Mechanisms involved in the establishment success of non-native pine bark beetles

VILARDO, GIMENA; CORLEY, JUAN C.; LANTSCHNER, M. VICTORIA

Lisboa

Congreso; Forest Health, Pathology and Entomology Conference; 2022

IUFRO

Bark beetles are a large and diverse group of insects commonly recognized as important forest pests and invaders. Understanding the mechanisms driving their establishment in new areas is important for predicting future invasions and improving management strategies. Our aim was to characterize population drivers of the establishment success of two recently arrived Eurasian pine bark beetle species in Patagonia (Argentina): Hylurgus ligniperda and Orthotomicus laricis. We performed field experiments to test how fitness of each species is determined by: (1) initial abundance - 1, 3, 5 or 10 couples- (Allee effects), (2) coexistence with other species (facilitation relationship) and (3) the use of ancient (Pinus sylvestries, P. nigra) vs novel (P. contorta, P. ponderosa, P. radiata) hosts. We found that H. ligniperda is able to establish a population starting from one couple only, and that the probability of leaving offspring was similar among all treatments (66-75% of 17 replicates). O. laricis was able to establish populations starting only from three or more couples, and left offspring in only 10% of the 18 incubated logs, suggesting it may be experiencing stronger Allee effects than H. ligniperda. We found that, despite the fact it is common to find both species together on the same stem, the fitness of each species did not improve when coexisting. On the contrary, H. ligniperda tends to leave more offspring when developing alone, while O. laricis showed similar performance with or in absence of H. ligniperda. We found that for H. ligniperda the probability of leaving offspring was similar when colonizing ancient vs. novel hosts, indicating that the previous history with pine trees is irrelevant in determining establishment. Our results show that H. ligniperda is more successful in establishing new populations than O. laricis, and could be explained by the difference in their life history traits and ecology. These findings contribute to a better understanding of the factors leading to successful bark beetle invasion events.