Global latitudinal variations in marine copepod diversity and environmental factors

Latitudinal gradients in diversity are among the most striking features in ecology. For terrestrial species, climate (i.e. temperature and precipitation) is believed to exert a strong influence on the geographical distributions of diversity through its effects on energy availability. Here, we provide the first global description of geographical variation in the diversity of marine copepods, a key trophic link between phytoplankton and fish, in relation to environmental variables. We found a polar-tropical difference in copepod diversity in the Northern Hemisphere where diversity peaked at subtropical latitudes. In the Southern Hemisphere, diversity showed a tropical plateau into the temperate regions. This asymmetry around the Equator may be explained by climatic conditions, in particular the influence of the Inter-Tropical Convergence Zone, prevailing mainly in the northern tropical region. Ocean temperature was the most important explanatory factor among all environmental variables tested, accounting for 54 per cent of the variation in diversity. Given the strong positive correlation between diversity and temperature, local copepod diversity, especially in extra-tropical regions, is likely to increase with climate change as their large-scale distributions respond to climate warming.

Variations in GDGT distributions through the water column in the South East Atlantic Ocean

The TetraEther indeX of 86 carbon atoms (TEX86) temperature proxy is widely used in reconstructions of past sea surface temperature. Most current calibrations are based on surface sediment distributions of the glycerol dialkyl glycerol tetraether lipids (GDGTs) that comprise TEX86 and assume that these GDGTs are exported from the upper mixed layer. However, GDGT export from deeper waters could impact sedimentary GDGT distributions and therefore TEX86 paleothermometry. Here we examine GDGT distributions in suspended particulate matter (SPM) and underlying sediments collected from the Southeast Atlantic Ocean. Our results reveal different GDGT distributions - specifically the ratio between GDGTs bearing 2 vs. 3 cyclopentyl moieties, [2/3] ratios - between surface, subsurface (>50-200 m) and deep water (>200 m) SPM, which suggests the occurrence of in situ (deep) production that is not apparent when considering TEX86. The GDGT distributions in sediments match those of subsurface waters rather than surface waters, suggesting that they have not been preferentially derived from the upper mixed layer; this is consistent with GDGT abundances being highest in shallow subsurface SPM (˜100 to 200 m). It remains unclear what governs the different [2/3] ratios throughout the water column, but it is likely related to a combination of temperature and thaumarchaeotal community structure.

'Pues no entiendo tus palabras, / y tus bofetones siento': Linguistic Subversion in Lope de Vega's 'El perro del hortelano'

En los últimos años los críticos han dedicado mucha atención a la investigación de las voces conflictivas de la obra dramática de Lope de Vega. Se ha enfatizado en particular el papel subversivo de la lengua, sobre todo desde la perspectiva de la teoría de los actos de habla. Este artículo sobre El perro del hortelano opera dentro de un marco teórico similar para analizar cómo las retóricas poco estables del honor y del amor conducen a una desintegración de estos códigos artificiales linguísticos. Además, sugieren la presencia de una inestabilidad social colectiva más siniestra y más comprometida fuera del escenario. La ironía dramática, que sostiene el encubrimiento y la revelación de la 'verdad' a lo largo de la obra, lleva a un desenlace más liminal que cerrado y, quizás, permite la recuperación de unas voces significativas que penetren más allá del tiempo y la época en que fue escrita la obra.

The periodic variations of a white-light flare observed with ULTRACAM

High time resolution observations of a white-light flare on the active star EQ PegB show evidence of intensity variations with a period of ≈10 s. The period drifts to longer values during the decay phase of the flare. If the oscillation is interpreted as an impulsively-excited, standing-acoustic wave in a flare loop, the period implies a loop length of ≈3.4 Mm and ≈6.8 Mm for the case of the fundamental mode and the second harmonic, respectively. However, the small loop lengths imply a very high modulation depth making the acoustic interpretation unlikely. A more realistic interpretation may be that of a fast-MHD wave, with the modulation of the emission being due to the magnetic field. Alternatively, the variations could be due to a series of reconnection events. The periodic signature may then arise as a result of the lateral separation of individual flare loops or current sheets with oscillatory dynamics (i.e., periodic reconnection).