, Volume 7, Issue 2, pp 125-136
Date: 18 Nov 2012

Host plant-mediated reaction norms in the European grapevine moth: evidence for evolutionary host shift from daphne to vine

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Abstract

It is widely assumed that in the late nineteenth century Lobesia botrana Den. and Schiff. shifted its food source from a wild shrub (Daphne gnidium L.) to vine (Vitis vinifera L.). We explored if host range expansion reflects an evolutionary host shift, whereby the new moth-host association was linked to adaptive changes. The reaction norms of larval survival, adult weight and development time were investigated in L. botrana under field conditions. Two moth strains were established from vine and daphne, and reciprocal infestations with neonate larvae were performed on both host plants over the three larval generations. All three traits showed phenotypic plasticity and genetic variation, variation for plasticity being only detected in larval survival. Comparisons between hosts within strains showed that (1) larval survival was higher on vine in 9 of 12 cases, (2) adult weight was lower on vine only in the first generation and (3) development time was shorter on vine in first generation, shorter on daphne in third generation and displayed a sex-related response in the second generation. Comparisons between strains within hosts evidenced moth-host adaptation as larval survival increased when strains developed on its original host. There was also evidence of moth-parasitoid coevolution because parasitism level was strain-dependent. We hypothesize that higher larval survival on vine, similar adult weight on both hosts in summer generations and lower predation risk in vineyards, might be among the fitness-related factors explaining evolutionary host shift to and worldwide adaptive success on vine of L. botrana.

Handling Editors: Yvan Rahbe and Heikki Hokkanen.