Succession in the southern part of the Canadian boreal forest

Forest succession following fire in a forest mosaic of northwestern Quebec has been studied in order to: (1) describe the successional pathways using communities of different ages and (2) evaluate convergence of successional pathways and possible effect of fire suppression on the establishment of steady-state communities. As a first step, ordination and classification techniques were used in order to remove changes in forest composition which are related to abiotic conditions. Then, ordinations based on tree diameter distributions were used to study shifts in species composition in relation to time since the last fire.Even under similar abiotic conditions, successional pathways are numerous. However, regardless of forest composition after fire, most stands show convergence toward dominance of Thuja occidentalis and Picea mariana on xeric sites and dominance of Abies balsamea and Thuja occidentalis on more mesic sites. Stable communities of >300 yr occur on xeric sites while on mesic sites directional succession still occurs after 224 yr. Nearly all species involved in succession are present in the first 50 yr following fire. Only Abies balsamea and Thuja occidentalis increase significantly in frequency during succession. Following initial establishment, successional processes can generally be explained by species longevity and shade tolerance. Early successional species may be abundant in the canopy for more than 200 yr while the rapid decrease of Picea glauca, a late successional species could be related to spruce budworm outbreaks. Considering the short fire rotation observed (about 150 yr), a steady-state forest is unlikely to occur under natural conditions, though it may be possible if fire is controlled.     

Fourfold polyphyly of the genus formerly known as Upucerthia, with notes on the systematics and evolution of the avian subfamily Furnariinae

The traditional avian subfamily Furnariinae, a group of terrestrial ovenbirds typical of the Andean and Patagonian arid zones, consists of the genera Furnarius, Cinclodes, Geositta, Upucerthia, Chilia, and Eremobius. We investigated phylogenetic relationships within the Furnariinae, with particular attention to the nine species of the genus Upucerthia, using nuclear and mitochondrial DNA sequences from all genera in the subfamily. Upucerthia was found to be highly polyphyletic, its constituent species forming four non-sister clades: (1) a basal lineage consisting of two Upucerthia species, U. ruficaudus and U. andaecola, as well as the monotypic genera Eremobius and Chilia; (2) a lineage consisting of U. harterti and U. certhioides, two species behaviorally divergent from other Upucerthia species; (3) a lineage consisting of U. serrana, which is not closely related to any other Upucerthia species; and (4) a lineage, sister to Cinclodes, consisting of the four Upucerthia species U. dumetaria, U. albigula, U. validirostris, and U. jelskii. The larger Furnariinae was also found to be highly polyphyletic; the terrestrial open country ecotype characteristic of this subfamily occurs in four unrelated clades in the family Furnariidae, including a basal lineage as well as derived lineages. Although the large degree of divergence among Upucerthia clades was not previously recognized, owing to ecological, behavioral, and morphological similarities, the groupings correspond closely to relationships suggested by plumage. This is in contrast to studies of other avian genera in which plumage patterns have been shown to be extensively convergent. The generic names Upucerthia and Ochetorhynchus are available for two of the former Upucerthia clades; new generic names may be warranted for the other two.     

Characterization of the transposon carrying the STII gene of enterotoxigenic Escherichia coli

Summary The Escherichia coli enterotoxin STII gene is carried by Tn4521. The terminal repeats of Tn4521 are composed of IS2 sequences; however, neither repeat is a complete IS2. In order to determine how this seemingly defective transposon could transpose, mutations were generated within Tn4521 to determine the regions essential for transposition. The left terminal repeat region was found to be non-essential, but the right terminal repeat area was demonstrated to be crucial for transposition. Within the right terminal repeat area is an open reading frame (ORF), capable of encoding a 159 amino acid protein, which was shown by frameshift mutation analysis to be required for transposition. This protein may be the transposase of Tn4521. A pair of 11 bp repeat sequences flanking the ORF was also found to be important. The right 11 bp repeat is part of the left IS2 terminal sequence, and the left 11 bp repeat is located about 300 bp upstream from the right IS2 terminal sequence located within the right terminal repeat region. The results of this study suggest that Tn4521 is a functional transposon and that the sequence including this pair of 11 bp sequences plus the intervening sequence is a transposable element which may be responsible for Tn4521 transposition.     

Hectorella: A member of the betalain-suborderChenopodiineae of the orderCentrospermae

Roots ofHectorella caespitosa Hook. f. were induced to produce a red pigment which was shown to be a betalain and not an anthocyanin. These data indicate thatHectorella belongs to theChenopodiineae, the betalain suborder of theCentrospermae, and excludes alignment with the anthocyanin family theCaryophyllaceae.     

Negotiations between animals and bacteria: the 'diplomacy' of the squid-vibrio symbiosis

A shared characteristic among animals is their propensity to form stable, beneficial relationships with prokaryotes. Usually these associations occur in the form of consortia, i.e. a diverse assemblage of bacteria interacting with a single animal host. These complex communities, while common, have been difficult to characterize. The two-partner symbiosis between the squid Euprymna scolopes and the marine luminous bacterium Vibrio fischeri offers the opportunity to study the interaction between animal and bacterial cells, because both partners can be cultured in the laboratory and the symbiosis can be manipulated experimentally. This system is being used to characterize the mechanisms by which animals establish, develop and maintain stable alliances with bacteria. This review summarizes the progress to date on the development of this model.     

Protection against suspended sand: the function of the branchial membrane in the blue mussel Mytilus edulis

Blue mussels (Mytilus edulis) living in estuaries have to cope with varying concentrations of suspended sand. Sand flowing through the inhalant siphons comes into the infrabranchial chamber. The inhalant siphon can be partially closed by the branchial membrane. As a result the inward flow decreases, and suspended sand sinks and can be eliminated. Experiments with mussels from three ecologically different locations showed about the same response of the branchial membrane on contact with suspended sand. The presence and function of the branchial membrane appears to be an adaptation of mussels to their estuarine environment.     

Evolution of the Australian flora through the Tertiary

The evolution of the Australian flora through the Tertiary has not been reviewed by a megafossil palaeobotanist for almost a century. Based on material available and published studies, the Australian Tertiary can be considered in three units: Eocene, Oligo-Miocene, and Pliocene. Key taxa in the Eocene includeCasuarinaceae, Proteaceae, Fagaceae, Podocarpaceae, andLauraceae. Many known Eocene deposits are interpreted as warm, humid rainforests.Oligo-Miocene floras reflect a climatic deterioration, with greater occurrence of sclerophylly and xerophylly. A reduction of tropical taxa is seen with an increase ofMyrtaceae and earliest records ofMimosaceae, Chenopodiaceae, andPoaceae. These trends continue into the Pliocene, which is not well represented in Australia.Problems needing to be addressed include the discrepancy between the pollen and megafossil records ofNothofagus, the origins of Australia's wet tropical taxa, and the role of fire in the early evolution of the Australian flora.     

On the nomenclature ofPan paniscus

In 1929 a subspecies of chimpanzee was classified asPan satyrus paniscus, a subspecies of theeastern chimpanzee, and elevated to species level,Pan paniscus, in 1933. Review of the literature indicates that this ape type was known since 1881 from several locations throughout the Congo Basin and first scientifically described in 1887 asTroglodytes niger var.marungensis, a subspecies of thewestern chimpanzee. The evidence presented here demonstrates that the synonymmarungensis was known and used as an earlier name. According to the International Code of Zoological Nomenclature, the earliest name awarded to a species is the one which has to be recognized in use. However, maintaining the emphasis on stability and assuming that to change the name would cause considerable confusion in the literature, it is this author's recommendation that the earlier namemarungensis be suppressed and the later synonympaniscus be conserved while an application is being considered for ruling by the International Commission on Zoological Nomenclature.     

Enzyme-linked immunosorbent assay for the activator protein specific for the enzymic hydrolysis of GM1 in urine

We have established a sensitive and specific enzyme-linked immunosorbent assay (ELISA) for the detection of the activator protein which stimulates the enzymic hydrolysis of G_M1 (G_M1-activator) in human urine. The level of G_M1-activator in 19 normal, adult urine samples was estimated to be 370.7±33.2 ng/ml. The amounts of G_M1-activator excreted in 24 h were estimated to be between 0.28 and 1.1 mg. The coefficient of variation for this method is 4.3% for the intra-assay and 14.4% for the inter-assay. Urine samples, without purification, can be used directly for the ELISA.     

Reliability of the resorcinol method for identifying isomorphic phases in the Gigartinaceae (Rhodophyta)

The Gigartinaceae are economically important because the carrageenans in this family are used for a variety of purposes including food stabilizers, food substitutes, pharmaceutical applications and cosmetics. The resorcinol method takes advantage of the different carrageenans found in life history phases in this family to identify nonreproductive phases, and consequently, a better understanding of the biology of this economically important family is possible. This study investigates sources of variability that could affect the accuracy of the resorcinol method in identifying phases within the Gigartinaceae. Vegetative disks of Iridaea splendens from different areas of the blade and disks containing reproductive structures all reacted consistently to the resorcinol reagent. The minimum size and testing conditions required to reliably identify phases at the germling stage of I. splendens were determined. Phases of I. splendens cannot be identified if blades are stored in 3% formaldehyde in seawater. Phases of I. splendens, I. lineare, I. heterocarpa, Rhodoglossum californicum and R. affine can be identified reliably at different times of the year. Manipulations of the resorcinol method improved its accuracy in identifying phases of Iridaea cornucopiae and Gigartina exasperata but the high percent of G. exasperata misidentified demonstrates that it cannot be assumed that the current resorcinol method works for all taxa in the Gigartinaceae.     

Microbial decomposition of urea in the Menai Straits

The assimilation of urea by the microbial population of the Menai Strait (Anglesey, U.K.) was studied over a seasonal cycle. Samples incubated in the light produced higher assimilation rates than samples incubated in darkness. Higher ratios assimilation of urea: chlorophyll a during a time of a probable nitrogen limiting condition may be indicative of the importance of urea for phytoplankton nutrition. Assimilation rates of urea were higher during the diatom and Phaeocystis bloom than in times of low standing crop.Phytoplankton seem to be the major utilizers of urea in the Menai Strait waters. Bacteria may also be important in the decomposition of urea. However, with the methods employed it was not possible to estimate the extent of their participation in the urea decomposition.     

Fine-scale genetic characterization of Plasmodium falciparum chromosome 7 encompassing the antigenic var and the drug-resistant pfcrt genes

The fact that malaria is still an uncontrolled disease is reflected by the genetic organization of the parasite genome. Efforts to curb malaria should begin with proper understanding of the mechanism by which the parasites evade human immune system and evolve resistance to different antimalarial drugs. We have initiated such a study and presented herewith the results from the in silico understanding of a seventh chromosomal region of the malarial parasite Plasmodium falciparum encompassing the antigenic var genes (coding pfemp1) and the drug-resistant gene pfcrt located at a specified region of the chromosome 7. We found 60 genes of various functions and lengths, majority (61.67%) of them were performing known functions. Almost all the genes have orthologs in other four species of Plasmodium, of which P. chabaudi seems to be the closest to P. falciparum. However, only two genes were found to be paralogous. Interestingly, the drug-resistant gene, pfcrt was found to be surrounded by seven genes coding for several CG proteins out of which six were reported to be responsible for providing drug resistance to P. vivax. The intergenic regions, in this specified region were generally large in size, majority (73%) of them were of more than 500 nucleotide bp length. We also designed primers for amplification of 21 noncoding DNA fragments in the whole region for estimating genetic diversity and inferring the evolutionary history of this region of P. falciparum genome.     

Transfer of members of the genus Falcivibrio to the genus Mobiluncus, and emended description of the genus Mobiluncus

It has long been thought that the genera Mobiluncus and Falcivibrio contain the same organisms. Using a polyphasic approach, it was found that Mobiluncus curtisii and Mobiluncus mulieris were the same as Falcivibrio vaginalis and Falcivibrio grandis, respectively. As the genus name Mobiluncus takes precedence, it is proposed that F. vaginalis and F. grandis be transferred to the genus Mobiluncus. In agreement with previous studies, results from phenotypic tests did not support the separation of M. curtisii strains into its two subspecies, M. curtisii subsp. curtisii and M. curtisii subsp. holmesii. Phenotypic complexity within M. curtisii dictates that the species should be treated as a complex until more in-depth analyses of the species have been performed. Phylogenetic analyses, based on 16S rRNA gene sequences, demonstrated that the genus Mobiluncus was associated with Varibaculum cambriense and the two subspecies of Actinomyces neuii, and that A. neuii is only distantly related to Actinomyces sensu stricto.     

Observations on the morphology of some North American nemertines with consequent taxonomic changes and a reassessment of the architectonics of the phylum

A majority of the nemertine species from the western North Atlantic were originally described from life in the nineteenth century. Many of these were established by A. E. Verrill who had ‘an eye for species’ no matter which phylum he was working with, and thus when living nemertines which he described are encountered, they can usually be recognized. The morphology of most of these species has never been reported; some may prove to be species described earlier from the eastern North Atlantic. Morphological observations on the nemertine species from the North East coast of the Pacific are inadequate and have prevented satisfactory comparison with species from Japan and eastern Russia. The morphology of some species collected in the Gulf of Maine and from Cape Cod, as well as a re-examination of some of the slides of type specimens of species from the west coast of North America, indicates that their generic placement must be re-examined. The architectonic plan of the heteronemertines postulated over 100 years ago can not be substantiated and is redescribed. Three new heteronemertean genera are described: Tenuilineus gen.n. Parvicirrus gen.n., Tarrhomyos gen.n.     

A reconsideration of the genusRabdosiella (Lamiaceae,Nepetoideae, Ocimeae)

The two generaPlectranthus andIsodon are compared and found to be very dissimilar.Isodon ist considered to be misplaced inOcimeae subtribePlectranthinae and apparently is more closely related to subtribeHyptidinae. The disjunct genusRabdosiella is compared to these two genera and regarded to be polyphyletic. The AfricanR. calycina (Benth.)Codd is returned toPlectranthus and calledP. calycinus Benth., while the AsianR. ternifolia (D. Don)Codd is placed inIsodon sect.Pyramidium and calledI. ternifolius (D. Don)Kudo.     

Utilized and potentially utilizable seaweeds on the Namibian coast: biogeography and accessibility

Of the 1500 km coast of Namibia, only 80 km is predominantly rocky, the remaining 1420 km being sandy with only minor rocky outcrops. At present two species are utilized, Gracilaria verrucosa for agar and Laminaria schinzii for human consumption. Other potentially utilizable seaweeds occurring on the coast are Ecklonia maxima for alginates, Suhria vittata for agar, Gigartina radula, G. stiriata and Aeodes orbitosa for carrageenans and Porphyra capensis for human consumption. Laminaria schinzii also can be used for alginate production. Due to the diamond-mining areas around the 80 km rocky area at Luderitz (26° 39 S), only 20 km are accessible; hence, at present the seaweeds are being exploited almost to their full potential. The species currently not being utilized could be used, however, to support the industry that already exists at Luderitz. To increase production, access to the diamond areas would have to be gained or a cultivation program initiated.     

Comparative ultrastructure of the zoospores of nine species ofNeochloris (Chlorophyta)

Nine species ofNeochloris can be divided into three groups on the basis of comparative ultrastructure of the flagellar apparatus, the cell wall and the pyrenoid of zoospores. In Group I,N. wimmeri andN. minuta, zoospores are thin-walled, pyrenoids are penetrated by stromal channels, and the basal bodies are in the clockwise absolute orientation and connected by the distal and two proximal fibers. In Group II,N. aquatica, N. vigenis, N. terrestris, N. pyenoidosa, andN. pseudostigmatica, zoospores are naked or covered by fuzzy material, pyrenoids are covered by a continuous starch sheath or invaginated by cytoplasmic channels, basal bodies are directly opposed, the distal fiber is differentiated into a ribbed structure at the central region, a striated microtubule-associated component (SMAC) is continuous between opposite two-membered rootlets and connected to the ribbed structure, proximal ends of basal bodies are covered by partial caps, each two-membered rootlet and a basal body are connected by a striated fiber to the X-membered rootlet associated with the opposite basal body, and the basal bodies, when oriented at wide angles, are joined at their proximal ends by core extensions. In Group III,N. pseudoalveolaris andN. cohaerens, zoospores are naked, pyrenoids are traversed by parallel thylakoids, basal bodies are in the counterclockwise absolute orientation and overlapped, and each X-membered rootlet is connected to the end of the opposite basal body by a terminal cap. It is suggested that the genusChlorococcopsis gen. nov. be erected for the Group I species. Group II, which includes the type species,N. aquatica, should be preserved asNeochloris. The group appears to be closely related to the coenobial generaPediastrum, Hydrodictyon, andSorastrum, and to have affinities with the coenocytic generaSphaeroplea andAtractomorpha as well. It is also suggested that the genusParietochloris gen. nov. be erected in thePleurastrophyceae for the species of Group III.