Travel Reference
In-Depth Information
tory experiments, but in the real world of a coral reef or a rainforest things
become much more complicated. In such a complex world, what exactly is
an ecological niche? Where does it begin and end? How much do two niches
have to dif er in order to support dif erent species?
Peter and Rosemary Grant and their colleagues have examined the nature
of ecological niches in the real world, and their relationship to speciation, in
archipelago range in size from the ecologically diverse Isabela, the largest
island at 4,640 square kilometers, down to tiny rocks that barely stick out
from the sea. The Grants found that an island's size determines the number
of species of fi nch that the island can support.
On the larger islands of the archipelago there tend to be large numbers
of a wide variety of seeds available, so that each species of seed-eating fi nch
Figure 70
Fisherman deploying their nets on the Irrawaddy River near Bagan in Myanmar.