Search

Polysiphoniais the largest genus of red algae, and several schemes subdividing it into smaller taxa have been proposed since its original description. Most of these proposals were not generally accepted, and currently the tribe Polysiphonieae consists of the large genusPolysiphonia(190 species), the segregate genusNeosiphonia(43 species) and 13 smaller genera (< 10 species each). In this paper, phylogenetic relationships of the tribe Polysiphonieae are analysed, with particular emphasis on the generaCarradoriella, Fernandosiphonia, Melanothamnus, Neosiphonia, Polysiphonia sensu stricto,StreblocladiaandVertebrata. We evaluated the consistency of 14 selected morphological characters in the identified clades. Based on molecular phylogenetic (rbcL and 18S genes) and morphological evidence, two speciose genera are recognized:Vertebrata(including the type species of the generaCtenosiphonia, Enelittosiphonia, BoergeseniellaandBrongniartella) andMelanothamnus(including the type species of the generaFernandosiphoniaandNeosiphonia). Both genera are distinguished from other members of the Polysiphonieae by synapomorphic characters, the emergence of which could have provided evolutionarily selective advantages for these two lineages. InVertebratatrichoblast cells are multinucleate, possibly associated with the development of extraordinarily long photoprotective trichoblasts.Melanothamnushas 3-celled carpogonial branches and plastids lying exclusively on radial walls of the pericentral cells, which similarly may improve resistance to damage caused by excessive light. Other relevant characters that are constant in each genus are also shared with other clades. The evolutionary origin of the generaMelanothamnusandVertebratais estimated as 75.7–95.78 and 90.7–138.66 Ma, respectively. Despite arising in the Cretaceous, before the closure of the Tethys Seaway,Melanothamnusis a predominantly Indo-Pacific genus and its near-absence from the north-eastern Atlantic is enigmatic. The nomenclatural implications of this work are that 46 species are here transferred toMelanothamnus, six species are transferred toVertebrata, and 13 names are resurrected forVertebrata. [ABSTRACT FROM PUBLISHER]

On the basis of comparative morphology and phylogenetic analyses of rbcL and LSU rDNA sequence data, a new genus, Gayliella gen. nov., is proposed to accommodate the Ceramium flaccidum complex ( C. flaccidum, C. byssoideum, C. gracillimum var. byssoideum, and C. taylorii), C. fimbriatum, and a previously undescribed species from Australia. C. transversale is reinstated and recognized as a distinct species. Through this study, G. flaccida (Kützing) comb. nov., G. transversalis (Collins et Hervey) comb. nov., G. fimbriata (Setchell et N. L. Gardner) comb. nov., G. taylorii comb. nov., G. mazoyerae sp. nov., and G. womersleyi sp. nov. are based on detailed comparative morphology. The species referred to as C. flaccidum and C. dawsonii from Brazil also belong to the new genus. Comparison of Gayliella with Ceramium shows that it differs from the latter by having an alternate branching pattern; three cortical initials per periaxial cell, of which the third is directed basipetally and divides horizontally; and unicellular rhizoids produced from periaxial cells. Our phylogenetic analyses of rbcL and LSU rDNA gene sequence data confirm that Gayliella gen. nov. represents a monophyletic clade distinct from most Ceramium species including the type species, C. virgatum. We also transfer C. recticorticum to the new genus Gayliella. [ABSTRACT FROM AUTHOR]

Morphological investigations identified 11 Ceramium Roth species, of the 18 previously reported from Brazil. Phylogenetic analyses of sequences of the chloroplast-encoded rbcL gene confirmed the presence of seven of these species. Three other species are reported from Brazil for the first time. Ceramium affine Setchell & Gardner and C. filicula Harvey ex Womersley were previously known only from the Pacific Ocean (Mexico and Australia, respectively). A new species, C. fujianum Barros-Barreto et Maggs sp. nov., is described here. Its general habit is similar to that of C. strictum sensu Harvey from Europe but it has one less periaxial cell than C. strictum; its cortical filament arrangement is closest to C. deslongchampsii Chauvin ex Duby, also from Europe, but whorled tetrasporangia partially covered by cortical cells differ strikingly from the naked protruding tetrasporangia of C. deslongchampsii. Ceramium species in which each periaxial cell cuts off transversely only a single basipetal cell formed a robust clade. The genus Ceramium as represented in Brazil is not monophyletic with respect to Centroceras Kützing and Corallophila Weber-van Bosse; Ceramium nitens, which has axial cells completely covered by rounded cortical cells formed by acropetal and basipetal filaments, did not group with any Ceramium clade but was weakly allied to a species of Corallophila. All three Brazilian Centroceras sequences were attributed to a single species, C. clavulatum. [ABSTRACT FROM AUTHOR]

Mastocarpus stellatus is a common intertidal red alga in the north Atlantic. Previous work showed that the species was divided into at least two breeding groups in the northeastern Atlantic, a northern one (absent in Spain and Portugal) and a southern one, which were almost completely inter-sterile. It also showed that, in laboratory culture, at least two types of life history were evident in this species (a sexual one and a ‘direct’ one). The distribution of these life histories appeared to have a north–south distribution. We have used molecular markers to confirm these results and expand the sampling in certain populations. Organellar markers showed that the breeding groups have different plastid and mitochondria haplotypes and appear to be distributed along a north–south gradient. Populations in southern England and northern France (Brittany) have mixed northern and southern breeding groups, except for the Rade du Brest, as was shown previously from culture studies. Results also show that most asexual plants have a plastid haplotype corresponding to the northern breeding group and a mitochondrial haplotype corresponding to the southern breeding group, a possible case of differential organellar inheritance and hybrid formation of an asexual life history. These results using molecular markers support previous conclusions and again emphasize the high levels of genetic variation in marine algae in Brittany. [ABSTRACT FROM AUTHOR]

Grateloupia is one of the most taxonomically complex genera of the Cryptonemiales. Of four species reported to occur in Ireland and Britain, only G. filicina (J.V. Lamouroux) C. Agardh and G. dichotoma J. Agardh are considered as native, with Grateloupia filicina var. luxurians A. Gepp & E.S. Gepp and G. doryphora (Montagne) Howe thought to be recent introductions. Sequence data from the plastid-encoded rbcL gene have been used to assist in clarifying the taxonomic position of these and other members of the Halymeniaceae from Ireland, Britain and neighbouring coasts. Molecular and morphological evidence indicate that the introduced alga G. filicina var. luxurians is only distantly related to the type species, G. filicina. It is here raised to species status as G. luxurians (A. Gepp & E.S. Gepp) R.J. Wilkes, L.M. McIvor & Guiry, stat. nov. A further species, Grateloupia minima P.L. Crouan & H.M. Crouan, has also been reported in the north-eastern Atlantic, but is currently considered as a seasonal or juvenile form of G. filicina. Based on morphological evidence and sequence data, G. minima is distinct from G. filicina, and is hereby reinstated. Although rarely reported, the closely related taxon, Dermocorynus montagnei P. L. Crouan & H. M. Crouan was also included in this study. Molecular and morphological data place Dermocorynus in a clade of Grateloupia species and we therefore propose that Dermocorynus be placed in synonymy with Grateloupia. The relationship between morphology and phylogeny within Grateloupia is discussed in the light of these results. [ABSTRACT FROM AUTHOR]

Despite a simple morphology and intensive studies carried out for more than two centuries, the systematics of the Prasiolales still presents several unsolved problems. The taxonomic relationships of several common species of Prasiolales, mostly from northern Europe, were investigated by a combination of morphological observations, culture experiments, and molecular analyses based onrbcL sequences. The results indicate thatRosenvingiellaandPrasiolaare separate genera. The capacity for production of tridimensional pluriseriate gametangia and the presence of unicellular rhizoids are the morphological features that discriminateRosenvingiellafrom filamentous forms ofPrasiola. The molecular data indicate that uniseriate filaments can be produced in at least three different species ofPrasiola. The genetic diversity of uniseriate filamentous Prasiolales is higher than their simple morphology would indicate, and the provisional retention ofSchizogoniumas independent genus is recommended. TherbcL phylogeny confirms thatPrasiola calophylla,P. crispa, andP. stipitataare distinct species, whereasP. stipitataandP. meridionalisare probably conspecific.Rosenvingiella polyrhizais a strictly marine alga, and most records ofRosenvingiellain Europe are referable toRosenvingiella radicans, proposed here as a new combination based onUlothrix radicans. This is a primarily terrestrial alga that can occur from upper intertidal rock to locations situated hundreds of kilometers inland. The great confusion that has arisen in Europe between these two species in the last century is mostly due to misidentifications of marine populations ofR. radicans. [ABSTRACT FROM AUTHOR]

AbstractIn Europe, the last 20 years have seen a spectacular increase in accidental introductions of marine species, but it has recently been suggested that both the actual number of invaders and their impacts have been seriously underestimated because of the prevalence of sibling species in marine habitats. The red alga Polysiphonia harveyi is regarded as an alien in the British Isles and Atlantic Europe, having appeared in various locations there during the past 170 years. Similar or conspecific populations are known from Atlantic North America and Japan. To choose between three competing hypotheses concerning the origin of P. harveyi in Europe, we employed rbcL sequence analysis in conjunction with karyological and interbreeding data for samples and isolates of P. harveyi and various congeners from the Pacific and North Atlantic Oceans. All cultured isolates of P. harveyi were completely interfertile, and there was no evidence of polyploidy or aneuploidy. Thus, this biological species is both morphologically and genetically variable: intraspecific rbcL divergences of up to 2.1% are high even for red algae. Seven rbcL haplotypes were identified. The four most divergent haplotypes were observed in Japanese samples from Hokkaido and south-central Honshu, which are linked by hypothetical ‘missing’ haplotypes that may be located in northern Honshu. These data are consistent with Japan being the centre of diversity and origin for P. harveyi. Two non-Japanese lineages were linked to Hokkaido and Honshu, respectively. A single haplotype was found in all North Atlantic and Mediterranean accessions, except for North Carolina, where the haplotype found was the same as that invading in New Zealand and California. The introduction of P. harveyi into New Zealand has gone unnoticed because P. strictissima is a morphologically indistinguishable native sibling species. The sequence divergence between them is 4–5%, greater than between some morphologically distinct red algal species. Two different types of cryptic invasions of P. harveyi have therefore occurred. In addition to its introduction as a cryptic sibling species in New Zealand, P. harveyi has been introduced at least twice into the North Atlantic from presumed different source populations. These two introductions are genetically and probably also physiologically divergent but completely interfertile. [ABSTRACT FROM AUTHOR]