Exploring the Effects of Plant Odors, from Tree Species of Differing Host Quality, on the Response of Lymantria dispar Males to Female Sex Pheromones

Abstract

A widely accepted hypothesis for host-plant selection in herbivorous insects is that ovipositing females select host-plants that maximize the survival and performance of their offspring. However, numerous studies indicate that this is not always the case for polyphagous species. Lymantria dispar is a highly polyphagous forest defoliator and has flightless females in some subspecies, resulting in a limited capacity to make host-choices. Males of other Lepidopteran species utilize a combination of sexual pheromones and plant volatiles in their mating choices and exhibit preferences among plant species. We explored the behavior of L. dispar males towards sexual pheromone in the presence and absence of plant volatiles and their ability to discriminate between two plant species with different degrees of suitability for their offspring: a suboptimal host (Pinus sylvestris), and an optimal host (Quercus robur). In no-choice wind tunnel assays, we found that rates of male success in locating a pheromone source were not altered by the presence of plant odors; however, the time spent by males searching for the pheromone source after reaching the full length of the tunnel was reduced by more than 50% in the presence of plant volatiles. In dual choice assays, males exhibited a clear preference for a combination of pheromones and plant volatiles over the pheromone alone. However, we did not find evidence of an innate ability to discriminate between the odors of optimal and suboptimal host plants. We discuss possible ecological and evolutionary explanations for these observations.

Coupling Transcriptomics and Behaviour to Unveil the Olfactory System of Spodoptera exigua Larvae

“…Notably we did not observe any larval specific OR. Similarly, no larval-specific ORs have been found in transcriptomic data from S. littoralis (although the number of larval expressed ORs was lower than what we observed in S. exigua: 22 out of 47), Dendrolimus punctatus and Lymantria dispar larvae (Poivet et al 2013, McCormick et al 2017. On the contrary, six larval-specific ORs have been identified in Bombyx mori (Tanaka et al, 2009), one in H. armigera (Di et al, 2017) and one in C. pomonella (Walker et al, 2016).…”

“…Contrary to ORs, we observed 14 larval-specific OBPs in S. exigua, and we can speculate they are involved in binding specific cues detected by larvae. One larvalspecific OBPs has been found in S. littoralis (Poivet et al, 2013), and 10 were found in L. dispar (McCormick et al, 2017), suggesting that the occurrence of larval specific OBP might be common in Lepidoptera. We observed the expression of the four pheromonebinding proteins (PBPs) in S. exigua larval heads.…”

“…In Lepidoptera, the study of olfaction has been mainly limited to adult stage, and focused on the understanding of sex-linked behaviours such as sex pheromone detection and egglaying substrate selection (Allison and Carde, 2016;García-Robledo and Horvitz, 2012;Haverkamp et al, 2018). In contrast, the molecular and physiological mechanisms that underlie olfactory behaviours in larvae are poorly understood and only few reports have described the chemosensory gene set expressed at the larval stage (Chang et al, 2017;Di et al, 2017;McCormick et al, 2017;Poivet et al, 2013;Tanaka et al, 2009;Walker et al, 2016) compared to the plethora of adult transcriptomes available (Montagné et al, 2015). Here, we identified chemosensory-related genes expressed in S. exigua larval heads using RNA-seq and RT-PCR data, expanding previous datasets built from adult data (Du et al, 2018;Zhang et al, 2018).…”

The role of herbivore‐ and plant‐related experiences in intraspecific host preference of a relatively specialized parasitoid

“…This contradicts the “mother knows best” hypothesis (Henry et al ., ; Chesnais et al ., ). In fact, preference‐performance hypothesis may not adequately explain host selection; possible conflicts between the needs of progeny and behavioral dynamics of mother insects should also be considered (Scheirs & De Bruyn, ; McCormick et al ., ). When hosts are abundant, optimal host use in parasitoids tend to be incremental, such that oviposition increases the probability of staying in a host patch to seek more hosts (Mills & Wajnberg, ; Kugimiya et al ., ).…”

Herbivore-Induced Changes in Cotton Modulates Reproductive Behavior in the Moth Spodoptera littoralis

“…For instance, mated female moths of Heliothis virescens and Manduca sexta avoided ovipositing on herbivore-damaged tobacco plants under laboratory and field conditions (De Moraes et al, 2001;Kessler and Baldwin, 2001). Thus, the effect of herbivore-induced chemical changes on host plant quality has been well studied from a post-mating perspective i.e., oviposition decisions in adult females or through the performance of the offspring (De Moraes et al, 2001;Kessler and Baldwin, 2001;Agrawal, 2005;McCormick et al, 2017). However, less effort has been dedicated to investigate the effect of herbivore-induced changes in host plant quality on pre-mating behaviors.…”