Seascape continuity plays an important role in determining patterns of spatial genetic structure in a coral reef fish.

Detecting patterns of spatial genetic structure (SGS) can help identify intrinsic and extrinsic barriers to gene flow within metapopulations. For marine organisms such as coral reef fishes, identifying these barriers is critical to predicting evolutionary dynamics and demarcating evolutionarily significant units for conservation. In this study, we adopted an alternative hypothesis-testing framework to identify the patterns and predictors of SGS in the Caribbean reef fish Elacatinus lori. First, genetic structure was estimated using nuclear microsatellites and mitochondrial cytochrome b sequences. Next, clustering and network analyses were applied to visualize patterns of SGS. Finally, logistic regressions and linear mixed models were used to identify the predictors of SGS. Both sets of markers revealed low global structure: mitochondrial ΦST=0.12, microsatellite FST=0.0056. However, there was high variability among pairwise estimates, ranging from no differentiation between sites on contiguous reef (ΦST=0) to strong differentiation between sites separated by ocean expanses≥20 km (maximum ΦST=0.65). Genetic clustering and statistical analyses provided additional support for the hypothesis that seascape discontinuity, represented by oceanic breaks between patches of reef habitat, is a key predictor of SGS in E. lori. Notably, the estimated patterns and predictors of SGS were consistent between both sets of markers. Combined with previous studies of dispersal in E. lori, these results suggest that the interaction between seascape continuity and the dispersal kernel plays an important role in determining genetic connectivity within metapopulations.

Detection of lower tropospheric responses to solar energetic particles at midlatitudes.

Solar energetic particles (SEPs) occasionally contribute additional atmospheric ionization beyond that arising from the usual galactic cosmic ray background. During an SEP event associated with a solar flare on April 11, 2013, the vertical ionization rate profile obtained using a balloon-borne detector showed enhanced ionization with a 26% increase at 20 km, over Reading, United Kingdom. Fluctuations in atmospheric electrical parameters were also detected at the surface, beneath the balloon's trajectory. As no coincident changes in geomagnetism occurred, the electrical fluctuations are very likely to be associated with increased ionization, as observed by the balloon measurements. The lack of response of surface neutron monitors during this event indicates that energetic particles that are not detected at the surface by neutron monitors can nevertheless enter and influence the atmosphere's weather-generating regions.

Self-recruitment in a Caribbean reef fish: a method for approximating dispersal kernels accounting for seascape.

Characterizing patterns of larval dispersal is essential to understanding the ecological and evolutionary dynamics of marine metapopulations. Recent research has measured local dispersal within populations, but the development of marine dispersal kernels from empirical data remains a challenge. We propose a framework to move beyond point estimates of dispersal towards the approximation of a simple dispersal kernel, based on the hypothesis that the structure of the seascape is a primary predictor of realized dispersal patterns. Using the coral reef fish Elacatinus lori as a study organism, we use genetic parentage analysis to estimate self-recruitment at a small spatial scale (<1 km). Next, we determine which simple kernel explains the observed self-recruitment, given the influx of larvae from reef habitat patches in the seascape at a large spatial scale (up to 35 km). Finally, we complete parentage analyses at six additional sites to test for export from the focal site and compare these observed dispersal data within the metapopulation to the predicted dispersal kernel. We find 4.6% self-recruitment (CI95% : ±3.0%) in the focal population, which is explained by the exponential kernel y = 0.915(x) (CI95% : y = 0.865(x) , y = 0.965(x)), given the seascape. Additional parentage analyses showed low levels of export to nearby sites, and the best-fit line through the observed dispersal proportions also revealed a declining function y = 0.77(x). This study lends direct support to the hypothesis that the probability of larval dispersal declines rapidly with distance in Atlantic gobies in continuously distributed habitat, just as it does in the Indo-Pacific damselfishes in patchily distributed habitat.

Lightning-induced extensive charge sheets provide long range electrostatic thunderstorm detection.

By combining electrostatic measurements of lightning-induced electrostatic field changes with radio frequency lightning location, some field changes from exceptionally distant lightning events are apparent which are inconsistent with the usual inverse cube of distance. Furthermore, by using two measurement sites, a transition zone can be identified beyond which the electric field response reverses polarity. For these severe lightning events, we infer a horizontally extensive charge sheet above a thunderstorm, consistent with a mesospheric halo of several hundred kilometers' extent.

A nonsemen copulatory fluid influences the outcome of sperm competition in Japanese quail.

Sperm competition is a powerful and widespread evolutionary force that drives the divergence of behavioural, physiological and morphological traits. Elucidating the mechanisms governing differential fertilization success is a fundamental question of sperm competition. Both sperm and nonsperm ejaculate components can influence sperm competition outcomes. Here, we investigate the role of a nonsemen copulatory fluid in sperm competition. Male Japanese quail possess a gland that makes meringue-like foam. Males produce and store foam independent of sperm and seminal fluid, yet transfer foam to females during copulation. We tested whether foam influenced the outcome of sperm competition by varying foam state and mating order in competitive matings. We found that the presence of foam from one male decreased the relative fertilization success of a rival, and that foam from a given male increased the probability he obtained any fertilizations. Mating order also affected competitive success. Males mated first fertilized proportionally more eggs in a clutch and had more matings with any fertilizations than subsequent males. We conclude that the function of foam in sperm competition is mediated through the positive interaction of foam with a male's sperm, and we speculate whether the benefit is achieved through improving sperm storage, fertilizing efficiency or retention. Our results suggest males can evolve complex strategies to gain fertilizations at the expense of rivals as foam, a copulatory fluid not required for fertilization, nevertheless, has important effects on reproductive performance under competition.

Dynamics of the Stokes pulse in a Brillouin amplifier.

We show that the output Stoke pulse from a continuously (CW) pumped stimulated Brillouin scattering (SBS) amplifier is the sum of the transmitted input Stokes pulse, which propagates undistorted through the medium without amplification and additional delay, and of a Stokes shifted pump signal reflected by the electrostrictively induced acoustic wave, which contributes to the Stokes output signal with a delay determined by the time required for build up of the acoustic wave.

Post-mating prezygotic barriers to gene exchange between hybridizing field crickets.

Studies of sexual selection in speciation have traditionally focused on mate preference, with less attention given to traits that act between copulation and fertilization. However, recent work suggests that post-mating prezygotic barriers may play an important role in speciation. Here, we evaluate the role of such barriers in the field crickets, Gryllus firmus and Gryllus pennsylvanicus. Gryllus pennsylvanicus females mated with G. firmus males produce viable, fertile offspring, but when housed with both species produce offspring sired primarily by conspecifics. We evaluate patterns of sperm utilization in doubly mated G. pennsylvanicus females and find no evidence for conspecific sperm precedence. The reciprocal cross (G. firmus female × G. pennsylvanicus male) produces no progeny. Absence of progeny reflects a barrier to fertilization rather than reduced sperm transfer, storage or motility. We propose a classification scheme for mechanisms underlying post-mating prezygotic barriers similar to that used for premating barriers.

Enhanced attraction between drops carrying fluctuating charge distributions.

The electrostatic force between conductive spheres is always attractive at small separations, irrespective of their mean charge, when the charge on the spheres is constant. In many situations, the charge may not be fixed, such as for water drops in the natural atmosphere which vary in size and charge. We show that the attractive force between charged conductive spheres increases with increasing charge variance. The importance of this unrecognized electrostatic effect between water drops is evaluated for its potential to enhance rain formation.

"Slow Light" in stimulated Brillouin scattering: on the influence of the spectral width of pump radiation on the group index: Reply.

We show that the claims in the Comment are misleading and in instances contradictory.

"Slow Light" in Stimulated Brillouin Scattering: on the influence of the spectral width of pump radiation on the group index: reply.

We show that the claims in the Comment arise from widespread misconceptions of the principles of both SBS and "slow light" phenomena.

Effect of acoustic wave inertia and its implication to slow light via stimulated Brillouin scattering in an extended medium.

An analytical solution of the basic coupled stimulated Brillouin scattering (SBS) equations is obtained which describes the evolution of a Stokes pulse injected into an extended Brillouin medium excited by CW pump radiation. We show that regardless of the pulse length of the input Stokes pulse the delay of the output Stokes pulse results entirely from the inertia of the acoustic wave excitation via the electrostrictive interaction of the Stokes pulse with CW pump radiation. This delay is the SBS build up time and not the SBS induced group delay normally attributed to slow light.

"Slow Light" in stimulated Brillouin scattering: on the influence of the spectral width of pump radiation on the group index.

An analytical solution of the basic coupled stimulated Brillouin scattering (SBS) equations is obtained in the Fourier domain, which describes the spectral evolution of the medium's response, and that of a Stokes pulse injected into this medium, when SBS is excited by non-monochromatic CW pump radiation. It shows that spectral broadening of pump radiation by any reasonable amount results in only minute increase of the spectral width of the resonant material's excitation in SBS, and cannot be effective in modifying the natural group index of the medium for the Stokes pulse.

Mitochondrial DNA size variation within individual crickets.

The mitochondrial DNA's of two closely related cricket species (genus Gryllus) share a size polymorphism as evidenced by analysis of restriction fragment patterns. Moreover, 12 of 100 field-collected crickets are heteroplasmic, that is these individuals have more than one size class of mitochondrial DNA. No heteroplasmy for restriction site variation is observed. Intraindividual variation in cricket mitochondrial DNA provides a useful marker for studying the transmission genetics of mitochondrial DNA. Available data on patterns of variation in mothers and offspring suggest that random segregation of mitochondrial DNA variants does not occur rapidly in cricket germ-cell lineages.

European corn borer: pheromone polymorphism or sibling species?

Electrophoretic analyses of the (Z) and (E) pheromone-attracted males of Ostrinia nubilalis (Hübner), the European corn borer, in an area of coexistence indicate that these strains are not freely interbreeding. Although the populations are morphologically indistinguishable, studies of allozyme, pheromone, and hybridization suggest that the (Z) and (E) entities are genetically differentiated, perhaps to the status of semi- or sibling species.

Abnormally low threshold gain of stimulated Brillouin scattering in long optical fiber with feedback.

We show that in the generation of stimulated Brillouin scattering (SBS) in long (> 1 km) fiber, the threshold for observing coherent Stokes emission occurs at notably lower gain than the classical lasing threshold gain for SBS. The effect is due coherent regenerative amplification of strong spontaneous Brillouin scattering, which occurs in the presence of feedback. The magnitude of the effect scales with the length of interaction.

Wolbachia plays no role in the one-way reproductive incompatibility between the hybridizing field crickets Gryllus firmus and G. pennsylvanicus.

Wolbachia are cytoplasmically inherited alpha-proteobacteria that can cause cytoplasmic incompatibility (CI) in insects. This incompatibility between sperm and egg is evident when uninfected females mate with infected males. Wolbachia-driven reproductive incompatibilities are of special interest because they may play a role in speciation. However, the presence of Wolbachia does not always imply incompatibility. The field crickets Gryllus firmus and G. pennsylvanicus exhibit a very clear unidirectional incompatibility and have been cited as a possible example of Wolbachia-induced CI. Here, we conduct curing experiments, intra- and interspecific crosses, cytological examination of Wolbachia in testes and Wolbachia quantifications through real-time PCR. All of our data strongly suggest that Wolbachia are not involved in the reproductive incompatibility between G. firmus and G. pennsylvanicus.

Threshold for stimulated Brillouin scattering in optical fiber.

We show that in optical fiber the threshold exponential gain, Gth, for stimulated Brillouin scattering initiated by spontaneous Brillouin scattering is functionally and strongly dependent on the material, length and numerical aperture of the fiber and the pump wavelength. For silica fiber we show that the value of G(th) at lambda congruent with 1 microm ranges from as low as approximately 5 in long fiber ( > or =few kms) to ~10-12 in fibers of approximately 100 m length and approximately 20-23 for very short fibers (<10 cm).

A three-dimensional magnetometer for motion sensing of a balloon-carried atmospheric measurement package.

An instrument is described which carries three orthogonal geomagnetic field sensors on a standard meteorological balloon package, to sense rapid motion and position changes during ascent through the atmosphere. Because of the finite data bandwidth available over the UHF radio link, a burst sampling strategy is adopted. Bursts of 9 s of measurements at 3.6 Hz are interleaved with periods of slow data telemetry lasting 25 s. Calculation of the variability in each channel is used to determine position changes, a method robust to periods of poor radio signals. During three balloon ascents, variability was found repeatedly at similar altitudes, simultaneously in each of three orthogonal sensors carried. This variability is attributed to atmospheric motions. It is found that the vertical sensor is least prone to stray motions, and that the use of two horizontal sensors provides no additional information over a single horizontal sensor.

Note: A miniature oscillating microbalance for sampling ice and volcanic ash from a small airborne platform.

A lightweight and low power oscillating microbalance for in situ sampling of atmospheric ice and volcanic ash is described for airborne platforms. Using a freely exposed collecting wire fixed at only one end to a piezo transducer, the instrument collects airborne materials. Accumulated mass is determined from the change in natural frequency of the wire. The piezo transducer is used in a dual mode to both drive and detect the oscillation. Three independent frequency measurement techniques are implemented with an on-board microcontroller: a frequency sweep, a Fourier spectral method, and a phase-locked loop. These showed agreement to ±0.3 Hz for a 0.5 mm diameter collecting wire of 120 mm long, flown to 19 km altitude on a weather balloon. The instrument is well suited to disposable use with meteorological radiosondes, to provide high resolution vertical profiles of mass concentration.

Ancient trans-Atlantic flight explains locust biogeography: molecular phylogenetics of Schistocerca.

The desert locust (Schistocerca gregaria) has been an important agricultural pest at least since biblical times. Although the ecology, physiology and behaviour of this insect species have been well characterized, its biogeographical origins and evolutionary history are more obscure. Schistocerca gregaria occurs throughout Africa, the Middle East and Western Asia, but all other species in the genus Schistocerca are found in the New World. Because S. gregaria has the capacity for extreme long-distance movement associated with swarming behaviour, dispersal may have played an important role in determining current distribution patterns. Some authors have argued that S. gregaria is the product of an eastward trans-Atlantic dispersal from North America to Africa; others consider it more likely that the New World taxa are the product of westward dispersal from Africa. Here, we present a mitochondrial DNA phylogeny of Schistocerca species that supports the monophyly of New World species (including the Galapagos endemic Halmenus) relative to S. gregaria. In concert with observed patterns of molecular divergence, and in contrast to previous morphological studies, our analysis indicates a single trans-Atlantic flight from Africa to South America, followed by extensive speciation and ecological divergence in the New World.