"Bottom-up" factors strongly influenced the spatial and temporal pattern of survival of Asphondylia atriplicis (Diptera: Cecidomyiidae) on Atriplex canescens (Chenopodiaceae) at three locations in Phoenix, Arizona, USA. In contrast, "top-down" effects of natural enemies did not influence the pattern of A. atriplicis mortality. Asphondylia atriplicis induces a fleshy, multilocular, rounded stem-gall near the apical meristems of Atriplex canescens.
Asphondylia atriplicis survival increased as gall size increased, and as the depth of larva in the gall increased. Larval mortality from unknown factors on A. atriplicis decreased with gall size. The interval parasitism rate did not change significantly with gall size.
The interval parasitism rate for the Eurytomid parasitoid group with the shortest ovipositor was negatively correlated with gall size, but interval parasitism by all other parasitoids was not influenced by gall size. Gall size was strongly influenced by the "bottom-up" forces of environmental and plant heterogeneity. Gall size varied among seasons, sites, and plants. Gall size and larval survival covaried in each season and site, and among plants.
Species 1: Diptera Cecidomyiidae Asphondylia atriplicis
Keywords: tritrophic interactions, gall-inducing insects
Back to Student Competition Display Presentations, Subsection Cd. Behavior and Ecology
Back to Student Competition Poster
Back to The 2002 ESA Annual Meeting and Exhibition