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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]

Species of Ulva occur worldwide in all aquatic habitats from freshwater through brackish to fully saline environments. The scarcity of stable morphological characters and the morphological plasticity linked to environmental conditions typical of species referred to this genus make identification and circumscription problematic. In Ireland and Britain the taxonomy of Ulva species has been uncertain, and only three species have been reported: Ulva lactuca, U. rigida and U. olivascens (later reassigned to Umbraulva olivascens). We reassessed the taxonomic status of this genus by combining morphological investigations with analyses of rbcL sequence data for 24 selected specimens from the Irish and southern British shores. This combination of methods allowed the identification of seven lineages, which were considered to represent the following species: Ulva rigida, U. scandinavica, U. lactuca, U. gigantea, U. rotundata, U. californica and Umbraulva olivascens. Of these, U. scandinavica, U. gigantea, U. rotundata and U. californica are newly reported; the distribution of U. olivascens was shown to be much wider than previously thought. The use of morphological features proved to be largely inconclusive and of limited value for circumscription of species. In the rbcL phylogeny, U. olivascens formed a sister clade to all other species. The results support the conspecificity of U. rigida, U. scandinavica and U. armoricana and the conspecificity of U. pseudocurvata and U. compressa already suggested in previous studies. [ABSTRACT FROM AUTHOR]

Botryocladia is a genus of marine red algae (Rhodophyta) generally found in tropical, subtropical and warm temperate seas. There are currently 35 described species, but the taxonomic status of many of these remains confused. Recently, the genus was split into two genera, with the new genus, Irvinea, described based on morphological and molecular evidence. Only one species, I. ardreana, is currently assigned to the newer genus. For this study, a number of cultured Botryocladia and Irvinea strains from the Mediterranean and Caribbean were examined. Each was examined microscopically and the key features currently used for identification were evaluated. Up to 1277 bp of the rbcL gene was PCR amplified for each isolate and directly sequenced. The molecular data confirm that the species currently considered as Botryocladia do not form a monophyletic group. Botryocladia boergesenii grouped in a clade with I. ardreana with the remaining Botryocladia species in a separate grouping. We propose the transfer of B. boergesenii to the genus Irvinea on the basis of the molecular and morphological data. Morphological and molecular data for the other species examined were also evaluated although little correlation between the morphological features and the rbcL data was observed. The taxonomic utility of some of the morphological features is called into doubt, although clear differences between the genera Botryocladia and Irvinea can be seen. In addition to the morphological features currently regarded as important intergeneric characters, the presence of branched vesicles as an indicator for species of Irvinea should be added. [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]