Abstract
Pine wilt disease (PWD) has a tremendous impact on worldwide forestlands, both from the environmental and economical viewpoints. Monochamus sp., a xylophagous insect from the Cerambycidae ...family, plays an important role in dissemination of the pinewood nematode, Bursaphelenchus xylophilus, the primary pathogenic agent of PWD. This study investigates, for the first time, the bacterial communities of Monochamus galloprovincialis collected from Portuguese Pinus pinaster trees and B. xylophilus free, using a metagenomics approach. Overall, our results show that natural bacterial communities of M. galloprovincialis are mainly composed by γ-proteobacteria, Firmicutes and Bacteroidetes, which may be a reflection of insects' feeding diet and habitat characteristics. We also report different bacterial communities' composition in the thorax and abdomen of M. galloprovincialis, with high abundance of Serratia sp. in both. Our results encourage further studies in the possible relationship between bacteria from the insect vector and B. xylophilus.
We reconstructed the phylogeography of European populations of
Monochamus galloprovincialis
(Coleoptera, Cerambycidae), the European vector of the pinewood nematode,
Bursaphelenchus xylophilus
. This ...study investigated the Quaternary history of
M. galloprovincialis
and tested whether environmental parameters and/or host tree species influenced the genetic structure of
M. galloprovincialis
populations. Twelve polymorphic microsatellite loci and a Bayesian analysis were applied to 1098 individuals of
M. galloprovincialis
from 45 European locations. The continental populations formed five main genetic clusters, typical of postglacial recolonization routes observed for temperate biota associated with pine trees. The distribution of clusters formed boundaries along mountain ranges, indicating a potential role of elevation as a large-scale barrier to dispersal for this species. The correlation between environmental parameters and the distribution of genetic clusters of
M. galloprovincialis
was investigated using a partial redundancy analysis and showed an effect of precipitation rather than host tree species. From an applied perspective, these results suggest that climatic conditions and elevation may constitute barriers to the dispersal of
M. galloprovincialis
and the associated PWN.
Energy allocation strategies have been widely documented in insects and were formalized in the context of the reproduction process by the terms ‘capital breeder’ and ‘income breeder’. We propose here ...the extension of this framework to dispersal ability, with the concepts of ‘capital disperser’ and ‘income disperser’, and explore the trade-off in resource allocation between dispersal and reproduction. We hypothesized that flight capacity was sex-dependent, due to a trade-off in energy allocation between dispersal and egg production in females. We used Monochamus galloprovincialis as model organism, a long-lived beetle which is the European vector of the pine wood nematode. We estimated the flight capacity with a flight mill and used the number of mature eggs as a proxy for the investment in reproduction. We used the ratio between dry weights of the thorax and the abdomen to investigate the trade-off. The probability of flying increased with the adult weight at emergence, but was not dependent on insect age or sex. Flight distance increased with age in individuals but did not differ between sexes. It was also positively associated with energy allocation to thorax reserves, which increased with age. In females, the abdomen weight and the number of eggs also increase with age with no negative effect on flight capacity, indicating a lack of trade-off. This long-lived beetle has a complex strategy of energy allocation, being a ‘capital disperser’ in terms of flight ability, an ‘income disperser’ in terms of flight performance and an ‘income breeder’ in terms of egg production.
Background and purpose: This work presents the first research on wood nematodes in Croatia and it was done in order to address the question of the impact of dendropathogenic nematodes in pine stands ...in the coastal region of Croatia. To reveal this impact, the first step is the isolation and proper identification of the species spectrum of the existing wood nematodes. The aim of this study was to identify wood nematode species isolated from different pine tree species (Pinus halepensis, P. nigra, P. maritima) throughout the coastal region of Croatia and to identify their status as either pathogens or saprofits, which should build the basis for further research and understanding of the negative influence of this organisms on the decline of Mediterranian pine stands.
Materials and methods: The research was carried out in 2013 and 2014 and it was done along the entire coastal region of Croatia. The experiments were carried out at two levels: by sampling wood nematodes and by monitoring pine longhorn beetles. Wood samples of dry or partly dry trees of P. nigra, P. halepensis and P. pinaster were collected throughout the year in the form of rings, branches, sawdust or wood chips without bark on different heights on the trees. Two techniques were used for the extraction of nematodes: Baermann funnel technique and Cobb`s method. In samples with an increased number of nematodes, some nematodes were separated and preserved in DESS solution for further morphological and molecular analysis. In the spring of 2014, the monitoring of pine longhorn beetle Monochamus galloprovincialis was done at 6 locations along the coastal region of Croatia were traps with pheromones were installed. The traps were placed in the treetops at a height of about 7 m in P. halepensis stands. The collected pine longhorn beetles were inspected for nematodes in the laboratory.
Results: Saprophytic nematodes from the families Rhabditidae, Diplogasteridae and Cephalobidae dominated in the samples. In 9 wood samples pathogenic nematodes which belong to the genus Bursaphelenchus: B. mucronatus, B. sexdentati and B. minutes were detected . The pine wood nematode B. xylophilus was not found in the collected samples. A total of 109 pine longhorn beetles have been caught in traps with pheromones and their analysis showed that neither B. xylophilus nor native wood nematodes were present on them..
Conclusions: This is the first record of wood nematodes in the coastal region of Croatia. The results of this research confirm the presence of nematodes and their possible influence on the process of pine decline of the Mediterranean pine species in Croatia. The presence of M. galloprovincialis, the vector of highly damaging B. Xylophilus, has been confirmed during this research.
Finding the right host plant for feeding and reproduction is crucial for herbivorous insects. Usually they need both visual and olfactory cues to locate and colonize their host plants, but the ...respective role of the two types of stimuli is difficult to disentangle. Model plants mimicking the shape and colour of natural hosts, combined with odours dispensers, are relevant tools for this purpose. We used dummy pines and cut branches of natural pines to investigate host attraction in Monochamus galloprovincialis, the insect vector of the pine wood nematode in Europe. We compared the behavioural response of males and females, sexually mature or immature, in a large climatic chamber and in an olfactometer. Immature females were significantly attracted by the sole odours released by pines. Immature males and mature males and females needed a combination of visual and olfactory cues to find the host tree. These findings suggest that beetles use both visual and chemical cues to locate pine trees but that relevant stimuli likely differ between beetles of different sex and sexual maturation status. Our results question the implementation of precautionary clear‐cuts around infested trees for limiting the spread of PWN.
The use of multiple sampling areas in landscape genetic analysis has been recognized as a useful way of generalizing the patterns of environmental effects on organism gene flow. It reduces the ...variability in inference which can be substantially affected by the scale of the study area and its geographic location. However, empirical landscape genetic studies rarely consider multiple sampling areas due to the sampling effort required. In this study, we explored the effects of environmental features on the gene flow of a flying long-horned beetle (
) using a landscape genetics approach. To account for the unknown scale of gene flow and the multiple local confounding effects of evolutionary history and landscape changes on inference, we developed a way of resampling study areas on multiple scales and in multiple locations (sliding windows) in a single large-scale sampling design. Landscape analyses were conducted in 3*10
study areas ranging in scale from 220 to 1,000 km and spread over 132 locations on the Iberian Peninsula. The resampling approach made it possible to identify the features affecting the gene flow of this species but also showed high variability in inference among the scales and the locations tested, independent of the variation in environmental features. This method provides an opportunity to explore the effects of environmental features on organism gene flow on the whole and reach conclusions about general landscape effects on their dispersal, while limiting the sampling effort to a reasonable level.
The pinewood nematode (PWN), Bursaphelenchus xylophilus, is the causal agent of pine wilt disease. The international economic impact of the introduction of the PWN into new areas has highlighted the ...need for the development of accurate and reliable detection methods of B. xylophilus, which are essential to define aspects of its control and management. In the present study, a methodology was developed for the direct detection of PWN by conventional PCR assay, with a species specific set of primers based on PWN satellite DNA, using total DNA extracted directly from maritime pine, Pinus pinaster, wood and bark samples, and from the insect vector, Monochamus galloprovincialis. This methodology involves homogenisation of wood, bark and insects using liquid nitrogen, DNA extraction and one or two PCR amplification steps, which permit the rapid and direct detection of one single nematode present in 100 mg of wood and bark and in one entire insect without the preliminary steps of nematode extraction.
Transmission of the pinewood nematode (PWN) Bursaphelenchus xylophilus (Steiner & Bührer) Nickle to Pinus pinaster Aiton branches through feeding wounds of its vector in Portugal, Monochamus ...galloprovincialis Olivier, was studied under laboratory conditions. All the B. xylophilus-infected beetles transmitted nematodes to branches they fed. The transmission was more frequent during the first 6 weeks after emergence, with transmission peaks during the second and the sixth week. The adult M. galloprovincialis transmitted nematodes for a mean of 5 weeks, independently of the beetle's sex or longevity. No relation was found between beetle feeding intensity and effective transmission of B. xylophilus to the branches. The nematode transmission ceased after the ninth week, even in insects which still had B. xylophilus on their bodies. The longevity of the nematode-free insects (control group) was slightly higher than the B. xylophilus-infected beetles, although with no significant difference. The results emphasize the necessity to control the immature stages of M. galloprovincialis prior to emergence and develop efficient strategies to capture and eliminate the recently emerged beetles, as majority of the nematode infection of healthy pine trees occurs during a short period of few weeks after beetle emergence.
Introduction
A myriad of volatile organic compounds (VOCs) released by terrestrial vegetation plays an important role in environmental sciences. A thorough chemical identification of these species at ...the molecular level is essential in various fields, ranging from atmospheric chemistry to ecology of forest ecosystems. In particular, the recognition of VOCs profiles in a context of plant–insect communication is a key issue for the development of forest protection tools.
Purpose
This work was aimed at the development of a simple, robust and reliable method for the identification of volatiles emitted from plant materials, which can attract or deter pest insects. Specifically, volatiles emitted from the bark of
Pinus sylvestris
were studied, which might attract the black pine sawyer beetle
Monochamus galloprovincialis
—a serious pest of the tree and a vector of a parasitic nematode
Bursaphelenchus xylophius.
Method
The volatiles from bark samples were collected using a solid-phase micro-extraction technique, and subsequently analysed by gas-chromatography/mass-spectrometry (GC/MS). The characterisation of the volatile fraction was based on the comparison with data in mass spectral libraries, and in most cases, with the available authentic standards. The identified compounds were screened against the available entomological data to select insect attractors.
Results
The identified components included terpenes (α-pinene, ∆-3-carene, and para-cymenene), oxygenated terpenes (α-terpineol and verbenone), sesquiterpenes (α-longipinene, longifolene, E-β-farnesene, γ-cadinene and pentadecane), and diterpenes (manoyl oxide and (+)-pimaral). Of these, longifolene and (+)-pimaral are of particular interest as plausible attractors for the
M. galloprovincialis
beetle that might find application in the construction of insect bait traps.
The parasitoid complex associated with Monochamus galloprovincialis (Olivier), vector of the pine wood nematode, is discussed. Four species of the family Braconidae and one Ichneumonidae were found ...associated with Monochamus galloprovincialis in Portugal, namely Atanycolus denigrator (Linnaeus), Atanycolus ivanowi (Kokujev), Cyanopterus flavator (Fabricius), Doryctes striatellus (Nees) (Braconidae), and Xorides depressus (Holmgren) (Ichneumonidae). Atanycolus ivanowi, Atanycolus denigrator, Doryctes striatellus and Xorides depressus are new species for Portugal fauna, and Monochamus galloprovincialis is recorded as a new host of Xorides depressus. A key for determination of the ichneumonoid parasitoids of the pine sawyer is provided for the Palaearctic fauna.
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