Year-to-year changes in unfertilized meadows of great species richness detected by point quadrat analysis

An experimental study site in an unfertilized meadow of great species richness at Negrentino (820 m) in Southern Switzerland has been investigated by successive point quadrat analysis since 1988. Two different managements, traditional mowing and abandonment, were realized on 3×6 plots of 200×220 cm. On each plot point frequency (sensu Goodall 1952) was sampled at spaces of 10 cm using the same 11×16 points every year. On all the plots 71 species were recorded within the four year period of 1988–1991.Small spatial differences and vegetational changes in time are interpreted on an ordination diagram of correspondence analysis. Differences between successional and fluctuational changes are recognized already in the early phase. On one plot a peak of phytocyclic fluctuation connected with a mass development of Trifolium repens was observed.Many species show significant year-to-year frequency changes. Taxa positively and negatively affected by abandonment are presented.Management and dry weather conditions in April and May are considered to be the main causes of trends and fluctuations.     

Nonequilibrium dynamics of sedge meadows grazed by cattle in southern Wisconsin

Equilibrium theory predicts that after disturbance, ecosystemseventually regain the structural and functional properties characteristic oftheir predisturbance condition. This study tested this idea by examining theeffects of cattle grazing and exclusion on the long-term structuralcharacteristics of sedge meadows in southern Wisconsin. To compare structuralchanges in mean percentage cover and height, repeated measures analysis wasconducted on two sedge meadows over a twenty year period from 1977 to 1997. Onesedge meadow was recovering from cattle grazing (cattle excluded in 1973) andthe other was a reference area (nearly undisturbed). Both of these study siteschanged structurally from 1977 to 1997, supporting non-equilibrium theory.Additional observations were made in a heavily and lightly grazed sedge meadowthat were surveyed in 1977. As based on the positions of subunits in anordination graph produced using Non-Metric Multidimensional Scaling (NMS), therecovery sedge meadow became less structurally similar to the grazed and moresimilar to the reference site over the 20 year study. However, from theperspective of mean maximum height in another NMS analysis, the recovery sedgemeadow became less similar to the reference site over time likely because by1997, a shrub carr of Cornus sericea had developed in therecovery sedge meadow that had been dominated by graminoids and forbs in 1977(mean maximum height: 1977 vs. 1997; 0 vs. 47 cm). Seedlings ofCornus sericea were invading the grazed sedge meadows andin the recovery sedge meadow (cattle excluded 4 years earlier) in 1977. A shrubcarr did not develop in the reference sedge meadow. Changes in the referencesite were relatively minor over this time interval; certain species eitherincreased or decreased in dominance, e.g., Carex strictaincreased in cover (1977 vs. 1997, 20 and 28 mean percentage (%) cover,respectively). A few short-term species of the recovery sedge meadow followedthe tenets of equilibrium theory. These became less common or disappeared4–9 years after cattle exclusion including Asterlanceolatus, Calamagrostis canadensis,Poa compressa, Solidago altissima andVerbena hastata. Some of these species were eaten andlikely spread by the cattle. This study suggests that the progression of sedgemeadow to shrub carr may not be an inevitable outcome of succession but insteadcan be a consequence of past cattle grazing history. Also, because the recoveryand the reference sedge both changed structurally over time, the tenets ofnon-equilibrium theory were supported by this study.     

Restoration of riparian meadows degraded by livestock grazing: above- and belowground responses

Riparian meadows in the western US are highly productive areas withinthe riparian corridor that have been extensively utilized for livestock grazingand that are often degraded. This study aimed to increase our understanding ofboth the functional responses and restoration potential of mesic meadow systemsin central Nevada, USA. Nitrogen addition and clipping treatments were used toexamine grazing effects, while aeration and revegetation were included toevaluate potential restoration treatments. Belowground response was determinedby examining gravimetric soil water content and rooting depth and activity.Aboveground response was determined for two key mesic meadow species,Carex nebrascensis and Poa pratensis,by quantifying gas exchange and water relations. Large yearly and seasonaldifferences among water tables largely determined the rooting activity anddepthin these mesic meadows and influenced treatment responses. Little rootingactivity occurred within or at the surface of the water table and rooting depthincreased as water table level lowered during the growing season. In general,nitrogen addition decreased rooting activity and depth relative to controls. Itresulted in less negative water potentials and photosynthetic rates that werehigher early in the growing season, but lower later in the growing season. Theeffects of nitrogen addition could be attributed to accelerated phenology andearlier senescence. Clipping resulted in less negative plant water potentialsinCarex and Poa, andPoa had higher photosynthetic rates immediately afterclipping but only for certain dates and comparisons. Aeration increased rootingactivity and depth where there was no confounding effect of water table. Also,predawn and midday water potentials were generally less negative forCarex and Poa in aerated plots.Establishment on the revegetation plots was dominated by annual and early seralspecies and, consequently, these plots exhibited reduced rooting depth andactivity early in the growing season and high root turnover. Results indicatethat water table depth and its effects on soil water are dominant factors indetermining the functional processes and recovery potentials of these riparianmeadows. Clipping had minimal effects on above- and belowground responses,perhaps because clipping was performed late in the growing season after plantshad begun to senescence. Nitrogen addition decreased rooting activity andaltered phenology, indicating deleterious effects. Aeration was effective atovercoming some of the negative affects of overgrazing and may be an effectiverestoration treatment. However, revegetation may have limited potential due toestablishment constraints of the dominant species.     

Cytological analysis of complex-heterozygotes in populations ofOenothera grandiflora (Onagraceae) in Alabama

Genetic analysis of unusual complex-heterozygous genotypes in populations ofO. grandiflora from Alabama (USA) has shown that these strains are composed of a typicalgrandiflora (B) complex and an altered B complex (designated as B^A) which probably contains genetic elements derived from an A genotype such as the beta complex ofO. biennis group 1. Analysis of the meiotic configurations of artificial hybrids between the new strains and a series of complexes of known segmental arrangement allowed determination of the arrangements of the unknown complexes. These data are evidence for origin of the altered B complexes.     

Automated multiple development method for determination of glycerol produced by wine yeasts

A rapid and efficient analytical method for the determination of glycerol in wines is described. This method utilizes high-performance thin layer chromatography (HPTLC) plates coupled with an automated multiple development system with an elution gradient based on acetonitrile–acetone–hexane on silica gel layers. The absence of clean-up procedures, sometimes only centrifugation, makes this method suitable also for the large-scale control of alcoholic beverages. In particular the capacity of different wine yeast species (Saccharomyces cerevisiae, Zygosaccharomyces bailii, Kloeckera apiculata and Saccharomycodes ludwigii) to produce glycerol was determined. Generally, the strains of S. cerevisiae produced elevated amounts of glycerol together with Z. bailii, whereas K. apiculata strains formed the lowest amounts of glycerol, exhibiting also a great strain variability.     

Microenvironmental and vegetational heterogeneity induced by phytogenic nebkhas in an arid coastal ecosystem

The nebkhas of woody plants represent distinct habitats in arid and semiarid ecosystems. Nebkhas are mounds composed of wind-borne sediment within or around shrub canopies. We studied the effects of widely spaced nebkhas of Retama raetam shrub on their microenvironment and associated herbaceous vegetation in the Mediterranean coast of Sinai Peninsula. Our measurements included nebkha size (height and width) and shrub size (canopy height and diameter). We identified four distinct microsites at each nebkha: crest, mid-slope, edge, and internebkha space. We measured soil temperature and moisture, photosynthetically active radiation (PAR), and soil properties. The plant species grown at each microsite were identified and their densities were measured. Average soil temperature and PAR were highest at internebkha space and lowest at nebkha crest. The maximum diurnal temperature and PAR of internebkhas exceeded that of nebkhas. Soil moisture and nutrient concentrations showed a gradient of spatial heterogeneity and were highest at the nebkha edge. Regression analysis indicated that total herbaceous plant density was significantly related to nebkha size, and to shrub canopy diameter and area. Detrended correspondence analysis indicated that patterns of species composition were correlated with the spatial variability in soil moisture and nutrient content along the gradient of increasing distance from the nebkha crest. It is assumed that shrub canopy and its nebkha interact in governing ecosystem functioning in this environment.     

Promotion of mid-successional seedling recruitment and establishment by Juniperus virginiana in a coastal environment

Positive interactions between Juniperus virginianaand woody seedlings may influence trends in primary succession along theAtlantic Coast of eastern North America. Woody species richness was greaterbeneath isolated J. virginiana trees than in more exposed,grass-covered dune sites on a Virginia, USA barrier island. Fleshy fruitedseedswere more abundant in the seed bank beneath J. virginianathan in adjacent exposed sites, suggesting that J.virginiana may be utilized by passerine birds. Photosyntheticallyactive radiation was reduced below J. virginiana, and soiltemperature fluctuations were moderated during the growing season. In addition,moisture content, organic matter, and chlorides were higher for soils underJ. virginiana than in exposed sites. For plantedPrunus serotina and Sassafras albidumseedlings, mortality was lower beneath J. virginiana ascompared with the exposed treatment; however, no S.albidumseedlings survived beyond mid-August. The effect of J.virginiana on the recruitment and distribution of mid-successionalwoody seedlings in coastal environments may be passive, through the non-randomdistribution of fleshy seeds by perching birds, or active, through increasedseedling survival due to J. virginiana initiatedalterations in microclimate and edaphic factors.     

Long-term competitive displacement of Typha latifolia by Typha angustifolia in a eutrophic lake

This study follows the outcome of long-term competition between a broad-leaved and a narrowleaved Typha species, T. latifolia and T. angustifolia respectively, in a eutrophic lake. The lake was bordered by a zone of T. latifolia, at one location interrupted by a T. angustifolia stand. Distributional changes of the T. angustifolia stand and the adjacent zone of T. latifolia were measured on aerial photographs (13 years) and along ground-level transects (6 years). A second stand of T. angustifolia was established with transplanted ramets within a formerly homogeneous zone of T. latifolia, and displacement between the two species was measured along ground-level transects after 6 years. Differences between the species in shoot performance were investigated to help explain the relative competitive abilities of the two Typha species. T. angustifolia expanded at the expense of T. latifolia at all water depths where both species occurred, except in very shallow water. Expansion rates suggest that T. angustifolia was not affected by the presence of T. latifolia in water depths exceeding 0.25 m. The Typha species were significantly negatively associated according to rank correlations of shoot densities, and changes of shoot densities, along the transects. These results suggest that T. angustifolia is competitively superior to T. latifolia, contradicting earlier studies. The higher competitive ability of T. angustifolia is consistent with its having taller shoots and a higher standing crop in early summer. Further, shoot height distributions indicated a closer integration of shoot emergence during spring in T. angustifolia than in T. latifolia. A high leaf area/shoot weight ratio suggest that T. latifolia may instead be relatively fast-growing, achieving competitive superiority over narrower-leaved Typha species during a transient period after simultaneous seedling establishment.     

Variability and structure of natural populations of Elymus caninus (L.) L. and their possible relationship with Hordelymus europaeus (L.) Jess. ex Harz as revealed by AFLP analysis

The AFLP method was used to study the inter-population variability of eight populations of Elymus caninus (L.) L. as well as three populations of Hordelymus europaeus (L.) Jess. ex Harz. In these studies a clear distinction was found between two phenotypes of E. caninus collected in the same locality. It also appeared that two populations of E. caninus representing the “pauciflorum” morphotype were clustered together, similarly as two populations of E. caninus exhibiting morphotype “caninus”. Additionally, the populations of the “pauciflorum” type were clustered together with all samples of H. europaeus. Furthermore, the same approach was applied to analyze the intra-population variability of E. caninus. The populations ranged from nearly uniform to as diverse as the samples collected from different localities. In some populations of this species the presence of off-type plants was revealed. Our data indicate the predominantly self-pollinating character of E. caninus and the possible genetic relationship between of E. caninus and H. europaeus. It is the second paper from the series: Biodiversity of wild Triticeae (Poaceae) in Poland, the first is: Mizianty M. 2005. Variability and structure of natural populations of Elymus caninus (l.) L. based on morphology. Pl. Syst. Evol. 251: 199–216.     

A new Escherichia coli gene, fdrA, identified by suppression analysis of dominant negative FtsH mutations

An Escherichia coli membrane protein, FtsH, has been implicated in several cellular processes, including integration of membrane proteins, translocation of secreted proteins, and degradation of some unstable proteins. However, how it takes part in such diverse cellular events is largely unknown. We previously isolated dominant negative ftsH mutations and proposed that FtsH functions in association with some other cellular factor(s). To test this proposal we isolated multicopy suppressors of dominant negative ftsH mutations. One of the multicopy suppressor clones contained an N-terminally truncated version of a new gene that was designated fdrA. The FdrA fragment suppressed both of the phenotypes — increased abnormal translocation of a normally cytoplasmic domain of a model membrane protein and retardation of protein export — caused by dominant negative FtsH proteins. The intact fdrA gene (11.9 min on the chromosome) directed the synthesis of a 60 kDa protein in vitro.     

Quantitative analysis of a stand of Pinus densiflora undergoing succession to Quercus mongolica ssp. crispula: 1. A 31-year record of growth and population dynamics of the canopy trees

We describe the population dynamics, growth of dominant species and plant biomass production in an ecosystem undergoing succession from Pinus densiflora dominance to Quercus mongolica ssp. crispula dominance. The diameter at breast height (DBH) was recorded for a period of 31 years. As DBH increased, the tree density decreased. We estimated the net biomass production of the canopy trees, the biomass of the understory and the average amount of litter. These results suggest that the biomass production of an ecosystem depends on its species composition. In order to estimate future ecosystem productivity, it is necessary to predict temporal changes in species composition.     

Detection of streptomycin resistance in Mycobacterium tuberculosis clinical isolates from China as determined by denaturing HPLC analysis and DNA sequencing

China is regarded by the World Health Organization as a major hot-spot region for Mycobacterium tuberculosis infection. Streptomycin has been deployed in China for over 50 years and is still widely used for tuberculosis treatment. We have developed a denaturing HPLC (DHPLC) method for detecting various gene mutations conferring drug resistance in M. tuberculosis. The present study focused on rpsL and rrs mutation analysis. Two hundred and fifteen M. tuberculosis clinical isolates (115 proved to be streptomycin-resistant and 100 susceptible by a routine proportional method) from China were tested to determine the streptomycin minimal inhibitory concentration (MIC), and subjected to DHPLC and concurrent DNA sequencing to determine rpsL and rrs mutations. The results showed that 85.2% (98/115) of streptomycin-resistant isolates harbored rpsL or rrs mutation, while rpsL mutation (76.5%, 88/115) dominated. MIC of 98 mutated isolates revealed no close correlation between mutation types and levels of streptomycin resistance. No mutation was found in any of the susceptible isolates. The DHPLC results were completely consistent with those of sequencing. The DHPLC method devised in this study can be regarded as a useful and powerful tool for detection of streptomycin resistance. This is the first report to describe DHPLC analysis of mutations in the rpsL and rrs genes of M. tuberculosis in a large number of clinical isolates.     

Phylogeny of Nannizzia incurvata,N. gypsea,N. fulva and N. otae by restriction enzyme analysis of mitochondrial DNA

Sequence divergence among Nannizzia incurvata, N. gypsea, N. fulva and N. otae was studied genetically using digestion profiles of mitochondrial DNA with restriction enzymes, Hae III, Hha I, Hind III and Xba I. Only N. fulva was subdivided into two types on restriction profiles. Phylogenetic relationships suggest that 1) N. gypsea is more closely related to N. fulva than N. incurvata, 2) the phylogenetic distance between N. otae and the other three species is larger than the distances between the other three species.     

Comparative analysis of <Emphasis Type="Italic">Pleurotus ostreatus</Emphasis> natural isolates

A comparative analysis was performed of the polymorphism of the oyster mushroom Pleurotus ostreatus (Fr.) Kumm naturally occurring strains isolated from the natural substrates from two geographically remote Russian natural preserves, the Central Forest Biosphere Tver State Preserve and the Moscow State University Zvenigorod Biological Station (Moscow oblast), and within the city of Moscow. The results of the frequency analysis for the allozyme loci alleles and for the sexual and somatic incompatibility groups are presented; the genetic structure and the interpopulation relations among 58 Pleurotus ostreatus dikaryotic strains are estimated. The natural samples from the Moscow and Tver oblasts are shown to have a high degree of polymorphism with a genetic differentiation of 0.743; in spite of their territorial remoteness, they are, however, actively exchanging genetic material. The natural fungal isolates form two reproductively isolated groups.__________Translated from Mikrobiologiya, Vol. 74, No. 2, 2005, pp. 231–238.Original Russian Text Copyright © 2005 by Shtaer, Yu. Belokon, M. Belokon, Shnyreva.     

aubergine mutations in Drosophila melanogaster impair P cytotype determination by telomeric P elements inserted in heterochromatin

Transposable P elements inserted in the heterochromatic Telomeric Associated Sequences on the X chromosome (1A site) of Drosophila melanogaster have a very strong capacity to elicit the P cytotype, a maternally transmitted condition which represses P element transposition and P-induced hybrid dysgenesis. This repressive capacity has previously been shown to be sensitive to mutant alleles of the gene Su(var)205, which encodes HP1 (Heterochromatin Protein 1), thus suggesting a role for chromatin structure in repression. Since an interaction between heterochromatin formation and RNA interference has been reported in various organisms, we tested the effect of mutant alleles of aubergine, a gene that has been shown to play a role in RNA interference in Drosophila, on the repressive properties of telomeric P elements. Seven out of the eight mutant alleles tested clearly impaired the repressive capacities of the two independent telomeric P insertions at 1A analyzed. P repression by P strains whose repressive capacities are not linked to the presence of P copies at 1A were previously found to be insensitive to Su(var)205; here, we show that they are also insensitive to aubergine mutations. These results strongly suggest that both RNA interference and heterochromatin structure are involved in the establishment of the P cytotype elicited by telomeric P elements, and reinforce the hypothesis that different mechanisms for repression of P elements exist which depend on the chromosomal location of the regulatory copies of P.Communicated by G. Reuter     

Gene identification in the obligate fungal pathogen Blumeria graminis by expressed sequence tag analysis

Powdery mildew of barley is caused by the obligate fungal pathogen Blumeria graminis f. sp. hordei. Haploid conidia of B. graminis, landing on the barley leaf, germinate to form first a primary germ tube and then an appressorial germ tube. The appressorial germ tube differentiates into a mature appressorium from which direct penetration of host epidermis occurs. Here we present data on 4908 expressed sequence tags obtained from B. graminis conidia. The combined sequences represent 2676 clones describing 1669 individual genes. Comparison with sequences from other pathogenic and nonpathogenic fungi defines hypotheses on the genes required for pathogenicity and growth on the host. The putative roles of some of the identified genes are discussed.     

The role of catastrophic death of Calluna in heathland dynamics

In the Breckland heaths of East Anglia large patches of Calluna are often killed by adverse climatic conditions or insect attack. This paper studies one site, Cavenham Heath, where large areas of Calluna were killed between 1976–1979, and shows that older stands were most affected, and recovery was slowest compared to either younger stands, or stands with an uneven-aged structure. Moreover, where Calluna death was most severe, directional succession to birch woodland was accelerated. At this site, although Calluna regeneration has been previously assumed to be initiated by endogenous factors (i.e. by the life cycle of the Calluna), it is also clearly interrupted by exogenous factors. The implications of these results for heathland conservation are discussed, and it is suggested that intervention management by cutting and burning, to maintain large areas of Calluna in the building phase, may be the most appropriate long term strategy.This work was funded in part by the Nature Conservancy Council as part of its research programme into nature conservation. I thank Mr D. Malins and Mrs D. Reynolds for assistance in both the field and the laboratory, Ms S. Ide and Mr J. Pattin-gale for preparing the figures, and Professor C. H. Gimigham, Dr J. Miles and Dr I. C. Prentice for helpful comments on earlier drafts of this paper.     

Distinction of species in Aureobasidium and related genera by PCR-ribotyping

Taxonomic markers for differentiation of the anamorph genera Aureobasidium, Hormonema and Kabatiella were developed using PCR-ribotyping with the primers 5.8S-R and LR7 for amplification and the restriction enzymes Alul, DdeI, Hhal, MspI and RsaI for digestion. Aureobasidium and Hormonema are optimally differentiated with MspI; DdeI is particularly useful to distinguish aureobasidium, Kabatiella and Selenophoma. Relationships of the anamorph genera Aureobasidium, Hormoneng and Kabatiella with the teleomorph genera Pringsheimia and Dothiora are discussed.     

An attempt to clarify taxonomic relationships in ``Verwandtschaftskreis der Gattung Ligusticum' (Umbelliferae-Apioideae) by molecular analysis

Relationships among the taxa of Umbelliferae, presumably close to Ligusticum and Selinum were investigated by two independent molecular taxonomic methods. 134 ITS 1-2 sequences were analyzed (29 new and 2 reinvestigated species) and immunochemical comparison of storage seed proteins for 38 species of Apioideae of Ligusticum affinity was performed, eight reference systems (antisera) were used. Both approaches yield similar results, showing the extremely polyphyletic nature of this group and some large genera (Ligusticum s.l., Selinum s.l., Pachypleurum) in the Umbelliferae. The independent status of the genera Magadania, Sphaenolobium, Arafoe, Lomatocarpa, Dimorphosciadium and some other segregates of Ligusticum, Cnidium and Selinum have been confirmed, but Cnidium proved to be unnatural even as currently circumscribed. In the group of East Asian taxa the genera Oreocome, Ligusticopsis, Cortia and Cortiella appeared to be closely related. Haplosphaera was shown to be a genus of Hansenia-Notopterygium group.