M. Coll et S. Izraylevich, WHEN PREDATORS ALSO FEED ON PLANTS - EFFECTS OF COMPETITION AND PLANT-QUALITY ON OMNIVORE-PREY POPULATION-DYNAMICS, Annals of the Entomological Society of America, 90(2), 1997, pp. 155-161
We consider an ecological system that consists of an omnivore that fee
ds on both herbivores and plants. The omnivore (an intraguild predator
in the system) and the prey (an intraguild prey) also are engaged in
asymmetric competitive interactions for a plant-related resource (feed
ing site). We present empirical data that show that the omnivorous bug
Orius insidiosus (Say) displaces its thrips prey from preferred sites
on plants. A companion study shows that plants vary greatly in their
suitability for this omnivore. We therefore developed a heuristic mode
l to study how such displacement and variation in plant suitability fo
r the omnivore affect the dynamic properties of the system. The model
predicts that an increase in plant suitability for the omnivore, which
results in increased plant-feeding, has a destabilizing effect and ma
y bring about chaos under some conditions. Likewise, the stability of
the system decreases with an increase in competitive interactions. Thu
s, plant-feeding and competition have destabilizing effects on food we
bs that include plant-feeding omnivores. In view of these findings, we
discuss mechanisms that may lead to the persistence of systems where
intraguild predators compete with their prey for plant-related resourc
es.