ISSN:0008-4026    

DOI:10.1139/cjbsubject99

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The frequency of sex morphs of the clonal plant,Glechoma hederaceaL., was recorded at ramet, clone, and population levels in the province of Skåne, South Sweden. In a random sample of 748 ramets at 31 sites, 68% of the ramets possessed only hermaphrodite flowers, 22% possessed only female flowers, and 10% were partially male sterile with both hermaphrodite and female flowers. At one-third of the sites, only one sex morph was found (mostly hermaphrodites). At the other sites, the proportion of female ramets and partially male-sterile ramets ranged from 3 to 100%. Multilocus genotypes were established using isozyme electrophoresis to study sex expression (stamen fertility) at different levels (among flowers within ramets, among ramets within genets, and among genets) in the field and for transplants raised under uniform greenhouse conditions. Sex expression was found to be genotype specific. Some genets were stable females or stable hermaphrodites, others being partially male sterile with a specific level of stamen fertility both in the field and in cultivation. Some multilocus genotypes showed great variation in stamen fertility among plots both in the field and in cultivation, indicating that sex expression in these genets was greatly influenced by environmental conditions. Stamen fertility varied temporally and spatially in ramets of the partially male-sterile sex types. Flower size was positively correlated with stamen fertility

ISSN:0008-4026    

DOI:10.1139/b99-134

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Sporocarps of epigeous ectomycorrhizal fungi and vegetation data were collected from eightTsugaheterophylla(Raf.) Sarg. -Pseudotsugamenziesii(Mirb.) Franco stands along a wet to dry gradient in Olympic National Park, Washington, U.S.A. One hundred and fifty species of ectomycorrhizal fungi were collected from a total sample area of 2.08 ha. Over 2 years, fungal species richness ranged from 19 to 67 taxa per stand. Sporocarp standing crop ranged from 0 to 3.8 kg/ha, averaging 0.58 kg/ha, 0.06 kg/ha in spring and 0.97 kg/ha in fall. Sporocarp standing crop and fungal species richness were correlated with precipitation. These results demonstrated that ectomycorrhizal fungal sporocarp abundance and species richness can be partly explained in terms of an environmental gradient.

ISSN:0008-4026    

DOI:10.1139/b99-144

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The final (limit) values for litter decomposition were estimated and, by extrapolating a linear relationship between accumulated litter mass loss and litter N concentration, the N concentration at the limit value (Nlimit) was estimated. The values for Nlimitwere compared with those of the A01layer (Nhumus) and of newly shed litter (Ninit). No difference was found between the A01and A02layers when their N concentrations were compared with the values for Nlimit. There was a highly significant linear relationship between Nlimitand Ninit(R2= 0.769 andp< 0.001). Likewise, there was a highly significant linear relationship between Nhumusand Ninit. When these two linear relationships were compared, there was no significant difference in slope, while there was a significant difference in the intercepts of 6.76 and 7.25 mg·g-1for Nhumusand Ninit, respectively. Thus, for a given site in our investigation, the estimated value for N concentration in humus would be 6.8% lower than the measured one.

ISSN:0008-4026    

DOI:10.1139/b99-141

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

A redundancy analysis (RDA) with following forward selection and variance partitioning was performed to evaluate whether character state variation in pleurocarpous mosses is best explained by higher level taxonomic position or a selected set of environmental parameters. The studied explanatory parameters explain ca. 30% of the total character state variation. Taxonomic position, reflecting the phylogenetic component, is the most important among the studied explanatory parameters, and the phylogenetic component on its own is relatively more important in explaining the variation in the gametophyte than in the sporophyte. Among the environmental parameters, the general habitat parameter was the most important, followed by the climatic zone, and the wetland to nonwetland gradient. In the RDA, gradients of the sporophyte character states are more important than those of the gametophyte. Those of the sporophyte relate to the degree of sporophyte specialization, whereas those of the gametophyte relate to characters associated with water conduction. Phylogenetic time lags are likely to account for the strong influence of the phylogenetic component in most cases, because correlations between taxonomic position and environmental parameters were very few, whereas convergent or parallel evolution is likely to explain the similar states found in strongly specialized sporophytes.

ISSN:0008-4026    

DOI:10.1139/b99-143

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The objective of this study was to evaluate the most important environmental factors determining the distribution of tree species within the riparian zone of Lake Duparquet, located in the southern boreal region of Quebec, Canada. Occurrence and relative basal area of 10 species were recorded within an altitudinal range of 200 cm above mean water level along 95 transects. Stepwise logistic regression and canonical correspondence analyses were performed on the overall data set as well as separately for the five geomorphological shore types distinguished (depositional flats, floodplains, beaches, terraces, and rock outcrops). The elevation gradient, representing seasonal floodings, is the main factor determining the distribution of the species. The differences between the geomorphological shore types with respect to composition and arrangement of the arborescent vegetation along the elevation gradient are at least partially explained by surficial substratum, topography, aspect, and fire. Exposure to wave activity seems to be of minor importance only. However, since they are the driving force of erosion and sedimentation, the waves are to a great part responsible for the morphological differentiation of the shoreline. The distribution of the tree species along a characteristic physiographic cross-section is illustrated for each geomorphological shore type.

ISSN:0008-4026    

DOI:10.1139/b99-147

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

To infer phylogenetic relationships among species ofHypomyces(Fr.) Tul and allied genera, partial sequences of the 28S rDNA were obtained for 21 strains representing 19 species. On the basis of these data and 38 sequences obtained from GenBank, phylogenetic analyses were performed using the programs PAUP and Pee-Wee.Hypomycesappears to be paraphyletic, with species having wet-conidial phialidic anamorphs more closely related to other genera.Hypomyces chrysostomusBerk & Broome is a sister group to the clade that includes species ofAphysiostromaBarrasa et al.,ArachnocreaMoravec, andHypocreaFr. Based on morphological and molecular evidence, a new genus,Sporophagomyces, is described forHypomyces chrysostomusand two allied species.Hypomyces broomeanusTul. forms one clade with species ofSphaerostilbellaSacc. and is transferred to this genus. The recognition ofArachnocreais justified. The integration ofCladobotryumNees species that are not known to undergo sexual reproduction withHypomycesspecies that possessCladobotryumanamorphs receives strong support, but the whole complex of these species appears to be paraphyletic. However, constraint trees, which require monophyly of all these ana- and pleo-morphic species, do not appear significantly less likely than the other trees obtained under maximum likelihood or parsimony criteria. For the remaining species ofHypomyces, four distinct lineages are distinguished.

ISSN:0008-4026    

DOI:10.1139/b99-148

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Seeds of the eastern North American herbaceous polycarpic perennialThalictrum mirabileSmall have differentiated but underdeveloped (small) embryos that are physiologically dormant at maturity in September. Physiological dormancy was broken effectively by cold stratification at 1°C, but embryos required temperatures15:6°C for growth after physiological dormancy was broken. Gibberellic acid substituted for cold stratification. Breaking of physiological dormancy in seeds exposed to natural temperatures in a greenhouse occurred during winter, and embryo growth and germination occurred in late winter - early spring. Furthermore, seeds in the greenhouse remained viable until the second and third (spring) germination seasons. Thus,T. mirabileseeds have the capacity to form a short-lived persistent soil seed bank. Buried seeds ofT. mirabileapparently go through an annual dormancy-nondormancy cycle. Seeds buried in September 1994 were nondormant when exhumed in April 1995 and April 1996 and incubated in light at 25:15°C for 2 weeks, but they were dormant in June 1995 and September 1995. Seeds ofT. mirabilehave nondeep simple morphophysiogical dormancy. This is the first report of nondeep simple morphophysiological dormancy being broken by cold, and not by warm, stratificati

ISSN:0008-4026    

DOI:10.1139/b99-149

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

We have tested the tacit assumption that the location of anthocyanic cells within a leaf affects the quality and quantity of light that is absorbed. Leaf optics are described forQuintinia serrataA. Cunn., a native New Zealand tree that is polymorphic for anthocyanin distribution and concentration. Anthocyanin production enhanced the absorptance of green-yellow wavelengths in proportion to pigment concentration. The reflectance of red light was independent of leaf anthocyanin content. Variation in the location of pigmented cells could not account for differences in leaf optics. The effects of anthocyanin on PAR absorptance were consistent across six further, unrelated species that bore red leaves. We conclude that anthocyanin concentration, rather than its histological distribution, has the greater impact on leaf optical properties.

ISSN:0008-4026    

DOI:10.1139/b99-153

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The growth rate hypothesis, which states that fast-growing plants support more herbivores than slow-growing plants, was tested with 12 native and 1 naturalized British grasses using the grain aphid (Sitobion avenae). Five aphids were enclosed with grasses for two weeks in a growth chamber. After 2 weeks, fast-growing plants had 38 aphids, whilst slow-growing plants had 6, which supports the growth-rate hypothesis. When aphid numbers were analysed on plants according to "CSR" theory (Grime 1977, 1979), ruderals (R) had 54, competitors (C) had 18, and stress tolerators (S) had 6. This supports the predictions of CSR theory. Furthermore, aphid numbers increased significantly with grass growth rates and a mollusc palatability index, although this largely resulted from a single outlier,Poa annua. Aphid number was not affected by hairs on grasses. Finally, the effect of aphid feeding on grasses was tested. Generally, the greatest change in total and aboveground biomass of the grasses was found in the ruderals, whilst stress tolerators had the least amount of change.

ISSN:0008-4026    

DOI:10.1139/b99-155

出版商:NRC Research Press    

年代:2000

数据来源: NRC