 |
Tri-trophic interactions - Dr. Coley  The
world may be green because plants are well defended, or because predators keep
herbivores below their carrying capacity. Tropical plants are extremely well
defended which suggests that bottom-up factors may dominate. However, I am just
beginning to examine the defensive characteristics of herbivores and the rates
of attack by their natural enemies in Panamanian rainforests. Surprisingly high
rates of parasitism (28%) and predation (13%/day for undefended caterpillars)
suggest that pressure from the third trophic level may be quite important. As
a result, caterpillars demonstrate a battery of physical, chemical and behavioral
traits that clearly evolved as defenses. Furthermore, I suggest that host plant
traits determine the life history traits of their herbivores, which in turn
affect their susceptibility to natural enemies. And finally, I am exploring
the possibility that changes in climate will influence the dynamics between
herbivores and the third trophic level. (Photo by Dan Janzen, Database of
Costa Rican caterpillars) |
Copyright University of Utah 2005