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Historically, the intertidal seaweeds Fucus serratus(Fs) and Fucus evanescens(Fe) were sympatric only along the western coast of Norway. In the mid-1890s, Fe(monoecious) was accidentally introduced into the Oslofjord. Putative hybridization with the endemic Fs(dioecious) was observed in Oslofjord by 1977 and in the Kattegat and western Baltic Seas by 1998. At Blushøj, Denmark (Kattegat Sea) putative Fs× Fehybrids were present only when densities of Feand Fsexceeded 14 and 2 m⊃-2, respectively. All of the 58 putative hybrids that were collected in 1999 were dioecious and intermediate in morphology. Essentially all (57 out of 58) were reproductively mature, but the oogonia possessed fewer and more variably sized eggs than either parent. Examination of each parental species and putative hybrids with nuclear, mitochondrial and chloroplast molecular markers confirmed the occurrence of hybridization. Furthermore, all of the hybrids possessed Fe-type chloroplasts and mitochondria, indicating that only the Feegg × Fssperm pairing was successful in the field. The reciprocal cross of Fsegg×Fesperm was absent in the field and significantly less successful in laboratory crossings. Asymmetrical hybridization has also been reported for several species of plants and animals.

Patterns of nuclear and organelle inheritance among artificial hybrids of the seaweeds Fucus serratus and F. evanescens were detected using single-strand conformation polymorphism (SSCP). Three alleles were identified in the 231 bp rDNA-ITS1 gene (nuclear): two in F. serratus and one in F. evanescens. Alleles differed by 1–2 bp and all hybrids possessed one allele from each parent. Two haplotypes were present in the 288 bp Rubisco spacer (chloroplast), differentiated by a 33 bp indel. Two haplotypes differing by a single nucleotide were found in a 135 bp region of nad11 gene (mitochondrion). Both organelles are maternally inherited, as all hybrids contained the haplotypes of the parent contributing the egg. Although laboratory hybrids among Fucus spp. have been produced previously, this is the first time that both nuclear and cytoplasmic genetic markers have been used to document inheritance patterns. SSCPs analysed on an automated sequencer offer a rapid and powerful approach for identifying suspected hybrids from field samples, as well as a screen for intraspecific and intra-individual variation in DNA regions prior to confirmation of variations by sequencing.

Abstract: In traditional chlorophytan systems the organizational level was the primary character for the distinction of main groups (classes and orders). For instance, in Fott (1971), the flagellate level corresponds with the Volvocales, the coccoid level with the Chlorococcales, the filamentous level with the Ulotrichales, the siphonocladous level with the Siphonocladales, and the siphonous level with the Bryopsidales. The new system presented here is an elaboration and emendation of recently proposed taxonomies and their underlying phylogenetic hypotheses, and it is mainly based on ultrastructural features which have become available over the last 15 years. The following criteria are used for the distinction of classes and orders: (1) architecture of the flagellate cell (flagellate cells are considered as the depositories of primitive characters); (2) type of mitosis-cytokinesis; (3) place of meiosis in the life history and, consequently, the sexual life history type; (4) organizational level and thallus architecture; (5) habitat type (marine versus feshwater and terrestrial); (6) chloroplast type. The following classes are presented: Prasinophyceae, Chlamydophyceae, Ulvophyceae (orders Codiolales, Ulvales, Cladophorales, Bryopsidales, Dasycladales), Pleurastrophyceae (?), Chlorophyceae s.s. (orders Cylindrocapsales, Oedogoniales, Chaetophorales), Zygnematophyceae, Trentepohliophyceae, Charophyceae (orders Klebsormidiales, Coleochaetales, Charales). The new system no longer reflects the traditional hypothesis of a stepwise evolutionary progression of organizational levels in which the flagellate level represents the most primitive lineage, the coccoid and sarcinoid levels lineages of intermediate derivation, and the filamentous, siphonocladous and siphonous levels the most derived lineages. Instead, it is now hypothesized that these levels have arisen over and over again in different chlorophytan lineages which are primarily characterized by their type of flagellate cell. The flagellate green algal classes Prasinophyceae (with organic body scales) and Chlamydophyceae probably represent bundles of highly conservative lineages that diverged very long ago. Consequently, extant genera and species in these classes can be expected to have emerged long ago. Fossil evidence points to a minimum age of 600 Ma of certain extant Prasinophycean genera, and molecular evidence to a minimum age of 400–500 Ma of a fewChlamydomonas species. On the contrary, the most derived “green algal” lineage, the Angiosperms, can be expected to consist of, on average, much younger genera and species. Fossil evidence points to a minimum age of genera of 5–60 Ma. Lineages of intermediate evolutionary derivation (Ulvophyceae, Chlorophyceae, Charophyceae) can be expected to encompass genera and species of intermediate age. Fossil and (limited) molecular evidence point to a minimum age of 230–70 Ma of extant genera in Bryopsidales, Dasycladales and Cladophorales (Ulvophyceae) and of 250–80 Ma of extant genera in Charales (Charophyceae).

Abstract: DNA-DNA hybridizations between single-copy nuclear DNA fromLaminaria digitata and total DNA fromL. saccharina, L. Hyperborea, L. rodriguezii, L. ochroleuca andChorda filum, respectively, show that these species ofLaminaria are genotypically closely related.Chorda filum is only distantly related withL. digitata. Based on the thermal elution patterns of the DNA hybrids, as quantified by ΔTm(e) values, it is hypothesized that all five species ofLaminaria evolved at about the same time from their most recent common ancestor some 15–19 Ma ago. This phylogenetic hypothesis is discussed in relation to the history of modern laminarialean distribution patterns.

Abstract: Genomic size and complexity were calculated for the pantropical chlorophyte,Dictyosphaeria cavernosa (Cladophorales). Genome characterization of the Hawaiian material by means of DNA renaturation studies showed highly repetitive (31.3%), middle repetitive (42.7%), and single-copy (25.8%) fractions; and an estimated haploid genome size of 1.79 pg DNA. A G:C content of 43% was calculated from a melting curve of DNA. Pacific and Caribbean isolates of this species were compared using single-copy nuclear DNA-DNA hybridization. Results show a relatively low thermal stability of the hybridized DNA (Δ Tm(e)=10C) which suggests that these Pacific and Caribbean lineages may have been separated for up to 55 Ma.

Genotypic relationships between a number of Anabaena strains, belonging to different species, were determined by means of comparison of their DNA base composition, DNA-DNA reassociation rates, thermal stability values of DNA-DNA hybrids, and electrophoretic behaviour of five different enzymes. In order to compare these relationships with morphological relationships between the strains tested, a numerical analysis of morphological traits was performed.DNA base compositions appeared to be almost identical. Intraspecific DNA DNA hybridizations showed high renaturation rates and high thermal stability values of hybrids, indicating a high degree of similarity of genomes of strains belonging to one species. Interspecific DNA-DNA hybridizations showed considerably lower renaturation rates and thermal stabilities, indicating considerable interspecific genetic differences. Electrophoretic patterns of enzymes more or less confirmed these findings, but also showed intraspecific differences.In general the results demonstrate that morphological similarities and differences between Anabaena strains are correlated with genetic similarities and differences, respectively.

Crustacean and cheliceratan hemocyanins (oxygen-transport proteins) and insect hexamerins (storage proteins) are homologous gene products, although the latter do not bind oxygen and do not possess the copper-binding histidines present in the hemocyanins. An alignment of 19 amino acid sequences of hemocyanin subunits and insect hexamerins was made, based on the conservation of elements of secondary structure observed in X-ray structures of two hemocyanin subunits. The alignment was analyzed using parsimony and neighbor-joining methods. Results provide strong indications for grouping together the sequences of the 2 crustacean hemocyanin subunits, the 5 cheliceratan hemocyanin subunits, and the 12 insect hexamerins. Within the insect clade, four methionine-rich proteins, four arylphorins, and two juvenile hormone-suppressible proteins from Lepidoptera, as well as two dipteran proteins, form four separate groups. In the absence of an outgroup sequence, it is not possible to present information about the ancestral state from which these proteins are derived. Although this family of proteins clearly consists of homologous gene products, there remain striking differences in gene organization and site of biosynthesis of the proteins within the cell. Because studies on 18S and 12S rRNA sequences indicate a rather close relationship between insects and crustaceans, we propose that hemocyanin is the ancestral arthropod protein and that insect hexamerins lost their copper-binding capability after divergence of the insects from the crustaceans.

We report the occurrence of a group I intron, 452 nucleotides in length, in the nuclear small-subunit ribosomal gene of the benthic seaweed Urospora penicilliformis, a member of the green algal class Ulvophyceae. Group I introns have been reported in fungi, myxomycetes, the ciliate genus Tetrahymena, and recently in five unicellular chlorophycean algae. The sequence of the conserved core of the U. penicilliformis group I intron was aligned with that of 15 other introns of this type, and the evolutionary relationships among these introns were examined. Comparison of the "intron" tree with phylogenetic hypotheses of the intron-harboring organisms shows that nuclear group I introns in green algae have arisen several times and are not lineage specific.

Caulerpa (Chlorophyta, Ulvophyceae) is a common marine tropical-subtropical genus of about 70 species, inhabiting the eulittoral zone on rocks and corals as well as mangroves. The genus is particularly diverse and abundant along southern Australian coasts, where it is thought to have originated. Here, we compare sequences from the nuclear ribosomal cistron among five species of Caulerpa, including nine populations of Caulerpa filiformis from two biogeographic regions: five from Australia and four from South Africa. Species relationships were well resolved by internal transcribed spacer (ITS) sequences and supported by high bootstrap values as follows: (C. geminata (C. simpliciuscula (C. trifaria (C. scalpelliformis (C. filiformis – Australia, C. filiformis – South Africa))))). Nucleotide divergence within C. filiformis was low with four and five nucleotide differences present in ITS1 and ITS2 respectively. Unexpectedly, the 5.8S rRNA gene showed eight nucleotide differences between the Australian and South African populations and may indicate cryptic species. The Australian C. filiformis is probably not a South African introduction. These sequences provide an independent means for assessment of species relationships and appear, in so far as limited taxon sampling permits, to follow chloroplast ultrastructural groupings proposed 20 years ago.

Caulerpa (Chlorophyta, Ulvophyceae) is a common marine tropical-subtropical genus of about 70 species, inhabiting the eulittoral zone on rocks and corals as well as mangroves. The genus is particularly diverse and abundant along southern Australian coasts, where it is thought to have originated. Here, we compare sequences from the nuclear ribosomal cistron among five species of Caulerpa, including nine populations of Caulerpa filiformis from two biogeographic regions : five from Australia and four from South Africa. Species relationships were well resolved by internal transcribed spacer (ITS) sequences and supported by high bootstrap values as follows: (C. geminata (C. simpliciuscula (C. trifaria (C. scalpelliformis (C. filiformis - Australia, C. filiformis - South Africa ))))). Nucleotide divergence within C. filiformis was low with four and five nucleotide differences present in ITS1 and ITS2 respectively. Unexpectedly, the 5.8S rRNA gene showed eight nucleotide differences between the Australian and South African populations and may indicate cryptic species. The Australian C. filiformis is probably not a South African introduction. These sequences provide an independent means for assessment of species relationships and appear, in so far as limited taxon sampling permits, to follow chloroplast ultrastructural groupings proposed 20 years ago.

Twenty-one Anabaena strains from freshwater origin were incubated in media containing 0%, 50% and 100% seawater. Growth, morphology and recovery were determined. All strains appeared to be halotolerant towards 50% seawater conditions. They all kept their normal morphology. A much less general pattern was observed for 100% seawater conditions. Mutual strain or species differences in halotolerance are discussed, also with regard to the appearance of Anabaena in habitats with fluctuating salinities.

Fucus serratus and F. evanescens commonly occur on Northern European shores. Nine microsatellite loci were developed for F. serratus (8–22 alleles, observed heterozygosities = 0.367–0.850) and one for F. evanescens (seven alleles, observed heterozygosity = 0.804). Cross-amplification was apparent, as five F. serratus loci were polymorphic in F. evanescens and 2–5 were polymorphic in F. vesiculosus, F. distichus, and F. spiralis.

Seven microsatellite loci were developed for Pleuronectes platessa, a commercially important flatfish found throughout northern European waters. The number of alleles per locus ranged from 11 to 33 and heterozygosities from 0.74 to 0.96. Cross-reactivity was tested against six other flatfish species. Significant amplification was found in all species from one to all seven of the loci.

Ascophyllum nodosum L. dominates rocky intertidal shores throughout the temperate North Atlantic. Six microsatellite loci were developed for A. nodosum using enriched libraries. The number of alleles ranged from 9 to 24 and heterozygosities from 0.2213 to 0.7785. Ascophyllum is monotypic. There was no cross-reactivity observed with Fucus serratus, F. vesiculosus or F. evanescens.