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Maerl beds are sensitive biogenic habitats built by an accumulation of loose-lying, non-geniculate coralline algae. While these habitats are considered hot-spots of marine biodiversity, the number and distribution of maerl-forming species is uncertain because homoplasy and plasticity of morphological characters are common. As a result, species discrimination based on morphological features is notoriously challenging, making these coralline algae the ideal candidates for a DNA barcoding study. Here, mitochondrial (COI-5P DNA barcode fragment) and plastidial (psbA gene) sequence data were used in a two-step approach to delimit species in 224 collections of maerl sampled from Svalbard (78°96'N) to the Canary Islands (28°64'N) that represented 10 morphospecies from four genera and two families. First, the COI-5P dataset was analyzed with two methods based on distinct criteria (ABGD and GMYC) to delineate 16 primary species hypotheses (PSHs) arranged into four major lineages. Second, chloroplast (psbA) sequence data served to consolidate these PSHs into 13 secondary species hypotheses (SSHs) that showed biologically plausible ranges. Using several lines of evidence (e.g. morphological characters, known species distributions, sequences from type and topotype material), six SSHs were assigned to available species names that included the geographically widespread Phymatolithon calcareum, Lithothamnion corallioides, and L. glaciale; possible identities of other SSHs are discussed. Concordance between SSHs and morphospecies was minimal, highlighting the convenience of DNA barcoding for an accurate identification of maerl specimens. Our survey indicated that a majority of maerl forming species have small distribution ranges and revealed a gradual replacement of species with latitude.

Effective monitoring of non-indigenous seaweeds and combatting their effects relies on a solid confirmation of the non-indigenous status of the respective species. We critically analysed the status of presumed non-indigenous seaweed species reported from the Mediterranean Sea, the Northeast Atlantic Ocean and Macaronesia, resulting in a list of 140 species whose non-indigenous nature is undisputed. For an additional 87 species it is unclear if they are native or non-indigenous (cryptogenic species) or their identity requires confirmation (data deficient species). We discuss the factors underlying both taxonomic and biogeographic uncertainties and outline recommendations to reduce uncertainty about the non-indigenous status of seaweeds. Our dataset consisted of over 19,000 distribution records, half of which can be attributed to only five species (Sargassum muticum, Bonnemaisonia hamifera, Asparagopsis armata, Caulerpa cylindracea and Colpomenia peregrina), while 56 species (40%) are recorded no more than once or twice. In addition, our analyses revealed considerable variation in the diversity of non-indigenous species between the geographic regions. The Eastern Mediterranean Sea is home to the largest fraction of non-indigenous seaweed species, the majority of which have a Red Sea or Indo-Pacific origin and have entered the Mediterranean Sea mostly via the Suez Canal. Non-indigenous seaweeds with native ranges situated in the Northwest Pacific make up a large fraction of the total in the Western Mediterranean Sea, Lusitania and Northern Europe, followed by non-indigenous species with a presumed Australasian origin. Uncertainty remains, however, regarding the native range of a substantial fraction of non-indigenous seaweeds in the study area. In so far as analyses of first detections can serve as a proxy for the introduction rate of non-indigenous seaweeds, these do not reveal a decrease in the introduction rate, indicating that the current measures and policies are insufficient to battle the introduction and spread of non-indigenous species in the study area. Non-indigenous seaweed species in the Northeast Atlantic Ocean, the Mediterranean Sea and Macaronesia are critically reanalysed. > 19,000 distribution records revealed considerable variation in diversity of non-indigenous seaweed species in the study area. Taxonomic and biogeographic uncertainties hamper a critical evaluation of the non-indigenous status of many seaweed species. [ABSTRACT FROM AUTHOR]

This work presents a taxonomic, floristic and chorological account of the most representative turf-forming species from sand-covered rocks along the Atlantic Iberian Peninsula, including in this Part 2 species belonging to six orders of the Rhodophyta and one of the Phaeophyceae. For each species are provided morphological descriptions, distribution maps, and/or COI-5P sequences, as well as taxonomic notes. The species studied are: Rhodothamniella floridula, Ceramium ciliatum, Erythroglossum lusitanicum, Hypoglossum hypoglossoides, Ptilothamnion sphaericum, Spermothamnion repens, Tiffaniella capitata, Gelidium crinale, G. spathulatum, Pterocladiella melanoidea, Calliblepharis hypneoides, Gymnogongrus griffithsiae, Plocamium maggsiae, Gastroclonium reflexum and Bachelotia antillarum. [ABSTRACT FROM AUTHOR]

In recent years (2007-2009), the distribution and associated flora of maerl beds in southern Portugal (Algarve) were investigated by dredging and SCUBA diving (12-30 m depth). The present work provides the first data on the non-coralline crustose flora associated with maerl beds in Portugal. Peyssonnelia bornetii is a new record for Atlantic European coasts, and new records for Portugal are "Rhododiscus pulcherrimus" (sporophyte phase of Atractophora hypnoides), Contarinia peyssonneliaeformis, "Cruoria rosea" (sporophyte phase of Halarachnion ligulatum), Peyssonnelia armorica, and "Aglaozonia chilosa" (sporophyte phase of Cutleria chilosa). In addition, the records of three other species (Hildenbrandia crouaniorum, Peyssonnelia dubyi, and Peyssonnelia harveyana) completed the distribution gap between the North Iberian Peninsula and the Macaronesian region. The female and carposporangial structures of C. peyssonneliaeformis and P. bornetii are described for the first time. The diversity and species composition observed are compared with previous studies from maerl beds in the northwestern Iberian Peninsula (Galicia) and neighboring areas in the Atlantic Ocean and Mediterranean Sea. In order to facilitate and promote further studies of the crustose flora of subtidal habitats along European coasts, an identification key is provided for the 26 crustose taxa associated with maerl and gravel beds of the Atlantic coast of the Iberian Peninsula. [ABSTRACT FROM AUTHOR]

Sand-covered rocks provide a particular habitat to benthic seaweeds, which must tolerate the stressful conditions imposed by the presence of sediments. Turf assemblages are dominant in this habitat, which is widely distributed along the Atlantic Iberian Peninsula, neverthelss their flora remained poorly known. This work presents a taxonomic, floristic and chorological account of the most representative Rhodomelaceae from sand-covered rocks along the Atlantic Iberian Peninsula. For each species we provided morphological descriptions, distribution maps, and/or COI-5P sequences, as well as taxonomic notes. The species studied are: Chondria coerulescens, Ctenosiphonia hypnoides, Herposiphonia cf. secunda f. tenella, Leptosiphonia schousboei, Lophosiphonia reptabunda, L. simplicissima sp. nov., Ophidocladus simpliciusculus, Polysiphonia caespitosa, P. devoniensis, P. foeti-dissima, P. fucoides, P. nigra, P. stricta, P. tripinnata, Pterosiphonia ardreana, P. parasitica, P. pennata and Streblocladia collabens. Among our taxonomical conclusions, we herein proposed a novel species Lophosiphonia simplicissima as well as the transfer of Streblo-cladia collabens to the genus Neosiphonia: Furthermore, the parasitic species Aiolocolax pulchellus is described and its taxonomic position is discussed. [ABSTRACT FROM AUTHOR]

Lainpisiphonia iberica gen. et sp. nov. is described on the basis of specimens collected from subtidal rocky bottom habitats on the Atlantic coast of the Iberian Peninsula. The new genus was distinguished by an erect habit, pseudodichotomous branching, and 9-11 pericentral cells. Plants were bright red to brown-red in colour, 3-6 cm high, firm at the base but ultimate divisions soft and flaccid. Cortication was thick but restricted to the base of large thalli. Plants were attached to the substratum by discoid holdfasts with the tips of decumbent branches reattaching by secondary discoid holdfasts or rhizoids cut off from pericentral cells. Trichoblasts and scar cells were absent and the branching was exogenous. Tetrasporangia were arranged in straight series of up to 15 segments. Sexual structures were not observed. Lampisiphonia was separated from other groups and genera of Polysiphonia sensu lato and the tribe Polysiphonieae by a combination of features that include the absence of trichoblasts and presence of a compact basal cortication. Furthermore, Lampisiphonia had tetrasporangia in a straight series, a feature to date considered unique to Polysiphonia sensu stricto. The phylogenetic relationship of Lainpisiphonia among the three resolved lineages of the Polysiphonia sensu lato was equivocal in our analyses and it was not clearly distinct from the Neosiphonia group and the multipericental group in morphological and molecular characters. Nevertheless, monophyly of Lampisiphonia and the Polysiphonia group was statistically rejected in small-subunit ribosomal DNA, rbcL and combined data with the Shimodaira-Hasegawa test. We therefore proposed Lampisiphonia as a new genus. [ABSTRACT FROM AUTHOR]

We studied crustose seaweeds associated with subtidal maërl beds and gravel bottoms in the Galician rías (NW Iberian Peninsula). Each species is described as well as its habitat and occurrence in maërl beds and gravel bottoms. We confirmed the great crustose species richness associated with European Atlantic maërl beds. We report a new species for the Atlantic Ocean ( Contarinia peyssonneliaeformis) and six new records for the Iberian Peninsula ( Atractophora hypnoides stage “ Rhododiscus pulcherrimus” , Peyssonnelia immersa, Scytosiphon lomentaria stage “ Microspongium gelatinosum” , Petroderma maculiforme, Pseudolithoderma roscoffense and Phycocelis foecunda). Peyssonnelia armorica is a new record for the Atlantic Iberian Peninsula and Peyssonnelia harveyana is a new record for the Galician coast. We provide for the first time observations on spermatangial structures in Cruoria cruoriaeformis occurring on the Atlantic Iberian Peninsula. The Galician crustose algal flora of subtidal maërl beds and gravel bottoms is increased up to 23 species (15 Rhodophyta and 8 Ochrophyta). Peyssonnelia rubra is excluded from the Galician flora. [ABSTRACT FROM AUTHOR]

In this study, 10 new records of subtidal Rhodophyta are given for the Atlantic coast of the Iberian Peninsula. Most of these species of benthic marine algae are characteristic of temperate regions. Two were known previously only for the Mediterranean Sea ( Gelidium bipectinatum and Gloiocladia microspora), and their distribution into the Atlantic Ocean has been enlarged in this study. The northern distribution limits in the Atlantic Ocean of six other species ( Nemastoma dichotomum, Predaea ollivieri, Predaea pusilla, Platoma cyclocolpa, Sebdenia dichotoma, and Sebdenia rodrigueziana) and the southern distribution limit of another species ( Schmitzia neapolitana) have been expanded. Description, habitats, and distributions of the species are also given. [ABSTRACT FROM AUTHOR]