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Brian C Husband - One of the best experts on this subject based on the ideXlab platform.
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no influence of water limitation on the outcome of competition between diploid and tetraploid chamerion angustifolium onagraceae
Journal of Ecology, 2015Co-Authors: Ken A Thompson, Brian C Husband, Hafiz MaheraliAbstract:Summary 1. Polyploid plants often occupy different geographic ranges than their diploid progenitors, but the causes of this segregation are poorly understood. Differential competitive abilities of cytotypes across an environmental gradient could be responsible for these observed geographic range differences. 2. Cytotypes of Chamerion angustifolium (Onagraceae) are mostly allopatric, and prior research indicates that tetraploids are more physiologically tolerant of water limitation and occupy drier habitats than diploids. We hypothesized that tetraploids are stronger competitors than diploids in soils where water is limited, which allows them to persist in dry habitats while diploids cannot. 3. We grew both cytotypes together in competition under water-limited and well-watered conditions. We varied both total plant density and the relative frequency of cytotypes among pots, which allowed us to separate the effects of intra-cytotypic and inter-cytotypic competition. 4. Both diploid and tetraploid plants were smaller in the water-limited treatment than in the wellwatered treatment. Nevertheless, there were no differences in the relative strength of intra-cytotypic and inter-cytotypic competition experienced by either cytotype across the watering treatments, indicating that diploids and tetraploids had equal competitive abilities in both treatments. 5. Synthesis. Competition for limiting resources is often proposed as a mechanism causing ecological and geographic segregation between diploid and polyploid cytotypes. Our results do not support the hypothesis that tetraploid Chamerion angustifolium plants are stronger competitors than diploids when water is limited. A differential ability to compete for water is likely not responsible for the observed ecological and geographic segregation between cytotypes in this species. Competition may not be a general mechanism that causes segregation between diploid and polyploid cytotypes in nature.
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adaptation of diploid and tetraploid chamerion angustifolium to elevation but not local environment
Evolution, 2013Co-Authors: Sara L Martin, Brian C HusbandAbstract:Polyploid organisms often have different geographic ranges than their diploid relatives. However, it is unclear whether this divergence is maintained by adaptation or results from historical differences in colonization. Here, we conducted a reciprocal transplant experiment with diploid and autotetraploid Chamerion angustifolium to test for adaptation at the ploidy and population level. In the Rocky Mountains, pure diploid populations occur at high elevations and pure autotetraploid populations occur at low elevations with mixed ploidy populations between. We planted 3134 seedlings in 2004 and 3890 juveniles (bolting) in 2005 among nine plots, three in each of the diploid, mixed ploidy, and tetraploid zones, and monitored survival until 2008. For both seedlings and juvenile plants, elevation significantly influenced survival. The juvenile plants also showed a significant ploidy by elevation interaction, indicating that diploids and tetraploids survived best at their native elevations. In contrast, we found no evidence of local adaptation to plot within elevation. This suggests that the current distribution of diploids and tetraploids across elevations is the result of adaptation and that genome duplication may have facilitated the invasion of lower elevation habitats by limiting the movement of maladapted alleles from diploid populations at higher elevations.
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population cytotype structure in the polyploid galax urceolata diapensiaceae
Heredity, 1999Co-Authors: Tracy L Burton, Brian C HusbandAbstract:The geographical distributions of diploid and polyploid Galax urceolata overlap in the Blue Ridge Mountains, USA. As part of an investigation into the evolutionary forces governing the establishment of polyploids and their coexistence with diploids, we examined the population frequencies of diploids, triploids and tetraploids in the area of overlap. Ploidy was inferred from estimates of DNA content, using flow cytometry, for 1570 individuals sampled from 42 populations. Across the entire sampling area, diploids and tetraploids were most abundant (55% and 34% of individuals, respectively), whereas triploids were least abundant (11%). Cytotype frequencies differed significantly among the northern, central and southern regions of the range (G = 649.02, d.f. = 4, P < 0.0001), with diploids most frequent in the north-east and least frequent in the south-west. Twenty-six per cent of the populations contained three cytotypes, 33% contained two, and 40% had a single cytotype. Populations with two cytotypes occurred in all possible cytotype combinations, but when triploids were present, they were always in the minority. Uniform populations were either diploid (81%) or tetraploid (19%), but never triploid. Overall, populations are predominantly diploid or tetraploid but rarely evenly mixed, suggesting disruptive selection for chromosome number in G. urceolata. The contribution of ecological sorting and frequency-dependent mating success to the distribution of polyploids and diploids is discussed.
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cytotype distribution at a diploid tetraploid contact zone in chamerion epilobium angustifolium onagraceae
American Journal of Botany, 1998Co-Authors: Brian C Husband, Douglas W SchemskeAbstract:In North America, the geographic distributions of diploid and tetraploid Chamerion (formerly Epilobium) angustifolium overlap in a narrow zone along the southern border of the boreal forest and along the Rocky Mountains. We examined the frequency and distribution of diploid and tetraploid cytotypes in a narrow (5 km) zone of sympatry across an elevational gradient and in putatively uniform diploid and tetraploid reference populations on the Beartooth Pass, in the Rocky Mountains of southern Montana-northern Wyoming. All five reference populations sampled were dominated by a single cytotype, but only one was completely uniform. In the zone of sympatry, 27 transects were sampled every 2 m for a total of 238 plants. Reproductive status (vegetative, flower buds, open flowers) was recorded, and the ploidy of each plant was determined by flow cytometry. Diploid and tetraploid plants predominated (36 and 55%, respectively) but were heterogeneously distributed among the transects. Six of the 27 transects were fixed for a single cytotype (four transects, diploid; two transects, tetraploid), and in seven others either diploids or tetraploids predominated (frequency .75%). Triploids represented 9% of the total sample and occurred most frequently in transects containing both diploids and tetraploids ( G 5 3.4, df 5 2, P 5 0.07). Diploids were more often reproductive (in bud, flower, or fruit) than either triploids or tetraploids ( G 5 12.0, df 5 2, P , 0.001) and were the only cytotype to have produced open flowers. These results suggest that the zone of sympatry is best characterized as a mosaic rather than a cline, with diploid and tetraploids in close proximity and that the distribution of polyploidy is regulated by ecological sorting in a heterogeneous physical environment.
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THE EFFECT OF INBREEDING IN DIPLOID AND TETRAPLOID POPULATIONS OF EPILOBIUM ANGUSTIFOLIUM (ONAGRACEAE): IMPLICATIONS FOR THE GENETIC BASIS OF INBREEDING DEPRESSION.
Evolution, 1997Co-Authors: Brian C Husband, Douglas W SchemskeAbstract:The partial dominance model for the evolution of inbreeding depression predicts that tetraploids should exhibit less inbreeding depression than their diploid progenitors. We tested this prediction by comparing the magnitude of inbreeding depression in tetraploid and diploid populations of the herbaceous perennial Epilobium angustifolium (Onagraceae). Inbreeding depression was estimated in the greenhouse for three tetraploid and two diploid populations at four life stages. The mating system of a tetraploid population was estimated and compared to a previous estimate for diploids. Tetraploids showed less inbreeding depression than diploids at all life history stages, and these differences were significant for seed-set and cumulative fitness, but not for germination, survival, or plant dry mass at nine weeks. This result suggests that the genetic basis of inbreeding depression may differ among life stages. The primary selfing rate of the tetraploid population was r = 0.43, which is nearly identical to that of a diploid population (r = 0.45), indicating that differences in inbreeding depression between diploids and tetraploids are probably not due to differences in the mating system. Cumulative inbreeding depression, calculated from the four life history stages, was significantly higher for diploids (x-=0.95) than for tetraploids (x-=0.67), supporting the partial dominance model of inbreeding depression.
Ake Olson - One of the best experts on this subject based on the ideXlab platform.
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estimating the fitness effect of deleterious mutations during the two phases of the life cycle a new method applied to the root rot fungus heterobasidion parviporum
Genetics, 2019Co-Authors: Pierrehenri Clergeot, Nicolas O Rode, Sylvain Glemin, Mikael Brandstrom Durling, Katarina Ihrmark, Ake OlsonAbstract:Many eukaryote species including taxa such as fungi or algae have a lifecycle with substantial haploid and diploid phases. A recent theoretical model predicts that such haploid-diploid lifecycles are stable over long evolutionary time scales when segregating deleterious mutations have stronger effects in homozygous diploids than in haploids and when they are partially recessive in heterozygous diploids. The model predicts that effective dominance, a measure that accounts for these two effects, should be close to 0.5 in these species. They also predict that diploids should have higher fitness than haploids on average. However, an appropriate statistical framework to conjointly investigate these predictions is currently lacking. In this study, we derive a new quantitative genetic model to test these predictions using fitness data of two haploid parents and their diploid offspring and genome-wide genetic distance between haploid parents. We apply this model to the root-rot basidiomycete fungus Heterobasidion parviporum , a species where the heterokaryotic (equivalent to the diploid) phase is longer than the homokaryotic (haploid) phase. We measured two fitness-related traits (mycelium growth rate and the ability to degrade wood) in both homokaryons and heterokaryons and we used whole-genome sequencing to estimate nuclear genetic distance between parents. Possibly due to a lack of power, we did not find that deleterious mutations were recessive or more deleterious when expressed during the heterokaryotic phase. Using this model to compare effective dominance among haploid-diploid species where the relative importance of the two phases varies should help better understand the evolution of haploid-diploid life cycles.
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Estimating the fitness effect of deleterious mutations during the two phases of the life cycle: a new method applied to the root-rot fungus Heterobasidion parviporum
Genetics, 2019Co-Authors: Pierrehenri Clergeot, Sylvain Glemin, Katarina Ihrmark, Nicolas Rode, Mikael Brandström-durling, Ake OlsonAbstract:Many eukaryote species, including taxa such as fungi or algae, have a lifecycle with substantial haploid and diploid phases. A recent theoretical model predicts that such haploid-diploid lifecycles are stable over long evolutionary time scales when segregating deleterious mutations have stronger effects in homozygous diploids than in haploids and when they are partially recessive in heterozygous diploids. The model predicts that effective dominance—a measure that accounts for these two effects—should be close to 0.5 in these species. It also predicts that diploids should have higher fitness than haploids on average. However, an appropriate statistical framework to conjointly investigate these predictions is currently lacking. In this study, we derive a new quantitative genetic model to test these predictions using fitness data of two haploid parents and their diploid offspring, and genome-wide genetic distance between haploid parents. We apply this model to the root-rot basidiomycete fungus Heterobasidion parviporum—a species where the heterokaryotic (equivalent to the diploid) phase is longer than the homokaryotic (haploid) phase. We measured two fitness-related traits (mycelium growth rate and the ability to degrade wood) in both homokaryons and heterokaryons, and we used whole-genome sequencing to estimate nuclear genetic distance between parents. Possibly due to a lack of power, we did not find that deleterious mutations were recessive or more deleterious when expressed during the heterokaryotic phase. Using this model to compare effective dominance among haploid-diploid species where the relative importance of the two phases varies should help better understand the evolution of haploid-diploid life cycles.
Sylvain Glemin - One of the best experts on this subject based on the ideXlab platform.
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estimating the fitness effect of deleterious mutations during the two phases of the life cycle a new method applied to the root rot fungus heterobasidion parviporum
Genetics, 2019Co-Authors: Pierrehenri Clergeot, Nicolas O Rode, Sylvain Glemin, Mikael Brandstrom Durling, Katarina Ihrmark, Ake OlsonAbstract:Many eukaryote species including taxa such as fungi or algae have a lifecycle with substantial haploid and diploid phases. A recent theoretical model predicts that such haploid-diploid lifecycles are stable over long evolutionary time scales when segregating deleterious mutations have stronger effects in homozygous diploids than in haploids and when they are partially recessive in heterozygous diploids. The model predicts that effective dominance, a measure that accounts for these two effects, should be close to 0.5 in these species. They also predict that diploids should have higher fitness than haploids on average. However, an appropriate statistical framework to conjointly investigate these predictions is currently lacking. In this study, we derive a new quantitative genetic model to test these predictions using fitness data of two haploid parents and their diploid offspring and genome-wide genetic distance between haploid parents. We apply this model to the root-rot basidiomycete fungus Heterobasidion parviporum , a species where the heterokaryotic (equivalent to the diploid) phase is longer than the homokaryotic (haploid) phase. We measured two fitness-related traits (mycelium growth rate and the ability to degrade wood) in both homokaryons and heterokaryons and we used whole-genome sequencing to estimate nuclear genetic distance between parents. Possibly due to a lack of power, we did not find that deleterious mutations were recessive or more deleterious when expressed during the heterokaryotic phase. Using this model to compare effective dominance among haploid-diploid species where the relative importance of the two phases varies should help better understand the evolution of haploid-diploid life cycles.
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Estimating the fitness effect of deleterious mutations during the two phases of the life cycle: a new method applied to the root-rot fungus Heterobasidion parviporum
Genetics, 2019Co-Authors: Pierrehenri Clergeot, Sylvain Glemin, Katarina Ihrmark, Nicolas Rode, Mikael Brandström-durling, Ake OlsonAbstract:Many eukaryote species, including taxa such as fungi or algae, have a lifecycle with substantial haploid and diploid phases. A recent theoretical model predicts that such haploid-diploid lifecycles are stable over long evolutionary time scales when segregating deleterious mutations have stronger effects in homozygous diploids than in haploids and when they are partially recessive in heterozygous diploids. The model predicts that effective dominance—a measure that accounts for these two effects—should be close to 0.5 in these species. It also predicts that diploids should have higher fitness than haploids on average. However, an appropriate statistical framework to conjointly investigate these predictions is currently lacking. In this study, we derive a new quantitative genetic model to test these predictions using fitness data of two haploid parents and their diploid offspring, and genome-wide genetic distance between haploid parents. We apply this model to the root-rot basidiomycete fungus Heterobasidion parviporum—a species where the heterokaryotic (equivalent to the diploid) phase is longer than the homokaryotic (haploid) phase. We measured two fitness-related traits (mycelium growth rate and the ability to degrade wood) in both homokaryons and heterokaryons, and we used whole-genome sequencing to estimate nuclear genetic distance between parents. Possibly due to a lack of power, we did not find that deleterious mutations were recessive or more deleterious when expressed during the heterokaryotic phase. Using this model to compare effective dominance among haploid-diploid species where the relative importance of the two phases varies should help better understand the evolution of haploid-diploid life cycles.
Pierrehenri Clergeot - One of the best experts on this subject based on the ideXlab platform.
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estimating the fitness effect of deleterious mutations during the two phases of the life cycle a new method applied to the root rot fungus heterobasidion parviporum
Genetics, 2019Co-Authors: Pierrehenri Clergeot, Nicolas O Rode, Sylvain Glemin, Mikael Brandstrom Durling, Katarina Ihrmark, Ake OlsonAbstract:Many eukaryote species including taxa such as fungi or algae have a lifecycle with substantial haploid and diploid phases. A recent theoretical model predicts that such haploid-diploid lifecycles are stable over long evolutionary time scales when segregating deleterious mutations have stronger effects in homozygous diploids than in haploids and when they are partially recessive in heterozygous diploids. The model predicts that effective dominance, a measure that accounts for these two effects, should be close to 0.5 in these species. They also predict that diploids should have higher fitness than haploids on average. However, an appropriate statistical framework to conjointly investigate these predictions is currently lacking. In this study, we derive a new quantitative genetic model to test these predictions using fitness data of two haploid parents and their diploid offspring and genome-wide genetic distance between haploid parents. We apply this model to the root-rot basidiomycete fungus Heterobasidion parviporum , a species where the heterokaryotic (equivalent to the diploid) phase is longer than the homokaryotic (haploid) phase. We measured two fitness-related traits (mycelium growth rate and the ability to degrade wood) in both homokaryons and heterokaryons and we used whole-genome sequencing to estimate nuclear genetic distance between parents. Possibly due to a lack of power, we did not find that deleterious mutations were recessive or more deleterious when expressed during the heterokaryotic phase. Using this model to compare effective dominance among haploid-diploid species where the relative importance of the two phases varies should help better understand the evolution of haploid-diploid life cycles.
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Estimating the fitness effect of deleterious mutations during the two phases of the life cycle: a new method applied to the root-rot fungus Heterobasidion parviporum
Genetics, 2019Co-Authors: Pierrehenri Clergeot, Sylvain Glemin, Katarina Ihrmark, Nicolas Rode, Mikael Brandström-durling, Ake OlsonAbstract:Many eukaryote species, including taxa such as fungi or algae, have a lifecycle with substantial haploid and diploid phases. A recent theoretical model predicts that such haploid-diploid lifecycles are stable over long evolutionary time scales when segregating deleterious mutations have stronger effects in homozygous diploids than in haploids and when they are partially recessive in heterozygous diploids. The model predicts that effective dominance—a measure that accounts for these two effects—should be close to 0.5 in these species. It also predicts that diploids should have higher fitness than haploids on average. However, an appropriate statistical framework to conjointly investigate these predictions is currently lacking. In this study, we derive a new quantitative genetic model to test these predictions using fitness data of two haploid parents and their diploid offspring, and genome-wide genetic distance between haploid parents. We apply this model to the root-rot basidiomycete fungus Heterobasidion parviporum—a species where the heterokaryotic (equivalent to the diploid) phase is longer than the homokaryotic (haploid) phase. We measured two fitness-related traits (mycelium growth rate and the ability to degrade wood) in both homokaryons and heterokaryons, and we used whole-genome sequencing to estimate nuclear genetic distance between parents. Possibly due to a lack of power, we did not find that deleterious mutations were recessive or more deleterious when expressed during the heterokaryotic phase. Using this model to compare effective dominance among haploid-diploid species where the relative importance of the two phases varies should help better understand the evolution of haploid-diploid life cycles.
Douglas W Schemske - One of the best experts on this subject based on the ideXlab platform.
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cytotype distribution at a diploid tetraploid contact zone in chamerion epilobium angustifolium onagraceae
American Journal of Botany, 1998Co-Authors: Brian C Husband, Douglas W SchemskeAbstract:In North America, the geographic distributions of diploid and tetraploid Chamerion (formerly Epilobium) angustifolium overlap in a narrow zone along the southern border of the boreal forest and along the Rocky Mountains. We examined the frequency and distribution of diploid and tetraploid cytotypes in a narrow (5 km) zone of sympatry across an elevational gradient and in putatively uniform diploid and tetraploid reference populations on the Beartooth Pass, in the Rocky Mountains of southern Montana-northern Wyoming. All five reference populations sampled were dominated by a single cytotype, but only one was completely uniform. In the zone of sympatry, 27 transects were sampled every 2 m for a total of 238 plants. Reproductive status (vegetative, flower buds, open flowers) was recorded, and the ploidy of each plant was determined by flow cytometry. Diploid and tetraploid plants predominated (36 and 55%, respectively) but were heterogeneously distributed among the transects. Six of the 27 transects were fixed for a single cytotype (four transects, diploid; two transects, tetraploid), and in seven others either diploids or tetraploids predominated (frequency .75%). Triploids represented 9% of the total sample and occurred most frequently in transects containing both diploids and tetraploids ( G 5 3.4, df 5 2, P 5 0.07). Diploids were more often reproductive (in bud, flower, or fruit) than either triploids or tetraploids ( G 5 12.0, df 5 2, P , 0.001) and were the only cytotype to have produced open flowers. These results suggest that the zone of sympatry is best characterized as a mosaic rather than a cline, with diploid and tetraploids in close proximity and that the distribution of polyploidy is regulated by ecological sorting in a heterogeneous physical environment.
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THE EFFECT OF INBREEDING IN DIPLOID AND TETRAPLOID POPULATIONS OF EPILOBIUM ANGUSTIFOLIUM (ONAGRACEAE): IMPLICATIONS FOR THE GENETIC BASIS OF INBREEDING DEPRESSION.
Evolution, 1997Co-Authors: Brian C Husband, Douglas W SchemskeAbstract:The partial dominance model for the evolution of inbreeding depression predicts that tetraploids should exhibit less inbreeding depression than their diploid progenitors. We tested this prediction by comparing the magnitude of inbreeding depression in tetraploid and diploid populations of the herbaceous perennial Epilobium angustifolium (Onagraceae). Inbreeding depression was estimated in the greenhouse for three tetraploid and two diploid populations at four life stages. The mating system of a tetraploid population was estimated and compared to a previous estimate for diploids. Tetraploids showed less inbreeding depression than diploids at all life history stages, and these differences were significant for seed-set and cumulative fitness, but not for germination, survival, or plant dry mass at nine weeks. This result suggests that the genetic basis of inbreeding depression may differ among life stages. The primary selfing rate of the tetraploid population was r = 0.43, which is nearly identical to that of a diploid population (r = 0.45), indicating that differences in inbreeding depression between diploids and tetraploids are probably not due to differences in the mating system. Cumulative inbreeding depression, calculated from the four life history stages, was significantly higher for diploids (x-=0.95) than for tetraploids (x-=0.67), supporting the partial dominance model of inbreeding depression.