2,258 research outputs found
Heteroplasmy due to chloroplast paternal leakage: another insight into Phragmites haplotypic diversity in North America
No full textChloroplasts contain several copies of their DNA, and intra-individual haplotypic variation (heteroplasmy) is common in plants, but unexplored in the cosmopolitan genus Phragmites. The aims of this study were to assess if heteroplasmy due to paternal leakage of the chloroplast occurs in Phragmites and which new insights into the evolutionary history of Phragmitesaustralis in North America can be identified from the heteroplasmic variation. Eight non-native P. australis haplotypes occur in North America and can interbreed with P. australis ssp. americanus and P. australis var. berlandieri, creating opportunities for biparental inheritance of distinctive haplotypes. The polymorphism in the trnT-trnL sequence length revealed seventeen cases of heteroplasmy worldwide, in contact zones of distantly related haplotypes and in known hybrid populations, nine of which occurred in North America. In America, the cloned sequences, combined with nuclear markers, identified recombined haplotypes between native P. australis ssp. americanus and invasive P. australis haplotype M, and between the species P. mauritianus and P. australis, due to chloroplast paternal leakage. The occurrence of heteroplasmy and recombined haplotypes suggest a local origin for some of the rare non-native haplotypes occurring in North America, and plastid leakage events in the evolutionary histories of P. australis ssp. americanus and P. australis var. berlandieri
Rivisiting Phragmites australis variation in the Danube Delta with DNA molecular techniques
No full textThe value of repetitive sequences in chloroplast DNA for phylogeographic inference: A comment on Vachon & Freeland 2011
No full textIn a recent Technical Advance article, Vachon and Freeland (2011, Molecular Ecology Resources, 11, 279-285.) evaluate the utility of repetitive and non-repetitive variation in the chloroplast genome for phylogeographic inference, using variation in Phragmites australis as an example. While we agree that repetitive and nonrepetitive regions evolve at different rates and homoplasy can impact results, we disagree with the conclusion that repetitive regions are inappropriate for large-scale phylogeographic studies. Here we describe limitations to the study dataset and analysis, and provide an alternative viewpoint on the utility of repetitive regions for phylogeographic studies. © 2012 Blackwell Publishing Ltd
Why are tall-statured energy grasses of polyploid species complexes potentially invasive? A review of their genetic variation patterns and evolutionary plasticity
No full textPerennial tall-statured grasses are regarded as a sustainable source of renewable energy for their high yields of lignocellulosic biomass, low resource input, wide ecological tolerance and capacity for storing large amounts of atmospheric CO2 in their perennial underground rhizome systems. These same traits, that make such crops agronomically attractive and sustainable, make these species highly competitive and potentially invasive. Several perennial energy crop grasses are outbreeding species that belong to cosmopolitan polyploid species complexes, i.e. groups of interbreeding species with ploidy variation. The cultivation of such highly productive and genetically diverse crops can have unwanted consequences through the evolution of invasive species. The goal of this review is to provide the scientific community, including agronomists, breeders, users and nature managers, with an introduction to the genetic dynamics occurring within the polyploid species complexes of the emerging energy species Arundo donax, Miscanthus × giganteus, Panicum virgatum, Phalaris arundinacea and Phragmites australis, and the broad biogeographical extent of their gene flow impact. Such aspects are difficult to predict, and are not captured by invasion risk assessments and by the sustainability certifications of the bioenergy supply chain. The review integrates literature from the phylogenetic, cytology, population ecology and agronomic research and focuses on the evolutionary processes that shape invasiveness that can be activated post-introduction by the dispersal of pollen, seeds and plant fragments from the energy crops to the environment. Due to the high genetic diversity of the crops, the adverse effects that genetic drift and founder effect can have on the establishment of small populations are very unlikely. On the contrary the data collected suggests that the risk of fostering panmictic continental invasive populations is high. Agronomic measures, regulations and genetic improvements that can contain dispersal from crops are discussed, as well as urgent research needs
Phylogeography reveals a potential cryptic invasion in the Southern Hemisphere of Ceratophyllum demersum, New Zealand's worst invasive macrophyte
No full textCeratophyllum demersum (common hornwort) is presently considered the worst invasive submerged aquatic macrophyte in New Zealand. We explored the global phylogeographic pattern of the species, based on chloroplast and nuclear DNA, in order to identify the origin of the invasive populations in New Zealand and to clarify if there were multiple introductions. The phylogeographic study identified geographically differentiated gene pools in North America, tropical Asia, Australia, and South Africa, likely native to these regions, and a recent dispersal event of a Eurasian-related haplotype to North America, New Zealand, Australia, and South Africa. At least two different invasive genotypes of this Eurasian-related haplotype have been found in New Zealand. One genotype is closely related to genotypes in Australia and South Africa, while we could not trace the closest relatives of the other genotype within our C. demersum sample set. Contrasting spectra of genetic distances in New Zealand and in a region within the native range (Denmark), suggest that the invasive population was founded by vegetative reproduction, seen as low genetic distances among genotypes. We also discovered the introduction of the same Eurasian-related haplotype in Australia and South Africa and that a cryptic invasion may be occurring in these continents
Areas with Natural Constraints to Agriculture: Possibilities and Limitations for The Cultivation of Switchgrass (Panicum Virgatum L.) and Giant Reed (Arundo Donax L.) in Europe
No full textThe European Union is facing complex issues concerning the achievement of GHG reduction goals. CO2 emissions could be reduced by a rational allocation of perennial lignocellulosic crops on unsuitable land for agriculture. These crops would also potentially reverse the increasing trend of soil depletion and land abandonment in Europe. The Joint Research Centre (JRC) identified biophysical constraints aimed at defining and unifying the definition of marginal land across Europe, and evaluating agricultural opportunities in these areas. In this study we evaluate possibilities and limitations for the cultivation of two of the most promising perennial biofuel crops (giant reed and switchgrass) in Europe, in areas with natural constraints (ANC land), as identified by the JRC. Based on the literature, both giant reed and switchgrass appear suitable for ANC land. Only shallow rooting depth and waterlogging can limit the establishment and agricultural mechanization of these rhizomatous plant species. Field tests in ANC land are needed to assess the potential yields provided by lignocellulosic crops under such limiting conditions. These results are fundamental to stimulate farmers’ acreage expansion and the development of a supply chain. Further research in the impact of lignocellulosic crops on the evolution of ANC ecosystems and lignocellulosic species is also needed to ensure a sustainable use of ANC land
Phenotypic traits of phragmites australis clones are not related to ploidy level and distribution range
No full textBackground and aims: Phragmites australis is a wetland grass with high genetic variability, augmented by its cosmopolitan distribution, clonal growth form and large variation in chromosome numbers. Different ploidy levels and ecotypes differ in morphology and ecophysiological traits, and may possess different levels of phenotypic variation. The aim of this study was to quantify the natural variation in ecophysiological characteristics of P. Australis, and to explore whether differences in ecophysiological traits can be related to ploidy levels or to the geographic origin of the clones. Methodology: Fifteen clones of P. australis from Europe and Asia/Australia, representing five ploidy levels (4x, 6x, 8x, 10x and 12x), were grown in a common garden design for 119 days. Plant growth and light-saturated rate of photosynthesis (Pmax), stomatal conductance (gs), water use efficiency (WUE) and concentrations of photosynthetic pigments and mineral ions in the leaves were measured. Principal results: The growth of the plants and most ecophysiological parameters differed significantly between clones. The mean maximum shoot height varied from 0.9 to 1.86 m, Pmax from 9.7 to 27 μmol m-2 s-1, gs from 0.22 to 1.41 mol m-2s-1 and WUE from 13 to 47 μmol mol-1. The concentrations of chlorophylls did not vary significantly between clones, but the chlorophyll a/b ratio and the concentrations of total carotenoids did. The observed differences were not explained either by the ploidy level per se or by the geographic origin or phylogenetic relationships of the clones. Conclusions: Phylogeographic relationships in P. australis on a global scale do not mirror the environment where the adaptations have evolved, and high phenotypic variation among and within clones complicates comparative studies. Future studies aimed at explaining differences in plant behaviour between P. australis populations should be careful in the selection of target genotypes and/or populations, and should avoid generalizing their findings beyond the genotypes and/or populations studied. © The Authors 2012
Oral History Interview, Carla Trujillo (1504)
No full textIn this interview, Carla Trujillo discusses her roots, which include being born in New Mexico and growing up in Northern California. Carla received her M.S. and Ph.D. degrees in Educational Psychology from UW-Madison and became an established author. To learn more about this oral history, download & review the index first (or transcript if available). It will help determine which audio file(s) to download & listen to.Carla Trujillo was born to a working class family in New Mexico and grew up in Northern California. Her extended family and roots are New Mexican (Chicana). She received her B.S. degree in Human Development from UC Davis, and her M.S. and Ph.D. degrees in Educational Psychology from the University of Wisconsin, Madison. Her dissertation focused on assessing differential treatment of underrepresented students in college classrooms. She is the editor of Living Chicana Theory and Chicana Lesbians: The Girls Our Mothers Warned Us About (Third Woman Press), winner of a Lambda Book Award and the Out/Write Vanguard Award. Her first novel, What Night Brings (Curbstone Press 2003), won the Miguel Marmol prize focusing on human rights. What Night Brings also won the Paterson Fiction Prize, the Latino Literary Foundation Latino Book Award, Bronze Medal from Foreword Magazine, Honorable Mention for the Gustavus Meyers Books Award, and was a LAMBDA Book Award finalist. Carla has also written various articles on identity and higher education. Her latest novel, Faith and Fat Chances, was a finalist for the 2012 PEN Bellwether Prize for socially engaged fiction and is forthcoming from Curbstone/Northwestern University Press. Carla works as the Assistant Dean for Graduate Diversity Program at U.C. Berkeley and has focused some of her recent activities on improving the work and classroom climate using Interactive Theater. She has lectured in Ethnic Studies at U.C. Berkeley and Mills College, and in Women’s Studies at S.F. State University. She has also taught fiction for the Sandra Cisneros Macondo Writers Program and the Lambda Literary Foundation’s Emerging Writers Program
Writers Talk Featuring Carla Buckley, Sarah Gridley, Paula McLain
No full textFeaturing Paula McLain, author of the memoir Like Family: Growing Up in Other People's Houses; poet Sarah Gridley; and Carla Buckley, author of the novel The Things that Keep us Here.The media can be accessed here: http://streaming.osu.edu/knowledgebank/cstw11/New_Voices-Carla_Buckley_Sarah_Gridley_Paula_McLain.mp3Ohio State University. Center for the Study and Teaching of Writin
Salinity effects on germination, seedlings and full-grown plants of upland and lowland switchgrass cultivars
No full textSoil salinization is one of the major threats affecting crop production, in particular in the Mediterranean basin where over 1 Mha are salt-affected. Growing lignocellulosic crops, such as switchgrass (Panicum virgatum L.), in marginal saline soils could represent a valuable opportunity to mitigate land abandonment while producing feedstock for biofuels. However, little is still known about salt tolerance of upland and lowland switchgrass cultivars. This study addressed the morphological and physiological responses of Shawnee (upland) and Alamo (lowland) to a range of salinity levels from 0 to 14 dS m−1. Two consecutive experiments were carried out: one in petri dish to test the response to salinity at germination and early growth stages, the other in pot to evaluate the response to salinity until flowering stage (full-grown plants). Both upland and lowland cultivars were able to grow until “critical” salinity levels (14 dS m−1) but their tolerance differed depending on growth stage. Alamo showed a higher tolerance to salinity than Shawnee at very early growth stages (germination/emergence), presenting a germination rate more than double that of Shawnee (60 vs. 19%, main effect cultivar). Nevertheless, Shawnee resulted in a higher tolerance at a full-grown stage likely due to a more efficient salt exclusion capacity, as indicated by the higher residual soil electric conductivity at the end of the experiment detected in Shawnee pots. Final biomass production was anyhow considerably significantly higher in Alamo than Shawnee under any tested salinity level, which demonstrated the improved ability of lowland cultivar to produce biomass compared to Shawnee which otherwise might have invested resources into exclusion mechanisms
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