Jacques Garcia

Human-mediated long-distance jumps of the pine processionary moth in Europe

Although climate change is currently affecting the distribution of many species, insects are particularly impacted because of their high sensitivity to temperature. The pine processionary moth, Thaumetopoea pityocampa, is a forest insect extending its distribution in response to climate warming. Some pioneer colonies were recently detected far beyond the main range, near Paris and in eastern France. This study tracked the origin and pathways of these pioneer colonies through a combined use of genetic markers, measurement of female flight capabilities, and comparative analyses of the natural enemy complexes. This study also aimed to determine the establishment capability beyond the main range, considering the survival rate during two recent cold periods. The larval survival rate was higher in pioneer colonies (which behave like urban heat islands) than in main range. The flight capacity of females would not have allowed them to come from the main range or the nearest established colonies, and molecular tools further showed that individuals from at least three pioneer colonies were not assigned or similar to individuals at the edge of the main range. Egg parasitoids were absent while pupal parasitoids were present in the pioneer colonies suggesting an introduction at the pupal stage. These approaches provided strong evidence that this species has been accidentally moved near Paris and to eastern France, supporting the hypothesis of human-mediated transportation over natural dispersal. This type of dispersal was unexpected because of risks from urticating hairs and the easy detection of the species.

Inter-tree variability in the induced defense reaction of Scots pine to single inoculations by Ophiostoma brunneo-ciliatum, a bark-beetle-associated fungus

Abstract In 1987 and 1988, 100 trees year −1 were characterized by their age, height, diameter, area of sapwood section at breast height and growth efficiency indices. At different periods in the year, they were each inoculated with Ophiostoma brunneo-ciliatum at two diametrically opposite locations on the bole. The characteristics of the induced defense reactions (length of reaction zone and total resin quantity) were read in the phloem. The defense reaction zones of old trees (75–115 years old) always contained a greater total quantity of induced resin than the young trees (27–40 years old). They were also longer than in the young trees in 1987. The length of the reaction zone was smaller in June than later in the year, but the quantity of resin remained the same. Growth efficiency was always negatively correlated with the length of the reaction zone, but its correlation with the total quantity of resin in the young trees varied according to the year. In the young trees, total resin quantity was always positively correlated with tree diameter and area of sapwood section. The results are discussed in relation to the resources involved in the trees induced response and with the levels of attack density thresholds above which the trees defense is overcome. It is suggested that these resources are mainly current photosynthates in the case of young trees, while they could be otherwise in the case of old trees. It is pointed out that whilst there is undoubtedly a relationship between single reactions to individual attacks and growth efficiency, the low correlation coefficients do not allow the conclusion that lesion length or total resin from this reaction can be used as indices of the trees defense capability.

Assessing Species Distribution Using Google Street View: A Pilot Study with the Pine Processionary Moth

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.

Preference-performance relationship and influence of plant relatedness on host use by Pityogenes chalcographus L.

1 Pityogenes chalcographus L. (Coleoptera: Scolytinae) causes damage in European coniferous forests, primarily on Picea abies L. Karst., but is also recorded on other native and exotic Pinaceae species. Estimating the adequacy between adult preference and larval performance of this beetle among its host‐range, as well as the influence of plant taxonomic relatedness on these parameters, would provide useful information on the beetles ability to shift onto novel hosts. 2 Choice and no‐choice assays were conducted under laboratory conditions. Adult preference and larval performance parameters among two native (Pinus sylvestris L. and Picea abies) and three exotic north American [Pinus contorta Dougl., Picea sitchensis (Bong.) Carr. and Pseudotsuga menziesii Mirbel (Franco)] conifer species were measured. 3 Pityogenes chalcographus exhibited a significant positive relationship between preference and performance. Picea abies was both the preferred and the most suitable host species for larval development. The closest relative, P. sitchensis, was the second best choice in terms of preference and performance. Pseudotsuga menziesii occupied an intermediate position for both beetle preference and performance, and Pinus spp. were the least suitable hosts for beetle development. 4 Adult preference and larval performance ranking among hosts provides little support to the plant taxonomic relatedness hypothesis. Taxonomic relatedness could play a role on the diet breadth, although only at a limited scale, within the genus Picea. At higher taxonomic levels, other factors such as bark thickness might be decisive.

Defence reactions of Norway spruce (Picea abies Karst.) to artificial insertion of Dendroctonus micans Kug. (Col., Scolytidae)

Swarming Dendroctonus micans were artificially inserted into Norway spruce on several occasions from 1987 to 1989. Resin flow was measured 2 cm below the beetle hole, either immediately below or 10 and 20 mm away on the same side as gallery extension. Four to six weeks later, the bark was removed and the status of the beetle recorded (alive, dead, successful or failed attacks, etc.), as were size and characteristics of the maternal gallery. The induced reaction was also characterized, by size and quantity of induced resin it contained (concentration and total quantity). Beetles and galleries were collected to test for the presence of fungi. In 1990, scarifications were performed on other spruces, and beetles were inserted into various holes located in relation to these slits; the same parameters as before were measured.

Wound reactions of Scots pine (Pinus sylvestris L) to attacks by Tomicus piniperda L. and Ips sexdentatus Boern. (Col., Scolytidae)

Bark beetles Tomicus piniperda and Ips sexdentatus were artificially inserted in Scots pines. Attacks were also provoked in other trees by attractants. Resin flow corresponding to each introduction was measured in the case of artificial insertions. In all cases, gallery length, reaction zone length and the total quantity of induced resin contained in the whole reaction were measured 5–6 weeks after insertions or attacks. The attempt of gallery construction (beginning of gallery boring) and the beginning of oviposition were also noted in each case, as well as the presence of associated fungi.

Do Fungi Influence the Establishment of Bark Beetles in Scots Pine

Most aggressive bark beetle species (Coleoptera: Scolytidae) are associated with fungi which play an important role in the establishment of these beetles on conifers. The success or failure of establishment appears to depend on the capability of the tree to defend itself, especially the so-called hypersensitive reaction directed against the associated fungi (Reid et al. 1967; Berryman 1972; Safranyik et al. 1975; Raffa and Berryman 1982, 1983; Christiansen and Hornvedt 198 3). However, almost nothing is known about the mechanisms of the establishment of the European bark beetles on their usual host trees except for Ips typocrraphus in Norway spruce.

Climate Warming and Past and Present Distribution of the Processionary Moths (Thaumetopoea spp.) in Europe, Asia Minor and North Africa

Pine processionary moth, Thaumetopea pityocampa, is a model insect indicator of global warming, the northwards and upwards range expansion of this Mediterranean species being directly associated with the recent warming up. The knowledge about the drivers of moth expansion is synthesized. A first standardized mapping of the northern expansion edge, from Western Europe to Turkey, is presented, then detailed for 20 countries of Europe, Asia Minor and North Africa, including future trends. Additional data about the responses of the other Thaumetopoea species are given. Finally, the chapter points out the importance of the man-mediated introductions in the expansion process.

Ecological Responses of Parasitoids, Predators and Associated Insect Communities to the Climate-Driven Expansion of the Pine Processionary Moth

The expansion of the pine processionary moth with climate warming is likely to modify the interactions with its associated arthropod and vertebrate communities of parasitoids, predators and competitors. A first section details the response of some egg parasitoids to moth expansion. Then, we investigate how insectivorous vertebrates (specialist birds, generalist birds and generalist bats) may or not be efficient predators of T. pityocampa on the range expansion gradients. Finally, we discuss whether the expansion of the moth in inner Alpine valleys may become a serious threat to the endangered Spanish moon moth by competing for the same pine needle resource.

An exhaustive inventory of coniferous trees in an agricultural landscape

Abstract Background Various species of forest trees are commonly used for ornamental purposes and are therefore frequently found in non-forest ecosystems. These trees constitute a significant component of the trees outside forests (TOF). Although increasingly recognized as prominent feature of agricultural lands and built-up areas, not much is known, however, about TOF since they are generally absent from forest inventories. New information In the present study, we focus on the coniferous tree species that constitute potential hosts for a forest defoliator, the pine processionary moth Thaumetopoea pityocampa Den. & Schiff. (Lepidoptera, Notodontidae). We carried out an exhaustive inventory of all pines (Pinus spp.), cedars (Cedrus spp.) and Douglas-fir (Pseudotsuga menziesii) in a 22 × 22 km study window located in the open-field region of Beauce in the centre of France. We recorded a total of 3834 individuals or small groups host trees corresponding a density of 7.9 occurrences per 100 ha. We provide the spatial coordinates of the points without differentiation between tree species.