Abstract. The genus,Reynoutria is represented,by four taxa in the Czech Republic – R. japonica va... more Abstract. The genus,Reynoutria is represented,by four taxa in the Czech Republic – R. japonica var. japonica and compacta, R. sachalinensis and R. · bohemica. Using isoenzyme analysis, we determined the degree of genotype,variability in all taxa and compared,clones of R. japonica var. japonica from the Czech Republic with those from Great Britain. While the rarely occurring tetraploid variety R. japonica
Atriplex tatarica is a heterocarpic species of disturbed habitats. Seeds of Atriplex tatarica do ... more Atriplex tatarica is a heterocarpic species of disturbed habitats. Seeds of Atriplex tatarica do not germinate immediately after shedding, but may remain in a dormant but viable state indefinitely. We investigated whether there were genetic and fitness differences between plants derived from seeds of the different fruit types germinated in different temperatures and salinities. Seeds that germinated in optimal and
Floras of several villages in the Bohemian,Karst Protected Area (Czech Republic) are compared ove... more Floras of several villages in the Bohemian,Karst Protected Area (Czech Republic) are compared over the time period of almost fifteen years and the trends in the performance,of alien plant species are described. Floristic list from,1980-81 was,compared,with the recent situation in 1995. Alien species were divided into archaeophytes, consisting of species introduced before 1500, and neophytes, introduced after 1500. From
Genetic admixture is supposed to be an important trigger of species expansions because it can cre... more Genetic admixture is supposed to be an important trigger of species expansions because it can create the potential for selection of genotypes suitable for new climatic conditions. Up until now, however, no continent-wide population genetic study has performed a detailed reconstruction of admixture events during natural species expansions. To fill this gap, we analysed the postglacial history of Alnus glutinosa, a keystone species of European swamp habitats, across its entire distribution range using two molecular markers, cpDNA and nuclear microsatellites. CpDNA revealed multiple southern refugia located in the Iberian, Apennine, Balkan and Anatolian Peninsulas, Corsica and North Africa. Analysis of microsatellites variation revealed three main directions of postglacial expansion: 1) from the northern part of the Iberian Peninsula to Western and Central Europe and subsequently to the British Isles, 2) from the Apennine Peninsula to the Alps, and 3) from the eastern part of the Balka...
Vegetative regeneration of individual genotypes of Asian Reynoutria taxa, which are invasive in t... more Vegetative regeneration of individual genotypes of Asian Reynoutria taxa, which are invasive in the Czech Republic, was studied in R. sachalinensis (five genotypes), R. japonica (a single genotype present in the country), and their hybrid R. 3bohemica (nine genotypes). Identity of genotypes was confirmed by isozyme analysis. Ten rhizome segments of each genotype were planted in a randomized block design.
We investigated to what extent the soil seed bank differed genetically and spatially in compariso... more We investigated to what extent the soil seed bank differed genetically and spatially in comparison to three consecutive life history stages (seedlings, mature plants, and fruiting plants) in a natural population of Atriplex tatarica . Representatives of particular life history stages from twenty subunits within a large population were randomly collected and subjected to allozyme analysis. Comparison of population polymorphism among various life history stages showed significant differences in observed heterozygosity ( H O ) and F statistics ( F IS and F ST ), but nonsignificant ones in the cases of number of alleles per polymorphic locus ( A ) and gene diversity ( H S ). These results indicate an increasing number of heterozygotes, a decreasing level of inbreeding and an increase of the partitioning genetic diversity among populations with increasing population age. Spatial autocorrelation was used to calculate f , the average co-ancestry coefficient between individuals within distance intervals of two meters along a 39 m long transect. Significant positive fine scale genetic structure was detected in mature and fruiting plants but not in soil seeds and seedlings stages. The results of the presented study on A. tatarica indicated that significant differences exist in genetic differentiation, differentiation in allele frequencies and spatial autocorrelation among early (soil seeds and seedlings) and late (mature and fruiting plants) life history stages but not within early and late ones. This pattern suggests that, rather than storing genetic variability in the soil or germination and establishment success, self-thinning might be the major microselective force in populations of A. tatarica .
Temporal patterns of immigration to the country were analysed using 668 alien species in the flor... more Temporal patterns of immigration to the country were analysed using 668 alien species in the flora of the Czech Republic for which the dates of the first record were available (64.8% of the total number of 1031 socalled neophytes, i.e. aliens introduced after the year 1500). After a period of initial slow increase lasting to the 1840s, the accumulation of neophytes over time could be best fitted by a linear model that explained 97% of the variance. The intensity of floristic research, which varied between periods, did not significantly affect the overall increase in the number of aliens. The effect of species traits on the year of introduction was evaluated, with continent of origin, introduction type (deliberate or accidental), life history, Grime's life strategy, onset of flowering, mode of dispersal and propagule size as explanatory variables. Species of European origin and CSR strategists arrived earlier than those with other origins and strategies. Deliberately introduced species appeared earlier than accidental arrivals, and those cultivated for utilitary reasons on average arrived earlier than ornamentals. Species capable of early flowering were remarkably more prevalent among early newcomers. A separate analysis of accidentally introduced American species also identified life history as a significant predictor of immigration time, with annuals being introduced earlier than biennials and perennials. The data contribute to an understanding of a crucial stage of the invasion process that has received little attention in the literature. The model "early alien" to Central Europe is a European species with a CSR strategy deliberately brought for cultivation as a utilitary plant. Once it escaped from cultivation, its establishment in the wild was favoured by its ability to flower early and, therefore, complete the life cycle.
The genus Reynoutria is represented by four taxa in the Czech Republic: Reynoutria japonica var. ... more The genus Reynoutria is represented by four taxa in the Czech Republic: Reynoutria japonica var. japonica, R. japonica var. compacta, R. sachalinensis and R. Qbohemica. By using¯ow cytometry, cytological variability within the genus is described based on 257 Reynoutria samples. The varieties of R. japonica are cytologically uniform, var. japonica is exclusively octoploid (2n = 8x = 88) and var. compacta occurs only as a tetraploid (2n = 4x = 44), but R. sachalinensis and R. Qbohemica exhibit some variation in chromosome numbers. Reynoutria sachalinensis is predominantly tetraploid (2n = 4 x = 44), but also occurs occasionally as hexaploid and octoploid cytotypes. The most common ploidy level in R. Qbohemica is hexaploid (2n = 6x = 66), but tetraploid and octoploid clones were also found. The four taxa occurring in the Czech Republic are described brie¯y and the possible origins of the cytotypes discussed.
Background and Aims Genetic variability was estimated for Atriplex tatarica from 25 populations i... more Background and Aims Genetic variability was estimated for Atriplex tatarica from 25 populations in the Czech Republic. Since its north-western range margin is in central Europe, a relationship between marginality and low within-population genetic diversity was tested in accordance with the Central-Marginal Model.
Background/Aims: Recently, new palaeoecological records supported by molecular analyses and palae... more Background/Aims: Recently, new palaeoecological records supported by molecular analyses and palaeodistributional modelling have provided more comprehensive insights into plant behaviour during the last Quaternary cycle. We reviewed the migration history of species of subgenus Alnus during the last 50,000 years in Europe with a focus on (1) a general revision of Alnus history since the Last Glacial Maximum (LGM), (2) evidence of northern refugia of Alnus populations during the LGM and (3) the specific history of Alnus in particular European regions.
We attempted to confirm that seed banks can be viewed as an important genetic reservoir by testin... more We attempted to confirm that seed banks can be viewed as an important genetic reservoir by testing the hypothesis that standing (aboveground) plants represent a nonrandom sample of the seed bank. We sampled multilocus allozyme genotypes from three species with different life history strategies: Amaranthus retroflexus, Carduus acanthoides, Pastinaca sativa. In four populations of each species we analysed the extent to which allele and genotype frequencies vary in consecutive life history stages including the summer seed bank, which has been overlooked up to now. We compared the winter seed bank (i.e., seeds collected before the spring germination peak), seedlings, rosettes, the summer seed bank (i.e., seeds collected after the spring germination peak) and fruiting plants. We found that: (1) All three species partitioned most of their genetic diversity within life history stages and less among stages within populations and among populations. (2) All genetic diversity parameters, except for allele frequencies, were similar among all life history stages across all populations in different species. (3) There were differences in allele frequencies among life history stages at all localities in Amaranthus retroflexus and at three localities in both Carduus acanthoides and Pastinaca sativa. (4) Allele frequencies did not differ between the winter and summer seed bank in most Carduus acanthoides and Pastinaca sativa populations, but there was a marked difference in Amaranthus retroflexus. In conclusion, we have shown that the summer seed bank is not genetically depleted by spring germination and that a majority of genetic diversity remains in the soil through summer. We suggest that seed banks in the species investigated play an important role by maintaining genetic diversity sufficient for recovery rather than by accumulating new genetic diversity at each locality.
The genus Reynoutria is represented by four taxa in the Czech Republic -R. japonica var. japonica... more The genus Reynoutria is represented by four taxa in the Czech Republic -R. japonica var. japonica and compacta, R. sachalinensis and R. · bohemica. Using isoenzyme analysis, we determined the degree of genotype variability in all taxa and compared clones of R. japonica var. japonica from the Czech Republic with those from Great Britain. While the rarely occurring tetraploid variety R. japonica var. compacta possesses low variability, the octoploid female clone of R. japonica var. japonica is genetically uniform in the 93 clones sampled and belongs to the same genotype that is present in the whole Europe. R. japonica var. japonica can be fertilized by the pollen of tetraploid R. sachalinensis and a hexaploid hybrid R. · bohemica is produced. In R. sachalinensis, 16 genotypes were found in the 50 clones sampled. R. · bohemica is genetically the most diverse taxon in the study area, with 33 genotypes recorded among 88 clones sampled.
Perspectives in Plant Ecology, Evolution and Systematics, 2008
Atriplex tatarica is a heterocarpic annual native to a wide area of Middle and western Central As... more Atriplex tatarica is a heterocarpic annual native to a wide area of Middle and western Central Asia, Asia Minor, North Africa, and Eastern Europe. It is an early successional species of disturbed habitats, in Central Europe mostly occupying road margins and waste places. This paper deals with taxonomic status, morphology, distribution, ecology, and population biology of this species with special emphasis on its population genetics.
Atriplex sagittata is a heterocarpic species producing three types of fruits which differ in morp... more Atriplex sagittata is a heterocarpic species producing three types of fruits which differ in morphology and ecological properties. This study focused on variation in biomass allocation into particular fruit types under different density and fertilization levels. The reduction in total weight under stressful conditions was accompanied by a reduction of reproductive structures in terms of both total fruit production and
Questions: 1. How does species richness of recipient communities affect Reynoutria invasion? 2. H... more Questions: 1. How does species richness of recipient communities affect Reynoutria invasion? 2. How does Reynoutria invasion change host community structure? 3. Are there any differences in habitat preferences among three closely related Reynoutria taxa? 4. How does the genetic structure of Reynoutria populations change along the course of a river? Location: River Jizera basin, north Bohemia, Czech Republic. Methods: Nine 0.25 km 2 plots were chosen along the river. Within each plot all main habitat types were determined and sampled using the Braun-Blanquet scale to determine the invasibility of various communities. The patches invaded by Reynoutria taxa and surrounding Reynoutria-free vegetation in the same habitat type were sampled as relevé pairs to compare the composition of invaded and non-invaded vegetation. In addition, to characterize the genetic structure of Reynoutria populations along the river, 30 samples from different clones were collected. Results and conclusions: 1. The species richness of communities has no influence on the success of Reynoutria invasion in the area studied. The combination of environmental conditions and propagule spread is more important to the invasion success than the number of species in the host community. 2. Reynoutria invasion greatly reduces species diversity. 3. R. japonica invaded more habitat types than R. sachalinensis and R. × bohemica. The hybrid R. × bohemica outcompetes the parental taxa at sites where both taxa co-occur. 4. Isozyme analysis revealed phenotype variability in the hybrid in contrast to the parental taxa. Different hybrid phenotypes are distributed randomly on the middle and lower reaches of the River Jizera; one of them dominates and the other three occur occasionally. This pattern supports the hypothesis that sexual reproduction occasionally occurs within Reynoutria taxa.
1 We investigated the effect of light quality, nitrogen supply, fruit size and age on germination... more 1 We investigated the effect of light quality, nitrogen supply, fruit size and age on germination of the three types of fruit produced by Atriplex sagittata . 2 Regardless of fruit type, seed germination was significantly reduced in the dark. Light quality had no significant effect on germination of seeds from fruit types A and B, both of which are dormant, but seeds from fruit type C, which are non-dormant, germinated better in green light (low photon flux and red : far-red ratio, simulating conditions in the canopy) than in white light. 3 Optimum nitrate concentration differed between seed types but, for all, germination was reduced at the highest concentration used. 4 The effects of cold stratification and its interaction with light and nitrogen effects were also studied. Strong interactions between stratification and light were found in all seed types but other interactions were less frequent. 5 Three size classes of type C fruit showed similar final germination percentages but large seeds germinated more slowly. 6 The effect of seed age was highly significant: over a 3 year period, the germinability of dormant seeds (types A + B) increased while that of non-dormant seeds (type C) fell. 7 The salt concentration in bracteoles of freshly ripened fruits was too low to mediate an inhibitory effect on germination. Moreover, the first autumn rain would be sufficient to remove all the salt from bracteoles. 8 Differences between fruit types in depth of dormancy, and in response to the quality of light and to nitrate concentration in the soil, allows A . sagittata to respond to the spatial and temporal variation in environmental conditions encountered by this annual of disturbed habitats.
1 Atriplex sagittata , an arly succesional, annual species of disturbed habitats in Central Europ... more 1 Atriplex sagittata , an arly succesional, annual species of disturbed habitats in Central Europe, produces three types of fruits. We studied the differences in dispersal between the fruit types in order to investigate their ecological roles. 2 The typical positive relationship between dispersal ability and germinability is not found in this species. Type A (ebracteate) fruits produced deeply dormant seeds and had the lowest dispersal potential, but of the two fruits with bracts, type B, with dormant seeds, was better dispersed by both water and wind than type C, which produces non-dormant seeds. 3 Wind, temperature and precipitation have significant effects on fruit release but their effects differ between fruit types. The release of fruit types with bracts was positively correlated with wind whereas all fruit types tended to be negatively correlated with precipitation and temperature range. 4 Type C fruit, which contains non-dormant seed, are absent from the soil in summer and have a Type II transient seed bank. Type A and B fruits, containing dormant seeds, form a persistent seed bank. 5 Heterocarpy, where fruit types show distinct ecological behaviour, enables colonizing species such as A. sagittata to survive both major disturbance ( by ensuring that some seeds persist) and unfavourable conditions (by spreading germination over a long period). 6 In A. sagittata , seed dynamics can be explained by the germination behaviour of seeds produced by the three types of fruit. All fruit types mature in autumn, but few of Type A fall from the mother plant until spring, when germination is probably inhibited because of insufficient stratification. Type C fruit, however, show peak dispersal in winter and the majority of these non-dormant seeds are able to germinate as soon as conditions become more suitable.
The heterocarpic species Atriplex tatarica produces two types of seeds. In this study, how basic ... more The heterocarpic species Atriplex tatarica produces two types of seeds. In this study, how basic population genetic parameters correlate with seed germinability under various experimental conditions was tested.
Flora - Morphology, Distribution, Functional Ecology of Plants, 2012
ABSTRACT For our study of the Chenopodium album aggregate, we selected those species of Euroasiat... more ABSTRACT For our study of the Chenopodium album aggregate, we selected those species of Euroasiatic origin that represent the diploid–polyploid complex in Central Europe: C. album (6x), C. ficifolium (2x), C. opulifolium (6x), C. striatiforme (4x), C. strictum (4x) and C. suecicum (2x). We especially focused on (a) the origin of polyploid species and (b) the frequency of hybridization between species with different ploidy levels. We did not find any direct evidence of the existence of hybrids between two species with different ploidy levels within the C. album group. The sample/standard ratio of tetraploid and hexaploid species does not equal multiples of that of diploid species, which suggests that (i) tetraploids are not diploid autopolyploids and that (ii) hexaploids have not evolved from diploid species alone. Moreover, we have not found any hybrid plant either in the field or even in the offspring resulting from our experimental crosses. In view of these results, we adhere to the opinion that Chenopodium species do not hybridize freely across ploidy levels. Our analysis of DNA amounts, however, suggests that C. album is an allopolyploid that has arisen by hybridization between a diploid and a tetraploid species the identity of which is unknown.
Flora - Morphology, Distribution, Functional Ecology of Plants, 2012
The ability of a species to adapt to sub-optimal conditions at the margin of its distribution ran... more The ability of a species to adapt to sub-optimal conditions at the margin of its distribution range and to cope with environmental stress is considered to be important for its successful geographic expansion. To ascertain the roles of phenotypic differentiation and plasticity in the expansion of the annual Atriplex tatarica, we compared plants from populations found in Marginal and Central areas of the species' range. We grew these plants under marginal climatic conditions in pots with different types of substrate. We assessed the population genetic structure at five putatively neutral allozyme loci to evaluate whether there was any evidence of reduced genetic diversity in Marginal populations compared to Central ones. We used the Q ST vs. F ST approach (while F ST gives a standardised measure of the genetic differentiation among populations for a genetic locus, Q ST measures the amount of genetic variance among populations relative to the total genetic variance) to ascertain the roles of adaptive vs. non-adaptive processes on phenotypic differentiation. Plants native to the Marginal area of the species' range flowered earlier and had a lower shoot mass and a higher reproductive allocation than plants native to the Central part of the species' range. The Marginal populations of Atriplex tatarica showed lower genetic diversity at allozyme loci and higher phenotypic differentiation than the Central populations. We recorded similar plastic responses to substrates in plants native to both regions. Our results indicate that Marginal populations of expanding A. tatarica maintain the ability to adapt locally and to elicit a plastic response to environmental stress, despite loss of genetic diversity.
Abstract. The genus,Reynoutria is represented,by four taxa in the Czech Republic – R. japonica va... more Abstract. The genus,Reynoutria is represented,by four taxa in the Czech Republic – R. japonica var. japonica and compacta, R. sachalinensis and R. · bohemica. Using isoenzyme analysis, we determined the degree of genotype,variability in all taxa and compared,clones of R. japonica var. japonica from the Czech Republic with those from Great Britain. While the rarely occurring tetraploid variety R. japonica
Atriplex tatarica is a heterocarpic species of disturbed habitats. Seeds of Atriplex tatarica do ... more Atriplex tatarica is a heterocarpic species of disturbed habitats. Seeds of Atriplex tatarica do not germinate immediately after shedding, but may remain in a dormant but viable state indefinitely. We investigated whether there were genetic and fitness differences between plants derived from seeds of the different fruit types germinated in different temperatures and salinities. Seeds that germinated in optimal and
Floras of several villages in the Bohemian,Karst Protected Area (Czech Republic) are compared ove... more Floras of several villages in the Bohemian,Karst Protected Area (Czech Republic) are compared over the time period of almost fifteen years and the trends in the performance,of alien plant species are described. Floristic list from,1980-81 was,compared,with the recent situation in 1995. Alien species were divided into archaeophytes, consisting of species introduced before 1500, and neophytes, introduced after 1500. From
Genetic admixture is supposed to be an important trigger of species expansions because it can cre... more Genetic admixture is supposed to be an important trigger of species expansions because it can create the potential for selection of genotypes suitable for new climatic conditions. Up until now, however, no continent-wide population genetic study has performed a detailed reconstruction of admixture events during natural species expansions. To fill this gap, we analysed the postglacial history of Alnus glutinosa, a keystone species of European swamp habitats, across its entire distribution range using two molecular markers, cpDNA and nuclear microsatellites. CpDNA revealed multiple southern refugia located in the Iberian, Apennine, Balkan and Anatolian Peninsulas, Corsica and North Africa. Analysis of microsatellites variation revealed three main directions of postglacial expansion: 1) from the northern part of the Iberian Peninsula to Western and Central Europe and subsequently to the British Isles, 2) from the Apennine Peninsula to the Alps, and 3) from the eastern part of the Balka...
Vegetative regeneration of individual genotypes of Asian Reynoutria taxa, which are invasive in t... more Vegetative regeneration of individual genotypes of Asian Reynoutria taxa, which are invasive in the Czech Republic, was studied in R. sachalinensis (five genotypes), R. japonica (a single genotype present in the country), and their hybrid R. 3bohemica (nine genotypes). Identity of genotypes was confirmed by isozyme analysis. Ten rhizome segments of each genotype were planted in a randomized block design.
We investigated to what extent the soil seed bank differed genetically and spatially in compariso... more We investigated to what extent the soil seed bank differed genetically and spatially in comparison to three consecutive life history stages (seedlings, mature plants, and fruiting plants) in a natural population of Atriplex tatarica . Representatives of particular life history stages from twenty subunits within a large population were randomly collected and subjected to allozyme analysis. Comparison of population polymorphism among various life history stages showed significant differences in observed heterozygosity ( H O ) and F statistics ( F IS and F ST ), but nonsignificant ones in the cases of number of alleles per polymorphic locus ( A ) and gene diversity ( H S ). These results indicate an increasing number of heterozygotes, a decreasing level of inbreeding and an increase of the partitioning genetic diversity among populations with increasing population age. Spatial autocorrelation was used to calculate f , the average co-ancestry coefficient between individuals within distance intervals of two meters along a 39 m long transect. Significant positive fine scale genetic structure was detected in mature and fruiting plants but not in soil seeds and seedlings stages. The results of the presented study on A. tatarica indicated that significant differences exist in genetic differentiation, differentiation in allele frequencies and spatial autocorrelation among early (soil seeds and seedlings) and late (mature and fruiting plants) life history stages but not within early and late ones. This pattern suggests that, rather than storing genetic variability in the soil or germination and establishment success, self-thinning might be the major microselective force in populations of A. tatarica .
Temporal patterns of immigration to the country were analysed using 668 alien species in the flor... more Temporal patterns of immigration to the country were analysed using 668 alien species in the flora of the Czech Republic for which the dates of the first record were available (64.8% of the total number of 1031 socalled neophytes, i.e. aliens introduced after the year 1500). After a period of initial slow increase lasting to the 1840s, the accumulation of neophytes over time could be best fitted by a linear model that explained 97% of the variance. The intensity of floristic research, which varied between periods, did not significantly affect the overall increase in the number of aliens. The effect of species traits on the year of introduction was evaluated, with continent of origin, introduction type (deliberate or accidental), life history, Grime's life strategy, onset of flowering, mode of dispersal and propagule size as explanatory variables. Species of European origin and CSR strategists arrived earlier than those with other origins and strategies. Deliberately introduced species appeared earlier than accidental arrivals, and those cultivated for utilitary reasons on average arrived earlier than ornamentals. Species capable of early flowering were remarkably more prevalent among early newcomers. A separate analysis of accidentally introduced American species also identified life history as a significant predictor of immigration time, with annuals being introduced earlier than biennials and perennials. The data contribute to an understanding of a crucial stage of the invasion process that has received little attention in the literature. The model "early alien" to Central Europe is a European species with a CSR strategy deliberately brought for cultivation as a utilitary plant. Once it escaped from cultivation, its establishment in the wild was favoured by its ability to flower early and, therefore, complete the life cycle.
The genus Reynoutria is represented by four taxa in the Czech Republic: Reynoutria japonica var. ... more The genus Reynoutria is represented by four taxa in the Czech Republic: Reynoutria japonica var. japonica, R. japonica var. compacta, R. sachalinensis and R. Qbohemica. By using¯ow cytometry, cytological variability within the genus is described based on 257 Reynoutria samples. The varieties of R. japonica are cytologically uniform, var. japonica is exclusively octoploid (2n = 8x = 88) and var. compacta occurs only as a tetraploid (2n = 4x = 44), but R. sachalinensis and R. Qbohemica exhibit some variation in chromosome numbers. Reynoutria sachalinensis is predominantly tetraploid (2n = 4 x = 44), but also occurs occasionally as hexaploid and octoploid cytotypes. The most common ploidy level in R. Qbohemica is hexaploid (2n = 6x = 66), but tetraploid and octoploid clones were also found. The four taxa occurring in the Czech Republic are described brie¯y and the possible origins of the cytotypes discussed.
Background and Aims Genetic variability was estimated for Atriplex tatarica from 25 populations i... more Background and Aims Genetic variability was estimated for Atriplex tatarica from 25 populations in the Czech Republic. Since its north-western range margin is in central Europe, a relationship between marginality and low within-population genetic diversity was tested in accordance with the Central-Marginal Model.
Background/Aims: Recently, new palaeoecological records supported by molecular analyses and palae... more Background/Aims: Recently, new palaeoecological records supported by molecular analyses and palaeodistributional modelling have provided more comprehensive insights into plant behaviour during the last Quaternary cycle. We reviewed the migration history of species of subgenus Alnus during the last 50,000 years in Europe with a focus on (1) a general revision of Alnus history since the Last Glacial Maximum (LGM), (2) evidence of northern refugia of Alnus populations during the LGM and (3) the specific history of Alnus in particular European regions.
We attempted to confirm that seed banks can be viewed as an important genetic reservoir by testin... more We attempted to confirm that seed banks can be viewed as an important genetic reservoir by testing the hypothesis that standing (aboveground) plants represent a nonrandom sample of the seed bank. We sampled multilocus allozyme genotypes from three species with different life history strategies: Amaranthus retroflexus, Carduus acanthoides, Pastinaca sativa. In four populations of each species we analysed the extent to which allele and genotype frequencies vary in consecutive life history stages including the summer seed bank, which has been overlooked up to now. We compared the winter seed bank (i.e., seeds collected before the spring germination peak), seedlings, rosettes, the summer seed bank (i.e., seeds collected after the spring germination peak) and fruiting plants. We found that: (1) All three species partitioned most of their genetic diversity within life history stages and less among stages within populations and among populations. (2) All genetic diversity parameters, except for allele frequencies, were similar among all life history stages across all populations in different species. (3) There were differences in allele frequencies among life history stages at all localities in Amaranthus retroflexus and at three localities in both Carduus acanthoides and Pastinaca sativa. (4) Allele frequencies did not differ between the winter and summer seed bank in most Carduus acanthoides and Pastinaca sativa populations, but there was a marked difference in Amaranthus retroflexus. In conclusion, we have shown that the summer seed bank is not genetically depleted by spring germination and that a majority of genetic diversity remains in the soil through summer. We suggest that seed banks in the species investigated play an important role by maintaining genetic diversity sufficient for recovery rather than by accumulating new genetic diversity at each locality.
The genus Reynoutria is represented by four taxa in the Czech Republic -R. japonica var. japonica... more The genus Reynoutria is represented by four taxa in the Czech Republic -R. japonica var. japonica and compacta, R. sachalinensis and R. · bohemica. Using isoenzyme analysis, we determined the degree of genotype variability in all taxa and compared clones of R. japonica var. japonica from the Czech Republic with those from Great Britain. While the rarely occurring tetraploid variety R. japonica var. compacta possesses low variability, the octoploid female clone of R. japonica var. japonica is genetically uniform in the 93 clones sampled and belongs to the same genotype that is present in the whole Europe. R. japonica var. japonica can be fertilized by the pollen of tetraploid R. sachalinensis and a hexaploid hybrid R. · bohemica is produced. In R. sachalinensis, 16 genotypes were found in the 50 clones sampled. R. · bohemica is genetically the most diverse taxon in the study area, with 33 genotypes recorded among 88 clones sampled.
Perspectives in Plant Ecology, Evolution and Systematics, 2008
Atriplex tatarica is a heterocarpic annual native to a wide area of Middle and western Central As... more Atriplex tatarica is a heterocarpic annual native to a wide area of Middle and western Central Asia, Asia Minor, North Africa, and Eastern Europe. It is an early successional species of disturbed habitats, in Central Europe mostly occupying road margins and waste places. This paper deals with taxonomic status, morphology, distribution, ecology, and population biology of this species with special emphasis on its population genetics.
Atriplex sagittata is a heterocarpic species producing three types of fruits which differ in morp... more Atriplex sagittata is a heterocarpic species producing three types of fruits which differ in morphology and ecological properties. This study focused on variation in biomass allocation into particular fruit types under different density and fertilization levels. The reduction in total weight under stressful conditions was accompanied by a reduction of reproductive structures in terms of both total fruit production and
Questions: 1. How does species richness of recipient communities affect Reynoutria invasion? 2. H... more Questions: 1. How does species richness of recipient communities affect Reynoutria invasion? 2. How does Reynoutria invasion change host community structure? 3. Are there any differences in habitat preferences among three closely related Reynoutria taxa? 4. How does the genetic structure of Reynoutria populations change along the course of a river? Location: River Jizera basin, north Bohemia, Czech Republic. Methods: Nine 0.25 km 2 plots were chosen along the river. Within each plot all main habitat types were determined and sampled using the Braun-Blanquet scale to determine the invasibility of various communities. The patches invaded by Reynoutria taxa and surrounding Reynoutria-free vegetation in the same habitat type were sampled as relevé pairs to compare the composition of invaded and non-invaded vegetation. In addition, to characterize the genetic structure of Reynoutria populations along the river, 30 samples from different clones were collected. Results and conclusions: 1. The species richness of communities has no influence on the success of Reynoutria invasion in the area studied. The combination of environmental conditions and propagule spread is more important to the invasion success than the number of species in the host community. 2. Reynoutria invasion greatly reduces species diversity. 3. R. japonica invaded more habitat types than R. sachalinensis and R. × bohemica. The hybrid R. × bohemica outcompetes the parental taxa at sites where both taxa co-occur. 4. Isozyme analysis revealed phenotype variability in the hybrid in contrast to the parental taxa. Different hybrid phenotypes are distributed randomly on the middle and lower reaches of the River Jizera; one of them dominates and the other three occur occasionally. This pattern supports the hypothesis that sexual reproduction occasionally occurs within Reynoutria taxa.
1 We investigated the effect of light quality, nitrogen supply, fruit size and age on germination... more 1 We investigated the effect of light quality, nitrogen supply, fruit size and age on germination of the three types of fruit produced by Atriplex sagittata . 2 Regardless of fruit type, seed germination was significantly reduced in the dark. Light quality had no significant effect on germination of seeds from fruit types A and B, both of which are dormant, but seeds from fruit type C, which are non-dormant, germinated better in green light (low photon flux and red : far-red ratio, simulating conditions in the canopy) than in white light. 3 Optimum nitrate concentration differed between seed types but, for all, germination was reduced at the highest concentration used. 4 The effects of cold stratification and its interaction with light and nitrogen effects were also studied. Strong interactions between stratification and light were found in all seed types but other interactions were less frequent. 5 Three size classes of type C fruit showed similar final germination percentages but large seeds germinated more slowly. 6 The effect of seed age was highly significant: over a 3 year period, the germinability of dormant seeds (types A + B) increased while that of non-dormant seeds (type C) fell. 7 The salt concentration in bracteoles of freshly ripened fruits was too low to mediate an inhibitory effect on germination. Moreover, the first autumn rain would be sufficient to remove all the salt from bracteoles. 8 Differences between fruit types in depth of dormancy, and in response to the quality of light and to nitrate concentration in the soil, allows A . sagittata to respond to the spatial and temporal variation in environmental conditions encountered by this annual of disturbed habitats.
1 Atriplex sagittata , an arly succesional, annual species of disturbed habitats in Central Europ... more 1 Atriplex sagittata , an arly succesional, annual species of disturbed habitats in Central Europe, produces three types of fruits. We studied the differences in dispersal between the fruit types in order to investigate their ecological roles. 2 The typical positive relationship between dispersal ability and germinability is not found in this species. Type A (ebracteate) fruits produced deeply dormant seeds and had the lowest dispersal potential, but of the two fruits with bracts, type B, with dormant seeds, was better dispersed by both water and wind than type C, which produces non-dormant seeds. 3 Wind, temperature and precipitation have significant effects on fruit release but their effects differ between fruit types. The release of fruit types with bracts was positively correlated with wind whereas all fruit types tended to be negatively correlated with precipitation and temperature range. 4 Type C fruit, which contains non-dormant seed, are absent from the soil in summer and have a Type II transient seed bank. Type A and B fruits, containing dormant seeds, form a persistent seed bank. 5 Heterocarpy, where fruit types show distinct ecological behaviour, enables colonizing species such as A. sagittata to survive both major disturbance ( by ensuring that some seeds persist) and unfavourable conditions (by spreading germination over a long period). 6 In A. sagittata , seed dynamics can be explained by the germination behaviour of seeds produced by the three types of fruit. All fruit types mature in autumn, but few of Type A fall from the mother plant until spring, when germination is probably inhibited because of insufficient stratification. Type C fruit, however, show peak dispersal in winter and the majority of these non-dormant seeds are able to germinate as soon as conditions become more suitable.
The heterocarpic species Atriplex tatarica produces two types of seeds. In this study, how basic ... more The heterocarpic species Atriplex tatarica produces two types of seeds. In this study, how basic population genetic parameters correlate with seed germinability under various experimental conditions was tested.
Flora - Morphology, Distribution, Functional Ecology of Plants, 2012
ABSTRACT For our study of the Chenopodium album aggregate, we selected those species of Euroasiat... more ABSTRACT For our study of the Chenopodium album aggregate, we selected those species of Euroasiatic origin that represent the diploid–polyploid complex in Central Europe: C. album (6x), C. ficifolium (2x), C. opulifolium (6x), C. striatiforme (4x), C. strictum (4x) and C. suecicum (2x). We especially focused on (a) the origin of polyploid species and (b) the frequency of hybridization between species with different ploidy levels. We did not find any direct evidence of the existence of hybrids between two species with different ploidy levels within the C. album group. The sample/standard ratio of tetraploid and hexaploid species does not equal multiples of that of diploid species, which suggests that (i) tetraploids are not diploid autopolyploids and that (ii) hexaploids have not evolved from diploid species alone. Moreover, we have not found any hybrid plant either in the field or even in the offspring resulting from our experimental crosses. In view of these results, we adhere to the opinion that Chenopodium species do not hybridize freely across ploidy levels. Our analysis of DNA amounts, however, suggests that C. album is an allopolyploid that has arisen by hybridization between a diploid and a tetraploid species the identity of which is unknown.
Flora - Morphology, Distribution, Functional Ecology of Plants, 2012
The ability of a species to adapt to sub-optimal conditions at the margin of its distribution ran... more The ability of a species to adapt to sub-optimal conditions at the margin of its distribution range and to cope with environmental stress is considered to be important for its successful geographic expansion. To ascertain the roles of phenotypic differentiation and plasticity in the expansion of the annual Atriplex tatarica, we compared plants from populations found in Marginal and Central areas of the species' range. We grew these plants under marginal climatic conditions in pots with different types of substrate. We assessed the population genetic structure at five putatively neutral allozyme loci to evaluate whether there was any evidence of reduced genetic diversity in Marginal populations compared to Central ones. We used the Q ST vs. F ST approach (while F ST gives a standardised measure of the genetic differentiation among populations for a genetic locus, Q ST measures the amount of genetic variance among populations relative to the total genetic variance) to ascertain the roles of adaptive vs. non-adaptive processes on phenotypic differentiation. Plants native to the Marginal area of the species' range flowered earlier and had a lower shoot mass and a higher reproductive allocation than plants native to the Central part of the species' range. The Marginal populations of Atriplex tatarica showed lower genetic diversity at allozyme loci and higher phenotypic differentiation than the Central populations. We recorded similar plastic responses to substrates in plants native to both regions. Our results indicate that Marginal populations of expanding A. tatarica maintain the ability to adapt locally and to elicit a plastic response to environmental stress, despite loss of genetic diversity.
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Papers by Bohumil Mandák