Mapping species spatial distribution using spatial inference and prediction requires a lot of data. Occurrence data are generally not easily available from the literature and are very time-consuming ...to collect in the field. For that reason, we designed a survey to explore to which extent large-scale databases such as Google maps and Google street view could be used to derive valid occurrence data. We worked with the Pine Processionary Moth (PPM) Thaumetopoea pityocampa because the larvae of that moth build silk nests 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 evaluating the presence of the PPM on a sampling grid covering the landscape under study. The outputs were compared to field data. We investigated two landscapes using grids of different extent and mesh size. Data derived from Google street view were highly similar to field data in the large-scale analysis based on a square grid with a mesh of 16 km (96% of matching records). Using a 2 km mesh size led to a strong divergence between field and Google-derived data (46% of matching records). 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. However, the accuracy of the output strongly depends on the spatial scales considered and on the sampling grid used. Other factors such as the coverage of Google street view network with regards to sampling grid size and the spatial distribution of host trees with regards to road network may also be determinant.
The pine processionary moth (
Dennis and Schiff.), one of the major defoliating insects in Mediterranean forests, has become an increasing threat to the forest health of the region over the past two ...decades. After a recent outbreak of
in Catalonia, Spain, we attempted to estimate the damage severity by capturing the maximum defoliation period over winter between pre-outbreak and post-outbreak images. The difference in vegetation index (dVI) derived from Landsat 8 was used as the change detection indicator and was further calibrated with Unmanned Aerial Vehicle (UAV) imagery. Regression models between predicted dVIs and observed defoliation degrees by UAV were compared among five selected dVIs for the coefficient of determination. Our results found the highest R-squared value (0.815) using Moisture Stress Index (MSI), with an overall accuracy of 72%, as a promising approach for estimating the severity of defoliation in affected areas where ground-truth data is limited. We concluded with the high potential of using UAVs as an alternative method to obtain ground-truth data for cost-effectively monitoring forest health. In future studies, combining UAV images with satellite data may be considered to validate model predictions of the forest condition for developing ecosystem service tools.
Molecular markers produced by next‐generation sequencing (NGS) technologies are revolutionizing genetic research. However, the costs of analysing large numbers of individual genomes remain ...prohibitive for most population genetics studies. Here, we present results based on mathematical derivations showing that, under many realistic experimental designs, NGS of DNA pools from diploid individuals allows to estimate the allele frequencies at single nucleotide polymorphisms (SNPs) with at least the same accuracy as individual‐based analyses, for considerably lower library construction and sequencing efforts. These findings remain true when taking into account the possibility of substantially unequal contributions of each individual to the final pool of sequence reads. We propose the intuitive notion of effective pool size to account for unequal pooling and derive a Bayesian hierarchical model to estimate this parameter directly from the data. We provide a user‐friendly application assessing the accuracy of allele frequency estimation from both pool‐ and individual‐based NGS population data under various sampling, sequencing depth and experimental error designs. We illustrate our findings with theoretical examples and real data sets corresponding to SNP loci obtained using restriction site–associated DNA (RAD) sequencing in pool‐ and individual‐based experiments carried out on the same population of the pine processionary moth (Thaumetopoea pityocampa). NGS of DNA pools might not be optimal for all types of studies but provides a cost‐effective approach for estimating allele frequencies for very large numbers of SNPs. It thus allows comparison of genome‐wide patterns of genetic variation for large numbers of individuals in multiple populations.
Insect outbreaks of increasing frequency and severity in forests are predicted due to climate change. Insect herbivory is known to promote physiological changes in forest trees. However, little is ...known about whether these plant phenotypic adjustments have cascading effects on tree microbial symbionts such as fungi in roots and foliage. We studied the impact of defoliation by the pine processionary moth in two infested Pinus nigra forests through a multilevel sampling of defoliated and non-defoliated trees. We measured tree growth, nutritional status and carbon allocation to chemical defenses. Simultaneously, we analysed the putative impact of defoliation on the needle endophytes and on the soil fungal communities. Higher concentrations of chemical defenses were found in defoliated trees, likely as a response to defoliation; however, no differences in non-structural carbohydrate reserves were found. In parallel to the reductions in tree growth and changes in chemical defenses, we observed shifts in the composition of needle endophytic and soil fungal communities in defoliated trees. Defoliated trees consistently corresponded with a lower biomass of ectomycorrhizal fungi in both sites, and a higher alpha diversity and greater relative abundance of belowground saprotrophs and pathogens. However, ectomycorrhizal alpha diversity was similar between non-defoliated and defoliated trees. Specific needle endophytes in old needles were strongly associated with non-defoliated trees. The potential role of these endophytic fungi in pine resistance should be further investigated. Our study suggests that lower biomass of ectomycorrhizal fungi in defoliated trees might slow down tree recovery since fungal shifts might affect tree-mycorrhizal feedbacks and can potentially influence carbon and nitrogen cycling in forest soils.
Today, climate change is one of the greatest threats facing forest ecosystems. It directly influences the geographical distribution of insects and increases epidemics of harmful insects. The present ...work took place in this context. It aimed to contribute to the knowledge of egg parasitoids that could affect the evolution of the pine processionary caterpillar Thaumetopoea pityocampa, a major forest pest in Algeria and Mediterranean countries. The study was carried out on 120 batches of eggs taken from the Atlas cedar at two sites in the Chelia cedar zone (case of eastern Algeria) in 2017. It allowed the analysis of a total of 37,943 eggs. At the first site, the hatch rate was 66%; the egg mortality rate increased at a rate of 15 %, and the parasitism rate was rather high at 18%. The second site was characterized by the parasitism rate lower by about 11%, while the egg mortality rate was relatively comparable in the order of 14% with a hatching rate of 75%. The eggs are more parasitized by Baryscapus servadeii (79%) than by Trichogramma embryophagum (17%), while Ooencyrtus pityocampae remains negligible (4%). Egg parasitoids are an important killer of Thaumetopoea pityocampa eggs.
The nature of “climate change” will differ with geographical regions and its final impact on ecosystems vary with the extent of temperature increase, changes in irradiance and levels of UVB, amount ...and patterns of precipitation and humidity, and alterations in the incidence and nature of abiotic disturbances. Despite many uncertainties, there is consensus in the fact that global warming already has and will have impact on the temporal and spatial dynamics of insect herbivores. Ectothermic organisms are affected by the changes in environmental conditions directly in dispersal, reproduction, development and mortality, and indirectly through altered plant nutritional quality, resistance and via community interactions. Ambiguous consequences are to be expected depending on the individual host plant and herbivore species, probably involving altered incidence and intensity of pest outbreaks and changes in distributional ranges. Regions that represent northern or upper limits of occurrence, such as the Alps or the boreal zone, are likely to be affected most by an increase in stability and population density of certain pest species, such as defoliating insects or bark beetles. At the same time, temperature increase and drought will render areas of distribution in southern and continental parts of Europe less suitable for heat susceptible species, which will probably not only result in northwards shifts, but range contractions. The review is based on chapters of the “Study on impacts of climate change on European forests and options for adaptation” led by the European Forest Institute (Efi) and on results of the EU project “PROMOTH - Global change and pine processionary moth: a new challenge for integrated pest management”.
Thaumetopoea pityocampa serves as illustrative example for insect herbivores whose latitudinal and altitudinal distribution is mainly controlled by temperature and already modified by global warming.
Processionary moths carry urticating setae, which cause health problems in humans and other warm-blooded animals. The pine processionary moth Thaumetopoea pityocampa has responded to global change ...(climate warming and increased global trade) by extending its distribution range. The subfamily Thaumetopoeinae consists of approximately 100 species. An important question is whether other processionary moth species will similarly respond to these specific dimensions of global change and thus introduce health hazards into new areas. We describe, for the first time, how setae are distributed on different life stages (adult, larva) of major groups within the subfamily. Using the available data, we conclude that there is little evidence that processionary moths as a group will behave like T. pityocampa and expand their distributional range. The health problems caused by setae strongly relate to population density, which may, or may not, be connected to global change.
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•Agent-Based Models are a useful approach to simulate forest pests’ dynamics.•INSTAR simulates the population dynamics of Thaumetopoea pityocampa in pine plantations.•The model has ...been calibrated and successfully reproduces the species’ phenology.•INSTAR has been designed to easily incorporate new information about the pest biology.•INSTAR has been designed in a modular way to allow an easy upgrade and reusability.
Pine plantations, very common in the Mediterranean basin, are recurrently affected by forest pests due to intrinsic characteristics (high density, low spatial heterogeneity) and external factors (consistent trend towards a warmer and drier climate). INSTAR is an Agent-Based Model aiming to simulate the population dynamics of the Thaumetopoea pityocampa forest pest. The model has been designed using a modular approach: several interconnected modules (submodels) facilitate the incorporation of new knowledge about the pest biology and can serve as template for the design of other similar models. The model is spatially and temporally explicit and allows its implementation under different climate and land use scenarios. INSTAR is described in detail in this manuscript using the standardized ODD (Overview, Design concepts and Details) protocol.
Temperature is known to be one of the main factors modulating the population dynamics of T. pityocampa. In order to be coherent and structurally realistic, INSTAR should faithfully reproduce the effect of this factor on the species’ phenology. This requirement has been assessed here through a consistency test of the submodules responsible for species development. This assessment is constituted by a calibration analysis of the pest phenology and a stress test performed by exposing the model to extreme climate inputs. As a result of calibration, the model successfully reproduces the phenology of the species in the simulated study area. Moreover, the stress test confirmed that the model behaves as expected when exposed to extreme input values. The results presented in this manuscript constitute a first internal validation of the development submodels. After this, INSTAR is ready for a deeper analysis consisting on a sensitivity and uncertainty analysis.
Bouzar-Essaidi K, Rahim N, Meftahi B, Benfekih L. 2023. Ecological characteristics of pine processionary moth Thaumetopoea pityocampa (Lepidoptera: Notodontidae) larval nests in pine and cedar ...forests of Algeria. Biodiversitas 24: 2107-2113. The pine processionary moth Thaumetopoea pityocampa) (Lepidoptera: Notodontidae) is one of the most serious pests of pine and cedar forests in Southern Europe and North Africa. In northern Algeria, outbreaks occur in the Aleppo pine (Pinus halepensis) forest, particularly in the semi-arid area and in the Atlas cedar forest (Cedrus atlantica) in the sub-humid elevation area. Under temperate and mountainous climates, the gregarious larvae of this winter-developing insect progressively build a large white, silky nest as a protective shelter during the winter period. We investigated the presence of nests and the environmental parameters (altitude, exposition) and their role in affecting the T. pityocampa density. Studies on nests of the pine processionary caterpillar were carried out in 2022 in two forest sites, namely Ghilas and El-Mroudj (NW Algeria). The mean (±SD) density of winter nests was higher in the cedar forest of El-Mroudj (1.22±0.26) than the Aleppo pine forest of Ghilas (1.62±0.60). The nest density differed with topographic orientation (F: 96.66, p<0.001). The nests of T. pityocampa caterpillars were directed mostly in the south side (the sunny part) of host trees, accounting for 48.5% and 43.5% of the total number of nests in El-Mroudj and Ghilas, respectively. At both sites, larval nest height was positively correlated with tree height (n = 126, P<0.001).
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