Deep mtDNA divergences indicate cryptic species in a fig-pollinating wasp

Background: Figs and fig-pollinating wasps are obligate mutualists that have coevolved for ca 90 million years. They have radiated together, but do not show strict cospeciation. In particular, it is now clear that many fig species host two wasp species, so there is more wasp speciation than fig speciation. However, little is known about how fig wasps speciate. Results: We studied variation in 71 fig-pollinating wasps from across the large geographic range of Ficus rubiginosa in Australia. All wasps sampled belong to one morphological species (Pleistodontes imperialis), but we found four deep mtDNA clades that differed from each other by 9–17% nucleotides. As these genetic distances exceed those normally found within species and overlap those (10–26%) found between morphologically distinct Pleistodontes species, they strongly suggest cryptic fig wasp species. mtDNA clade diversity declines from all four present in Northern Queensland to just one in Sydney, near the southern range limit. However, at most sites multiple clades coexist and can be found in the same tree or even the same fig fruit and there is no evidence for parallel sub-division of the host fig species. Both mtDNA data and sequences from two nuclear genes support the monophyly of the "P. imperialis complex" relative to other Pleistodontes species, suggesting that fig wasp divergence has occurred without any host plant shift. Wasps in clade 3 were infected by a single strain (W1) of Wolbachia bacteria, while those in other clades carried a double infection (W2+W3) of two other strains. Conclusion: Our study indicates that cryptic fig-pollinating wasp species have developed on a single host plant species, without the involvement of host plant shifts, or parallel host plant divergence. Despite extensive evidence for coevolution between figs and fig wasps, wasp speciation may not always be linked strongly with fig speciation

Atypical eye contact in autism: Models, mechanisms and development

An atypical pattern of eye contact behaviour is one of the most significant symptoms of Autism Spectrum Disorder (ASD). Recent empirical advances have revealed the developmental, cognitive and neural basis of atypical eye contact behaviour in ASD. We review different models and advance a new ‘fast-track modulator model’. Specifically, we propose that atypical eye contact processing in ASD originates in the lack of influence from a subcortical face and eye contact detection route, which is hypothesized to modulate eye contact processing and guide its emergent specialization during development

Evidence for suppressed mid-Holocene northeastern Australian monsoon variability from coral luminescence

Summer monsoon rainfall in northeastern (NE) Australia exhibits substantial interannual variability resulting in highly variable river flows. The occurrence and magnitude of these seasonal river flows are reliably recorded in modern inshore corals as luminescent lines. Here we present reconstructed annual river flows for two ~120 year mid-Holocene windows based on luminescence measurements from five cores obtained from three separate coral colonies. We were able to cross-date the luminescence signatures in four cores from two of the colonies, providing confidence in the derived reconstruction. Present-day NE Australian rainfall and river flow are sensitive to El Niño–Southern Oscillation (ENSO) variability, with La Niña (El Niño) events typically associated with wetter (drier) monsoon seasons. Thus, our replicated and annually resolved coral records provide valuable insights into the northern Australian summer monsoon and ENSO variability at a key period (6 ka) when greenhouse gas levels and ice sheet cover were comparable to the preindustrial period but orbital forcing was different. Average modern and mid-Holocene growth characteristics were very similar, suggesting that sea surface temperatures off NE Australia at 6 kyr were also close to present values. The reconstructed river flow record suggests, however, that the mid-Holocene Australian summer monsoon was weaker, less variable from year to year (possibly indicative of reduced ENSO variability), and characterized by more within-season flood pulses than present. In contrast to today, the delivery of moisture appears to have been dominated by eastward propagating convective coupled waves associated with the Madden-Julian Oscillation

Three-voice textures in the mid-15th-century English Mass cycle

I n writing any form of polyphony, composers had to balance a range of priorities that formed a matrix of related and sometimes conflicting conventions governing contrapuntal possibilities. For works that utilize pre-existent materials in the form of cantus firmi or chant paraphrases, such as some Mass cycles, a further range of constraints is given by the very nature of this material. It is within this matrix of different compositional concerns that composers sought to develop their musical argument and to give voice to their own compositional identities. An understanding of style, be that pertaining to a composer or an entire national, chronological or generic group, can only be reached through an understanding of these competing compositional principles, how they were prioritized, and what room they allowed for individual answers to common compositional questions. The stated aim of the conference from which this collection of essays is drawn was to ‘face the music of medieval England’. The focus of this contribution is to provide a window through which we might do that, in the context of a small and self-contained repertory, namely the three-voice Mass cycle as cultivated in mid-15th-century England. This repertory has the advantage of boasting a wealth of scholarship that looks at different aspects of its contrapuntal handling. The discussion below brings together Andrew Kirkman’s comprehensive study of voice range with Margaret Bent’s work on grammatical function, as well as making some refinements based on an analysis of the nature of pre-existent material found in some of the repertory.2 This discussion offers new perspectives on some apparently unusual Mass cycles that appear to sit outside of the norms—perspectives which might shed light on issues of authorship, provenance and chronology. Specifically, I wish to turn my attention to issues of range and grammatical function within a particularly unusual anonymous Mass cycle from the Strahov Codex, the Veni creator spiritus Mass, and within three Sine nomine cycles by Bedyngham, Standley and Tik. My hope here is not just to face the music, but what stands behind it as well

Comparing initial-data sets for binary black holes

We compare the results of constructing binary black hole initial data with three different decompositions of the constraint equations of general relativity. For each decomposition we compute the initial data using a superposition of two Kerr-Schild black holes to fix the freely specifiable data. We find that these initial-data sets differ significantly, with the ADM energy varying by as much as 5% of the total mass. We find that all initial-data sets currently used for evolutions might contain unphysical gravitational radiation of the order of several percent of the total mass. This is comparable to the amount of gravitational-wave energy observed during the evolved collision. More astrophysically realistic initial data will require more careful choices of the freely specifiable data and boundary conditions for both the metric and extrinsic curvature. However, we find that the choice of extrinsic curvature affects the resulting data sets more strongly than the choice of conformal metric.Comment: 18 pages, 12 figures, accepted for publication in Phys. Rev.

Relativistic dust disks and the Wilson-Mathews approach

Treating problems in full general relativity is highly complex and frequently approximate methods are employed to simplify the solution. We present comparative solutions of a infinitesimally thin relativistic, stationary, rigidly rotating disk obtained using the full equations and the approximate approach suggested by Wilson & Mathews. We find that the Wilson-Mathews method has about the same accuracy as the first post-Newtonian approximation.Comment: 4 Pages, 5 eps-figures, uses revtex.sty. Submitted to PR

Influence of reactor wall conditions on etch processes in inductively coupled fluorocarbon plasmas

The influence of reactor wall conditions on the characteristics of high density fluorocarbon plasma etch processes has been studied. Results obtained during the etching of oxide, nitride, and silicon in an inductively coupled plasma source fed with various feedgases, such as CHF3, C3F6, and C3F6/H2, indicate that the reactor wall temperature is an important parameter in the etch process. Adequate temperature control can increase oxide etch selectivity over nitride and silicon. The loss of fluorocarbon species from the plasma to the walls is reduced as the wall temperature increased. The fluorocarbon deposition on a cooled substrate surface increases concomitantly, resulting in a more efficient suppression of silicon and nitride etch rates, whereas oxide etch rates remain nearly constant

Corotating and irrotational binary black holes in quasi-circular orbits

A complete formalism for constructing initial data representing black-hole binaries in quasi-equilibrium is developed. Radiation reaction prohibits, in general, true equilibrium binary configurations. However, when the timescale for orbital decay is much longer than the orbital period, a binary can be considered to be in quasi-equilibrium. If each black hole is assumed to be in quasi-equilibrium, then a complete set of boundary conditions for all initial data variables can be developed. These boundary conditions are applied on the apparent horizon of each black hole, and in fact force a specified surface to be an apparent horizon. A global assumption of quasi-equilibrium is also used to fix some of the freely specifiable pieces of the initial data and to uniquely fix the asymptotic boundary conditions. This formalism should allow for the construction of completely general quasi-equilibrium black hole binary initial data.Comment: 13 pages, no figures, revtex4; Content changed slightly to reflect fact that regularized shift solutions do satisfy the isometry boundary condition

Phase transitions and noise crosscorrelations in a model of directed polymers in a disordered medium

We show that effective interactions mediated by disorder between two directed polymers can be modelled as the crosscorrelation of noises in the Kardar-Parisi-Zhang (KPZ) equations satisfied by the respective free energies of these polymers. When there are two polymers, disorder introduces attractive interactions between them. We analyze the phase diagram in details and show that these interactions lead to new phases in the phase diagram. We show that, even in dimension $d=1$, the two directed polymers see the attraction only if the strength of the disorder potential exceeds a threshold value. We extend our calculations to show that if there are $m$ polymers in the system then $m$-body interactions are generated in the disorder averaged effective free energy.Comment: To appear in Phys. Rev. E(2000