Do sexual pheromone traps provide biased information of the local gene pool in the pine processionary moth? P. Salvato, M. Simonato, L. Zane*, T. Patarnello*†, L. Masutti and A. Battisti Universita ` di Padova, DAAPV-Entomologia, Via dell’Universita ` 16, 35020 Legnaro, Italy, *Universita ` di Padova, Dip. Biologia, Via G. Colombo 3, 35121 Padova, Italy and yUniversita ` di Padova, Facolta ` di Medicina Veterinaria, Via dell’Universita ` 16, 35020 Legnaro, Italy Abstract 1 Sexual pheromone traps are commonly used to monitor populations of the pine processionary moth, Thaumetopoea pityocampa, assuming that trapped males are representative of the breeding population. 2 For seven Italian populations, mitochondrial haplotypes (COI and COII) of adult males caught in traps were compared with those of larvae obtained from egg batches laid in the same year, to test whether the males trapped were representative of the local populations. 3 The distribution of haplotype frequencies revealed substantial homogeneity between adult males and larvae samples from the same population, except for Aosta Ruines Verre`s, a population recently expanding in the south-western Alps. In this case, the results suggested that trapped males were recruited over a wider area than local moths because haplotype diversity was higher than that of larvae. 4 A further analysis of this population using nuclear markers (AFLP) confirmed that adults, collected in pheromone traps, were genetically different from the larvae emerging in the same stand. 5 In conclusion, the assumption that trapped males are representative of breed- ing populations was confirmed for core populations, but has not been verified for the recently established population of Aosta Ruines Verre`s. This should encourage discussion with respect to the reliability of pheromone traps in monitoring programmes of the pest, especially at the range’s edge. Keywords Distribution range edge, genetic diversity, monitoring, pine proces- sionary moth, sex pheromone trap. Introduction Traps baited with sexual pheromones have often been used to monitor the population densities of Lepidopteran pests in Integrated Pest Management programmes (Muirhead- Thomson, 1991), assuming that trapped males are repre- sentative of the breeding population (McNeil, 1991). Pheromone traps have also been used to gain information about the dispersal ability of male moths through mark – release recapture experiments (Schneider, 1999). However, in both cases, it is not clear whether males caught in pher- omone traps are representative of local populations and reflect normal conditions of dispersal. The attraction range of pheromone traps for male moths has been found to be in the order of hundreds of metres (Schlyter, 1992; Zhang et al., 1996), thus suggesting that individuals are collected from a restricted area, and that the response to pheromone traps may be dependent on age (Elkinton & Carde´, 1980) and mating status (Hennebery & Clayton, 1984; Bergh & Seabrook, 1986). In particular, behavioural factors, such as trap avoidance when females are calling (Knight & Croft, 1987) and mate competition between local and immigrant males, can con- fuse the pattern, leading to over-representation of immi- grants in the pheromone traps. The pine processionary moth Thaumetopoea pityocampa (Denis & Schiffermu¨ ller) (Lepidoptera Thaumetopoeidae) is a pest that is currently expanding its range of distribution at upper elevations and latitudes as a likely consequence of climate change (Goussard et al., 1999). Pheromone trapping Correspondence: A. Battisti. Tel.: þ39 0498 272804; fax: þ390498 272810; e-mail: andrea.battisti@unipd.it Agricultural and Forest Entomology (2005) 7, 127–132 # 2005 The Royal Entomological Society