FOOD-WEB STABILITY - THE INFLUENCE OF TROPHIC FLOWS ACROSS HABITATS

In nature, fluxes across habitats often bring both nutrient and energe tic resources into areas of low productivity from areas of higher prod uctivity. These inputs can alter consumption rates of consumer and pre dator species in the recipient food webs, thereby influencing food web stability. Starting from a well-studied tritrophic food chain model, we investigated the impact of allochthonous inputs on the stability of a simple food web model. We considered the effects of allochthonous i nputs on stability of the model using four sets of biologically plausi ble parameters that represent different dynamical outcomes. We found t hat low levels of allochthonous inputs stabilize food web dynamics whe n species preferentially feed on the autochthonous sources, while eith er increasing the input level or changing the feeding preference to fa vor allochthonous inputs, or both, led to a decoupling of the food cha in that could result in the loss of one or all species. We argue that allochthonous inputs are important sources of productivity in many foo d webs and their influence needs to be studied further. This is especi ally important in the various systems, such as caves, headwater stream s, and some small marine islands, in which more energy enters the food web from allochthonous inputs than from autochthonous inputs.