Population Structure and Spatial Delineation of Consumer Communities in the Everglades

The trophic ecology of Everglades fishes is poorly documented. In tropical-fish communities, hydrologic seasonality greatly affects patterns of food-resource use, such as local and long-range movements among habitats, seasonal changes in diets, diet specializations, the presence and seasonality of diet overlaps, etc. (Lowe-McConnell 1975; Winemiller 1989, 1990).

We analyzed Everglades native and introduced fish diets to identify the most important invertebrate and plant prey, and to compare trophic positions of species within and among three habitats and two seasons (Fig. 1). We used the complementary techniques of stomach and stable isotope analysis for both instantaneous and time-integrated views of animal diets (Vander Zanden and Rasmussen 1996).

We then compared diet patterns in the temperate Everglades fish community with those from seasonal aquatic systems in the tropics. We posed the following hypotheses in examining those patterns:

1: Herbivory and omnivory are common trophic states in the Everglades.

2: Seasonal changes in diets within a habitat are usual .

3: Specialization in diet is common; generalists are rare.

4: Diet overlap is highest during high-water periods when food is plentiful.

This study is a first step in using data from across habitats and seasons for use in constructing a empirical food web for the Everglades marsh.