Dramatic effects of an invasive outbreak species on fitness of a native herbivorous species is mediated by plants

FERNANDEZ PATRICIA CARINA; MARK ZIERDEN; CLAY MORROW; RICK LINDROTH

Conferencia; VI ALAEQ meeting; 2021

FCEN, UBA

Biodiversity of insects is threatened worldwide. Biological invasions are amongthe main drivers of species decline, frequently through direct competition ofshared hosts or indirect impacts of pesticide treatment. Here we studied apoorly explored topic: Legacy effects of invasive herbivores that alter thechemical profile of plants to the detriment of later-occurring native insects. Weevaluated the impact of foliar chemistry as altered by the early season invasiveinsect LD (Lymantria dispar) on performance of the mid-summer native insectAP (Antheraea polyphemus), using multiple genotypes of trembling aspen(Populus tremuloides). In a first experiment, 2 treatments were performed in latespring: treatment H, where 3 rd instar LD were allowed to feed for 1 week onselected aspen branches and treatment C, control without feeding damage.After one month, in midsummer, AP neonates were deployed to all H and Cselected branches. Larval survival and growth performance were evaluatedafter one month. In a second experiment, 5 aspen genotypes were selected at 2different sites: site A= control trees, and site B= trees totally defoliated andreflushed after a LD outbreak. Individual leaves from trees at both sites wereoffered in the lab to individual L3 AP in Petri dishes in a no-choice design.Larval performance was evaluated until moulting to L4 or dead. Results showthat AP survival and performance was strongly determined by aspen genotype.High phenolic glycosides (PG) levels correlated with high mortality rates andpoor AP performance. Legacy effects were not evident in the 1 st experiment,after low levels of GM feeding damage. However, after the LD outbreak, PGsincreased in reflushed leaves leading to dramatic impairment of native APperformance. Our findings shed light on unexplored impacts of invasive specieson native herbivores and open a new area of research on legacy effects ofbiological invasions.