The range expansion of the pine processionary moth in a changing world: How a well understood multifactorial process could tangle up (original) (raw)
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Human-mediated long-distance jumps of the pine processionary moth in Europe
2012
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. Keywords Climate change Á Flight capacity Á Genetic assignment tests Á Human mediated dispersal Á Invasion Á Natural enemies Á Urticating caterpillar Electronic supplementary material The online version of this article (
Annals of Forest Science, 2014
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Ecological Archives M075-009-A1
2000
2005. Population cycles in the pine looper moth: dynamical tests of mechanistic hypotheses. Ecological Monographs 75:259-276.
Forest Ecology and Management, 2014
The pine processionary moth (Thaumetopoea pityocampa, PPM) is one of the most destructive pests in Mediterranean woodlands. Assessment of PPM impact involves the quantification of pest damage at the stand level from visual evaluations by forestry technicians, using different infestation indices. One such index, widely used in national and regional forest monitoring programmes, is an ordinal index that ranges from no infestation (0) to massive defoliation (5). This index now offers an outstanding opportunity to investigate patterns and processes in PPM population dynamics. Its use as a proxy for insect population density requires, however, knowledge on the relationship between stand defoliation and population density-related measures, which is something that has not been explored to date. In this study, we investigated the relationship between the infestation index, quantifying damage at the stand level by the PPM, and fined-grained measures of PPM population size (number of egg batches, number of hatched caterpillars, number of winter tents) within and between generations. We used data from a long-term monitoring programme conducted in three pine woodland stands at Mora de Rubielos, Spain, for a 19-year period. Generalized linear models (GLM) were fitted in order to test the following hypotheses: (1) high values of population density-related variables, on a log basis, will cause high defoliation in the coming winter (within generation); and (2) high defoliation rates will be associated with high stocks of population size at the next generation of PPM (between generations). Our results indicate that, within the same generation, there was a poor relationship between the infestation index and all three fine-grained measures of population size (maximum R 2 = 0.442), possibly as a result of post-sampling larval survival over winter due to climatic factors. Goodness of fit was higher for PPM population density-related measures in the next generation and the infestation index (maximum R 2 = 0.735). Overall, the results suggest that visual evaluation of pest damage by PPM at the stand level provides an accurate proxy for population size at the next generation, and therefore opens the potential to the use of this index to investigate PPM population dynamics where no direct measures of population size exist.
EXPANSION OF GEOGRAPHIC RANGE IN THE PINE PROCESSIONARY MOTH CAUSED BY INCREASED WINTER TEMPERATURES
Ecological Applications, 2005
Global warming is predicted to cause distributional changes in organisms whose geographic ranges are controlled by temperature. We report a recent latitudinal and altitudinal expansion of the pine processionary moth, Thaumetopoea pityocampa, whose larvae build silk nests and feed on pine foliage in the winter. In north-central France (Paris Basin), its range boundary has shifted by 87 km northwards between 1972 and 2004; in northern Italy (Alps), an altitudinal shift of 110-230 m upwards occurred between 1975 and 2004. By experimentally linking winter temperature, feeding activity, and survival of T. pityocampa larvae, we attribute the expansions to increased winter survival due to a warming trend over the past three decades. In the laboratory we determined the minimum nest and night air temperatures required for larval feeding and developed a mechanistic model based on these temperature thresholds. We tested the model in a translocation experiment that employed natural temperature gradients as spatial analogues for global warming. In all transects we transferred colonies of T. pityocampa larvae to sites within zones of historical distribution, recent distribution, and outside the present range. We monitored air and nest temperature, incoming solar radiation, larval phenology, feeding activity, and survival. Early-season temperature effects on phenology were evident, with delayed development of colonies in the more extreme (colder) sites. In the coldest months, our model was consistent with the observed patterns of feeding activity: Feeding was progressively reduced with increasing latitude or elevation, as predicted by the lower number of hours when the feeding threshold was reached, which negatively affected final survival. Insolation raised nest temperature and increased feeding activity on the south but not the north aspect. Prolonged temperature drops below the feeding thresholds occurred at all sites, leading to starvation and partial mortality. Nonetheless, even the most extreme sites still allowed some feeding and, consequently, up to 20% colony survival and successful pupation. Given that the present distribution of the oligophagous T. pityocampa is not constrained by the distribution of its actual or potential hosts, and that warmer winters will cause the number of hours of feeding to increase and the probability of the lower lethal temperature to decrease, we expect the trend of improved survival in previously prohibitive environments to continue, causing further latitudinal and altitudinal expansion. This work highlights the need to develop temperature-based predictive models for future range shifts of winter-limited species, with potential applications in management.
Journal of Biogeography, 2010
Aim We investigated the Quaternary history of the pine processionary moth, Thaumetopoea pityocampa, an oligophagous insect currently expanding its range. We tested the potential role played by mountain ranges during the post-glacial recolonization of western Europe.Location Western Europe, with a focus on the Pyrenees, Massif Central and western Alps.Methods Maternal genetic structure was investigated using a fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene. We analysed 412 individuals from 61 locations and performed maximum likelihood and maximum parsimony phylogenetic analyses and hierarchical analysis of molecular variance, and we investigated signs of past expansion.Results A strong phylogeographic pattern was found, with two deeply divergent clades. Surprisingly, these clades were not separated by the Pyrenees but rather were distributed from western to central Iberia and from eastern Iberia to the Italian Peninsula, respectively. This latter group consisted of three shallowly divergent lineages that exhibited strong geographic structure and independent population expansions. The three identified lineages occurred: (1) on both sides of the Pyrenean range, with more genetically diverse populations in the east, (2) from eastern Iberia to western France, with a higher genetic diversity in the south, and (3) from the western Massif Central to Italy. Admixture areas were found at the foot of the Pyrenees and Massif Central.Main conclusions The identified genetic lineages were geographically structured, but surprisingly the unsuitable high-elevation areas of the main mountainous ranges were not responsible for the spatial separation of genetic groups. Rather than acting as barriers to dispersal, mountains appear to have served as refugia during the Pleistocene glaciations, and current distributions largely reflect expansion from these bottlenecked refugial populations. The western and central Iberian clade did not contribute to the northward post-glacial recolonization of Europe, yet its northern limit does not correspond to the Pyrenees. The different contributions of the identified refugia to post-glacial expansion might be explained by differences in host plant species richness. For example, the Pyrenean lineage could have been trapped elevationally by tracking montane pines, while the eastern Iberian lineage could have expanded latitudinally by tracking thermophilic lowland pine species.