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Heinz Mullerscharer - One of the best experts on this subject based on the ideXlab platform.
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the population genetics of the fundamental cytotype shift in invasive centaurea stoebe s l genetic diversity genetic differentiation and small scale genetic structure differ between cytotypes but not between ranges
Biological Invasions, 2016Co-Authors: Walter Durka, Christoph Rosche, Isabell Hensen, Heinz Mullerscharer, Patrik Mraz, Matthias Hartmann, Susanne LachmuthAbstract:Polyploids are overrepresented in invasive species. Yet, the role of genetic diversity and drift in colonization success of polyploids remains unclear. Here, we investigate genetic diversity, genetic differentiation and small-scale genetic structure in our model system, the three geo-cytotypes of Centaurea stoebe: monocarpic diploids and Polycarpic (allo)tetraploids coexist in the native range (Eurasia), but only tetraploids are reported from the invasive range (North America). For each geo-cytotype, we investigated 18–20 populations varying in size and habitat type (natural vs. ruderal). Population genetic analyses were conducted at eight microsatellite loci. Compared to diploids, tetraploids revealed higher genetic diversity and lower genetic differentiation, whereas both were comparable in tetraploids between both ranges. Within spatial distances of a few meters, diploid individuals were more strongly related to one another than tetraploids. In addition, expected heterozygosity in diploids increased with population size and was higher in natural than in ruderal habitats. However, neither relationship was found for tetraploids. The higher genetic diversity of tetraploid C. stoebe may have enhanced its colonization abilities, if genetic diversity is correlated with fitness and adaptive capabilities. Furthermore, the inheritance of a duplicated chromosome set as well as longevity and frequent gene flow reduces drift in tetraploids. This counteracts genetic depletion during initial introductions and in subsequent phases of small or fluctuating population sizes in ruderal habitats. Our findings advocate the importance of studying colonization genetic processes to gain a more mechanistic understanding of the role of polyploidy in invasion dynamics.
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cytotype differences modulate eco geographical differentiation in the widespread plant centaurea stoebe
Ecology, 2013Co-Authors: Min A Hahn, Heinz MullerscharerAbstract:The evolution of optimal life history strategies is central for the fitness of organisms in a given environment. Besides divergent selection, other factors may determine regional patterns of differentiation and contribute to life history evolution. In a common-garden environment over three years, we examined life history differentiation across different eco-geographical regions and effects of a specialist root-insect herbivore in the widespread European plant Centaurea stoebe, spotted knapweed. This plant occurs as two cytotypes with contrasting life cycles: monocarpic diploids and Polycarpic tetraploids. In addition, the tetraploid cytotype has more recently become invasive in North America. We found significant regional differentiation in traits related to the timing of reproduction and reproductive allocation, but contrasting patterns in diploids and tetraploids. In diploids the degree of regional differentiation was higher compared to native tetraploids, and in the latter compared to invasive tetraplo...
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cytotype differences modulate eco geographical differentiation in the widespread plant centaurea stoebe
Ecology, 2013Co-Authors: Min A Hahn, Heinz MullerscharerAbstract:The evolution of optimal life history strategies is central for the fitness of organisms in a given environment. Besides divergent selection, other factors may determine regional patterns of differentiation and contribute to life history evolution. In a common-garden environment over three years, we examined life history differentiation across different eco-geographical regions and effects of a specialist root-insect herbivore in the widespread European plant Centaurea stoebe, spotted knapweed. This plant occurs as two cytotypes with contrasting life cycles: monocarpic diploids and Polycarpic tetraploids. In addition, the tetraploid cytotype has more recently become invasive in North America. We found significant regional differentiation in traits related to the timing of reproduction and reproductive allocation, but contrasting patterns in diploids and tetraploids. In diploids the degree of regional differentiation was higher compared to native tetraploids, and in the latter compared to invasive tetraplo...
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anthropogenic disturbance as a driver of microspatial and microhabitat segregation of cytotypes of centaurea stoebe and cytotype interactions in secondary contact zones
Annals of Botany, 2012Co-Authors: Patrik Mraz, Gillianne Bowmann, Alexandre Farkas, Barbora Singliarova, Rudolf P Rohr, Stanislav Španiel, Andreas Keller, Olivier Broennimann, Heinz MullerscharerAbstract:† Background and Aims In a mixed-ploidy population, strong frequency-dependent mating will lead to the elimination of the less common cytotype, unless prezygotic barriers enhance assortative mating. However, such barriers favouring cytotype coexistence have only rarely been explored. Here, an assessment is made of the mechanisms involved in formation of mixed-ploidy populations and coexistence of diploid plants and their closely related allotetraploid derivates from the Centaurea stoebe complex (Asteraceae). † Methods An investigation was made of microspatial and microhabitat distribution, life-history and fitness traits, flowering phenology, genetic relatedness of cytotypes and intercytotype gene flow (cpDNA and microsatellites) in six mixed-ploidy populations in Central Europe. † Key Results Diploids and tetraploids were genetically differentiated, thus corroborating the secondary origin of contact zones. The cytotypes were spatially segregated at all sites studied, with tetraploids colonizing preferentially drier and open microhabitats created by human-induced disturbances. Conversely, they were rare in more natural microsites and microsites with denser vegetation despite their superior persistence ability ( Polycarpic life cycle). The seed set of tetraploid plants was strongly influenced by their frequency in mixed-ploidy populations. Triploid hybrids originated from bidirectional hybridizations were extremely rare and almost completely sterile, indicating a strong postzygotic barrier between cytotypes. † Conclusions The findings suggest that tetraploids are later immigrants into already established diploid populations and that anthropogenic activities creating open niches favouring propagule introductions were the major factor shaping the non-random distribution and habitat segregation of cytotypes at fine spatial scale. Establishment and spread of tetraploids was further facilitated by their superior persistence through the perennial life cycle. The results highlight the importance of non-adaptive spatio-temporal processes in explaining microhabitat and microspatial segregation of cytotypes.
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evidence for a combination of pre adapted traits and rapid adaptive change in the invasive plant centaurea stoebe
Journal of Ecology, 2010Co-Authors: Martin L Henery, Urs A Treier, Urs Schaffner, Patrik Mraz, Gillianne Bowman, Emilie Gexfabry, Heinz MullerscharerAbstract:Summary 1. Introduced plants have the potential to rapidly evolve traits of ecological importance that may add to their innate potential to become invasive. During invasions, selection may favour genotypes that are already pre-adapted to conditions in the new habitat and, over time, alter the characteristics of subsequent generations. 2. Spotted knapweed (Centaurea stoebe) occurs in two predominantly spatially separated cytotypes in its native range (Europe–Western Asia), but currently only the tetraploid form has been confirmed in the introduced range (North America), where it is invasive. We used several common garden experiments to examine, across multiple populations, whether tetraploids and diploids from the native range differ in life cycle, leaf traits and reproductive capacity and if such differences would explain the predominance of tetraploids and their advance into new habitats in the introduced range. We also compared the same traits in tetraploids from the native and introduced range to determine whether any rapid adaptive changes had occurred since introduction that may have enhanced invasive potential of the species in North America. 3. We found tetraploids had lower specific leaf area, less lamina dissection and fewer, narrower leaves than diploids. Diploids exhibited a monocarpic life cycle and produced few if any accessory rosettes. Diploids produced significantly more seeds per capitulum and had more capitula per plant than tetraploids. In contrast, the vast majority of European tetraploids continued to flower in both seasons by regenerating from multiple secondary rosettes, demonstrating a predominantly Polycarpic life cycle. 4. During early growth tetraploids from North America achieved greater biomass than both tetraploids and diploids from the native range but this did not manifest as larger above-ground biomass at maturity. In North American tetraploids there was also evidence of a shift towards a more strictly Polycarpic life cycle, less leaf dissection, greater carbon investment per leaf, and greater seed production per capitulum. 5. Synthesis. Our results suggest that the characteristics of tetraploid C. stoebe pre-adapted them (compared to diploid conspecifics) for spread and persistence of the species into habitats in North America characterized by a more continental climate. After the species’ introduction, small but potentially important shifts in tetraploid biology have occurred that may have contributed significantly to successful invasion.
Min A Hahn - One of the best experts on this subject based on the ideXlab platform.
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cytotype differences modulate eco geographical differentiation in the widespread plant centaurea stoebe
Ecology, 2013Co-Authors: Min A Hahn, Heinz MullerscharerAbstract:The evolution of optimal life history strategies is central for the fitness of organisms in a given environment. Besides divergent selection, other factors may determine regional patterns of differentiation and contribute to life history evolution. In a common-garden environment over three years, we examined life history differentiation across different eco-geographical regions and effects of a specialist root-insect herbivore in the widespread European plant Centaurea stoebe, spotted knapweed. This plant occurs as two cytotypes with contrasting life cycles: monocarpic diploids and Polycarpic tetraploids. In addition, the tetraploid cytotype has more recently become invasive in North America. We found significant regional differentiation in traits related to the timing of reproduction and reproductive allocation, but contrasting patterns in diploids and tetraploids. In diploids the degree of regional differentiation was higher compared to native tetraploids, and in the latter compared to invasive tetraplo...
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cytotype differences modulate eco geographical differentiation in the widespread plant centaurea stoebe
Ecology, 2013Co-Authors: Min A Hahn, Heinz MullerscharerAbstract:The evolution of optimal life history strategies is central for the fitness of organisms in a given environment. Besides divergent selection, other factors may determine regional patterns of differentiation and contribute to life history evolution. In a common-garden environment over three years, we examined life history differentiation across different eco-geographical regions and effects of a specialist root-insect herbivore in the widespread European plant Centaurea stoebe, spotted knapweed. This plant occurs as two cytotypes with contrasting life cycles: monocarpic diploids and Polycarpic tetraploids. In addition, the tetraploid cytotype has more recently become invasive in North America. We found significant regional differentiation in traits related to the timing of reproduction and reproductive allocation, but contrasting patterns in diploids and tetraploids. In diploids the degree of regional differentiation was higher compared to native tetraploids, and in the latter compared to invasive tetraplo...
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Increased population growth rate in invasive polyploid Centaurea stoebe in a common garden
Ecology Letters, 2012Co-Authors: Min A Hahn, Yvonne M. Buckley, Heinz Müller-schärerAbstract:Biological invasions are inherently demographic processes, but trait differences between native and introduced genotypes are rarely linked to population growth rates. Native European Centaurea stoebe occurs as two cytotypes with different life histories (monocarpic diploids, Polycarpic tetraploids); however, only tetraploids have been found in its introduced range in North America. In a common garden experiment using artificial populations, we compared the demographic performance of the three geo-cytotypes in the presence and absence of a specialist herbivore using periodic matrix models. We found no difference in population growth rate between the two European cytotypes and no significant effects of herbivory in all geo-cytotypes. However, there was a pronounced increase in population growth rate for North American compared with European tetraploids due to increased seed production and juvenile establishment. These results suggest that genetic drift or rapid evolution, rather than pre-adaptation through polyploidy may explain the invasion success of tetraploids.
Anna Traveset - One of the best experts on this subject based on the ideXlab platform.
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annual variability in seed production by woody plants and the masting concept reassessment of principles and relationship to pollination and seed dispersal
The American Naturalist, 1998Co-Authors: Carlos M Herrera, Pedro Jordano, Javier Guitian, Anna TravesetAbstract:ABSTRACT By analyzing 296 published and unpublished data sets describing annual variation in seed output by 144 species of woody plants, this article addresses the following questions. Do plant species naturally fall into distinct groups corresponding to masting and nonmasting habits? Do plant populations generally exhibit significant bimodality in annual seed output? Are there significant relationships between annual variability in seed production and pollination and seed dispersal modes, as predicted from economy of scale considerations? We failed to identify distinct groups of species with contrasting levels of annual variability in seed output but did find evidence that most Polycarpic woody plants seem to adhere to alternating supra‐annual schedules consisting of either high or low reproduction years. Seed production was weakly more variable among wind‐pollinated taxa than animal‐pollinated ones. Plants dispersed by mutualistic frugivores were less variable than those dispersed by either inanimate me...
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annual variability in seed production by woody plants and the masting concept reassessment of principles and relationship to pollination and seed dispersal
The American Naturalist, 1998Co-Authors: Carlos M Herrera, Pedro Jordano, Javier Guitian, Anna TravesetAbstract:By analyzing 296 published and unpublished data sets describing annual variation in seed output by 144 species of woody plants, this article addresses the following questions. Do plant species naturally fall into distinct groups corresponding to masting and nonmasting habits? Do plant populations generally exhibit significant bimodality in annual seed output? Are there significant relationships between annual variability in seed production and pollination and seed dispersal modes, as predicted from economy of scale considerations? We failed to identify distinct groups of species with contrasting levels of annual variability in seed output but did find evidence that most Polycarpic woody plants seem to adhere to alternating supra-annual schedules consisting of either high or low reproduction years. Seed production was weakly more variable among wind-pollinated taxa than animal-pollinated ones. Plants dispersed by mutualistic frugivores were less variable than those dispersed by either inanimate means or animals that predominantly behave as seed predators. We conclude that there are no objective reasons to perpetuate the concept of mast fruiting in the ecological literature as a shorthand to designate a distinct biological phenomenon. Associations between supra-annual variability in seed output and pollination and seed dispersal methods suggest the existence of important reproductive correlates that demand further investigation.
Maria C Albani - One of the best experts on this subject based on the ideXlab platform.
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pep1 regulates perennial flowering in arabis alpina
Nature, 2009Co-Authors: Renhou Wang, Sara Farrona, Coral Vincent, Anika Joecker, Heiko Schoof, Franziska Turck, Carlos Alonsoblanco, George Coupland, Maria C AlbaniAbstract:Annual plants complete their life cycle in one year and initiate flowering only once, whereas perennials live for many years and flower repeatedly. How perennials undergo repeated cycles of vegetative growth and flowering that are synchronized to the changing seasons has not been extensively studied. Flowering is best understood in annual Arabidopsis thaliana, but many closely related species, such as Arabis alpina, are perennials. We identified the A. alpina mutant perpetual flowering 1 (pep1), and showed that PEP1 contributes to three perennial traits. It limits the duration of flowering, facilitating a return to vegetative development, prevents some branches from undergoing the floral transition allowing Polycarpic growth habit, and confers a flowering response to winter temperatures that restricts flowering to spring. Here we show that PEP1 is the orthologue of the A. thaliana gene FLOWERING LOCUS C (FLC). The FLC transcription factor inhibits flowering until A. thaliana is exposed to winter temperatures, which trigger chromatin modifications that stably repress FLC transcription. In contrast, PEP1 is only transiently repressed by low temperatures, causing repeated seasonal cycles of repression and activation of PEP1 transcription that allow it to carry out functions characteristic of the cyclical life history of perennials. The patterns of chromatin modifications at FLC and PEP1 differ correlating with their distinct expression patterns. Thus we describe a critical mechanism by which flowering regulation differs between related perennial and annual species, and propose that differences in chromatin regulation contribute to this variation.
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the development of issr derived scar markers around the seasonal flowering locus sfl in fragaria vesca
Theoretical and Applied Genetics, 2004Co-Authors: Maria C Albani, Nicholas H Battey, M J WilkinsonAbstract:Fragaria vesca is a short-lived perennial with a seasonal-flowering habit. Seasonality of flowering is widespread in the Rosaceae and is also found in the majority of temperate Polycarpic perennials. Genetic analysis has shown that seasonal flowering is controlled by a single gene in F. vesca, the SEASONAL FLOWERING LOCUS (SFL). Here, we report progress towards the marker-assisted selection and positional cloning of SFL, in which three ISSR markers linked to SFL were converted to locus-specific sequence-characterized amplified region (SCAR1–SCAR3) markers to allow large-scale screening of mapping progenies. We believe this is the first study describing the development of SCAR markers from ISSR profiles. The work also provides useful insight into the nature of polymorphisms generated by the ISSR marker system. Our results indicate that the ISSR polymorphisms originally detected were probably caused by point mutations in the positions targeted by primer anchors (causing differential PCR failure), by indels within the amplicon (leading to variation in amplicon size) and by internal sequence differences (leading to variation in DNA folding and so in band mobility). The cause of the original ISSR polymorphism was important in the selection of appropriate strategies for SCAR-marker development. The SCAR markers produced were mapped using a F. vesca f. vesca × F. vesca f. semperflorens testcross population. Marker SCAR2 was inseparable from the SFL, whereas SCAR1 mapped 3.0 cM to the north of the gene and SCAR3 1.7 cM to its south.
Richard M Amasino - One of the best experts on this subject based on the ideXlab platform.
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Minireview Floral induction and monocarpic versus Polycarpic life histories
2014Co-Authors: Richard M AmasinoAbstract:has uncovered subtle differences in control of a gene that represses flowering which contributes to the Polycarpic habit. There are two extremes of life-history strategies in plants and animals- semelparity and iteroparity [1]. Semelparity is sometimes referred to as the ‘big-bang reproductive strategy ’ [2], as semelparous species devote most of their energy and resources to maximizing the number of offspring in a single cycle of reproduction, and die soon after reproducing. Semelparity may be advantageous when the prospects for long-term survival are low. Iteroparous species, in contrast, reproduce multiple times, a strategy that may be advantageous when prospects for long-term survival are good. In the plant kingdom, there are extreme examples of both strategies. At one end of the iteroparous spectrum ar
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floral induction and monocarpic versus Polycarpic life histories
Genome Biology, 2009Co-Authors: Richard M AmasinoAbstract:Recent work in Arabis alpina, a perennial relative of Arabidopsis, has uncovered subtle differences in control of a gene that represses flowering which contributes to the Polycarpic habit.