Resource dependent stability in an experimental laboratory resource-herbivore-carnivore system

Summary

Long term predation systems were studied in the laboratory. Three species of beans (azuki bean, blackeye bean, and Red Kidney bean) were the resources, one species of bean weevil (Mexican bean weevil (KS)) the herbivore, and two species of parasitic wasps (Anisopteromalus calandrae (ja), andHeterospilus prosopidis (hp)) the carnivores. Several combinations of the three components were maintained for up to 770 days.

System persistence was dependent on the combination of species. The azuki bean-KS-ja system was the most stable; the herbivore and carnivore coexisted during the entire period of time (over 700 days). The azuki-KS-hp system was less stable, and hp wasp was eventually eliminated. Stability was primarily dependent on the species of carnivore due to differences in their searching ability.

The blackeye-KS-ja system always ended with the extinction of both herbivore and carnivore in a short period of time, although the blackeye-KS-hp system terminated with blackeye-KS. The stability of predation system is also heavily dependent on the kind of resources on which prey lives.

When the two species of wasps were introduced simultaneously, the unstable one (hp with azuki, and ja with blackeye) characterized the system dynamics. The effect of stabilizing species was minimal. Thus random introduction of more predator species did not make the system more stable.