摘要:

Natural populations of the evergreen shrub,Thymelaea hirsuta(L.) Endl., were studied over 6 years at five desert habitats, in terms of seedling recruitment and adult survival and as a function of plant size and gender class. Habitat and time significantly influenced mortality of both reproductive and non-reproductive plants. Plant size also significantly affected adult mortality. Seedling recruitment varied significantly with habitat and year and approached zero some years. Significant among-year and among-population variation in population growth rates were observed over the 6 years of study, and all populations declined in size (ranging from −1.7% per year at the coastal dune site to −10.9% per year at the inland plateau site). Spearman rank correlation analysis between habitats ranked according to a north–south gradient and demographic variables indicates that this gradient is associated with a pattern of lower seedling emergence and survival and a lower population growth rate and greater mortality for all size-classes ofThymelaeaplants. In experimental botanic garden plots, germination of seed collected from five natural populations, and seedling survival in the following year were assessed under conditions of high, medium, and low seedling density. Seedling emergency differed significantly according to maternal habitat. With regular watering, seeding survival to one year was 72% (averaged across habitats and densities). This compares with 64% for seedlings grown at the highest density, suggesting that the intense mortality observed under field conditions is more likely to be a result of water shortage than intraspecific competition.Key words: Egyptian desert,Thymelaea hirsuta, germination and establishment, seedlings, recruitment, competition, population growth rate.

ISSN:0008-4026    

DOI:10.1139/b97-914

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Genetic relationships between 23 eastern Canadian isolates of the entomopathogenPaecilomyces farinosus(Holm ex S.F. Gray) Brown & Smith were investigated by comparison of DNA fragments produced by restriction enzyme digestion of polymerase chain reaction amplified ribosomal RNA intergenic spacer regions. The variation observed was limited to 40% or less of these regions. AllP.farinosusisolates were very dissimilar to isolates of the entomopathogensBeauveria bassiana(Bals.) Vuill. andPaecilomyces fumosoroseus(Wize) Brown & Smith. SeventeenP.farinosusisolates from six different hosts and diverse habitats yielded identical or nearly identical results. Two groups, each with three isolates from two different hosts, were distinct from the main group of isolates. Each of the threeP.farinosusgroups included some isolates that produced synnemata and some that did not, indicating multiple evolutionary losses of the ability to produce this sporulation structure. We conclude that eastern CanadianP.farinosus, while genetically and phenotypically variable, is not composed largely of strains with strict ecological requirements.Key words: entomopathogenic fungus, population biology, RFLP, ribosomal RNA intergenic spacer.

ISSN:0008-4026    

DOI:10.1139/b97-915

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

To show phylogenetic relationships among the smut fungi and their relatives, we sequenced a part of the nuclear LSU rDNA from 43 different species of smut fungi and related taxa. Our data were combined with the existing sequences of seven further smut fungi and 17 other basidiomycetes. Two sets of sequences were analyzed. The first set with a representative number of simple septate basidiomycetes, complex septate basidiomycetes, and smut fungi was analyzed with the neighbor-joining method to estimate the general topology of the basidiomycetes phylogeny and the positions of the smut fungi. The tripartite subclassification of the basidiomycetes into the Urediniomycetes, Ustilaginomycetes, and Hymenomycetes was confirmed and two groups of smut fungi appeared. The smut generaAurantiosporium,Microbotryum,Fulvisporium, andUstilentylomaare members of the Urediniomycetes, whereas the other smut species tested are members of the Ustilaginomycetes withEntorrhizaas a basal taxon. The second set of 46 Ustilaginomycetes was analyzed using the neighbor-joining and the maximum parsimony methods to show the inner topology of the Ustilaginomycetes. The results indicated three major lineages among Ustilaginomycetes corresponding to the Entorrhizomycetidae, Exobasidiomycetidae, and Ustilaginomycetidae. The Entorrhizomycetidae are represented byEntorrhizaspecies. The Ustilaginomycetidae contain at least two groups, the Urocystales and Ustilaginales. The Exobasidiomycetidae include five orders, i.e., Doassansiales, Entylomatales, Exobasidiales, Georgefischeriales, and Tilletiales, andGraphiola phoenicisandMicrostroma juglandis. Our results support a classification mainly based on ultrastructure. The description of the Glomosporiaceae is emended. The Doassansiopsaceae, Melanotaeniaceae, and Urocystaceae are proposed as new taxa.Key words: basidiomycete systematics, LSU rDNA, Microbotryales, molecular phylogeny, smut fungi, Ustilaginomycetes.

ISSN:0008-4026    

DOI:10.1139/b97-916

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

A morphological and anatomical study of the mycorrhizas onPinus strobusL. was conducted on seedlings excavated from St.-Williams nursery in southern Ontario. Micro- and macro-scopic characters were used to classify the morphotypes into complexes and, when possible, genera and species. An E-strain fungus, fungi from theMycelium radicis atrovirens(MRA) complex, and an unidentified ascomycetous "red-type" fungus formed ectendomycorrhizal (EECM) associations, whileTubersp.,Hebelomasp., andThelephora terrestrisformed ectomycorrhizal (ECM) associations in the nursery. Cultures ofHebelomasp., the E-strain fungus,Tubersp., and two morphologically distinct MRA fungi (MRA1, later identified asPhialophora finlandiaWang & Wilcox, and MRA2, unidentified) were isolated from field-collected morphotypes and re-inoculated ontoPinus strobusseedlings grown in semisterile pot cultures for 4 months. In the resynthesis experiment, the E-strain fungus formed EECM with sparse intracellular colonization, andTubersp. formed ECM with characteristic cystidia and densely packed mantles, as they had in the field. However, unlike the MRA field specimens,Phialophora finlandiaformed ECM in pot culture.Hebelomasp., normally an ECM former with conifer seedlings, did not form mycorrhizal structures under the given culture conditions, and neither did the MRA2 isolate.Key words: ectomycorrhiza, ectendomycorrhiza,Pinus strobus,Tubersp.,Phialophora finlandia, E-strain.

ISSN:0008-4026    

DOI:10.1139/b97-917

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Isozyme-based genetic diversity, morphological characters, and growth rate at different temperatures were compared in a worldwide collection of 125 isolates presumed to bePythium irregulareBuisman. The isozyme data was analysed with previously published data forPythium ultimumTrow andPythium sylvaticumCampbell & Hendrix. UPGMA cluster analysis yielded a dendrogram with four distinct groups:P.ultimum,P.sylvaticum, and two forP.irregulare. PutativeP.irregulareisolates were separated into 33 multilocus genotypes defined by 11 isozyme loci: group A contained 116 isolates in 25 genotypes, and group B, 8 isolates in 7 genotypes. One genotype with a single isolate was determined asP.sylvaticum. Based on the isozyme analysis, group B was considered a distinct taxonomic entity from group A, but lacked any unique morphological character. There was a wide range in oogonium and oospore sizes among different isolates ofP.irregulare, with those in group B generally being larger. Some isolates in group A had well developed oogonial spines, but others were essentially spineless, whereas all those in group B were spineless. Both groups A and B contained isolates with distinctly aplerotic oospores and others with essentially plerotic oospores. Antheridial number and shape were highly variable both within and among isolates in the two groups. Growth rate over a range of temperatures varied among isolates in both groups and was not a reliable taxonomic criterion. The irregular shape of oogonia and, when present, oogonial spines were the only reliable characters for distinguishingP.irregulareisolates from other taxa.Key words: taxonomy, Oomycetes, Pythiaceae,Pythium ultimum,Pythium sylvaticum.

ISSN:0008-4026    

DOI:10.1139/b97-918

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Aecial and telial host range, interfertility, teliospore dimensions, and amount of nuclear DNA were determined forPuccinia reconditacollected either worldwide from species of cultivated wheats (Triticum aestivumandTriticum turgidumssp.durumand rye (Secale cereale), or from wild emmer (Triticum turgidumssp.dicoccoides) and four species of wild wheat (Aegilops) in Israel. The results indicate that the collections belong in two major groups: Group I (from cultivated wheats and wild emmer), which hasThalictrum speciosissimum(in the Ranunculaceae) as principal aecial host; and Group II (principally from wild wheats or rye), which has several species in the Boraginaceae, such asAnchusa aggregata,Anchusa italica,Echium glomeratum, andLycopsis arvensisas aecial hosts. In glasshouse experiments, intercrosses could be made readily among collections within Groups I and II but not between the two groups. Group I consisted of all collections fromTriticum aestivum,Triticum turgidumssp.dicoccoides, and most collections fromTriticum turgidumssp.durum. For Group I collections, four species ofAegilops,Hordeum maritimum,S.cereale, as well asTriticum aestivumandTriticum turgidumssp.durumand ssp.dicoccoidescould all serve as telial host in glasshouse experiments. Group II consisted of four types, all clearly different from Group I. Type A was fromTriticum turgidumssp.durumfound in fields nearAnchusa italica, which was its only aecial host;Triticum aestivum,Triticum turgidumssp.durum, andTriticum turgidumssp.dicoccoidescould serve as telial hosts. Type B was fromAegilops ovataand hadE.glomeratum,Anchusa undulata, andL.arvensisas aecial hosts. Type C was fromAegilops longissima,Aegilops sharonensis, andAegilops variabilisand hadAnchusa aggregata,Anchusa undulataandL.arvensisas aecial hosts. Type D was fromS.cerealeand hadL.arvensisandAnchusa undulataas aecial hosts. In addition to differences in host range, teliospores were wider and bigger in cross sectional area, and nuclear DNA content of pycniospores was 1.3–1.6 times greater in Group II than in Group I. The results suggest that Groups I and II have evolved separately for an extended period and are now morphologically distinct and genetically isolated from each other. Furthermore, differences in both telial and aecial host species, in teliospore dimensions, and in amount of nuclear DNA indicate that subgroups within Group II are beginning to show genetic divergence.Key words: aecial hosts,Aegilops,Anchusa,Echium,Hordeum, leaf rust,Lycopsis,Puccinia recondita,Puccinia triticina,Secale,Thalictrum,Triticum.

ISSN:0008-4026    

DOI:10.1139/b97-919

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Somatic incompatibility assays and random amplified polymorphic DNA (RAPD) analysis were assessed and compared for use in monitoring the survival of introduced strains ofPhlebiopsis gigantea, a fungal biocontrol agent used againstHeterobasidion annosumroot rot. Overall there was concordance between the two methods. All incompatible strains exhibited different RAPD profiles whilst compatible ones, with two exceptions, had the same RAPD profile. Somatic incompatibility tests and RAPD profiles generated by three primers, from which 11 markers were retained, could distinguish field-tested strains from among 60 strains from a population collected in Quebec and Ontario. Furthermore, both methods allowed us to clearly demonstrate the presence of inoculated strains 1 year after treatment. The combined use of these techniques provides a valuable tool for discriminating between differentP.giganteastrains and conducting epidemiological studies.Key words:Heterobasidion annosum, vegetative incompatibility, random amplified polymorphic DNA, biological control,Pinus resinosa.

ISSN:0008-4026    

DOI:10.1139/b97-920

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

In the course of a preliminary chemosystematic study ofAsphodelusspecies, six flavonoids were first isolated and identified fromA.ramosussubsp.ramosusvar.ramosus. Only flavone structures were found. Two of them are rare C-glycoside structures and were observed only in the samples from one of the two geographic areas. So, flavonoids might be used as markers in the study of theAsphodelusgenus organization.Key words:Asphodelus ramosus, Liliaceae, flavonoids, C-glycosylflavones, chemosystematics.

ISSN:0008-4026    

DOI:10.1139/b97-921

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Eastern North America and temperate eastern Asia reportedly share a relatively high number of taxa of macrofungi (mushrooms and relatives), including a number of taxa that have putative eastern North America – temperate eastern Asia disjunct distributions. These reports have been used to imply an affinity between the mycota (fungal equivalent of flora and fauna) of the two regions. To date, however, this affinity has not been examined in detail. A comparison of north temperate macrofungal mycotas was undertaken to examine the similarity between these regions. We used two methods in this study: (i) direct comparison of taxon lists and (ii) calculation of the Simpson Coefficient of similarity from lists of selected taxa. These analyses were based on field work, herbarium records, and published taxonomic treatments forAmanita,Lactarius,Ramaria, and Boletaceae. Results of these analyses document that taxonomic similarity between eastern North America and temperate eastern Asia mycotas can be quite high. In all cases, the calculated similarity values for eastern North America – temperate eastern Asia comparisons are higher than those between either region of North America and Europe or between western North America and eastern Asia. Furthermore, the eastern North American and temperate eastern Asian disjunct distributions of macrofungi are usually limited to the level of species or lower.Key words: biogeography, China, disjunct distribution, macrofungi, North America, Simpson Coefficient.

ISSN:0008-4026    

DOI:10.1139/b97-922

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Inorganic carbon fluxes were simulated by a mathematical model using an equilibrium hypothesis for a wide range of conditions in a closed system composed of air-grown cells ofSynechococcusUTEX 625 in a reaction vessel connected to a mass spectrometer. The metabolic scheme took into account the input fluxes of CO2and HCO3−transport into the cells, the output fluxes of CO2and HCO3−efflux, the diversion of Q toward the formation of the internal C2pool, and photosynthetic CO2fixation. The equations expressed the variation in concentration of each inorganic species outside and inside the cell as a function of time. The input fluxes were previously characterized by their kinetic constants (K1/2andVm) both during initial uptake occurring upon illumination of the cells and under steady-state photosynthesis conditions. The efflux rates of the various Cispecies from the cells were investigated under a wide variety of experimental conditions. Using these efflux rates, the permeability coefficients of the cell for CO2and HCO3−were calculated previously. Using the kinetic constants for CO2and HCO3−transport, the permeability coefficients of the cell for CO2and HCO3−and the geometrical characteristics of the cells, the model simulated precisely the [HCO3−]/[CO2] ratio and the [CO2] and [O2] changes in the extracellular medium as well as the rate of filling of the internal Cipool under various conditions. Accurate fitting of experimental data with calculated values were possible only when the intracellular Cispecies were assumed to be in equilibrium throughout the entire cell volume. Results are discussed and compared with those given by previous hypotheses.Key words:SynechococcusUTEX 625, blue green algae, cyanobacteria, mathematical model, active CO2transport, active HCO3−transport, steady state, photosynthesis, Ciconcentrating mechanism.

ISSN:0008-4026    

DOI:10.1139/b97-923

出版商:NRC Research Press    

年代:1997

数据来源: NRC