Abstract
Understanding mechanisms underlying insects’ host choice and plant susceptibility is important to the study of plant-insect interactions in general, and in the context of plant invasions. This study investigates the oviposition and feeding choices of the specialist weevil Exapion ulicis on the invasive plant species Ulex europaeus, gorse. To do so, we studied the oviposition and feeding preferences of the weevil in choice experiments, using pods and flowers, respectively, from gorses grown in a common garden. The plants used came from regions with different infestation histories: Brittany and Scotland belong to the native range, where the weevil is present, while Reunion and New Zealand belong to the invasive range, where the weevil was not initially introduced with gorse. Results of these experiments suggest that the oviposition choice of E. ulicis females is driven by cues located at the surface of pods and inside them, including pod size and pod seed content. Feeding-choice experiments showed a different pattern of preference compared to oviposition. Taken together with previous studies, our results reveal that E. ulicis uses several traits to choose its host, including whole-plant traits, flower traits and pod traits.
Highlights
The choice of a host plant is crucial for fitness in phytophagous insects
Oviposition choice of phytophagous insects can follow the optimal foraging theories initially developed for parasitoids [6]
The oviposition behaviour of E. ulicis females consists of sequential steps: (i) the female walks, exploring, and eventually climbs onto a pod; (ii) she explores the pod and (iii) may start to bore a hole with her rostrum through the pod wall
Summary
The choice of a host plant is crucial for fitness in phytophagous insects. In particular, females are generally selected to choose the oviposition sites that will maximize the performance (survival, fecundity) of their offspring (Optimal Oviposition Theory) [1,2]. Plant traits that may influence this choice include external factors that act at a distance (e.g., plant size, volatiles) or by contact (e.g., tissue thickness), and internal factors (e.g., primary and secondary metabolites), often in an integrated way [5]. These cues can provide the insect with information for host plant recognition, and information about plant quality, defenses, and the presence of competitors or enemies. Oviposition choice of phytophagous insects can follow the optimal foraging theories initially developed for parasitoids [6]. Oviposition choice of phytophagous insects has been much less studied than oviposition choice of parasitoids
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