When considered carefully, many "unnamed" autopolyploids fulfill the requirements of multiple species concepts, including the biological, taxonomic, diagnosability, apomorphic, and evolutionary species concepts. Compared to the diploid parent, the autopolyploids noted above possess distinct geographic ranges, can be distinguished morphologically, and are largely reproductively isolated (via a diversity of mechanisms including reproductive and ecological isolation). These five autopolyploids (and probably many others) represent distinct evolutionary lineages; we therefore suggest that they be considered distinct species and also provide a system for naming them.
