EVOLUTION OF THE FUCACEAE (PHAEOPHYCEAE) INFERRED FROM nrDNA-ITS

Sequences of the internal transcribed spacer region (ITS-1, 5.8S, and ITS-2) of nuclear ribosomal DNA were obtained from 16 species representing all six genera of Fucaceae ( Ascophyllum, Fucus, Hesperophycus, Pelvetia, Pelvetiopsis, and Xiphophora ) plus one outgroup ( Hormosira ). Parsimony analysis indicated that the family Fucaceae is monophyletic and that the northern hemisphere taxa are highly divergent from the only southern hemisphere genus, Xiphophora. The genus Pelvetia is not monophyletic because the European P. canaliculata is more closely related to Fucus, Hesperophycus, and Pelvetiopsis than to other Pelvetia species. We establish Silvetia, gen. nov. and transfer the 3 Pacific species of Pelvetia to the new genus. Fucus is monophyletic and not ancestral in the Fucaceae. The ITS sequences identified two strongly supported lineages within Fucus, one with F. serratus sister to the clade containing F. gardneri, F. distichus, and F. evanescens and a second including F. vesiculosus, F. spiralis, F. ceranoides, and F. virsoides. The ITS was not useful for resolving relationships within each of these clusters and between populations of F. vesiculosus. Within-individual variation in ITS sequences is high in Fucus, a derived genus, compared to Ascophyllum, a more ancestral genus. Mapping of the two characters that form the basis of Powell's model for speciation in the Fucaceae showed that 1) number of eggs per oogonium has not followed a gradual reduction and that 2) monoecy/dioecy has changed several times during evolution of this family.     

Dispersal and recruitment of a canopy-forming intertidal alga: the relative roles of propagule availability and post-settlement processes

The daily settlement of eggs and zygotes of the monoecious brown alga Pelvetia compressa (J. Agardh) De Toni was measured on artificial substrata in areas inside and outside patches of adults in the high intertidal zone of central California. Settlement was generally 1–2 orders of magnitude higher under the adult canopy. This pattern seems to be due to the synchronous release of gametes during the daytime low tide. The release of gametes also appears periodic over longer time scales (e.g., 3- and 14-day cycles). In spite of the high availability of propagules under the adult canopy, juveniles were most abundant outside patches, where propagule availability was lower. In both areas, juveniles were disproportionately associated with patches of a red algal turf [primarily Endocladia muricata (Postels & Ruprecht) J. Agardh and Masticarpus papillata (C. Agardh) Kützing]. The turf, which is less common under the P. compressa canopy, may offer protection from dislodgment, grazing, and/or desiccation and thus facilitate recruitment at this site. Overall, post-settlement processes appear more important in determining population structure than does the availability of propagules in areas in and around patches of adults. However, the apparent small range of dispersal of P. compressa may make propagule availability an important limitation to the establishment of new populations and may restrict gene flow between populations. Received: 31 October 1997 / Accepted: 31 August 1998     

Secondary spread of invasive species: historic patterns and underlying mechanisms of the continuing invasion of the European rockweed Fucus serratus in eastern North America

Post-establishment spread of invasive species is a major determinant of their impact, but the spatial pattern and temporal rhythm of secondary spread are often poorly known or understood. Here we examine the spread of the European rockweed Fucus serratus over 1,500 km of shoreline after its initial discovery in Pictou, Nova Scotia (Canada) in 1868. Building upon earlier periodic surveys, we document the current distribution of this invader and provide a historic analysis of the invasion, including the integration of the recently-detected multiple introductions from Europe. The initial spread was rapid in the southern Gulf of St. Lawrence (6.0 km year⁻¹), likely due to both natural spread in a favorable environment and the extensive regional shipping traffic at the time which linked Pictou to several key ports in eastern Canada and northeast USA. Later spread, especially along the Atlantic coast of Nova Scotia, was slower (recently 0.9 km year⁻¹), but included several major jumps (~50–500 km), undoubtedly due to human-mediated transport. Although the spatial extent of the invasion has increased over the past 140 years, it has experienced several remarkable events: apparent local extinctions of northern satellite populations, a major retraction (100–150 km) along the northwestern limits of its continuous range, and stalled invasions at several points and times during its southward progression. Distributional data suggest that this invader is excluding congeners in shallow zones and possibly kelp species in deeper zones. Genetic data from one contact zone showed hybridization with native F. distichus but no evidence for introgression in migrating F. serratus. Hybridization and several other reproductive traits likely contribute to the competitive dominance of the invader in this environment.     

苏云金芽胞杆菌幕虫亚种晶胞粘连现象与晶体蛋白基因cry26Aa所在质粒有关

苏云金芽胞杆菌幕虫亚种T02菌株的伴胞晶体在芽胞外壁内侧形成,呈现晶胞粘连的现象。在此菌株中克隆了cry26 Aa和cry28 Aa两个基因,并对晶胞粘连现象与质粒的相关性做了系统研究。通过消除幕虫亚种T02菌株的质粒,得到了仅消除cry26 Aa所在质粒的菌株BMB1151和无质粒的菌株BMB1152。通过穿梭载体将cry26 Aa和cry28 Aa两个基因分别和同时转化无质粒突变株BMB1152并表达,形成的晶体与芽胞独立存在不能粘连,表明在幕虫亚种染色体背景下仅仅cry的表达不能形成晶胞粘连现象,从而推断晶胞粘连现象可能与幕虫亚种两个基因所在的质粒有关;进一步的研究发现将cry26 Aa在仅消除cry26 Aa所在质粒的突变株BMB1151中表达,形成的晶体与芽胞也分别独立存在不能粘连,从而进一步推断幕虫亚种晶胞粘连现象与cry26 Aa所在质粒有关。     

RECENT VERSUS RELIC: DISCERNING THE GENETIC SIGNATURE OF FUCUS VESICULOSUS (HETEROKONTOPHYTA; PHAEOPHYCEAE) IN THE NORTHWESTERN ATLANTIC1

Fucus vesiculosus L. is one of the most widespread macrophytes in the northwestern Atlantic, ranging from North Carolina (USA) to Greenland (DK). We investigated genetic diversity, population differentiation, patterns of isolation by distance, and putative glacial refugial populations across seven locations from North Carolina (USA) to Cape Breton Island, Nova Scotia (Canada), with microsatellite analyses. Distinct northern versus southern (Delaware–North Carolina) populations were revealed by microsatellite data. Five of six microsatellite loci were fixed in populations in North Carolina, suggesting a recent founder event or a bottleneck, and the same homozygous genotype was found in herbarium materials collected on the North Carolina coast from more than 60 years ago. An additional set of individuals from the northern limit in Greenland was included in our analysis of mitochondrial intergenic spacer (mt IGS) haplotypes in the northwestern Atlantic. Remarkably, 184 of 188 F. vesiculosus specimens from North Carolina to Greenland shared the same haplotype. Recent colonization of the North American shore from Europe is hypothesized based upon the ubiquity of this common haplotype, which was earlier reported from Europe.     

SUBMISSION AND RETRIEVAL OF AN ALIGNED SET OF NUCLEIC ACID SEQUENCES

An important part of many studies published in the Journal of Phycology is the construction and analysis of an alignment of related nucleotide sequences. These alignments are valuable to other investigators, especially when the data provide a basis for more than one possible alignment. Publication of alignments, however, is prohibitively expensive, and the data are difficult to retrieve and use in this form. Several electronic archives for these alignments now exist, and information is provided here on the submission and retrieval of alignments at the National Center for Biotechnology Information (NCBI), the European Bioinformatics' Institute (EBI), and TreeBASE. Emphasis is placed on the use of Sequin and Entrez at the NCBI, because these programs have been modified recently and they provide a fluid and integrated system to submit and retrieve sequence and alignment records and related information. Other useful features of Entrez (e.g. free Medline searches) are noted.     

Stimulation of yeast ascospore germination and outgrowth by S-adenosylmethionine.

The supplementation of S-adenosylmethionine (SAM) to germination medium stimulated the accumulation of [14C]uracil from the medium into germinating cells, as well as its incorporation into ribonucleic acid during germination and outgrowth of ascospores of Saccharomyces cerevisiae. In addition to uracil, the accumulation of leucine, cytosine, serine, and methionine was also stimulated by the extracellular addition of this sulfonium compound. The SAM-stimulatory effect was dose dependent; half-maximal stimulation was observed at about 50 muM. The effect exerted by SAM supplementation appeared to be specific for SAM and for germination and outgrowth. In the absence of SAM biosynthesis (in the presence of cycloleucine), spores were inhibited in their ability to accumulate label, whereas the supplementation of SAM completely reversed the cycloleucine-induced inhibition of accumulation. In addition to accumulation and incorporation, the kinetics of bud formation during outgrowth were also stimulated by exogenous SAM. The stimulation of budding by SAM was amplified in an ethionine-resistant strain. These observations suggest that SAM may be essential for the initiation of cell division during the breaking of spore dormancy.     

An improved cosmid vector for the cloning of equine herpesvirus DNA

We have modified the commercial cosmid vector, triple helix vector (THV), such that I-Sce-I restriction endonuclease sites flank the cloning site. I-Sce-I is a rare-cutting endonuclease which recognizes an 18-bp sequence. It does not restrict the genome of either of the equine herpesvirus 1 or 4 (EHV-1 and EHV-4) strains we have cosmid cloned. Thus, cosmid- cloned EHV fragments can be excised intact from the vector by I-Sce-I digestion, facilitating production of large overlapping EHV fragments for use in transfections to produce recombinant virus.     

PREDICTING DESICCATION STRESS IN MICROSCOPIC ORGANISMS THE USE OF AGAROSE BEADS TO DETERMINE EVAPORATION WITHIN AND BETWEEN INTERTIDAL MICROHABITATS1

We describe an easy and inexpensive way to determine whether intertidal microhabitats remain wet during tidal emersion. This new technique uses agarose beads (120 üm diameter when fully hydrated) that shrink in a graded fashion as they dry. The agarose beads allow variability in surface wetness to be gauged over distances of less than 1 mm. Describe this parameter of microclimate is important in order to predict the likelihood and spatial pattern of survival of settled larvae, reproductive propagules, and other microscopic stages in the life histories of organisms growing in intertidal and other water-stressed environments. For the brown seaweed Pelvetia fastigiata (J. Ag.) DeToni (Fucales, Phaeophyta), the use of agarose beads demonstrated that survival of zygotes during tidal emersion was highes at those sites that remain damp. Temperature alone was found to be an unreliable measure of wetness within a single microhabitat (e.g. red algal turf).