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

Abstract

Longhorn beetles are among the most important groups of invasive forest insects worldwide. In parallel, they represent one of the most well-studied insect groups in terms of chemical ecology. Longhorn beetle aggregation-sex pheromones are commonly used as trap lures for specific and generic surveillance programs at points of entry and may 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 a pheromone channel that is different to that of native species active at the same time of year and day, allowing for unhindered mate location (i.e., pheromone-free space hypothesis). In this study, we first tested the attractiveness of single pheromone components (i.e., racemic 3-hydroxyhexan-2-one, racemic 3-hydroxyoctan-2-one, and syn-2,3-hexanediol), and their binary and tertiary combinations, to native and exotic longhorn beetle species in Canada and Italy. Second, we exploited trap catches to determine their seasonal flight activity. Third, we used pheromone-baited "timer traps" to determine longhorn beetle daily flight activity. The response to single pheromones and their combinations was mostly species specific but the combination of more than one pheromone component allowed catch of multiple species simultaneously in Italy. The response of the exotic species to pheromone components, coupled with results on seasonal and daily flight activity, provided partial support for the pheromone-free space hypothesis. This study aids in the understanding of longhorn beetle chemical ecology and confirms that pheromones can play a key role in longhorn beetle invasions.

Exploiting trap color to improve surveys of longhorn beetles

“…The difference in color preference might be linked either to the colors of the most commonly visited flowers or to differences in the (visual guided) mate-finding behavior. X. stebbingi and X. colonus, for example, are mainly crepuscular or nocturnal species (Rassati et al 2020), whereas X. antilope is mainly diurnal, with maximal activity in the late morning to early afternoon (Molander et al 2019). This difference is also reflected in their body coloration: X. antilope is black with yellow stripes and likely mimic vespid wasps (Mitchell et al 2017), X. stebbingi and X. colonus are reddish-grayish, which likely allow them to camouflage when moving on tree bark.…”

Biological Strategies of Invasive Bark Beetles and Borers Species

“…In practice, the biological traits are not the only predictors of a potential invasion. Other factors should also be examined, for example, climatic conditions of pest risk analysis area [ 199 ] (or, as an approximation, biogeographic origin [ 151 ]), host range [ 151 ], and pheromone communication of native species that can complicate the establishment of alien species with similar semiochemicals [ 206 , 207 ].…”

Diel Rhythmicity of Field Responses to Synthetic Pheromone Lures in the Pine Sawyer Monochamus saltuarius

“…A previous study aimed to assess diel flight activity patterns of longhorn beetles either by exploiting timer traps, an instrument that rotates trap jars at programmable intervals [ 41 , 42 ], or manually removing trapped beetles from baited traps at certain time intervals [ 30 ]. Both approaches have some cons: timer traps are relatively costly, while manually removing the trapped individuals is labor-intensive.…”

“…Light is one of the factors that regulates flight activity [ 43 ]. Coleoptera comprise not only diurnal and nocturnal species [ 19 , 30 , 41 , 42 ], but also crepuscular species [ 44 ]. Therefore, to understand the diel rhythm of the response to PA, we divided the day into four time periods: time period A, 05:00–11:00 (included dawn), time period B, 11:00–17:00 (the highest temperatures of the day), time period C, 17:00–23:00 (included dusk), and time period D, 23:00–05:00 (nighttime).…”