Modelling the invasion dynamics of the African citrus psyllid: The role of human-mediated dispersal and urban and peri-urban citrus trees

The African citrus psyllid, Trioza erytreae (Del Guercio) (Hemiptera, Triozidae), is native to tropical Africa and invasive species in North America and Europe. The main host plants are citrus, displaying a preference for lemon trees. This psyllid was recently detected in the northwest region of the Iberian Peninsula, both in Spain and Portugal. Here, we used a model combining a reaction-diffusion model to a stochastic long- distance dispersal model to simulate the invasion dynamics of T. erytreae in Portugal. The psyllid spread in Portugal was simulated between 2015 and 2021 for different combinations of model parameters: two fecundity levels; spread with and without stochastic long-distance dispersal; single or two introductions of T. erytreae; and considering or not the urban and peri-urban citrus trees, besides citrus orchards, estimated using Google Street view imagery. The incorporation of long-distance human mediated dispersal significantly improved the F1-score in the model validation using the official reports as the observed data. Concomitantly, the dispersal rate of T. erytreae in Portugal was on average about 66 km/year, whereas removing long-distance dispersal events, the observed mean was 7.8 ± 0.3 km/year. The dispersal was mainly towards the south along the coastline, where human population is concentrated. The inclusion of the estimated citrus trees outside orchards areas significantly increased the F1-score in the model validation, revealing the importance these isolated host plants hold as stepping stones for the species current invasion and possibly for other species alikeinfo:eu-repo/semantics/publishedVersio

Utilisation des données Google Street View pour cartographier la distribution géographique des espèces. Une étude préliminaire de la processionnaire du pin (Thaumetopoea pityocampa)

Article publié suite à l'événement : MEDINSECT 3 ; Hammamet-Tunis (Tunisie) - (2012-05-08 - 2012-05-11).Mapping species distribution is an important and useful task to monitor invasive species spread or native species expansion under climate change. Unfortunately it requires a lot of occurrence data that are not easily available from literature and that are very time-consuming to collect in the field. For that reason, we designed a survey with the aim to explore to which extent large-scale databases such as Google Street View could be used to derive valid occurrence data. We worked with an insect species, the Pine Processionary Moth (PPM) Thaumetopoea pityocampa because the larvae of that moth build silk nests on its host tree that are easily visible. The presence of the species at one location can therefore be inferred from visual records derived from the panoramic views available from Google Street View. We designed a standardized procedure allowing the evaluation of the presence of the PPM on a large sampling grid (covering 46 848 km2) located in France. Field sampling has been conducted in parallel, which allowed a straightforward comparison between field and Google-derived datasets. Data derived from Google Street View were highly similar to field data as we found an accuracy (percentage of field values correctly predicted using Google Street View) of 92.9%. We conclude that Google database might provide useful occurrence data for mapping the distribution of species which presence can be visually evaluated such as the PPM. More data are needed, however, to assess the range of spatial scales at which Google Street View actually provides reliable occurrence data.La cartographie de la distribution géographique des espèces est importante pour suivre l’évolution des aires de distribution d’espèces invasives ou d’espèces natives en expansion géographique. Malheureusement, les données nécessaires sont parfois difficilement accessibles à partir de la littérature et sont coûteuses à collecter sur le terrain. Pour cette raison, nous avons conçu une étude dans le but d'explorer dans quelle mesure il est possible d’utiliser les bases de données telles que Google Street View (GSV) pour obtenir des données d’occurrence valides. Nous avons choisi de travailler avec une espèce d’insecte, la chenille processionnaire du pin (PP) Thaumetopoea pityocampa car les larves de cette espèce se développent dans le feuillage des arbres hôtes et tissent un nid blanc aisément visible. La présence de l'espèce dans un site donné peut donc être facilement renseignée en examinant les vues panoramiques disponibles pour de nombreuses localités dans la base de données de Google Street View. Nous avons conçu une procédure standardisée permettant d'évaluer la présence de la PP à partir des données GSV et nous l’avons mise en oeuvre sur une aire d’étude couvrant 46 848 km2dans la région Centre en France. La distribution de l’espèce a également été décrite à l’aide d’échantillonnages réalisés sur le terrain. Les données issues de l’examen des images Google Street View ont été comparées aux données de terrain et se sont révélées de bons estimateurs de la présence de la processionnaire du pin avec une précision (proportion de valeurs correctement estimées) de 92.9% sur notre zone d’étude pour un maillage de 16 km x 16 km. Ces résultats suggèrent que l’exploitation des bases de données de GSV pourrait permettre de produire des données écologiques intéressantes pour les espèces dont la présence peut être estimée visuellement à partir de photographies. Des études complémentaires sont cependant nécessaires pour mieux cerner la gamme d’échelles spatiales auxquelles GSV fournit des données d’occurrence fiables

Sensitivity Achieved by the LIGO and Virgo Gravitational Wave Detectors during LIGO's Sixth and Virgo's Second and Third Science Runs

See paper for full list of authors - Associated data products are publicly accessible here https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=63432We summarize the sensitivity achieved by the LIGO and Virgo gravitational wave detectors for low-mass compact binary coalescence (CBC) searches during LIGO's sixth science run and Virgo's second and third science runs. We present strain noise power spectral densities (PSDs) which are representative of the typical performance achieved by the detectors in these science runs. The data presented here and in the accompanying web-accessible data files are intended to be released to the public as a summary of detector performance for low-mass CBC searches during S6 and VSR2-3

Role of Human-Mediated Dispersal in the Spread of the Pinewood Nematode in China

Background: Intensification of world trade is responsible for an increase in the number of alien species introductions. Human-mediated dispersal promotes not only introductions but also expansion of the species distribution via long-distance dispersal. Thus, understanding the role of anthropogenic pathways in the spread of invading species has become one of the most important challenges nowadays. Methodology/Principal Findings: We analysed the invasion pattern of the pinewood nematode in China based on invasion data from 1982 to 2005 and monitoring data on 7 locations over 15 years. Short distance spread mediated by long-horned beetles was estimated at 7.5 km per year. Infested sites located further away represented more than 90% of observations and the mean long distance spread was estimated at 111–339 km. Railways, river ports, and lakes had significant effects on the spread pattern. Human population density levels explained 87% of the variation in the invasion probability (P,0.05).Since 2001, the number of new records of the nematode was multiplied by a factor of 5 and the spread distance by a factor of 2. We combined a diffusion model to describe the short distance spread with a stochastic,individual based model to describe the long distance jumps. This combined model generated an error of only 13% when used to predict the presence of the nematode. Under two climate scenarios (stable climate or moderate warming), projections of the invasion probability suggest that this pest could expand its distribution 40–55% by 2025. Conclusions/Significance: This study provides evidence that human-induced dispersal plays a fundamental role in the spread of the pinewood nematode, and appropriate control measures should be taken to stop or slow its expansion. This model can be applied to Europe, where the nematode had been introduced later, and is currently expanding its distribution. Similar models could also be derived for other species that could be accidentally transported by humans

Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network

Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects

Search for eccentric black hole coalescences during the third observing run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass M>70 M⊙) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities 0<e≤0.3 at 0.33 Gpc−3 yr−1 at 90\% confidence level

Ultralight vector dark matter search using data from the KAGRA O3GK run

Among the various candidates for dark matter (DM), ultralight vector DM can be probed by laser interferometric gravitational wave detectors through the measurement of oscillating length changes in the arm cavities. In this context, KAGRA has a unique feature due to differing compositions of its mirrors, enhancing the signal of vector DM in the length change in the auxiliary channels. Here we present the result of a search for U(1)B−L gauge boson DM using the KAGRA data from auxiliary length channels during the first joint observation run together with GEO600. By applying our search pipeline, which takes into account the stochastic nature of ultralight DM, upper bounds on the coupling strength between the U(1)B−L gauge boson and ordinary matter are obtained for a range of DM masses. While our constraints are less stringent than those derived from previous experiments, this study demonstrates the applicability of our method to the lower-mass vector DM search, which is made difficult in this measurement by the short observation time compared to the auto-correlation time scale of DM

Clear cuttings imposed by EU regulations are not sufficiently effective to eradicate the invasive pine wood nematode in non-fragmented pine forests

Abstract 1. The invasive pine wood nematode (PWN) Bursaphelenchus xylophilus is one of the most serious threats to pine forests across the world. Detected in Europe in 1999, it has largely spread despite containment measures. 2. Following the European Union regulations, the requested eradication measure is to fell, remove and dispose of all susceptible plants within a clear-cut zone (CCZ) of a radius of 500 m around any infected tree. This measure is controversial since its effectiveness is questioned. 3. An individual-based model, describing the dispersal of the nematode vector and the nematode transmission, was used to estimate the relationship between the radius and the effectiveness of the CCZ at eradicating the PWN. 4. Clear-cutting of a 500-m radius is poorly effective in non-fragmented pine forests since it reduces the number of PWN transmissions by only 0.6%–11.5%. To significantly reduce the number of transmissions, the radius should be between 14 and 38 km, which is not technically nor ethically feasible. 5. Policy implications. Our results, based on model simulations at a fine spatial scale, prove that clear-cutting susceptible trees 500 m around any infested tree—as requested by EU regulation to eradicate the PWN—is not effective in large and continuous pine forests. Instead, strengthened surveillance and sanitation felling could be explored