PARENT SESSION
Oral Session #36: Animal Community Ecology.
Presiding: S. Simonson
Tuesday, August 6. 8:00 AM to 11:30 AM. Mesquite Room, Radisson.
The effects of trophic subsidy on an adjacent ecosystem: an experimental test in the Gulf of California.
Talley, Drew*,1,3, Huxel, Gary1, Piņero, Francisco2, 1 University of South Florida, Tampa, FL3 University of California, Davis, CA2 Universidad de Granada, Granada, Spain
ABSTRACT- Marine production has been demonstrated to have profound effects on terrestrial communities of the islands in the Gulf of California. An important vector for the transport of marine production onto islands is through the activities of seabirds. This transport occurs in two distinct ways: 1) through the deposition of guano which fuels terrestrial plant production, and in turn affects terrestrial detrital communities, and 2) through the input of carrion, much of it in the form of nesting birds or chicks which do not survive the nesting season. We are in the first of a 3-year experiment designed to elucidate the relative effects (magnitude and form) of these two mechanisms on the terrestrial fauna of islands in Bahiá de los Angeles, Baja California, Mexico. Replicate plots treated with carrion amendments, plant amendments, or controls (no amendments), were established on two islands in the summer of 2001. Initial results revealed treatment effects on island arthropod community composition; with some species (e.g., Dermestid beetles) preferentially selected carrion amendments, and other species were better represented in plant-amended plots. Species abundances and community composition also showed seasonal and spatial patterns, both within and between islands. Stable isotope analysis further revealed temporal and spatial structure in the flow of amendments through the terrestrial food web. These two pathways of influence of a highly productive marine habitat on low-productivity terrestrial areas appear to have very different effects on island communities. Examining the interaction between juxtaposed productive and unproductive habitats may help to provide us with a more general model of the fundamental interrelationships of ecosystems which are usually considered only separately.
KEY WORDS: trophic subsidy, marine input, islands, baja california