摘要:

Differentiation of most North American spruce (Picea) species can be done based on needle morphology and anatomy.Picea brewerianaS. Watson,Picea chihuahuanaMartìnez,Picea mariana(Mill.) BSP,Picea martineziiPatterson, andPicea rubensSarg. needles have two continuous resin ducts extending from near the base to near the tip.Picea engelmanniiParry ex Engelm.,Picea glauca(Moench) Voss,Picea pungensEngelm.,Picea mexicanaMartìnez, andPicea sitchensis(Bong.) Carr. needles have variable numbers of short, intermittent resin ducts or sacs. Within each of these groups, most species could be differentiated based on cross-sectional shape, resin-duct diameter, and resin-duct position.Picea marianaandP. rubens, andP. glaucaandP. engelmanniiare two pairs with similar needles, but they can be differentiated using linear discriminant analysis based on resin-duct diameter and position in cross section. Paleoecological and paleoclimatological studies may be facilitated by species-level identification of plant macrofossils because of different ecological adaptations of each species. Resin-duct continuity patterns are generally consistent with current taxonomic classifications, except forP. glauca. Based on our results, together with DNA and crossing studies,P. glaucais apparently more closely related toP. engelmanniiandP. sitchensisthan toP. rubensandP. mariana, with which it is often classified.Picea pungensis probably more distantly related toP. engelmanniithan has been assumed in some previous classifications.Picea martineziiandP. chihuahuanamay be very closely related to each other.Key words: spruce,Picea, North America, needle, resin duct, anatom

ISSN:0008-4026    

DOI:10.1139/b00-111

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

On the island of Öland the weed,Silene vulgaris(Moench) Garcke, and the endemic,Silene unifloraRoth ssp.petraea, hybridize when brought into contact by anthropogenic disturbance. Variation was studied in transects across a hybrid zone where a linear population ofS. vulgariscrossed the native habitat ofS. uniflorassp.petraea. Plants were scored for 20 morphological characters. Although individual characters showed clinal trends between weed and endemic, all plants were assignable to one or other parental species. Only 14% of the 554 scored plants showed intermediacy in one or a few characters, and ordinations showed two separate groups of samples. The low number of intermediates is discussed in terms of character choice, habitat separation, disturbance history, and reproductive ecology. The results of the study are consistent with the earlier observation that the species have remained morphologically distinct on Öland, despite evidence of sparse introgression of allozymes from weed to endemic. Disturbance is necessary not only for the creation of intermediate (hybrid) habitats but also for the establishment of the weedy parent. The transient nature ofS. vulgarispopulations is likely to be important in limiting introgression intoS. uniflorassp.petraeaunder the present disturbance regime.Key words: genetic assimilation, hierarchical partitioning of diversity, habitat disturbance, introgression, rare species, cline

ISSN:0008-4026    

DOI:10.1139/b00-113

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

We examined the development of ovules and components of reproductive yield as they related to plant size and fruit position within plants ofAlliaria petiolata(M. Bieb.) Cavara and Grande from three sites. We found that both factors affected fruit and seed production, and patterns of ovule fate. Larger plants were more fecund than their smaller counterparts, while proximally positioned flowers within an inflorescence produced more seeds. Maternal investment was regulated according to plant mass at two levels: among fruits (small plants had significantly lower fruit-set than did large plants), and within fruits (small plants had significantly fewer ovules and significantly higher proportions of aborted ovules per fruit than did large plants). All absolute measures of reproduction had positive linear relationships with plant size, but a threshold size for flowering was not found. Most proportional measures of reproduction were independent of plant size. Small plants produced the same relative proportions of total seed number and total seed mass per unit plant dry mass as large plants. Therefore, proportional reproductive allocation did not vary with plant size. However, small plants produced proportionately more flowers per unit dry mass. Small plants may be maximizing their overall fitness through increased allocation to male function (flower production).Key words:Alliaria petiolata, plant-size effects, fruit-position effects, reproductive allocation, patterns of ovule abortion, seed maturation.

ISSN:0008-4026    

DOI:10.1139/b00-110

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Coast redwood (Sequoia sempervirens(D. Don) Endl.) has long-lived individual trees that can reproduce both sexually and asexually. Allozyme markers indicate that, in old-growth populations in northern California, 15-34% of clones are multistemmed. Of those, they have few stems per clone, and none are very spatially pervasive. There is much variety in the clonal configurations observed, including circular, linear, and (or) disjunct arrangements. Visual assessment is a poor predictor of clonal identity and fairy ring structures more often than not contain multiple genotypes. In this first allozyme study of coast redwood, high levels of genetic variation are observed, higher than those observed for most other western conifers. These levels are perhaps related to the species' hexaploid condition, ancient phylogenetic lineage, and historically broader natural range. There are also generally high levels of genotypic diversity. Upland sites, with more frequent and intense fires, do not differ significantly in genotypic diversity from the more mesic lowland sites. Population structure in coast redwood seems to resemble the classic pattern for many open-pollinated conifers: much diversity within and little among populations. However, this is not a rangewide study. The current levels and structure of genetic and genotypic diversity in old-growth populations suggests episodic recruitment. The long-lived nature of individual stems and the capacity for asexual reproduction may allow clones to exist indefinitely, thus challenging some of the generalizations in evolutionary theory that are based on sexually reproducing species.Key words: clones, asexual reproduction, allozyme diversity, conifer, gymnosperm, polyploid.

ISSN:0008-4026    

DOI:10.1139/b00-114

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Few studies of inbreeding depression have focused on species producing both showy, chasmogamous (CH) flowers and self-pollinated, cleistogamous (CL) flowers. The goals of this investigation were to measure the level of inbreeding depression in the North American violet,Viola canadensisL., and to determine if any fitness differences were linked to floral type (CH versus CL) rather than to cross type (self versus outcross). Hand pollinations were carried out to produce self- and outcross-pollinated CH progeny, and CL seeds were also collected. In a greenhouse, selfed and outcrossed CH flowers produced similar numbers of seeds, and both types of progeny had similar survival rates and comparable numbers of CH flowers, although outcrossed CH progeny had 14% greater vegetative biomass than selfed CH progeny. The level of inbreeding depression inV. canadensiswas low, indicating that there may be few drawbacks to selfing in this species. A comparison of CL and self-pollinated CH progeny showed that, although there were differences in CH flower number, overall fitness differences were minimal. The similar performance of selfed (CL and CH) and outcrossed progeny in early life-history stages ofV. canadensissuggests a history of inbreeding in the population.Key words: cleistogamy, inbreeding depression, outcrossing, selfing,Viola canadensis.

ISSN:0008-4026    

DOI:10.1139/b00-115

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The finding of new individuals of a clonal plant,Juncus gerardi, raised the question of modalities for the colonization of new sites by this species. Indeed, the existence of seedlings has not been observed in the field, nor reported in the literature for European marshes. Among the parameters limiting recruitment, we examined the soil seed bank, which appeared extremely small. Many seeds could be found in bovine feces but few were found in equine feces. Futhermore, bovines are not only important for seed dispersion, but also for the improvement of the germinative capacities: the seed germination rate ofJuncus gerardiwas doubled after digestive transit. Germination testing showed that this species is largely tolerant to salinity (from 0 to 26,4 mS·cm-1). The germination rate was maximal with a thermoperiod of 10-20°C but null for a 0-10°C thermoperiod. Germination was improved by immersion and was light dependent. The critical phase for colonization success in new habitats could be primarily seedling survival. Recruitment success inJuncus gerardiseems to be a rare event, requiring the combination of favorable conditions related to climate and gap openings in swards.Key words: germinative capacities, feces, clonal plant, grazers, endozoochory, pasture

ISSN:0008-4026    

DOI:10.1139/b00-117

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

This study compared the sensitivity to, and uptake and distribution of, cadmium (Cd) in three tree species, Norway spruce (Picea abies(L.) Karst.), Scots pine (Pinus sylvestrisL.), and European white birch (Betula pendulaRoth),as well as different populations of these species. Seedlings of each species from three regions (southern, central, and northern parts of Sweden) were cultivated in nutrient solution and treated with varying concentrations of Cd. Sensitivity was determined by using the Weibull function on root and shoot dry weight and root length measurements. Cd uptake and translocation were analysed. The results on root sensitivity revealed that birch and spruce were the least and most sensitive species, respectively, to both the external and tissue levels of Cd. In terms of shoot sensitivity, however, birch was the only species affected by Cd, i.e., the most sensitive species. Pine and birch had similar Cd uptake, while spruce had lower uptake and translocation of Cd compared with the others. There were also differences in sensitivity within the species. The central ecotype of all species tended to be the most Cd resistant. The central ecotype of spruce and birch had the lowest Cd uptake, whereas the central ecotype of spruce and pine had the lowest translocation of Cd to the shoot.Key words: birch, cadmium, pine, sensitivity, spruce, uptake.

ISSN:0008-4026    

DOI:10.1139/b00-119

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Ribosomal DNA sequences were amplified from subfossils of the ascolichenUmbilicaria cylindrica(L.) Delise ex Duby collected at the ablating edges of Greenland glaciers. Surprisingly, phylogenetic analysis indicated that the amplified rDNA sequences were not closely related to those of the lichen-forming fungus but rather represented two groups of psychrophilic basidiomycetes (orders Cystofilobasidiales and Sporidiales) and one group of ascomycetes (order Leotiales). Two of these groups, the Sporidiales and the Leotiales, include other fungi previously detected in DNA extracted from the grass clothing of the Tyrolean Iceman desiccated and frozen for over 3000 years and also in 2000- and 4000-year-old ice core samples from northern Greenland. Large subunit ribosomal DNA sequences representing the group Cystofilobasidiales were nearly identical to those of the basidioyeast saprobeMrakia frigida. The adjacent internal transcribed spacer sequence was more than 98% similar to those from three samples ofU. cylindricafrom different sites that had been subjected to ice burial for various lengths of time, suggesting they also wereMrakiasequences. Although ancient contamination of multipleU. cylindricaspecimens with fungi such asMrakiacannot be ruled out, it is more probable that saprobic colonization of the subfossil tissues by psychrophilic fungi proceeded during recent ice melt.Key words: ancient DNA, small subunit ribosomal DNA, 18S ribosomal DNA, phylogenetic analysis, psychrophilic fungi, lichen-forming fungi.

ISSN:0008-4026    

DOI:10.1139/b00-120

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Determining factors involved in root polymorphism were studied in young hevea seedlings (Hevea brasiliensisMull. Arg.) following an experimental block of the tap root in the laboratory, using minirhizotron grown plants. The authors show that this block promotes different morphogenetic modifications in the root system: regrowth of the early secondary roots having the largest external apex, high density of the ramification zone in the taproot apical area, large growth (associated with an important external diameter at the apex), and orthogeotropism of the sequential secondary roots emerging after the treatment in the zone close to the blockage site. The evolution of morphogenetic potentialities of sequential secondary roots following an inhibition of the taproot growth was confirmed using other cultivation set ups, under controlled (aeropinic) or natural (underground observation windows) conditions. Overall results show that the expression of the early morphogenetic potential acquired by the roots can be modulated by the environmental conditions exerting their effect during their development. Notably, the active growth correlations existing between the taproot and the secondary axes confer a high plasticity to the root system which will permit its adaptation to heterogeneous or restricting environments. These correlative influences are discussed in the frame of an hormono-trophic model for the root morphogenetic determinism, essentially based on taproot dominancy.Key words: articial block, growth correlations, root system, morphogenesis, minirhizotron,Hevea brasiliensis.[Journal translation]

ISSN:0008-4026    

DOI:10.1139/b00-118

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Bryonia albaL. (Cucurbitaceae) is a herbaceous Eurasian vine that predominantly reproduces clonally (asexually) through apomixis. We assessed the magnitude and distribution of clonal diversity within and among 23 recently established populations ofB. albain its new range in the western United States, based on the distribution of multilocus isozyme genotypes. Fifty-two unique clones were detected: 30 in the nine populations from eastern Washington and northern Idaho, and the remaining 22 in 14 populations from western Montana, northern Utah, and southern Idaho. On average, each population ofB. albawas composed of 6.4 clones, and the proportion of distinguishable clones was 0.275. Multilocus diversity (D) was 0.632 and multilocus evenness (E) was 0.556. Twenty-six of 52 clones (50%) were restricted to a single population, and, on average, each clone occurred in 2.83 populations. Compared with other clonally reproducing plant species, this vine possesses moderate to high levels of clonal diversity in its new range in the western United States. This diversity appears to be a consequence of the events associated with its introduction (including multiple introductions), founder effects, and the proportion of sexual to apomictic reproduction within populations.Key words: invasive vine, apomixis, multilocus genotypes, clonal diversity and evenness,Bryonia alba, Cucurbitaceae.

ISSN:0008-4026    

DOI:10.1139/b00-116

出版商:NRC Research Press    

年代:2000

数据来源: NRC