Julio Afonso-Carrillo

Blitzkrieg in a marine invasion: Caulerpa racemosa var. cylindracea (Bryopsidales, Chlorophyta) reaches the Canary Islands (north-east Atlantic)

On the basis of morphological and genetic studies (rDNA ITS1, 5.8S, ITS2, and a 18S rDNA intron), we confirm here that Caulerpa racemosa var. cylindracea (Sonder) Verlaque, Huisman et Boudouresque, a southwestern Australian taxon recently introduced into the Mediterranean Sea also occurs in the Canary Islands. This is the first report of C. racemosa var. cylindracea in the Atlantic. It was observed for the first time in the Canary Archipelago in 1997–1998. The speed and regional scale of expansion (north Atlantic Ocean and the Mediterranean Sea) of this invasive species appear to be among the most dramatic ever recorded. The possible outcome of this introduction in the Atlantic is discussed.

Distribution and reproductive phenology of the seagrass Cymodocea nodosa (Ucria) Ascherson in the Canary Islands

Abstract Cymodocea nodosa (Ucria) Ascherson is the most common seagrass in the Canary Islands. Data about its insular distribution as well as observations on its flowering, fruiting and seed germination are shown. Cymodocea nodosa forms scattered meadows mainly along the southeastern coasts of these islands. The reproductive phenology was studied in meadows at El Medano, south of Tenerife. Flowering was detected from March to July, when fertile shoots were observed. Fruiting began in April and fruits were observed attached to shoots until December. Throughout the year numerous fruits were detected buried in the sediment. Seed germination was observed from February to September.

Contrasting geographical distributions as a result of thermal tolerance and long-distance dispersal in two allegedly widespread tropical brown algae.

Background Many tropical marine macroalgae are reported from all three ocean basins, though these very wide distributions may simply be an artifact resulting from inadequate taxonomy that fails to take into account cryptic diversity. Alternatively, pantropical distributions challenge the belief of limited intrinsic dispersal capacity of marine seaweeds and the effectiveness of the north-south oriented continents as dispersal barriers. We aimed to re-assess the distribution of two allegedly circumtropical brown algae, Dictyota ciliolata and D. crenulata, and interpret the realized geographical range of the respective species in relation to their thermal tolerance and major tectonic and climatic events during the Cenozoic. Methodology/Principal Findings Species delimitation was based on 184 chloroplast encoded psbA sequences, using a Generalized Mixed Yule Coalescent method. Phylogenetic relationships were inferred by analyzing a six-gene dataset. Divergence times were estimated using relaxed molecular clock methods and published calibration data. Distribution ranges of the species were inferred from DNA-confirmed records, complemented with credible literature data and herbarium vouchers. Temperature tolerances of the species were determined by correlating distribution records with local SST values. We found considerable conflict between traditional and DNA-based species definitions. Dictyota crenulata consists of several pseudocryptic species, which have restricted distributions in the Atlantic Ocean and Pacific Central America. In contrast, the pantropical distribution of D. ciliolata is confirmed and linked to its significantly wider temperature tolerance. Conclusions/Significance Tectonically driven rearrangements of physical barriers left an unequivocal imprint on the current diversity patterns of marine macroalgae, as witnessed by the D. crenulata–complex. The nearly circumglobal tropical distribution of D. ciliolata, however, demonstrates that the north-south oriented continents do not present absolute dispersal barriers for species characterized by wide temperature tolerances.

Distribution of the Epiphytes along the Leaves of Cymodocea nodosa in the Canary Islands

The distribution of the epiphytes along the oldest leaf of shoots of Cymodocea nodosa was studied during a two-year cycle, from June 1990 to May 1992, in terms of number of species and cover. The difference in age between the base (the youngest part) and the apex (the oldest part) of the leaves allowed a study of the effect of the age of the host on the epiphyte community. A continuous increase in the number of species was observed along the oldest leaf of each shoot, from basal to apical segments. While the permanent epiphyte species were present everywhere, the seasonal and the occasional species were concentrated on the apical segments of the leaves and the occasional epiphytes showed their highest abundance in winter. The greatest development of the individuals, the high number of species as well as the high densities found towards the apical segments resulted in remarkable differences of cover along the leaves, from 0% at the basal segments to more than 600% reached at the apical segments in some months during the study period. The highest mean percentage cover by epiphytes on the oldest leaf of a shoot was detected in winter while the lowest was obtained in spring-summer. The Rhodophyta showed a quantitative dominance of more than 90% of cover in relation to the rest of the algal divisions, the Ceramiales and the Corallinales being the epiphytes which mainly contributed throughout the year. Results on cover and number of species of epiphytes permitted the distinguishing of three stages of development of the epiphytic community along the leaves: initiation, transition and maturity. Annual variations in the number of species as well as in the cover of the epiphytes along the oldest leaves were directly related to the growth rate and life-time of the leaves of Cymodocea nodosa. During the life-time of the leaves there was no succession of species in the epiphytic community but, from basal to apical segments, the epiphyte species were more developed and abundant, and the epiphytic community became more diverse.

MESOPHYLLUM SPHAERICUM SP. NOV. (CORALLINALES, RHODOPHYTA): A NEW MAËRL-FORMING SPECIES FROM THE NORTHEAST ATLANTIC1

Mesophyllum sphaericum sp. nov. is described based on spherical maërl individuals (up to 10 cm) collected in a shallow subtidal maërl bed in Galicia (NW Spain). The thalli of these specimens are radially organized, composed of arching tiers of compact medullary filaments. Epithallial cells have flattened to rounded outermost walls, and they occur in a single layer. Subepithallial initials are as long as, or longer than the daughter cells that subtend them. Cell fusions are abundant. Multiporate asexual conceptacles are protruding, mound‐like with a flattened pore plate, lacking a peripheral raised rim. Filaments lining the pore canal and the conceptacle roof are composed of five to six cells with straight elongate and narrow cells at their base. Carposporangial conceptacles are uniporate, protruding, and conical. Spermatangial conceptacles were not observed. Molecular results placed M. sphaericum near to M. erubescens, but M. sphaericum is anatomically close to M. canariense. The examination of the holotype and herbarium specimens of M. canariense indicated that both species have pore canal filaments with elongate basal cells, but they differ in number of cells (five to six in M. sphaericum vs. four in M. canariense). Based on the character of pore canal filaments, M. canariense shows similarities with M. erubescens (three to five celled). The outermost walls of epithallial cells of M. canariense are flared compared to the round to flattened ones of M. erubescens, the latter being widely accepted for the genus Mesophyllum. The addition of M. sphaericum as new maërl‐forming species suggests that European maërl beds are more biodiverse than previously understood.

Niche partitioning and the coexistence of two cryptic dictyota (Dictyotales, Phaeophyceae) species from the Canary Islands

Coexistence in a homogeneous environment requires species to specialize in distinct niches. Sympatry of cryptic species is of special interest to both ecologists and evolutionary biologists because the mechanisms that facilitate their persistent coexistence are obscure. In this study, we report on two sympatric Dictyota species, D. dichotoma (Huds.) J. V. Lamour. and the newly described species D. cymatophila sp. nov., from the Canary Islands. Gene sequence data (rbcL, psbA, nad1, cox1, cox3, and LSU rDNA) demonstrate that D. dichotoma and D. cymatophila do not represent sister species. Rather, D. cymatophila and D. dichotoma have converged on a nearly identical morphology, only to be distinguished with detailed morphometric observations. Both species co‐occur in eulittoral pools and the shallow subtidal in Tenerife. Even though D. cymatophila was more dominant in wave‐exposed places and D. dichotoma in less exposed areas, the spatial distribution of both species overlapped in intermediate habitats. The species display radically different phenologies. D. dichotoma reached its highest density in winter and early spring and disappeared nearly completely in autumn, while D. cymatophila dominated the study site from July until November. The timing of gamete release also differs between both species, D. dichotoma releasing gametes twice every lunar cycle, while the release of gametes in D. cymatophila occurred roughly every other day.

Sublittoral and Deep-Water Red and Brown Algae New from the Canary Islands

Abstract Nine species of sublittoral and deep-water red and brown algae are reported from the Canary Islands for the first time. The reports of the Western Atlantic species Gloiocladia atlantica (Searles) R.E.Norris and Rosenvingea antillarum (P. et H.Crouan) M. J.Wynne are the first from the Eastern Atlantic Ocean. The presence of Feldmannophycus rayssiae (J. et G. Feldmann) Augier et Boudouresque, Fauchea repens (C.Agardh)Montagne et Bory and Halichrysis depressa (J.Agardh) F. Schmitz, previously known from the Mediterranean Sea and the adjacent Atlantic coasts, place their southernmost known limit of distribution in the Canary Islands. Stypopodium schimperi (Buchinger ex Kützing) Verlaque et Boudouresque is reported for the first time in the Atlantic Ocean, although it is present in the Mediterranean Sea, probably as a Lessepsian species. The records of the widely distributed Stylonema cornu-cervi Reinsch, Acrochaetium infestans M. Howe et Hoyt and Spatoglossum schroederi (C. Agardh) Kützing were not unexpected. Data concerning morphology, habitat and geographical distribution of these species are presented. Observations on the scantly documented sublittoral species Schimmelmannia schousboei (J.Agardh) J.Agardh and Dictyopteris plagiogramma (Montagne)Vickers are also given. In the dioecious Schimmelmannia schousboei, which has been formerly accepted as a doubtful record for the Canary Islands, the reproductive morphology is described including the previously unreported spermatangia. Dictyopteris plagiogramma was recently included in a checklist of Canarian species of Dictyopteris and is discussed in detail here.

Changes in subtidal assemblages in a scenario of warming: proliferations of ephemeral benthic algae in the Canary Islands (eastern Atlantic Ocean).

The present work analysed the main changes in subtidal algal assemblages in the last decade in an oceanic archipelago (Canary Islands--eastern Atlantic Ocean). Changes result from increases in cover of ephemeral benthic algae, such as the non-native chlorophyte Pseudotetraspora marina and the native cyanophytes Blennothrix lyngbyacea, Schizothrix calcicola and Schizothrix mexicana. Ephemeral algae overgrow subtidal assemblages which are extensively dominated by Lobophora variegata, but competitively do not exclude other species. Increases in the abundance of species coincided with a warming of about 2 °C in surface seawater temperature (SST) linked to the weakening of the Cold Canary Current and the Northwestern African upwelling. Shifts in the distribution and cover of ephemeral species follow the SST gradient from warmer waters in the western islands to colder waters in the eastern ones. While in the warmest western islands, species have spread quickly colonizing all type of substrates in just a few years (2005-2008), the occurrence of ephemerals towards the coldest eastern islands is yet inconspicuous.

An integrative systematic approach to species diversity and distribution in the genus Mesophyllum (Corallinales, Rhodophyta) in Atlantic and Mediterranean Europe

For the first time, a comprehensive assessment of Mesophyllum species diversity and their distribution in Atlantic Europe and the Mediterranean Sea is presented based on molecular (COI-5P, psbA) and morphological data. The distribution ranges were redefined for the four species collected in this study: M. alternans, M. expansum, M. macroblastum and M. sphaericum. Mesophyllum sphaericum, which was previously known only from a single maerl bed in Galicia (NW Spain), is reported from the Mediterranean Sea. The known range of M. expansum (Mediterranean and Macaronesia) was extended to the Atlantic Iberian Peninsula. The occurrence of M. alternans was confirmed along the Atlantic French coast south to Algarve (southern Portugal). Mesophyllum lichenoides was only recorded from the Atlantic, whereas M. macroblastum appears to be restricted to the Mediterranean Sea. A positive correlation was observed between maximum Sea Surface Temperature (SSTmax) and the depth at which M. expansum was collected, suggesting that this species may compensate for higher SST by growing in deeper habitats where the temperature is lower. The latter indicates that geographic shifts in the distribution of coastal species as a result of global warming can possibly be mitigated by changes in the depth profile at which these species occur. Mesophyllum expansum, an important builder of Mediterranean coralligenous habitats, may be a good target species to assess its response to climate change.

Contribution to the Seaweed Flora of the Canary Islands: New Records of Florideophyceae

Seven species of Florideophyceae are reported from the Canary Islands for the first time: Predaea huismanii Kraft, Platysiphonia caribaea Ballantine et Wynne, Jania longifurca Zanardini, Spermothamnion flabellatum Bornet, Callithamnion decompositum J. Agardh, Helminthocladia agardhiana Dixon and Rissoella verruculosa (Bertolini) J. Agardh. Data concerning ecological conditions, geographical distribution, morphology, anatomy and phenology are presented. Observations on Platysiphonia miniata (C. Agardh) B0rgesen which has previously only been reported once from the Canary Islands, are also given.