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| | 1. |
2010 Apr 13 |
Dominance of Epiphytic Filamentous Thiothrix spp. on an Aquatic Macrophyte in a Hydrothermal Vent Flume in Sedge Bay, Yellowstone Lake, Wyoming.
Konkol NR, Bruckner JC, Aguilar C, Lovalvo D, Maki JS
Microb Ecol. 2010 Apr 13; [Epub ahead of print]
Abstract
Sublacustrine hydrothermal vents, geysers, and fumaroles impart regions of Yellowstone Lake with distinctive chemical compositions that generate unique freshwater habitats and support diverse microbial life. Some microbial communities within Sedge Bay manifest themselves as accumulations of white-colored films on the surfaces of aquatic macrophytes located within the hydrothermal flow of vents. It was hypothesized that the white films were the product of microbial growth, particularly sulfur-oxidizing bacteria. An investigation of the relevant biological compounds in the vent waters was conducted. Microscopy, non-culture molecular techniques, and phylogenetic analysis were used to assay the bacterial diversity associated with the films. Microscopic analysis of the white films revealed the presence of long filaments (>200 mum) that contained sulfur granules. Filaments with these characteristics were not detected on the normal macrophyte samples. Nucleic acids were extracted from the surface of macrophyte coated with the white film (SB1, SB2) and from the surface of an uncoated macrophyte (SC). 16S ribosomal (rRNA) genes were amplified with the polymerase chain reaction (PCR) and cloned. Amplified ribosomal DNA restriction analysis (ARDRA) was used to examine 100 clones from each library and identify unique phylotypes. S(Chao1) and the Shannon Index, mathematical measures of richness and heterogeneity, were employed to assess the ARDRA pattern diversity of each sample. The SC community contained 50 unique phylotypes, predominantly cyanobacteria and proteobacteria, and was the most heterogeneous. SB1 and SB2 communities were less heterogeneous and dominated by Thiothrix. Dilution to extinction PCR conducted with specific primers indicated that the relative abundance of Thiothrix 16S rRNA gene copies in all three samples were similar. However, reduced sulfur compounds from the vent resulted in a more narrow habitat that supported the sulfur-oxidizing Thiothrix in the white film to the exclusion of cyanobacteria and other proteobacteria found on the normal macrophyte. The majority of 16S rRNA gene sequences obtained in this study displayed similarities </=98% to any known sequence in public data bases which suggests an abundance of new bacterial species in Sedge Bay.
[Pubmed: 20386899]
| | 2. |
2010 Jun 9 |
X-ray muCT imaging technique reveals corm microstructures of an arctic-boreal cotton-sedge, Eriophorum vaginatum.
Bogart SJ, Spiers G, Cholewa E
J Struct Biol. 2010 Jun 9; [Epub ahead of print]
Abstract
X-ray computed tomography (CT), a non-destructive imaging technique, has recently been effectively applied to botanical research. In this study an X-ray muCT technique was developed to allow for anatomical study of the overwintering corms of Eriophorum vaginatum, an ecologically important sedge species in arctic tussock-tundra and boreal peatlands. Using a GE Medical MS8X-130 X-ray muCT scanner, optimal imaging parameters included scanning isolated corms at 80kVp and 100muA with a 3500ms exposure time and an isotropic voxel size of 10mum. A Gaussian blur image filter with a blur radius (sigma) of 2 pixels was applied to the optimal dataset to improve visual detection and contrast of tissues while removing 99.2% of image noise. Using the developed X-ray muCT technique several undocumented anatomical characteristics of the corm were identified including the vascular connection between a parent corm and branching cormel and the 3D shape of sclereid clusters. The 3D structure of sclereid clusters was determined whereby the perimeter of their lance shape is greatly reinforced by sclereids with thicker secondary cell walls as compared to those of the interior of the cluster. The structure of sclereid clusters and their association with leaf traces suggests they may be stabilizing the corm-leaf connection to protect vascular tissues from physical damage. The proposed X-ray muCT technique is an excellent tool for determination of the 3D structure of E. vaginatum corms and may be used to detect alterations in tissue structure and chemistry in response to environmental change in this and other Cyperaceous species.
[Pubmed: 20541609]
| | 3. |
2010 Sep |
Favorable fragmentation: river reservoirs can impede downstream expansion of riparian weeds.
Rood SB, Braatne JH, Goater LA
Ecol Appl. 2010 Sep;20(6):1664-77.
Abstract
River valleys represent biologically rich corridors characterized by natural disturbances that create moist and barren sites suitable for colonization by native riparian plants, and also by weeds. Dams and reservoirs interrupt the longitudinal corridors and we hypothesized that this could restrict downstream weed expansion. To consider this "reservoir impediment" hypothesis we assessed the occurrences and abundances of weeds along a 315-km river valley corridor that commenced with an unimpounded reach of the Snake River and extended through Brownlee, Oxbow, and Hells Canyon reservoirs and dams, and downstream along the Snake River. Sampling along 206 belt transects with 3610 quadrats revealed 16 noxious and four invasive weed species. Ten weeds were upland plants, with Canada thistle (Cirsium arvense) restricted to the upstream reaches, where field morning glory (Convolvulus arvensis) was also more common. In contrast, St. John's wort (Hypericum perforatum) was more abundant below the dams, and medusahead wildrye (Taeniatherum caput-medusae) occurred primarily along the reservoirs. All seven riparian species were abundant in the upstream zones but sparse or absent below the dams. This pattern was observed for the facultative riparian species, poison hemlock (Conium maculatum) and perennial pepperweed (Lepidium latifolium), the obligate riparian, yellow nut sedge (Cyperus esculentus), the invasive perennial, reed canary grass (Phalaris arundinacea), and three invasive riparian trees, Russian olive (Elaeagnus angustifolia), false indigo (Amorpha fruticosa), and tamarisk (Tamarix spp.). The hydrophyte purple loosestrife (Lythrum salicaria) was also restricted to the upstream zone. These longitudinal patterns indicate that the reservoirs have impeded the downstream expansion of riparian weeds, and this may especially result from the repetitive draw-down and refilling of Brownlee Reservoir that imposes a lethal combination of drought and flood stress. The dams and reservoirs may also interrupt hydrochory, the downstream flow of seeds and clonal fragments. We thus conclude that with some operational patterns, dams and reservoirs can impede the downstream expansion of riparian weeds.
[Pubmed: 20945766]
| | 4. |
2011 Jan |
Assessing the recovery potential of alpine moss-sedge heath: Reciprocal transplants along a nitrogen deposition gradient.
Armitage HF, Britton AJ, Woodin SJ, van der Wal R
Environ. Pollut. 2011 Jan;159(1):140-7.
Abstract
The potential of alpine moss-sedge heath to recover from elevated nitrogen (N) deposition was assessed by transplanting Racomitrium lanuginosum shoots and vegetation turfs between 10 elevated N deposition sites (8.2-32.9 kg ha(-1) yr(-1)) and a low N deposition site, Ben Wyvis (7.2 kg ha(-1) yr(-1)). After two years, tissue N of Racomitrium shoots transplanted from higher N sites to Ben Wyvis only partially equilibrated to reduced N deposition whereas reciprocal transplants almost matched the tissue N of indigenous moss. Unexpectedly, moss shoot growth was stimulated at higher N deposition sites. However, moss depth and biomass increased in turfs transplanted to Ben Wyvis, apparently due to slower shoot turnover (suggested to result partly from decreased tissue C:N slowing decomposition), whilst abundance of vascular species declined. Racomitrium heath has the potential to recover from the impacts of N deposition; however, this is constrained by the persistence of enhanced moss tissue N contents.
[Pubmed: 20888678]
| | 5. |
2010 Nov 8 |
Long-term effects of elevated UV-B radiation on photosynthesis and ultrastructure of Eriophorum russeolum and Warnstorfia exannulata.
Haapala JK, Mörsky SK, Saarnio S, Suokanerva H, Kyrö E, Silvola J, Holopainen T
Sci Total Environ. 2010 Nov 8; [Epub ahead of print]
Abstract
The depletion of stratospheric ozone above the Arctic regions may increase the amount of UV-B radiation to which the northern ecosystems are exposed. In this paper, we examine the hypothesis that supplemental UV-B radiation may affect the growth rate and photosynthesis of boreal peatland plants and could thereby affect the carbon uptake of these ecosystems. In this study, we report the effects of 3-year exposure to elevated UV-B radiation (46% above ambient) on the photosynthetic performance and ultrastructure of a boreal sedge Eriophorum russeolum and a moss Warnstorfia exannulata. The experiment was conducted on a natural fen ecosystem at Sodankylä in northern Finland. The effects of UV-B radiation on the light response of E. russeolum CO(2) assimilation and the maximal photochemical efficiency of photosystem II in a dark-adapted state (F(v)/F(m)) were measured in the field. In addition, the effect of supplemental UV-B radiation on organelles of photosynthetic cells was studied by electron microscopy. The UV-B treatment had no effect on the CO(2) assimilation rate of either species, nor did it affect the structure of the cell organelles. On chlorophyll fluorescence, the UV-B exposure had only a temporary effect during the third exposure year. Our results suggested that in a natural ecosystem, even long-term exposure to reasonably elevated UV-B radiation levels does not affect the photosynthesis of peatland plants.
[Pubmed: 21062664]
| | 6. |
2010 Oct 05 |
Phenological Changes in the Concentration of Alkaloids of Carex brevicollis in an Alpine Rangeland.
Busqué J, Pedrosa MM, Cabellos B, Muzquiz M
J. Chem. Ecol. 2010 Nov;36(11):1244-54. Epub 2010 Oct 05.
Abstract
Carex brevicollis (Cyperaceae) is a plant of mesic grasslands in calcareous mountains of southern Europe. It contains two different β-carboline alkaloids, brevicolline and brevicarine, the first of which is thought to produce abortions in mammals. In the rangeland of Aliva, within the Picos de Europa massif in northern Spain, the abundance of Carex brevicollis has been linked with the occurrence of teratogenesis in early gestating cows grazing in early summer. The concentration of alkaloids was measured in the summers of 2007 and 2008, at intervals of 2 weeks, at different altitudes within the rangeland (1,350, 1,600, and 1,850 m) and from different parts of the sedge (leaves, reproductive stems, and inflorescences). Estimated growing degree days were related to the flowering phenology of Carex brevicollis and were used to analyse its relation with the concentration of alkaloids. Brevicarine concentration was higher in inflorescences and brevicolline in leaves. Although it also depended on the zone and year, the concentrations of both alkaloids were related one to another in leaves and inflorescences but not in stems. Both alkaloids decreased with growing degree days in the inflorescences and showed no response in leaves. Our findings suggest that brevicarine, not brevicolline, could be the teratogen in pregnant cattle in this region. This hypothesis is supported by the observed frequent consumption of inflorescences and scarce consumption of leaves of Carex brevicollis by grazing livestock, and also by the coincidence of the toxicity in early pregnant cows with the flowering time of the sedge.
[Pubmed: 20890795]
| | 7. |
2010 Oct 1 |
Selective microspore abortion correlated with aneuploidy: an indication of meiotic drive.
Furness CA, Rudall PJ
Sex Plant Reprod. 2010 Oct 1; [Epub ahead of print]
Abstract
Selective megaspore abortion (monomegaspory) probably arose once in seed plants and occurs routinely in more than 70% of angiosperm species, representing one of the key characters of a heterosporous life history. In contrast, selective microspore abortion leading to pollen dispersal as pseudomonads (here termed monomicrospory) apparently arose at least twice independently within angiosperms, though it occurs in a limited number of taxa. Remarkably, similar examples of monomicrospory occur in members of two distantly related angiosperm families: the sedge family (Cyperaceae) and the epacrid subfamily (Styphelioideae) of the eudicot family Ericaceae. In sedges, monomicrospory is derived directly from normal tetrads, whereas epacrid pseudomonads apparently evolved via an intermediate stage, in which variable sterility occurs in a single tetrad. Our comparison of these two examples of selective microspore abortion highlights a correlation with aneuploidy, indicating that non-random chromosome segregation caused by monomicrospory could drive chromosomal mutations to rapid fixation through meiotic drive.
[Pubmed: 20886239]
| | 8. |
2010 Aug 28 |
Methane flux dynamics during mire succession.
Leppälä M, Oksanen J, Tuittila ES
Oecologia. 2010 Aug 28; [Epub ahead of print]
Abstract
Vegetation, temperature and hydrology are major factors controlling wetland methane (CH(4)) dynamics. In order to test their importance, we measured CH(4) emissions and environmental characteristics over 2 years from five mires representing a successional sequence, ranging in age from 178 to 2,520 years. We hypothesized CH(4) emissions to be higher from the sedge-dominated fens than from the older bog stage. The more constant hydrological conditions at later successional stages as a consequence of the thicker peat layer appeared to result in lower temporal variation in CH(4) emissions. Accordingly, the other controls, temperature and vegetation, had an effect on CH(4) emissions only when the water table was sufficiently high. The seasonal variation in CH(4) emissions was controlled by temperature only at the oldest study site, which had the lowest variation in water table. Within-season variation in emissions related to plant phenology was highest at the fen stage, which was dominated by aerenchymatous plants with a strong seasonal pattern, namely sedges and forbs. In contrast to our hypothesis, CH(4) emissions increased with mire age towards the bog stage. However, the trend did not emerge during a rainy growing season, due to a rise in CH(4) emissions at the younger stages. The results may imply two different mechanisms during mire succession: while old mires are able to avoid the perturbation associated with variation in the water table and maintain their function as CH(4) emitters, young mires are exposed to perturbation but are able to recover their function.
[Pubmed: 20803033]
| | 9. |
2010 Aug |
Community and ecosystem effects of intraspecific genetic diversity in grassland microcosms of varying species diversity.
Fridley JD, Grime JP
Ecology. 2010 Aug;91(8):2272-83.
Abstract
Studies of whether plant community structure and ecosystem properties depend on the genetic diversity of component populations have been largely restricted to species monocultures and have involved levels of genetic differentiation that do not necessarily correspond to that exhibited by neighboring mature individuals in the field. We established experimental communities of varying intraspecific genetic diversity, using genotypes of eight species propagated from clonal material of individuals derived from a small (100-m2) limestone grassland community, and tested whether genetic diversity (one, four, and eight genotypes per species) influenced community composition and annual aboveground productivity across communities of one, four, and eight species. Eight-species communities were represented by common grass, sedge, and forb species, and four- and one-species communities were represented by four graminoids and the dominant grass Festuca ovina, respectively. After three years of community development, there was a marginal increase of species diversity with increased genetic diversity in four- and eight-species communities, and genetic diversity altered the performance of genotypes in monospecific communities of F. ovina. However, shifts in composition from genetic diversity were not sufficient to alter patterns of community productivity. Neighborhood models describing pairwise interactions between species indicated that genetic diversity decreased the intensity of competition between species in four-species mixtures, thereby promoting competitive equivalency and enhancing species equitability. In F. ovina monocultures, neighborhood models revealed both synergistic and antagonistic interactions between genotypes that were reduced in intensity on more stressful shallow soils. Although the dependence of F. ovina genotype performance on neighborhood genetic composition did not influence total productivity, such dependence was sufficient to uncouple genotype performance in genetic mixtures and monocultures. Our results point to an important connection between local genetic diversity and species diversity in this species-rich ecosystem but suggest that such community-level dependence on genetic diversity may not feedback to ecosystem productivity.
[Pubmed: 20836449]
| | 10. |
2010 Jul 1 |
Ecosystem response to elevated CO(2) levels limited by nitrogen-induced plant species shift.
Langley JA, Megonigal JP
Nature. 2010 Jul 1;466(7302):96-9.
Abstract
Terrestrial ecosystems gain carbon through photosynthesis and lose it mostly in the form of carbon dioxide (CO(2)). The extent to which the biosphere can act as a buffer against rising atmospheric CO(2) concentration in global climate change projections remains uncertain at the present stage. Biogeochemical theory predicts that soil nitrogen (N) scarcity may limit natural ecosystem response to elevated CO(2) concentration, diminishing the CO(2)-fertilization effect on terrestrial plant productivity in unmanaged ecosystems. Recent models have incorporated such carbon-nitrogen interactions and suggest that anthropogenic N sources could help sustain the future CO(2)-fertilization effect. However, conclusive demonstration that added N enhances plant productivity in response to CO(2)-fertilization in natural ecosystems remains elusive. Here we manipulated atmospheric CO(2) concentration and soil N availability in a herbaceous brackish wetland where plant community composition is dominated by a C(3) sedge and C(4) grasses, and is capable of responding rapidly to environmental change. We found that N addition enhanced the CO(2)-stimulation of plant productivity in the first year of a multi-year experiment, indicating N-limitation of the CO(2) response. But we also found that N addition strongly promotes the encroachment of C(4) plant species that respond less strongly to elevated CO(2) concentrations. Overall, we found that the observed shift in the plant community composition ultimately suppresses the CO(2)-stimulation of plant productivity by the third and fourth years. Although extensive research has shown that global change factors such as elevated CO(2) concentrations and N pollution affect plant species differently and that they may drive plant community changes, we demonstrate that plant community shifts can act as a feedback effect that alters the whole ecosystem response to elevated CO(2) concentrations. Moreover, we suggest that trade-offs between the abilities of plant taxa to respond positively to different perturbations may constrain natural ecosystem response to global change.
[Pubmed: 20596018]
| | 11. |
2011 May 6 |
Trace element uptake by Eleocharis equisetina (spike rush) in an abandoned acid mine tailings pond, northeastern Australia: Implications for land and water reclamation in tropical regions.
Lottermoser BG, Ashley PM
Environ Pollut. 2011 May 6; [Epub ahead of print]
Abstract
This study was conducted to determine the uptake of trace elements by the emergent wetland plant species Eleocharis equisetina at the historic Jumna tin processing plant, tropical Australia. The perennial emergent sedge was found growing in acid waters (pH 2.45) and metal-rich tailings (SnAsCuPbZn). E. equisetina displayed a pronounced acid tolerance and tendency to exclude environmentally significant elements (Al, As, Cd, Ce, Co, Cu, Fe, La, Ni, Pb, Se, Th, U, Y, Zn) from its above-substrate biomass. This study demonstrates that geobotanical and biogeochemical examinations of wetland plants at abandoned mined lands of tropical areas can reveal pioneering, metal-excluding macrophytes. Such aquatic macrophytes are of potential use in the remediation of acid mine waters and sulfidic tailings and the reclamation of disturbed acid sulfate soils in subtropical and tropical regions.
[Pubmed: 21550704]
| | 12. |
2011 May 13 |
Herbiconiux flava sp. nov., and emended description of the genus Herbiconiux.
Hamada M, Komukai C, Tamura T, Evtushenko LI, Vinokurova NG, Suzuki KI
Int J Syst Evol Microbiol. 2011 May 13; [Epub ahead of print]
Abstract
The rod-shaped, non-motile and non-endospore-forming strain NBRC 16403(T) (=VKM Ac-2058(T)) was isolated from the phyllosphere of a sedge (Carex sp.). 16S rRNA gene sequencing studies indicated that strain NBRC 16403(T) was closely related to the type strains of Herbiconiux solani (98.6 %), Herbiconiux ginsengi (97.8 %) and Herbiconiux moechotypicola (97.8 %). The peptidoglycan (B2γ type) contained D- and L-2,4-diaminobutyric acids, D-alanine, glycine and threo-3-hydroxyglutamic acid which almost fully substituted glutamic acid. The predominant menaquinones were MK-10 and MK-11. The polar lipid pattern comprised diphosphatidylglycerol, phosphatidylglycerol and three glycolipids, along with, along with minor amounts of other polar lipids. The major fatty acids were anteiso-C(15:0), iso-C(16:0) and anteiso-C(17:0); no cyclohexyl-C(17:0) was detected. The DNA G+C content was 71.0 mol%. The results of phylogenetic analysis and DNA-DNA hybridization, along with differences of strain NBRC 16403(T) from the recognized Herbiconiux species in phenotypic characteristics, indicate that a novel species of the genus Herbiconiux, for which the name Herbiconiux flava sp. nov. is proposed. The type strain is NBRC 16403(T) (=VKM Ac-2058(T)).
[Pubmed: 21571941]
| | 13. |
2010 Dec 14 |
Dynamics of chromosome number and genome size variation in a cytogenetically variable sedge (Carex scoparia var. scoparia, Cyperaceae).
Chung KS, Weber JA, Hipp AL
Am. J. Bot. 2011 Jan;98(1):122-9. Epub 2010 Dec 14.
Abstract
• Premise of the study: High intraspecific cytogenetic variation in the sedge genus Carex (Cyperaceae) is hypothesized to be due to the "diffuse" or non-localized centromeres, which facilitate chromosome fission and fusion. If chromosome number changes are dominated by fission and fusion, then chromosome evolution will result primarily in changes in the potential for recombination among populations. Chromosome duplications, on the other hand, entail consequent opportunities for divergent evolution of paralogs. In this study, we evaluate whether genome size and chromosome number covary within species. • Methods: We used flow cytometry to estimate genome sizes in Carex scoparia var. scoparia, sampling 99 plants (23 populations) in the Chicago region, and we used meiotic chromosome observations to document chromosome numbers and chromosome pairing relations. • Key results: Chromosome numbers range from 2n = 62 to 2n = 68, and nuclear DNA 1C content from 0.342 to 0.361 pg DNA. Regressions of DNA content on chromosome number are nonsignificant for data analyzed by individual or population, and a regression model that excludes slope is favored over a model in which chromosome number predicts genome size. • Conclusions: Chromosome rearrangements within cytogenetically variable Carex species are more likely a consequence of fission and fusion than of duplication and deletion. Moreover, neither genome size nor chromosome number is spatially autocorrelated, which suggests the potential for rapid chromosome evolution by fission and fusion at a relatively fine geographic scale (<350 km). These findings have important implications for ecological restoration and speciation within the largest angiosperm genus of the temperate zone.
[Pubmed: 21613090]
| | 14. |
2010 Dec 02 |
Greater seasonal carbon gain across a broad temperature range contributes to the invasive potential of Phalaris arundinacea (Poaceae; reed canary grass) over the native sedge Carex stricta (Cyperaceae).
He Z, Bentley LP, Holaday AS
Am. J. Bot. 2011 Jan;98(1):20-30. Epub 2010 Dec 02.
Abstract
• Premise of the study: Most invasive plants grow faster and produce more biomass than the species that they displace, but physiological mechanisms leading to invasive success are poorly understood. To foster novel control approaches, our goal was to determine whether the grass Phalaris arundinacea possessed superior physiological strategies that contributed to its success over native sedges. • Methods: Data for spring, summer, and autumn diel gas-exchange, leaf morphology, and nitrogen content for plants of P. arundinacea and Carex stricta in water-saturated, drained, and periodically flooded sites in northern Indiana, USA, were compared with similar data for plants in a greenhouse. • Key results: Phalaris arundinacea had higher maximum CO(2) assimilation (A) across a broad range of temperatures, greater summer/autumn net carbon gain, higher water use efficiencies, larger leaf areas per shoot, and higher specific leaf areas than did C. stricta. Species differences in gas-exchange data were similar in the greenhouse. However, long-term flooding reduced A for P. arundinacea. Greater declines in leaf A and nitrogen content from July to October compared to P. arundinacea were suggestive of earlier leaf senescence for C. stricta. • Conclusions: We propose that superior daily and seasonal carbon gain, especially during rhizome carbohydrate storage in the summer and autumn, contribute to the success of invasive P. arundinacea over C. stricta. This advantage may be enhanced by frequent summer/autumn heat waves. The poor performance of P. arundinacea during long-term flooding is consistent with C. stricta's dominance in water-saturated soil, implying that water management strategies could be crucial to controlling P. arundinacea.
[Pubmed: 21613081]
| | 15. |
2010 Jul 26 |
Phylogeography of the Japanese common sedge, Carex conica complex (Cyperaceae), based on chloroplast DNA sequence data and chromosomal variation.
Yano O, Ikeda H, Hoshino T
Am. J. Bot. 2010 Aug;97(8):1365-76. Epub 2010 Jul 26.
Abstract
• Premise of the study: Genetic and chromosomal variations in plants are often reflected in the geographical distribution patterns. Therefore, identifying such phylogeographical patterns on population is important for understanding the process of plant diversification and speciation, and analyzing both molecular and cytological aspects is necessary. • Methods: We investigated the phylogeographic pattern and genetic diversity of the widespread Japanese sedge, Carex conica complex, based on chloroplast DNA haplotypes and chromosomal variations. • Key results: Sixteen distinct haplotypes were detected from 258 individuals in the C. conica complex inferred from the cpDNA sequences of intergenic spacer (IGS) between atpB and rbcL, IGS between trnT and trnL, trnL intron, and IGS between trnL and trnF. Most haplotypes showed distinct geographical structures. Phylogenetic analyses revealed two major clades, clades I and II, among 16 haplotypes of the complex. The haplotypes of clade I were mainly found in eastern Japan, while most haplotypes of clade II were found in western Japan. Four intraspecific aneuploids of 2n = 32, 34, 36, and 38, with forming normal bivalents in meiotic divisions, were also found in the complex. The geographical distribution of these intraspecific aneuploids corresponded well with those of the haplotypes. • Conclusions: Our results suggest that the genetic diversity and chromosomal variations in the C. conica complex may have originated from contractions and expansions of geographical ranges affected by Quaternary climatic oscillations.
[Pubmed: 21616889]
| | 16. |
2011 Sep 17 |
Fossil sedges, macroplants, and roots from Olduvai Gorge, Tanzania.
Bamford MK
J Hum Evol. 2011 Sep 17; [Epub ahead of print]
Abstract
A variety of macroplants has been recorded and collected from the eastern paleolake margin of Olduvai Gorge, Tanzania, from Upper Bed I and Lower Bed II, dated at ∼1.7-1.85 Ma. The plant groups represented are sedges, grasses, and woody and herbaceous dicotyledons. Most of these plants are fragmented, but the roots are in situ. The modes and quality of preservation, however, are very variable. Silicification is the dominant type of preservation; it ranges from high quality faithful replacement of cells resulting in silicified wood and sedge culms that are identifiable on the basis of their internal anatomy, to poor quality biotubes lacking internal anatomy or external features that prevent assignment to a specific plant or invertebrate origin. In between this range are silicified roots and grass culms identified by their external anatomy, and leaf and stem impressions. Interpretation of the paleoecology is limited by the quality of preservation. The in situ root horizons are useful for recognizing paleo-surfaces. The best quality preservation where internal anatomy is preserved occurs at HWK E and MCK, localities that are in the middle of the fault compartments so the vegetation can be reconstructed for these sites. Some sedge culms are described, illustrated, and identified as possible species of Cyperus, Fuirena, and Schoenoplectus.
[Pubmed: 21930291]
| | 17. |
2011 Jul 5 |
Active Methanotrophs in Two Contrasting North American Peatland Ecosystems Revealed Using DNA-SIP.
Gupta V, Smemo KA, Yavitt JB, Basiliko N
Microb Ecol. 2011 Jul 5; [Epub ahead of print]
Abstract
The active methanotroph community was investigated in two contrasting North American peatlands, a nutrient-rich sedge fen and nutrient-poor Sphagnum bog using in vitro incubations and (13)C-DNA stable-isotope probing (SIP) to measure methane (CH(4)) oxidation rates and label active microbes followed by fingerprinting and sequencing of bacterial and archaeal 16S rDNA and methane monooxygenase (pmoA and mmoX) genes. Rates of CH(4) oxidation were slightly, but significantly, faster in the bog and methanotrophs belonged to the class Alphaproteobacteria and were similar to other methanotrophs of the genera Methylocystis, Methylosinus, and Methylocapsa or Methylocella detected in, or isolated from, European bogs. The fen had a greater phylogenetic diversity of organisms that had assimilated (13)C, including methanotrophs from both the Alpha- and Gammaproteobacteria classes and other potentially non-methanotrophic organisms that were similar to bacteria detected in a UK and Finnish fen. Based on similarities between bacteria in our sites and those in Europe, including Russia, we conclude that site physicochemical characteristics rather than biogeography controlled the phylogenetic diversity of active methanotrophs and that differences in phylogenetic diversity between the bog and fen did not relate to measured CH(4) oxidation rates. A single crenarchaeon in the bog site appeared to be assimilating (13)C in 16S rDNA; however, its phylogenetic similarity to other CO(2)-utilizing archaea probably indicates that this organism is not directly involved in CH(4) oxidation in peat.
[Pubmed: 21728037]
| | 18. |
2011 Jul 28 |
Reduced density and nest survival of ground-nesting songbirds relative to earthworm invasions in northern hardwood forests.
Loss SR, Blair RB
Conserv. Biol. 2011 Oct;25(5):983-92. Epub 2011 Jul 28.
Abstract
European earthworms (Lumbricus spp.) are spreading into previously earthworm-free forests in the United States and Canada and causing substantial changes, including homogenization of soil structure, removal of the litter layer, and reduction in arthropod abundance and species richness of understory plants. Whether these changes affect songbirds that nest and forage on the forest floor is unknown. In stands with and without earthworms in the Chequamegon-Nicolet National Forest, Wisconsin (U.S.A.), we surveyed for, monitored nests of, and measured attributes of habitat of Ovenbirds (Seiurus aurocapillus) and Hermit Thrushes (Catharus guttatus), both ground-dwelling songbirds, and we sampled earthworms at survey points and nests. Bird surveys indicated significantly lower densities of Ovenbirds and Hermit Thrushes in relation to Lumbricus invasions at survey point and stand extents (3.1 and 15-20 ha, respectively). Modeling of Ovenbird nest survival (i.e., the probability that nestlings successfully fledge) indicated that lower survival probabilities were associated with increased sedge cover and decreased litter depth, factors that are related to Lumbricus invasions, possibly due to reduced nest concealment or arthropod abundance. Our findings provide compelling evidence that earthworm invasions may be associated with local declines of forest songbird populations.
[Pubmed: 21797927]
| | 19. |
2011 Oct 19 |
Ecophysiological mechanisms characterising fen and bog species: focus on variations in nitrogen uptake traits under different soil-water pH.
Nakamura T, Nakamura M
Oecologia. 2011 Oct 19; [Epub ahead of print]
Abstract
Although the productivity and nitrogen (N)-use traits of mire plants differ dramatically between fens and bogs, soil N richness does not necessarily differ, whereas the soil-water pH is distinctly lower in bogs than in fens. The ecophysiological mechanisms underlying these relations are unclear. To assess the relative availability of N forms in relation to soil-water pH, we focused on the net N uptake rate per unit root weight (NNUR), glutamine synthetase activity and nitrate reductase activity, and performed reciprocal transplant experiments with the seedlings of fen (Carex lyngbyei) and bog (C. middendorffii) sedge species in intact habitat sites. The soil-water pH was clearly lower at the bog site, but the NH(4) (+), NO(3) (-) or dissolved organic-N concentrations did not differ between the fen and bog sites. The activity of both enzymes for inorganic-N assimilation did not differ among the sites and species. However, the fen species grown at bog sites showed a drastic decrease in the NNUR, suggesting a suppression of organic-N uptake. The bog species showed no NNUR difference between the sites. These results indicate that inorganic-N availability does not differ between the two habitats, but organic-N availability is lowered in a low-pH bog, particularly in the case of fen species. Therefore, the relative availability of N forms shows species-specific variations that depend on the differences in the soil-water pH of root zone, even at similar N richness, which would play a key role in plant distribution strategies in relation to the fen-bog gradient.
[Pubmed: 22009342]
| | 20. |
2011 Mar 16 |
The C(4) plant lineages of planet Earth.
Sage RF, Christin PA, Edwards EJ
J. Exp. Bot. 2011 May;62(9):3155-69. Epub 2011 Mar 16.
Abstract
Using isotopic screens, phylogenetic assessments, and 45 years of physiological data, it is now possible to identify most of the evolutionary lineages expressing the C(4) photosynthetic pathway. Here, 62 recognizable lineages of C(4) photosynthesis are listed. Thirty-six lineages (60%) occur in the eudicots. Monocots account for 26 lineages, with a minimum of 18 lineages being present in the grass family and six in the sedge family. Species exhibiting the C(3)-C(4) intermediate type of photosynthesis correspond to 21 lineages. Of these, 9 are not immediately associated with any C(4) lineage, indicating that they did not share common C(3)-C(4) ancestors with C(4) species and are instead an independent line. The geographic centre of origin for 47 of the lineages could be estimated. These centres tend to cluster in areas corresponding to what are now arid to semi-arid regions of southwestern North America, south-central South America, central Asia, northeastern and southern Africa, and inland Australia. With 62 independent lineages, C(4) photosynthesis has to be considered one of the most convergent of the complex evolutionary phenomena on planet Earth, and is thus an outstanding system to study the mechanisms of evolutionary adaptation.
[Pubmed: 21414957]
| | 21. |
2011 Mar |
Factors influencing differential larval habitat productivity of Anopheles gambiae complex mosquitoes in a western Kenyan village.
Mala AO, Irungu LW
J Vector Borne Dis. 2011 Mar;48(1):52-7.
Abstract
The study was undertaken to characterize factors influencing differential productivity of Anopheles gambiae complex mosquitoes at larval habitats in a rural village in western Kenya.
[Pubmed: 21406738]
| | 22. |
2011 |
Patient relations office facilitate community engagement: using internet-based correspondence to encourage discussion at the University Health Network.
Rogers S, Sedge E
Healthc Q. 2011;14(2):101-5.
[Pubmed: 21841402]
| | 23. |
2011 Nov 28 |
Microsatellite primers in Carex moorcroftii (Cyperaceae), a dominant species of the steppe on the Qinghai-Tibetan Plateau.
Liu W, Zhou Y, Liao H, Zhao Y, Song Z
Am. J. Bot. 2011 Dec;98(12):e382-4. Epub 2011 Nov 28.
Abstract
• Premise of the study: Microsatellite markers were developed in Carex moorcroftii, a rhizomatous clonal sedge that dominates the steppes and meadows of the Qinghai-Tibetan Plateau. • Methods and Results: Using the combined biotin capture method, 30 microsatellite primer sets were isolated and characterized. Twenty-two of these markers showed polymorphism, and the number of alleles per locus ranged from two to 11 across 96 individuals from four populations. • Conclusions: These markers provide a useful tool to investigate the clonal structure and mating system of C. moorcroftii.
[Pubmed: 22123716]
| | 24. |
2011 Sep 13 |
Territory choice during the breeding tenure of male sedge warblers.
Zając T, Bielański W, Solarz W
Behav Ecol Sociobiol. 2011 Dec;65(12):2305-2317. Epub 2011 Sep 13.
Abstract
A territorial male can shift the location of its territory from year to year in order to increase its quality. The male can base its decision on environmental cues or else on its breeding experiences (when territory shift is caused by breeding failure in previous seasons). We tested these possible mechanisms of territory choice in the sedge warbler (Acrocephalus schoenobaenus), a territorial migrating passerine that occupies wetlands. This species bases its territory choices on an environmental cue: tall wetland vegetation cover. We found that the magnitude of territory quality improvement between seasons (measured as the area of tall wetland vegetation) increased throughout the early stages of a male's breeding career as a result of territory shifts dependent on the earliness of arrival. The distance the territory was shifted between seasons depended negatively on the previous year's territory quality and, less clearly, on the previous year's mating success. On the other hand, previous mating or nesting success had no influence on territory quality improvement between seasons as measured in terms of vegetation. The results imply that tall wetland vegetation is a long-term, effective environmental cue and that a preference for territories in which this type of landcover prevails has evolved into a rigid behavioral mechanism, supplemented by short-term individual experiences of breeding failure.
[Pubmed: 22162903]
| | 25. |
2011 Jun |
[Spatial analysis of Oncomelania snail information based on grid data-driven].
Liu G, Huang QY, Liu YZ, Wang JT, Peng F, Liu NM
Zhongguo Xue Xi Chong Bing Fang Zhi Za Zhi. 2011 Jun;23(3):253-7.
Abstract
To explore the relationship between the Oncomelania snail situation and the distance to the water source, soil humidity, vegetation and water level in flood seasons in the islets of Changsha Section of the Xiang River.
[Pubmed: 22164484]
| | 26. |
2011 Dec 27 |
Characterization and cross application of novel microsatellite markers for a rare sedge, Lepidosperma gibsonii (Cyperaceae).
Barrett MD, Wallace MJ, Anthony JM
Am J Bot. 2011 Dec 27; [Epub ahead of print]
Abstract
• Premise of the study: Ten polymorphic microsatellite loci for the rare sword sedge Lepidosperma gibsonii (Cyperaceae) were characterized for the future study of population structure, hybridization, and clonality.• Methods and Results: Twenty samples from each of three populations were screened with the markers to assess genetic variation. Observed population heterozygosities ranged from 0.35 to 1.00, and number of alleles observed per locus ranged from eight to 23. No departures from Hardy-Weinberg equilibrium were detected for any locus in any population. Single samples from 14 species were screened to examine the transferability of the microsatellites to other species of Lepidosperma. At least eight out of 10 loci amplified in all species tested.• Conclusions: These loci will be useful for studying genetic variation, hybridization, dispersal, and breeding systems in Lepidosperma, a ubiquitous element of the flora of southern Australia.
[Pubmed: 22203656]
| | 27. |
2012 Jan 18 |
Importation of Hyalomma marginatum, vector of Crimean-Congo haemorrhagic fever virus, into the United Kingdom by migratory birds.
Jameson LJ, Morgan PJ, Medlock JM, Watola G, Vaux AG
Ticks Tick Borne Dis. 2012 Jan 18; [Epub ahead of print]
Abstract
Hyalomma marginatum ticks are an important vector of Crimean-Congo haemorrhagic fever virus which can result in a severe and potentially fatal disease in humans. Given the continued emergence of clinical cases in Eurasia and focalised upsurges of H. marginatum populations in Europe, it seemed prudent to assess the potential of this vector species to be introduced into the United Kingdom. Immature forms of H. marginatum are frequent ectoparasites of passerine birds many of which migrate from Africa to the UK each spring. Incoming birds were inspected for ticks during the spring migration in 2010 and 2011. A total of 68 ticks was collected from 971 birds (29 bird species), 21% (14) of the ticks were identified as H. marginatum. Oenanthe oenanthe (Northern wheatear) and Sylvia communis (Whitethroat) were found to be infested by this tick in both years and with multiple ticks. Single specimens were also removed from Acrocephalus schoenobaenus (Sedge warbler) and Phoenicurus phoenicurus (Common redstart) in 2010. This study provides the first contemporary evidence for substantial importation of this tick species into the UK.
[Pubmed: 22300969]
| | 28. |
2012 Feb 19 |
Diversification rates and chromosome evolution in the most diverse angiosperm genus of the temperate zone (Carex, Cyperaceae).
Escudero M, Hipp AL, Waterway MJ, Valente LM
Mol Phylogenet Evol. 2012 Feb 19; [Epub ahead of print]
Abstract
The sedge family (Cyperaceae: Poales; ca. 5600 spp.) is a hyperdiverse cosmopolitan group with centres of species diversity in Africa, Australia, eastern Asia, North America, and the Neotropics. Carex, with ca. 40% of the species in the family, is one of the most species-rich angiosperm genera and the most diverse in temperate regions of the Northern Hemisphere, making it atypical among plants in that it inverts the latitudinal gradient of species richness. Moreover, Carex exhibits high rates of chromosome rearrangement via fission, fusion, and translocation, which distinguishes it from the rest of the Cyperaceae. Here, we use a phylogenetic framework to examine how the onset of contemporary temperate climates and the processes of chromosome evolution have influenced the diversification dynamics of Carex. We provide estimates of diversification rates and map chromosome transitions across the evolutionary history of the main four clades of Carex. We demonstrate that Carex underwent a shift in diversification rates sometime between the Late Eocene and the Oligocene, during a global cooling period, which fits with a transition in diploid chromosome number. We suggest that adaptive radiation to novel temperate climates, aided by a shift in the mode of chromosome evolution, may explain the large-scale radiation of Carex and its latitudinal pattern of species richness.
[Pubmed: 22366369]
| | 29. |
2012 Jun 12 |
Seed rain and its relationship with above-ground vegetation of degraded Kobresia meadows.
Shang ZH, Yang SH, Shi JJ, Wang YL, Long RJ
J Plant Res. 2012 Jun 12; [Epub ahead of print]
Abstract
Seed rain is a crucial element in vegetation regeneration, but has been rarely studied in high altitude regions, particularly degraded Kobresia meadow. Weed infestation is a distinctive feature of pasture degradation in Kobresia meadows on the Tibetan plateau, the ecological mechanism of which is closely related with vegetation's seed rain. In this paper we assess the effect of vegetation degradation on seed rain and consider its implication for restoration of degraded Kobresia meadows in the headwater area of Yellow river, through analysis of seed species composition, number of seeds landing per m(2) of soil surface, and their relationship with above ground vegetation. Vegetation degradation had an impact on the species composition and numbers of seeds in seed rain and their relationship with above-ground vegetation. Within the un-degraded meadow, which provided a closed vegetation cover, 35 % of the seed rain was of sedge and gramineae species. However, within the degraded meadows, as the extent of degradation increased, so the total number of seeds m(-2) increased, with those derived from sedge and gramineae species forming a declining proportion of the total. Degradation of Kobresia meadow on the Tibetan plateau is exacerbated by the seed input of weed species (such as Oxytropis ochrocephala, Carum carvi, Aconitum pendulum, Pedicularis kansuensis in this study). Therefore, a major priority for the restoration of such degraded meadows should be the elimination of these weeds from the above ground vegetation by human intervention.
[Pubmed: 22688506]
| | 30. |
2012 May 30 |
Flowering dynamics and pollination system of the sedge Rhynchospora ciliata (Vahl) Kükenth (Cyperaceae): does ambophily enhance its reproductive success?
Costa AC, Machado IC
Plant Biol (Stuttg). 2012 May 30; [Epub ahead of print]
Abstract
Cyperaceae are characteristically anemophilous, but there are some reports of species re-adapted to entomophily, such as Rhynchospora ciliata. Our objective was to investigate: (1) the distribution pattern of flowers in inflorescences of Rhynchospora ciliata; (2) the dynamics of its anthesis; and (3) whether R. ciliata is pollinated by bees, by wind or by both. Additionally, we tested the hypotheses: (i) the hypsophylls and/or anthers attract pollinators, and (ii) biotic vectors enhance the reproductive success of R. ciliata. We analysed floral biology, dynamics of anthesis, frequency and behaviour of insects visiting flowers; we also carried out experiments on flower attractiveness, pollination by wind and reproductive success. Rhynchospora ciliata has flowers with anemophilous attributes, including anthers exposed during anthesis; however, the anthers (here considered a mixed trait) together with the white hypsophylls can be considered as attributes that favour entomophily. Both wind and four species of bee were considered as pollen vectors of R. ciliata. Through flower attractiveness tests, we observed that the hypsophylls do not affect the frequency of pollinating bees and that the absence of exposed anthers affects the average number of visits, probably because pollen is the only floral resource. Reproductive tests indicate that R. ciliata is self-incompatible and that ambophily enhances its reproductive success.
[Pubmed: 22646523]
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