Range expansion of the Pine Processionary Moth in Europe - I. Mechanisms underlying PPM expansion in France in relation to global warming
Year: 2005
Type: conference-paper
Abstract: the core and expanding areas in France. Microsatellite analysis (5 loci) did not show any isolation by distance in the core area when the flight-of-bird distances are considered. However, when the values of Fixation index (Fst) were plotted against distances circumventing Massif Central, isolation by distance was verified (Mantel test). We therefore hypothesized the existence of two corridors (northwestern and northeastern) for gene flow corresponding to different ways of expansion from the Mediterranean area, the populations still communicating by the southern Mediterranean range. In the expansion area of Paris Basin, the populations of the northern front appeared slightly but significantly divergent from these of the core area and from these of the Eastern Front, suggesting two ways for expansion in that area. In the Paris Basin, the shift of the latitudinal front was estimated to have progressed of 86.7 km between 1972 and 2004, with a notable acceleration (55.6 km) during the last 10 years. The expansion coincided with a rapid increase in minimum winter temperature in both core and front area (+1.1 °C and + 0.9 °C, respectively). To test for larval survival potential, we used natural gradients to simulate weather conditions experienced by larvae during winter. From 2002 to 2004, larval colonies were translocated from core to front (two sites) and post-front areas (two sites) along two transects, using either two egg masses (2002) or 200 1stinstar larvae (20032004) implanted per tree on 10 trees per site. A datalogger was used in each site to record the weather variables (T, RH, Isolation) on tree and into nest (probe). The same experiment was done in the French Alps to compare the survival at the altitudinal front. Under the 2002-2004 conditions, PPM larvae survived largely above the present front line in Paris Basin. In the southern Alps, PPM larvae also survived at altitudes much higher (>1800 m) than the current front line (1250 m). In two sites of the Alps, lethal temperatures Pine processionary moth (PPM) constitutes a good model for studying the response of forest insects to global warming. PPM is a Mediterranean insect clearly expanding polewards. Its larval development occurs during winter and is therefore highly sensitive to minor changes in weather conditions. Moreover, the larvae build large white winter « nests », which could be easily surveyed by foresters to estimate the levels of infestation. PPM is the most important species of forest defoliator in southern Europe but it also impacts health of humans and pets because of its urticating hairs (dermatitis). Previous studies revealed that PPM cycle is largely controlled by winter weather conditions, the requirements for larval survival being assessed as follows: mean January minimum higher than -4 °C, annual solar radiation larger than 1800 h (to heat nests during winter), whilst lethal temperature was estimated at -16 °C. However, PPM surveys done since the 1960s using a permanent network of pine stands in France revealed a significant progression in both latitude and altitude between 1992 and 2002. This expansion seemed to coincide with a large increase in winter temperatures and in insolation as well but no clear evidence was provided for such relationships. Therefore, an European Project entitled PROMOTH (“Global change and pine processionary moth: a new challenge for integrated pest management”) was initiated since 2002 to address the following targets: (i) analysis of the genetic structuration of PPM populations in core and expanding areas using microsatellite markers; (ii) cartography and modelling of the expansion development in space and time; (iii) identify the physiological responses of the larvae to local variations in climate; and (iv) compare the parasitism in core and expanding areas. To analyze the genetic structuration of PPM populations, larvae were sampled in more than 50 sites throughout
Source: HAL
Institutions: Zoologie forestière, University of Padua
Language: English
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W1560016332