Response of native and exotic longhorn beetles to common pheromone components provides partial support for the pheromone-free space hypothesis

Longhorn beetles are among the most important groups of invasive forest in-sects worldwide.In parallel,they represent one of the most well-studied insect groups interms of chemical ecology.Longhorn beetle aggregation-sex pheromones are commonlyused as trap lures for specific and generic surveillance programs at points of entry andmay play a key role in determining the success or failure of exotic species establishment.An exotic species might be more likely to establish in a novel habitat if it relies on apheromone channel that is different to that of native species active at the same time of yearand day,allowing for unhindered mate location(i.e.,pheromone-free space hypothesis).Inthis study,we first tested the attractiveness of single pheromone components(i.e.,racemic3-hydroxyhexan-2-one,racemic 3-hydroxyoctan-2-one,and syn-2,3-hexanediol),and theirbinary and tertiary combinations,to native and exotic longhorn beetle species in Canadaand ltaly.Second,we exploited trap catches to determine their seasonal flight activity.Third,we used pheromone-baited"timer traps"to determine longhorn beetle daily flightactivity.The response to single pheromones and their combinations was mostly speciesspecific but the combination of more than one pheromone component allowed catch ofmultiple species simultancously in ltaly.The response of the exotic species to pheromonecomponents,coupled with results on seasonal and daily flight activity,provided partialsupport for the pheromone-free space hypothesis.This study aids in the understanding oflonghorn beetle chemical ecology and confirms that pheromones can play a key role inlonghorn beetle invasions.