摘要:

Phytophagous insects are natural bioassays that may be used to segregate closely related plant taxa. To examine the value of this method, we conducted a comprehensive survey of insects and arachnids in a natural zone of overlap and hybridization between Fremont (Populus fremontii) and narrowleaf cottonwood (Populus angustifolia). Three categories of trees were distinguished by leaf morphology and identified by previous genetic analyses as Fremont, F1and BC1hybrids, and complex backcrosses (BC2–BC4). These trees were subsequently reclassified by a discriminant function analysis of their associated herbivores. The level of concordance between the two methods was 98% (n = 43 trees). Because insect distributions may reflect differences in plant morphology, chemistry, phenology, and other characters, insect bioassays may be a more rigorous method of distinguishing closely related plant taxa than reliance solely on morphological or chemical analyses. In contrast with chemical and genetic analyses, insect surveys can be quickly done in the field at minimal cost. Insect bioassays will not replace current methods of distinguishing closely related plant taxa, but they may be useful for supplementing current methods.Key words:Populus, discriminant function analysis, insect–plant interaction, host selection, plant taxonomy.

ISSN:0008-4026    

DOI:10.1139/b95-001

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Flow cytometry has been used to estimate nuclear DNA content of 13Coffeaspecies (Rubiaceae) native to Africa. Twelve diploid (2n = 22) and one tetraploid (C.arabica, 2n = 44) species were investigated. Isolated nuclei from 77 genotypes were stained with propidium iodide (PI; not base specific). Thirty-nine genotypes were stained with 4′,6-diamidino-2-phenylindole (DAPI; AT specific). Nuclear DNA content (2C values), estimated with PI, ranged from 0.95 to 1.78 pg. By aggregative clustering, three groups of accessions with increasing DNA content were identified. Three species, namelyC.sessiliflora,C.racemosa, andC.pseudozanguebariae, had a low DNA content (0.90 – 1.30 pg). Three species, namelyC.eugenioides,C.stenophylla, andC. sp. F, were exclusively found in the intermediate group (1.31 – 1.60 pg). The remaining species were distributed between the intermediate group and the last group (1.61 – 1.80 pg). The values determined for theCoffeaspecies are compared, inter- and intra-specifically, to those of other angiosperm species. The observed differences are discussed according to the ecogeographic origin of the species, their phenological characteristics, and the fertility of the F1interspecific hybrids.Key words: Africa,Coffea, flow cytometry, nuclear DNA content, genome evolution.

ISSN:0008-4026    

DOI:10.1139/b95-002

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Monoterpene emissions from intact 5- to 29-month-old loblolly and slash pine seedlings contained α-pinene, camphene, β-pinene, myrcene, sabinene, β-phellandrene, and limonene. α-Pinene made up > 50% of the volatiles from both species. β-Pinene was significantly more abundant in slash (35.6%) than in loblolly pine (15.3%), while myrcene was significantly more abundant in loblolly (10.9%) than in slash pine (3.4%). Cuticular lipids represented 0.11 and 0.06% of the dry weight biomass of shoots from loblolly and slash pines, respectively. Species differences in cuticular lipid composition were primarily in relative proportions of a group of unidentified compounds that appear to be saturated and unsaturated diols and (or) hydroxy alcohols with chain lengths of about 18 carbons. 10-Nonacosanol made up 16.2 and 14.1% of the total lipids recovered from loblolly and slash pines, respectively. The Nantucket pine tip moth,Rhyacionia frustrana(Comstock), may use these chemical differences to distinguish the susceptible loblolly pines from the resistant slash pines.Key words:Pinus taeda,Pinus elliottii, monoterpene emissions, cuticular lipids,Rhyacionia frustrana.

ISSN:0008-4026    

DOI:10.1139/b95-003

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Two new species ofPhialocephalawere isolated from the periderm of living branches of forest trees in Germany. In culture,Phialocephala compactaKowalski & Kehr sp.nov., found onAlnus, is characterized by crowded conidiogenous heads that become deeply pigmented with age.Phialocephala scopiformisKowalski & Kehr sp.nov., isolated fromPiceaand other conifers, develops elongated, complex conidiogenous heads with up to 15 series of branches in culture. The taxonomic placement of both new species and their role in endophytism and in natural pruning of branches is discussed.Key words:Picea abies,Alnus glutinosa,Phialocephala compacta,Phialocephala scopiformis, branch pruning fungi.

ISSN:0008-4026    

DOI:10.1139/b95-004

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The pioneer vegetation of five distinct littoral zones along the middle Adour River (SW France) was investigated during three successive low water periods. There was a high year to year variability in the hydrology of the river during the period of study with a normal (1987), a wet (1988), and a dry year (1989). Changes in population and life forms density of both native and exotic species were analyzed. Communities were species rich when 45% of the 428 species present in the study area (2-km-long stretch) were found in the 10 × 10 m plots. Most of the species were annuals, but perennials were also abundant. The exotic component represented nearly 20% of the species and of the total number of individuals. There was high spatial variability in pioneer communities; sites of the main river channel differed from those along abandoned arms in species composition and population densities. The communities responded to changes in the hydrology of the preceding growing season. Sharp year to year differences were found in population and species density. The nature of the hydrological change drove those changes. Plots located in the oldest arms of the river showed a greater sensitivity to flooding conditions than those located in young littoral zones, with an increase in hygrophilous species. Alternatively, plots adjacent to active river channels showed greater sensitivity to drought conditions, as the density of short-lived and exotic species increased. Comparatively, exotics appeared to be more sensitive to the type of hydrological changes than natives. Warmer years also affected native plants, which reacted like invasive species. Relationships between the observed changes, the level of hydrological disturbance, and the recent history of each site are discussed in this paper with the possibility of using introduced species as descriptors of climatic and hydrologic changes.Key words: riparian vegetation, pioneer community, community structure, biological invasions, hydrological perturbation, variability.

ISSN:0008-4026    

DOI:10.1139/b95-005

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The effects of the insecticide fenitrothion (O,O-dimethyl-O-(3-methyl-4-nitrophenyl)phosphorothioate) were investigated on the unicellular phytoplanktonAnkistrodesmus falcatus,Chlamydomonas reinhardtii,Chlamydomonas segnis,Chlorella pyrenoidosa,Naviculasp.,Scenedesmus obliquus,Selenastrum capricornutum, andStaurastrumsp. at concentrations of 0.1, 1.0, and 10 mg∙L−1. Following a 24-h exposure, total lipids, fatty acid profiles, and bioaccumulation of fenitrothion into algal cells were determined for the above species. Total lipids may play an important role in determining sensitivity of phytoplankton to fenitrothion stress over 96-h exposures. A saturation occurred inA.falcatusmembranes represented by the 5.4 and 4.3% increases in palmitic (16:0) and oleic (18:1) acids, respectively, and 1.8 and 7.6% decreases in linoleic (18:2) and linolenic (18:3) acids, respectively. This resulted in a shift from a profile dominated by linolenic (18:3) acid to one dominated by the more saturated oleic (18:1) acid. Bioconcentration factors (BCF), or the ratio of the total radiocarbon associated with algae, calculated for viableChlamydomonas reinhardtiiandChlamydomonas segniscells were 293 and 124, respectively. BCFs for dead cells were 1261 and 1025 for the same species, respectively. These investigations showed differential insecticide bioaccumulation between species. This bioaccumulation was shown to be correlated with the total lipid content of algal cells.Key words: algae, fatty acids, fenitrothion, lipids, pesticid

ISSN:0008-4026    

DOI:10.1139/b95-006

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Relationships between forest structure and species composition were examined in three age-classes of temperate rain forest in southern coastal British Columbia. Old forests (> 250 years) exhibited greater structural and compositional heterogeneity than young (31–60 years) and mature (61–80 years) forests. Size-class distributions of living and dead standing trees in the three age groups suggested both qualitative and quantitative differences in regeneration and mortality processes. The canonical correlation between structure and composition was high (Rc = 0.84), but a substantial amount of total variation remained unexplained by the analysis. Principal component analysis (PCA) axis 1 of species composition separated the lower elevation (warmer and drier) mature forests from the higher elevation (cooler and wetter) young and old forests. PCA axis 1 of structure separated the young and mature forests as a group from the old forests. PCAs of the separate age-classes indicated weaker compositional – structural linkages than with all age-classes combined. Study area differences explained greater proportions of variation in young and mature forests (up to 53%) than in old forests (< 10%). The results indicate a slow recovery process following impacts from human disturbance in coastal forests.Key words: canonical correlation analysis, old-growth temperate rain forest, principal component analysis, species composition, forest structure.

ISSN:0008-4026    

DOI:10.1139/b95-007

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Podosordaria venezuelensis(Ascomycotina, Xylariaceae) is described and illustrated. It is characterized by the long-stalked, glabrous stromata, ascospore shape and size, and germ slit length, differing from morphologically similar taxa in spore morphology and distribution. A key to all currently accepted species of this fungal genus is provided.Key words:Podosordaria, Xylariaceae, coprophilous, taxonomy, Venezuela.

ISSN:0008-4026    

DOI:10.1139/b95-008

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Invasion of lodgepole pine sapwood by blue-stain fungi was followed for 7 weeks after infestation by the mountain pine beetle,Dendroctonus ponderosae. During this period all sapwood was heavily stained blue and blue-stain fungi were always isolated close to the front of visible occlusion.Ophiostoma clavigerumandOphiostoma montiumwere commonly isolated, both of which are known to be carried in the mycangia of the mountain pine beetle.Ophiostoma montiumwas most frequently isolated, but when both fungi were presentO.clavigerumwas always at the leading edge of fungal penetration. On averageO.montiumtrailed 7.3 mm behindO.clavigerum. Other microorganisms were seldom isolated.Key words: lodgepole pine,Dendroctonus ponderosae, fungal succession, blue-stain fungi.

ISSN:0008-4026    

DOI:10.1139/b95-009

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Grubbing of roots and rhizomes of salt-marsh graminoids by lesser snow geese at La Pérouse Bay, Manitoba, on the Hudson Bay coast, has resulted in a vegetational mosaic. Bare sites, devoid of vegetation, occur adjacent to intact swards (high biomass sites). At some sites destruction of swards is incomplete (low biomass sites). In 1991 and 1992, highest soil salinities occurred in midsummer; surface sediments were flushed of salts by meltwater in spring and by tides in autumn. By late July, in both years, the soil was hypersaline in low biomass and bare sites, unlike that in the high biomass sites. The highest soil salinities were recorded in bare sites, especially in large bare patches. Aboveground plant biomass (g∙m−2) was a much better predictor of the salinity of soil water than the water content or redox potential of soil. Evaporative loss of water from tubes buried in sediments was higher in bare sites compared with that in vegetated sites. Differences in evaporation between sites led to large differences in the salinity of soil water but only small differences in soil water content. The upward movement of salts from buried Tyrell Sea sediments appears responsible for the development of hypersaline conditions.Key words: grubbing, goose grazing, plant biomass, sodium, soil water, hypersalinit

ISSN:0008-4026    

DOI:10.1139/b95-010

出版商:NRC Research Press    

年代:1995

数据来源: NRC