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

An updated and annotated list of marine Brown Algae (Phaeophyceae) of the Caribbean Coast of the Republic of Panama

Thirty-six taxa of brown macroalgae (Phaeophyceae) are reported for the Caribbean coast of the Republic of Panama including 16 new records. Most of the species diversity is restricted to two families, Dictyotaceae and Sargassaceae. This updated list represents an increase in known algal diversity for Panama of approximately 80%, but diversity is probably underestimated as revealed by comparison to the Colombian and Costa Rican floras which harbor many species not yet recorded in the marine flora of Panama. In total species diversity, Panama’s brown algal flora is considerably less diverse than Caribbean Colombia but comparable to Caribbean Costa Rica. In addition to presenting a comprehensive species list, we propose the synonymy of Dictyota pfaffii Schnetter with D. friabilis Setchell and D. jamaicensis W.R. Taylor with D. crenulata J. Agardh and discuss other taxonomic problems regarding the Caribbean Dictyotales

An updated and annotated list of marine Brown Algae (Phaeophyceae) of the Caribbean Coast of the Republic of Panama

Thirty-six taxa of brown macroalgae (Phaeophyceae) are reported for the Caribbean coast of the Republic of Panama including 16 new records. Most of the species diversity is restricted to two families, Dictyotaceae and Sargassaceae. This updated list represents an increase in known algal diversity for Panama of approximately 80%, but diversity is probably underestimated as revealed by comparison to the Colombian and Costa Rican floras which harbor many species not yet recorded in the marine flora of Panama. In total species diversity, Panama’s brown algal flora is considerably less diverse than Caribbean Colombia but comparable to Caribbean Costa Rica. In addition to presenting a comprehensive species list, we propose the synonymy of Dictyota pfaffii Schnetter with D. friabilis Setchell and D. jamaicensis W.R. Taylor with D. crenulata J. Agardh and discuss other taxonomic problems regarding the Caribbean Dictyotales

<i>Phyllodictyon robustum</i> (Setchell <i>et</i> Gardner) comb. nov (Siphonocladales, Chlorophyta), a morphologically variable species from the tropical Pacific coast of America

The systematic positions of Cladophoropsis robusta and Willeella Mexicana, both occurring along the tropical Pacific coast of America, have long been uncertain. Willeella Mexicana has been generally accepted as a synonym of C. robusta, which is currently placed in the genus Struveopsis. Reinvestigation of type material and recently collected specimens from Mexico and Panama, including culture observations, along with a molecular phylogenetic analysis inferred from rDNA ITS1-5.8S-ITS2 sequences, confirm that both taxa belong to the same, morphologically variable species. Thallus architecture ranges from stipitate, Struveopsis-like blades (produced by apical cell divisions and formation of opposite and flabellate branches) to Valoniopsis-like plants, composed of coarse, cylindrical filaments with lateral branches initiated by lenticular cells. Additionally, DNA sequence data and morphological features such as branching pattern of blade filaments, presence of tenacular cells and crystalline cell inclusions provide evidence that Struveopsis robusta falls within the Phyllodictyon clade and is most closely related with the Atlantic-Caribbean Phyllodictyon pulcherrimum, with the Indo-Pacific Phyllodictyon orientale forming a sister species. The binomial Phyllodictyon robustum (Setchell et Gardner) comb. nov. is thus proposed

Deuterium pellet injector gun design

The Deuterium Pellet Injector (DPI), an eight-pellet pneumatic injector, is being designed and fabricated for the Tokamak Fusion Test Reactor (TFTR). It will accelerate eight pellets, 4 by 4 mm maximum, to greater than 1500 m/s. It utilizes a unique pellet-forming mechanism, a cooled pellet storage wheel, and improved propellant gas scavenging

Simplified eight-shot pneumatic pellet injector for plasma fueling applications on the Princeton Beta Experiment (PBX) and on the Advanced Toroidal Facility (ATF)

Plasma fueling via injection of solid hydrogenic pellets has expanded the operating range for tokamaks and stellarators to higher densities than attainable with gas puffing. Pellet injection has also resulted in improved plasma energy confinement in tokamak discharges for which the pellet or pellets penetrate deep into the plasma core. The eight-shot pneumatic pellet injector described herein has been developed for use on the Princeton Beta Experiment (PBX) and on the Advanced Toroidal Facility (ATF) for routine plasma fueling and for confinement optimization studies. The injector is based upon the so-called ''pipe-gun'' concept, which generates deuterium and hydrogen pellets by direct condensation in the gun barrel tubes, segments of which are cooled below the hydrogen triple point temperature by contact with a liquid helium cooled block. Control of the pellet length is achieved both by regulating the deuterium fill pressure and by establishing temperature gradients along the barrel tubes. This injector features eight independent gun barrel assemblies mounted around the perimeter of a single cold block, each coupled to an ORNL-designed fast propellant valve. Thus, the injector is capable of injecting arbitrarily programmable sequences of up to eight pellets of sizes ranging from 1 mm to 3 mm at speeds up to 1500 m/s. 10 refs., 8 figs

Design and testing of a dual 8-T 380-mm/12-T 220-mm split superconducting solenoid for ORNL

A superconducting high field magnet facility has recently been prepared for operation at the Oak Ridge National Laboratory (ORNL). The facility consists of a background NbTi coil and an insert coil made of Nb/sub 3/Sn tape. The background coil produces an 8-T central field, with a peak field of 8.8 T, in a bore of 380 mm and contains radial access ports of 67-mm diam. Details of magnet design both for the background coil and insert coil will be presented. The protection scheme will be discussed and test results will be given