The Meat-Farming Ants: Predatory Mutualism Between Melissotarsus Ants (Hymenoptera: Formicidae) and Armored Scale Insects (Hemiptera: Diaspididae)

Ant agricultural mutualisms are common, well studied, and receive attention from scientific and public spheres due to shared similarities with human agriculture (i.e. ant/fungus ‘crop farming’ and ant/insect ‘dairy farming’). They also serve as important model systems for studying many facets of mutualism. This study reveals that the repertoire of ant agriculture may also include ‘meat farming’. Predatory mutualisms occur between Melissotarsus ants and various species of armored scale insects. This dissertation employs a multi-disciplinary approach to investigate the evolutionary history and nature of ant/diaspidid mutualisms. Chapter 1 reviews the current state of knowledge regarding species composition of these associations and includes descriptions of three new diaspidid species. Also included is a discussion on new observations of foraging behaviors gathered from multiple colonies of Melissotarsus emeryi in South Africa. Chapter 2 reconstructs the phylogeny of the Aspidiotini tribe of armored scale insects from molecular data for 127 species from 31 genera. Nearly all known ant-associated diaspidids belong to the tribe Aspidiotini. The majority of aspidiotine genera are found to be paraphyletic as currently defined and recommendations to increase taxonomic stability for this tribe are provided. Myrmecophily among diaspidids has evolved no fewer than six times independently, four times within the Aspidiotini and two additional origins recorded from the Diaspidini. Relationships between ants/diaspidids are labile at the species level and partnerships can shift. However, several clades of ant-specialized diaspidids have evolved indicating that some relationships can be stable on an evolutionary timescale. Chapter 3 investigates the diet and relative trophic position of Melissotarsus ants by analyzing stable isotopic enrichment of δ15N and δ13C, and by assaying ant gut contents for diaspidid COI mtDNA fragments. Diaspidid DNA is consistently amplified from gut contents of worker ants. Isotopic analyses indicate a strong positive relationship between δ15N and δ13C isotopes of worker ants and associated diaspidids; most variation in worker isotopes can be explained by variation in diaspidid isotopes. Worker ants are calculated to be approximately one trophic level above associated diaspidids. These dietary studies indicate that Melissotarsus ants are predators of mutualistically associated diaspidids. Predation plays a central role in the establishment and maintenance of ant/diaspidid mutualisms

Direct Detection of Giant Close-In Planets Around the Source Stars of Caustic-Crossing Microlensing Events

We propose a direct method to detect close-in giant planets orbiting stars in the Galactic bulge. This method uses caustic-crossing binary microlensing events discovered by survey teams monitoring the bulge to measure light from a planet orbiting the source star. When the planet crosses the caustic, it is more magnified than the source star; its light is magnified by two orders of magnitude for Jupiter size planets. If the planet is a giant close to the star, it may be bright enough to make a significant deviation in the light curve of the star. Detection of this deviation requires intensive monitoring of the microlensing light curve using a 10-meter class telescope for a few hours after the caustic. This is the only method yet proposed to directly detect close-in planets around stars outside the solar neighborhood.Comment: 4 pages, 2 figures. Submitted to ApJ Letter

Angular Radii of Stars via Microlensing

We outline a method by which the angular radii of giant and main sequence stars in the Galactic bulge can be measured to a few percent accuracy. The method combines ground-based photometry of caustic-crossing bulge microlensing events, with a handful of precise astrometric measurements of the lensed star during the event, to measure the angular radius of the source, theta_*. Dense photometric coverage of one caustic crossing yields the crossing timescale dt. Less frequent coverage of the entire event yields the Einstein timescale t_E and the angle phi of source trajectory with respect to the caustic. The photometric light curve solution predicts the motion of the source centroid up to an orientation on the sky and overall scale. A few precise astrometric measurements therefore yield theta_E, the angular Einstein ring radius. Then the angular radius of the source is obtained by theta_*=theta_E(dt/t_E) sin(phi). We argue that theta_* should be measurable to a few percent accuracy for Galactic bulge giant stars using ground-based photometry from a network of small (1m-class) telescopes, combined with astrometric observations with a precision of ~10 microarcsec to measure theta_E. We find that a factor of ~50 times fewer photons are required to measure theta_E to a given precision for binary-lens events than single-lens events. Adopting parameters appropriate to the Space Interferometry Mission (SIM), ~7 min of SIM time is required to measure theta_E to ~5% accuracy for giant sources in the bulge. For main-sequence sources, theta_E can be measured to ~15% accuracy in ~1.4 hours. With 10 hrs of SIM time, it should be possible to measure theta_* to ~5% for \~80 giant stars, or to 15% for ~7 main sequence stars. A byproduct of such a campaign is a significant sample of precise binary-lens mass measurements.Comment: 13 pages, 3 figures. Revised version, minor changes, required SIM integration times revised upward by ~60%. Accepted to ApJ, to appear in the March 20, 2003 issue (v586

Femtolens Imaging of a Quasar Central Engine Using a Dwarf Star Telescope

We show that it is possible to image the structure of a distant quasar on scales of $\sim 1\,$AU by constructing a telescope which uses a nearby dwarf star as its ``primary lens'' together with a satellite-borne ``secondary''. The image produced by the primary is magnified by $\sim 10^5$ in one direction but is contracted by 0.5 in the other, and therefore contains highly degenerate one-dimensional information about the two-dimensional source. We discuss various methods for extracting information about the second dimension including ``femtolens interferometry'' where one measures the interference between different parts of the one-dimensional image with each other. Assuming that the satellite could be dispatched to a position along a star-quasar line of sight at a distance $r$ from the Sun, the nearest available dwarf-star primary is likely to be at \sim 15\,\pc\,(r/40\,\rm AU)^{-2}. The secondary should consist of a one-dimensional array of mirrors extending $\sim 700\,$m to achieve 1 AU resolution, or $\sim 100\,$m to achieve 4 AU resolution.Comment: 12 pages including 3 embedded figure

NEW SINGLE-COPY NUCLEAR GENES FOR USE IN SCALE INSECT SYSTEMATICS

Despite the advent of next-generation sequencing, the polymerase chain reaction (PCR) and Sanger sequencing remain useful tools for molecular identification and systematics. To date, molecular systematics of scale insects has been constrained by the paucity of loci that researchers have been able to amplify with available PCR primers. Due to the rapid molecular evolution of scale insects, “universal” primers, and even primers developed for their sister taxon the Aphidoidea, typically fail. We used transcriptome data for two diaspidids, Acutaspis umbonifera (Newstead) and Chrysomphalus aonidum (Linnaeus), together with a published aphid genome, to design novel PCR primer sets for scale insects. Our primers amplify fragments of eight single-copy genes: ATP-dependent RNA helicase (DHX8), translation initiation factor5 (IF5X1), DNA replication licensing factor (Mcm2), double-strand break repair protein (MRE11A), serine/threonine- protein phosphatase (PPP1CB), DNA-directed RNA polymerase II (RNApII), ribonucleoside-diphosphate reductase (RRM1), signal recognition particle receptor (SRPα), neuronal PAS domain-containing protein 4 (NPAS4), and cleft lip and palate transmembrane protein 1 (TP1). Here we report the results of tests of amplification success and phylogenetic utility of these primer sets across the Diaspididae and nine other families of Coccomorpha

Quantum and classical chaos for a single trapped ion

In this paper we investigate the quantum and classical dynamics of a single trapped ion subject to nonlinear kicks derived from a periodic sequence of Guassian laser pulses. We show that the classical system exhibits diffusive growth in the energy, or 'heating', while quantum mechanics suppresses this heating. This system may be realized in current single trapped-ion experiments with the addition of near-field optics to introduce tightly focussed laser pulses into the trap.Comment: 8 pages, REVTEX, 8 figure

A direct empirical proof of the existence of dark matter

We present new weak lensing observations of 1E0657-558 (z=0.296), a unique cluster merger, that enable a direct detection of dark matter, independent of assumptions regarding the nature of the gravitational force law. Due to the collision of two clusters, the dissipationless stellar component and the fluid-like X-ray emitting plasma are spatially segregated. By using both wide-field ground based images and HST/ACS images of the cluster cores, we create gravitational lensing maps which show that the gravitational potential does not trace the plasma distribution, the dominant baryonic mass component, but rather approximately traces the distribution of galaxies. An 8-sigma significance spatial offset of the center of the total mass from the center of the baryonic mass peaks cannot be explained with an alteration of the gravitational force law, and thus proves that the majority of the matter in the system is unseen.Comment: Accepted for publication in ApJ