Temporal variations of vegetative features, sex ratios and reproductive phenology in a Dictyota dichotoma (Dictyotales, Phaeophyceae) population of Argentina

This paper addresses the phenology of a Dictyota dichotoma population from the North Patagonian coasts of Argentina. The morphology of the individuals was characterized, and analyses of the temporal variations of vegetative features, diploid and haploid life cycle generations and sex ratios are provided. Individuals, represented by growing sporophytes and gametophytes, occurred simultaneously throughout the year. Morphological variables showed temporal variation, except the width and height of medullary cells, which did not vary between seasons. All vegetative variables were significantly correlated with daylength. Besides, frond length, frond dry mass and apical and basal branching angles were significantly correlated with seawater temperatures. Vegetative thalli were less abundant than haploid and diploid thalli. Sporophytes were less abundant than male and female gametophytes. Male gametophytes dominated in May, August, October and January, and female gametophytes were more abundant in September, November, December, February and March. The formation of female gametangia showed a significant correlation with daylength, and the highest number of gametangia was registered in spring. In general, the male/female sex ratio varied between 1:2 and 1:1. Apical regions were more fertile than basal regions. Our data about frequency in the formation of reproductive structures and male/female ratios are the first recorded in the Dictyota genus and thus could not be compared with populations from other regions of the world. Significant morphological variation was observed in thalli of both life cycle generations, regarding length and dry mass, number of primary branches and branching basal angle. In general, all variables analyzed varied seasonally except cortical cell width.Fil: Gauna, Maria Cecilia. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Ecología Acuática; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto Argentino de Oceanografía (i); ArgentinaFil: Caceres, Eduardo Jorge. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Ficología y Micología; ArgentinaFil: Parodi, Elisa Rosalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto Argentino de Oceanografía (i); Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Ecología Acuática; Argentin

Adiciones a la flora de algas marinas bentónicas de El Hierro (islas Canarias)

Veinticinco especies de algas marinas bentónicas (cinco Cyanophyta, catorce Rhodophyta y seis Chlorophyta) son citadas por primera vez para la isla de El Hierro. Las especies fueron recolectadas en el eulitoral y el sublitoral en la zona de uso tradicional de la ‘Reserva Marina del Mar de Las Calmas’. Se presentan datos sobre el hábitat y la distribución regional de las especies.Twenty-five species of benthic marine algae (five Cyanophyta, fourteen Rhodophyta, and six Chlorophyta) are reported for the first time for the island of El Hierro. Species were collected in the eulittoral and sublittoral in the zone for traditional activities of the ‘Reserva Marina del Mar de Las Calmas’. Data concerning the habitat and the regional distribution of the species are presented

Evidence for deep phylogenetic conservation of exonic splice-related constraints:Splice-related skews at exonic ends in the brown alga <em>Ectocarpus</em> are common and resemble those seen in humans

The control of RNA splicing is often modulated by exonic motifs near splice sites. Chief among these are exonic splice enhancers (ESEs). Well-described ESEs in mammals are purine rich and cause predictable skews in codon and amino acid usage toward exonic ends. Looking across species, those with relatively abundant intronic sequence are those with the more profound end of exon skews, indicative of exonization of splice site recognition. To date, the only intron-rich species that have been analyzed are mammals, precluding any conclusions about the likely ancestral condition. Here, we examine the patterns of codon and amino acid usage in the vicinity of exon–intron junctions in the brown alga Ectocarpus siliculosus, a species with abundant large introns, known SR proteins, and classical splice sites. We find that amino acids and codons preferred/avoided at both 3′ and 5′ ends in Ectocarpus, of which there are many, tend, on average, to also be preferred/avoided at the same exon ends in humans. Moreover, the preferences observed at the 5′ ends of exons are largely the same as those at the 3′ ends, a symmetry trend only previously observed in animals. We predict putative hexameric ESEs in Ectocarpus and show that these are purine rich and that there are many more of these identified as functional ESEs in humans than expected by chance. These results are consistent with deep phylogenetic conservation of SR protein binding motifs. Assuming codons preferred near boundaries are “splice optimal” codons, in Ectocarpus, unlike Drosophila, splice optimal and translationally optimal codons are not mutually exclusive. The exclusivity of translationally optimal and splice optimal codon sets is thus not universal

Contrasting Geographical Distributions as a Result of Thermal Tolerance and Long-Distance Dispersal in Two Allegedly Widespread Tropical Brown Algae

BackgroundMany 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 FindingsSpecies 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/SignificanceTectonically 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

Distinctive morphological features, life-cycle phases and seasonal variations in subtropical populations of <i>Dictyota dichotoma</i> (Dictyotales, Phaeophyceae)

Although it has been suggested that the distribution of Dictyota dichotoma is probably restricted to the European Atlantic Ocean and the Mediterranean Sea, its occurrence in the Canary Islands (new southernmost distribution limit) is confirmed by nuclear ribosomal sequence data (LSU rDNA). Even though D. dichotoma has been described and illustrated prominently in early studies of brown algae, the species remains difficult to characterize due to considerable morphological plasticity. An exhaustive analysis of several quantitative characters confirms significant morphological variation both seasonally and between life-cycle phases. The species may be characterized in the Canary Islands only by the following qualitative features: erect thallus attached by a single holdfast, subdichotomous branches always of similar width, straight terminal segments and smooth margins and an entirely unilayered medulla. In the Canary Islands, D. dichotoma is an aseasonal annual with at least three overlapping generations in which sporophytes and gametophytes grow simultaneously. Thallus life span seems to be less than 3 months. The species occurs throughout the year, but as cryptic microthalli in autumn. Two abundance peaks were detected with the maximum value in February (6.2 thalli m-2). The optimum reproductive stage (88.3% fertile specimens) occurred in winter and the maximum vegetative stage (maximum thallus length: 18.6 cm) in summer. Sporophytes outnumbered gametophytes throughout the year, with ratios decreasing from 13.2 +/- 1.1 in winter to 1.9 +/- 0.2 in summer. Gametophytes made up to 25% of the population and fertile thalli were always dominant. The populations from the Canaries exhibited a temporal displacement compared to northern populations with the favorable period in the coldest season (winter) and the resting period in the warmest season (autumn)

Niche partitioning and the coexistence of two cryptic <i>Dictyota</i> (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

Phylogeny and temporal divergence of the seagrass family Zosteraceae using one nuclear and three chloroplast loci

<p>Seagrasses are among the most productive habitats in the marine realm, performing several crucial physical and biological ecosystem services. One group of seagrasses is the family Zosteraceae, which includes three to four genera and >20 species inhabiting temperate waters of both the northern and southern hemisphere. Species delineation depends on the type of data used, ranging from morphological to molecular. The main goal of this study was to better understand the evolution and divergence within the family, using a broad taxon sampling (>90 individuals) representing all species across the entire biogeographical range in both hemispheres and a four-locus approach (ITS1, matK, rbcL, psbA-trnH). The concatenated four-locus analysis supported earlier studies showing four genera in the family: Phyllospadix, Zostera, Nanozostera and Heterozostera. Four species were resolved within the genus Zostera, four within Nanozostera and two within Heterozostera. No distinction was revealed between H. nigracaulis (Australia) and H. chiliensis (Chile), suggesting a very recent introduction to Chile. A time-calibrated phylogeny using the rbcL gene revealed an early divergence of Zostera-Nanozostera/Heterozostera at 14.4 Ma, followed by a late Miocene radiation of Nanozostera-Heterozostera at 6.4 Ma, and the H. polychalymas-H. nigracaulis/tasmanica/chiliensis split at 2.3 Ma. Zostera asiatica diverged from other species of Zostera at 4.6 Ma. Phylogenetic analyses indicated that matK was the most informative single locus, whereas psbA-trnH (a widely used barcoding locus) was unable to resolve any entities within the Zosteraceae. A commonly used barcoding combination for plants, rbcL/matK, distinguished all genera, but was unable to resolve several species.</p>