Oviposition Decision of the Weevil Exapion ulicis on Ulex europaeus Depends on External and Internal Pod Cues

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.

A mini-review on the impact of common gorse in its introduced ranges

“…A wide range of arthropods, especially, insect assemblages have been identified as associated with U. europaeus . Most of the literature extractions provide information of arthropod interactions with the plant in its’ native range (Hill 1982 ; Stone 1986 ; Hill et al 2000 ; Hill et al 2001; Hornoy et al 2013a ). The whole plant (roots, leaves, spines, stems, shoots, flowers, and seeds) contains edible parts for both adults and larval stages of arthropods.…”

“…Dead plant material also provides a great source for detritus utilizing arthropods (Harris et al 2004 ). Some of them have been recorded to feed on common gorse exclusively, while generalist feeders may prefer to feed on the plant only when other food is becoming scarce (Hill 1982 ; Stone 1986 ; Harman et al 1996 ; Hill et al 2000 ; Clements et al 2001 ; Sixtus 2004 ; Davies et al 2005 ; Hayes 2007 ; Hornoy et al 2013a ).…”