Does landscape composition alter the spatiotemporal distribution of the pine processionary moth in a pine plantation forest?

Abstract

Landscape composition and physiognomy affect community structure and species distribution across space and time. The pine processionary moth (PPM) (Thaumetopoea pityocampa Den. & Schiff., Lepidoptera, Notodontidae) is a common pine defoliator throughout southern Europe and Mediterranean countries. We surveyed the spatiotemporal distribution of the PPM in a pine plantation forest in southwestern France and used the density of the winter nests as a proxy for population density. The study spanned 4 years (2005)(2006)(2007)(2008) and showed a high temporal variability in nest density. We found a strong edge effect with nest densities at stand edges more than twice as large as within-stand densities. At the landscape scale, the spatial distribution of the moth exhibited a significant spatial autocorrelation in 3 out of 4 years of our study. The spatial scales of the autocorrelation ranged from ca. 2 km to more than 22 km. We found a positive correlation between spatial distributions corresponding to certain sampling years, but the relationship was not systematic. Landscape configuration appeared to be an important driver of the PPM spatial pattern. Bivariate Moran's I correlograms showed that patch richness density as well as the percentage of local landscape covered by various land uses were correlated with population density. The study showed that accounting for landscape characteristics may be important in order to understand forest insect pest distribution, even in cases where the host species is abundant and homogeneously distributed throughout the study area, e.g., pure plantation forests.

Metapopulation modelling and area-wide pest management strategies evaluation. An application to the Pine processionary moth

“…All the correlograms are interpreted for distances ≤15,000 m. None of the tests highlights any significant autocorrelation (probability level equal to 0.01) of and between PPM pest abundance. The obtained results partially agree with Samalens and Rossi (2011) who, unlike us, considered a spatially homogeneous landscape. Fig.…”

Effect of host tree density and apparency on the probability of attack by the pine processionary moth

“…This finding questions the host concentration hypothesis, according to which insect load should be greater in stands containing a larger number of host trees (Root, 1973). By contrast, it is consistent with the long-range dispersal capacities (several km) of the PPM (Robinet et al, 2012) and with the observation of spatial autocorrelations of PPM densities of the order of several kilometers (Samalens and Rossi, 2011). In our study area, maritime pine plantations account for more than 90% of the land cover (Samalens, 2009).…”

Trees outside forests in agricultural landscapes: spatial distribution and impact on habitat connectivity for forest organisms

“…In addition, we used the edge density metric (ED) to quantify the shape and complexity of the habitat patches (Turner et al 2001). This index appeared of interest given that the PPM is known to preferentially colonize forest stand edges (Samalens and Rossi 2011). Computations were done under R with the package SDMTools (VanDerWal et al 2014).…”