Herbivore-constructed leaf shelters on Salix eriocarpa shoots affect arthropod communities

Abstract

We observed the abundance of leaf shelters, aphids, other herbivores, and predators on willow trees, Salix eriocarpa, from May to October 2003. There was a positive correlation between the growth rate of aphids and the number of ants per shoot, suggesting ant attendance to aphids. Although the mean abundance of leaf shelters per shoot was rather low (1.7–2.2) throughout the observation period, aphids preferred to use shoots with leaf shelters compared with those without leaf shelters. The abundance of ants was positively influenced by the presence of leaf shelters and aphids from May to August. The abundance of other herbivores was positively influenced by leaf shelters, but negatively influenced by aphid presence from May to August. Furthermore, leaf shelters had a positive effect on the abundance of predators from July to October. These data suggest that a relatively low abundance of naturally occurring leaf shelters per shoot influenced the arthropod communities on S. eriocarpa, and the effect of those leaf shelters on each type of arthropod varied according to the season.