Host use in Orgyia trigotephras (Erebidae, Lymantriinae) during outbreak: effects on larval performance and egg predation
2015
Ezzine, Olfa | Branco, Manuela | Villemant, C. (Claire) | Schmidt, Stefan | Nouira, Said | Ben Jamâa, Mohamed Lahbib
KEY MESSAGE : During outbreak, a discrepancy between larval performance and the main host used for egg laying was found in Orgyia trigotephras. It results mostly from intraspecific competition, but reduced egg mortality on the less suitable host plant may play a secondary role. CONTEXT : Host range of polyphagous herbivores often comprises plants of low nutritional quality, which may however provide other benefits to the animal. Understanding the effect of host plants use on insect fitness and its population dynamics are central questions in insect-plant ecology. O. trigotephras Boisduval is a polyphagous Mediterranean defoliator. During outbreaks, larvae are frequently found on two unrelated host species, Pistacia lentiscus L. and Quercus coccifera L. AIM : The aim of this study was to clarify the effect of population density on host use and the effects of host tree on insect performance. METHODS : The realized fecundity and egg mortality were measured during 3 years showing different population levels of the defoliator. Larval performance on the two host species was analyzed. RESULTS : Larvae fed on Q. coccifera had faster development, lower mortality, higher female/male ratio, and higher fecundity than larvae fed on P. lentiscus. Yet, at high population densities, under high intraspecific competition, P. lentiscus was the most used for egg laying. During outbreak, higher levels of parasitism by Aprostocetus sp. and predation by Coccidiphila rungsella Nel and Brusseaux were found on eggs laid on Q. coccifera compared to those laid on P. lentiscus. CONCLUSIONS : The results indicate a discrepancy between host use and larvae performance, possibly ruled by resources exploitation and intraspecific competition. The reduced egg predation on P. lentiscus during outbreaks might also provide an indirect benefit to the insect.
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