摘要:

Despite the fact that the genusAulacoseiraThwaites is a common component of phytoplankton communities in many North American water bodies, there are relatively few taxonomic based surveys utilizing the scanning electron microscope (SEM). In addition, based on the current literature, some species are difficult to identify or distinguish from other taxa. We present taxonomic and morphological observations on 19 taxa based primarily on collections made in Connecticut, U.S.A., and from central and northern Canada.Aulacoseira ambigua(Grunow) Simonsen,Aulacoseira subarctica(O. Müller) Haworth, andAulacoseira tenella(Nygaard) Simonsen were the most common species encountered in Connecticut, whileAulacoseira islandica(O. Müller) Simonsen,Aulacoseira granulata(Ehrenberg) Simonsen,A.subarctica, andA.ambiguawere the dominant species from many central Canada localities. In the Canadian Shield region, specimens of theAulacoseira disions(Ehrenberg) Simonsen group, theAulacoseira lirata(Ehrenberg) Ross in Hartley group, andAulacoseira perglabra(Oestrup) Haworth were more common. We had the most difficulty identifying taxa in theA.distortsandA.perglabracomplexes and distinguishingA.liratafromAulacoseira alpigena(Grunow) Krammer. The primary objectives of the paper were to provide an additional source of high-resolution SEM micrographs for many of the more common species ofAulacoseira, comment on the morphological detail of each taxon, and to discuss the difficulties we encountered using the current literature to identify some of the species. A few ecological observations are also provided. Lastly, we propose two new combinations,Aulacoseira pseudoamericana(Camburn) comb.nov. andAulacoseira distansvar.nivaloides(Camburn) comb.nov.Key words: diatoms,Aulacoseira, North America, taxonomy, morphology.

ISSN:0008-4026    

DOI:10.1139/b97-894

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

The interactive effects of SO2and NO3−on the green-algal lichenRamalina farinacea(L.) Ach. were investigated using the degree of chlorophyll phaeophytinization and ultrastructural damage to theTrebouxiaphotobiont. Thalli were submitted to several factorial design experiments in which they were exposed to mean SO2concentrations ranging from 118 to 140 nmol∙mol−1plus or minus aqueous solutions of NO3−at either 50 or 1000 μmol∙L−1, for 6–14 days. Interactive effects of SO2and NO3−were synergistic when the effects of each individual pollutant were slight. However, this pattern reverted to additive effects, and sequentially to antagonistic effects as the detrimental impact of SO2alone became more severe. Despite this transition, neutralization of the damaging impact of SO2by simultaneous treatment with NO3−was not observed. The results show that interactions between SO2and NO3−were variable, but predictable on the basis of the expected effects following exposure to each pollutant alone. The coincidence of this empirical pattern with those observed in previous studies suggests involvement of unspecific causes. The wider ecological significance of interactions between SO2and NO3−is discussed in the light of other findings with respect to the effects of air pollution on lichens in the field.Key words: air pollution, sulphur dioxide, nitrate, interactive effects, lichens, pigments, ultrastruct

ISSN:0008-4026    

DOI:10.1139/b97-895

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

During a 3-year study of the ectomycorrhizal fungi of subalpine forests in the Front Ranges of the Canadian Rockies, species ofRussulaandLactariuswere conspicuous mycobionts of both erect and krummholz forms ofAbies lasiocarpa(Hook.) Nutt. andPicea engelmanniiParry. Morphological identifications of Russulaceous mycorrhizae were confirmed by comparing polymerase chain reaction amplified ribosomal DNA (internal transcribed spacer region) with that of sporocarp tissue. Restriction fragment length polymorphism analysis usingAluI,HhaI,HinfI, andRsaI gave a distinctive profile for each of 14 Russulaceous sporocarps and facilitated the identification of five mycorrhizae. Mantles formed by Lactarii (Lactarius alnicola,Lactarins caespitosus, andLactarius deliciosusvar.areolatus) exhibit characteristic laticifers and pigments comparable to the associated sporocarp. Those formed by species ofRussula(R.brevipesandR.silvicola) bear distinctive cystidia or sulphovanillin-reactive cells.Key words: ITS,Lactarius, RFLP,Russula, subalpine, tree line.

ISSN:0008-4026    

DOI:10.1139/b97-896

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

The clonal shrubAmelanchier nantucketensisis andropetalous; a variable number of petals as well as normal anthers both bear germinable pollen. To determine whether floral density associated with andropetaly is related to activity of native bees on flowers, we comparedAmelanchier nantucketensistoAmelanchier humilisandAmelanchier stolonifera, which have sterile petals. In samples from four Maine sites, floral density inAmelanchier nantucketensiswas 30.3% greater than that forAmelanchier humilisand 39.5% greater than that forAmelanchier stolonifera; inAmelanchier nantucketensis, flowers were more numerous per cubic metre and distance between flowers was shorter. There was a significant correlation across all sites and species between the number of flowers per plant and number of inflorescences visited per bee in 10 min (r = 0.711,p = 0.0001). Statisticalttests separatedAmelanchier nantucketensisfrom bothAmelanchier humilisandAmelanchier stoloniferaby plant height, nearest stem, nearest flower, and number of inflorescences visited per bee during 10 min. Plant species classification in a canonical discriminant analysis was 83–93% correct with four plant variables, namely distance to nearest flower, distance to nearest inflorescence, plant width, and plant height. Our findings support optimal foraging theory in that bee visits increase with floral density in theseAmelanchierspecies.Key words:Amelanchier, andropetaly, bees, floral density, morphology, Maine.

ISSN:0008-4026    

DOI:10.1139/b97-897

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Pollinator preference has been demonstrated to depend on floral morphology in some plant groups. We tested bee preference forAmelanchier nantucketensis, which has pollen-bearing petals or andropetals, overAmelanchier humiliswith its normal petals when these flower together at two Maine sites. In an array experiment with equal floral display forAmelanchier nantucketensisandAmelanchier humilis, almost twice as many bees approached the latter first. Bees responded to some aspect of the larger flowers ofAmelanchier humiliswhen number of inflorescences and height above the ground were similar. We captured 539 bees in 43 species individually on flowers, in malaise traps, and in sweeps; most were common, widely distributed solitary and eusocial bees. Bee species diversity differed slightly between plant species, and guilds differed; 11 bee species were unique toAmelanchier nantucketensis, including 39 individuals ofAndrena milwaukiensis, and three species were unique toAmelanchier humilis. For 29 bee species shared by both plant species, abundance onAmelanchier nantucketensiswas greater than onAmelanchier humilisfor 62%, less for 14%, and the same for 24%. Bees might be attracted toAmelanchier nantucketensisless by andropetaly than by proximity of flowers to the ground, floral density, or unidentified features.Key words:Amelanchier, bees, foraging, morphology, Maine, species diversity.

ISSN:0008-4026    

DOI:10.1139/b97-898

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Seed morphology (testa ornamentation and seed shape) and allozyme variation were investigated in three closely related and partially sympatric taxa ofSilenein the Nordic region. Within this region,Silene vulgarisis a widespread weed of anthropogenic habitats. The two subspecies ofSilene unifloraare restricted to naturally open habitats; ssp.uniflorahas a coastal distribution, whereas the Swedish endemic, ssp.petraea, is restricted to limestone habitats on the islands of Öland and Gotland. All three taxa show a seed ornamentation polymorphism, with individuals producing either tubercled or smooth ("armadillo") seeds. Both seed morphology and allozymes show a separation between the two speciesSilene vulgarisandSilene unifloraand support the present taxonomic treatment of the endemic "petraea" as a subspecies ofSilene uniflora. Tubercled seeds predominate inSilene vulgarisand armadillo seeds predominate inSilene uniflora. However, there is considerable between-population variation in seed morph frequencies within taxa. In contrast to the other two taxa, populations ofSilene uniflorassp.petraeaconsistently show intermediate frequencies of both seed morphs.Silene uniflorassp.petraeahas the lowest between-population component of diversity in both seed shape (18–46%) and allozymes (0.8%) and shows no significant geographic structure in any of the character sets. BothSilene uniflorassp.unifloraandSilene vulgarisshow significant geographic differentiation in allozymes and seed morphology. The highest between-population component of diversity was found inSilene uniflorassp.uniflora, where 17% of the total allozyme diversity and 39–82% of the seed shape diversity are accounted for by differences between populations.Key words: allozymes, geographic differentiation, diversity, seed shape, elliptic Fourier coefficients, Landmark characters.

ISSN:0008-4026    

DOI:10.1139/b97-899

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

We used random amplified polymorphic DNA (RAPD) markers to examine the distribution of genotypes ofPalmaria mollis(Setchell et Gardner) van der Meer et Bird, a red alga. We sampled populations along the Northeast Pacific coast from northern Washington to southwestern Alaska, an area extensively glaciated during the last ice age. Our objective was to determine whether the tracks of postglacial recolonization could be extracted from the extant pattern of genotype distribution in a species with limited dispersal capabilities. Thirty-eight individuals from 14 sites were sampled for RAPD markers using nine different random primers. As expected, individuals from the same population were more closely related to each other than to individuals from other populations. Relationships among populations, however, did not necessarily reflect geographic proximity. Rather, populations fell into groups corresponding approximately to outer and inner coastal sites: the northwestern end of Vancouver Island and the Queen Charlotte Islands formed one outer coast group, which associated with sites from Prince William Sound, the Alaska Peninsula, and Sitka, Alaska; the eastern side of Vancouver Island and Ketchikan, Alaska, represented one group of inner sites, which associated with sites near Juneau, Alaska and the eastern end of the Strait of Juan de Fuca. We conclude that this pattern does not represent a single postglacial recolonization event.Key words: biogeography, dispersal, genetic distance,Palmaria mollis, RAPDs, Rhodophyta.

ISSN:0008-4026    

DOI:10.1139/b97-900

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Size at which reproduction occurs was examined in two populations ofOenothera biennisoccupying contrasting habitats: (1) a gravel embankment without complete canopy closure, and (2) a second-year successional field with a closed canopy. One hundred plants were randomly harvested from each site and weighed. A greater proportion of plants reproduced in the closed versus open canopy site (83 versus 61%). There was no difference in mean size at reproduction between the two sites; however, variation in size at reproduction was greater in the closed site where both the smallest and largest plants were found. In the smallest size category, more plants reproduced in the closed than in the open site, indicating that the minimum size required for reproduction is smaller in the closed site. We suggest that plants reproduce at a smaller size in the closed site because of the marked stem elongation associated with reproduction in this species, which increases the ability of plants to compete for light. This question was addressed in a garden experiment in which seedlings were transplanted into either weeded plots (i.e., an open canopy) or a successional field (i.e., a closed canopy). Half the plants at each site were left as vegetative controls and the other half treated with gibberellic acid to induce bolting. Bolting had no effect on growth in the open canopy but increased growth in the closed canopy as predicted.Key words: time of reproduction,Oenothera biennis, life history variation, stem elongation, bolting, size at reproduction, phenotypic plasticity.

ISSN:0008-4026    

DOI:10.1139/b97-901

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Greenhouse studies were conducted to test allelopathic effects ofArtemisia campestrisssp.caudataon seed germination and seedling growth of several sand-dune species and colonization by mycorrhizal fungi. The aqueous extracts ofA.campestrisshowed no inhibitory effect on seed germination, seedling elongation, or dry-weight growth of plants at lower concentrations (10 and 50%), but 100% concentration of the extracts caused varying degrees of inhibition depending on the test species. The mixing of dry leaves of seedlings ofA.campestristo the sand showed severe inhibition ofElymus canadensisseedlings. The percent germination of test species in soil from the rhizosphere ofA.campestriswas significantly lower than that of the control. The leaf area and dry weight were also lower but the differences were not significant. The aqueous extract inhibited mycorrhizal fungal colonization in roots of three sand-dune grasses.Key words: allelopathy,Artemisia campestrisssp.caudata, seed germination, seedling growth, mycorrhizal fungi.

ISSN:0008-4026    

DOI:10.1139/b97-902

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

The inward and outward fluxes of inorganic carbon in illuminated cell suspensions of air-grownAnabaena variabiliswere measured by mass spectrometry under conditions of inorganic carbon disequilibrium. The inclusion of 25 mM NaCl significantly enhanced both inward inorganic carbon influx during CO2fixation and outward CO2efflux when CO2fixation was blocked by the Calvin cycle inhibitor, iodoacetamide. At low, steady-state concentrations of inorganic carbon (< 100μM), CO2fixation was nearly entirely supported by HCO3−transport in the presence of 25 mM NaCl. At approximately 150 μM inorganic carbon, the contributions of CO2and HCO3−transport to CO2fixation were about equal. Above this, CO2transport provided most of the substrate for CO2fixation. The affinity (K0.5) of photosynthesizing cells for CO2, HCO3−and total inorganic carbon was determined and mean values of 1.7, 9.5, and 8.2 μM, respectively, were determined. Maximum rates of inward CO2and HCO3−transport and CO2fixation during steady state were 255.7, 307.3, and 329.1 μmol∙mg−1Chl∙h−1, respectively. Permeability coefficients for CO2of 9.8 × 10−8 m∙s−1and 2.8 × 10−7 m∙s−1were calculated for the plasma membrane and carboxysomal surface areas, respectively, from the dark efflux rates assuming an internal pH of 7.2. A permeability coefficient for HCO3−across the plasma membrane of 7.6 × 10−9 m∙s−1was calculated from the dark inorganic carbon efflux corrected for the corresponding dark CO2efflux. Sodium sulphide (Na2S, 200 μM) blocked CO2transport. In the presence of 25 mM NaCl, net CO2efflux was approximately seven times greater than in its absence, when CO2transport and fixation were both blocked, indicating greater CO2leakage as a result of larger internal inorganic carbon pools in the presence of NaCl. The rapidity and amount of C16O2generated from the exchange of18O from18O-enriched HCO3−with water in cell suspensions suggested that the internal inorganic carbon pool may be rapidly equilibrated.Key words:Anabaena variabilis, CO2-concentrating mechanism, CO2transport, HCO3−transport, CO2efflux, permeability co

ISSN:0008-4026    

DOI:10.1139/b97-903

出版商:NRC Research Press    

年代:1997

数据来源: NRC