Travel Reference
In-Depth Information
Figure 77
These caterpillars, probably of Nymphalid butterfl ies, swarm over a leaf in the
Lambir forest of Sarawak, Borneo.
Janzen and Connell visualized a process in which the seedlings of a tree
are at a disadvantage when they are close to the parental tree, but at an advan-
tage when they are further away. The result will be a dynamic, constantly
shifting pattern of trees of many dif erent species within the forest.
As a cluster of trees of a given species grows up, it accumulates the patho-
gens that are adapted to prey on this species. Any seeds that happen to fall
to the ground within the cluster of adults are unlikely to survive because
of all the pathogens and predators in the area. But if the adults can manage
to broadcast some of their seeds outside the clusters, a few of these widely
dispersed seeds will eventually establish new clusters. This is because they
will fall in relatively pathogen-free zones. Then, as these new clusters begin
to mature, they attract herbivores and pathogens and begin to run into the
same reproductive problem as the original cluster.
