Elevated ozone modifies the feeding behaviour of the common leaf weevil on hybrid aspen through shifts in developmental, chemical, and structural properties of leaves

In this study, we tested the impact of moderately elevated ozone (O-3) - 1.5 x ambient, equivalent to predicted near-future ozone concentrations - on the feeding behaviour of the common leaf weevil Phyllobius pyri L. (Coleoptera: Curculionidae), on two hybrid aspen [Populus tremula x Populus tremuloides (Salicaceae)] clones (clones 55 and 110) differing in ozone sensitivity using the open-air ozone exposure site in Kuopio, Finland. Three host-selection tests (test between treatments, test between clones, and test between treatments* clones) with common leaf weevil females were carried out in the laboratory in the 2nd year of ozone exposure. The beetles were offered two (four for the tests between treatments and clones) freshly cut leaf discs from first flush leaves. After 24 h, the beetles were removed and the leaf disc area consumed was measured. In the field, the unfolding of the buds was followed and samples were taken for anatomical and chemical (salicylates, condensed tannins, nitrogen, and water content) leaf analyses. Phyllobius pyri significantly preferred leaves from clone 55 to those from clone 110 in the ambient air treatment, whereas this preference was less evident under elevated ozone. Leaves from ozone-exposed trees were significantly preferred to leaves grown in ambient air. Our results suggest that the preference of clone 55 and of ozone-exposed leaves can be explained by phenotypic properties of the plant and prevailing ozone concentration through shifts in leaf development process, phenolic composition, and leaf thickness.