Introduction - The Darwinian Tourist - page 4

out painstaking censuses of all the trees in a half-square-kilometer plot, so
that they can follow what happens to this piece of forest over time. 1 I have
played a small role in this project, by providing them with some statistical
tools that help to explain why Mudumalai and other tropical forests remain
so diverse.
The results obtained by this group of ecologists show that evolutionary
and ecological processes have maintained the diversity of this forest. Their
research gives us a glimpse of a past world even more packed with plant
and animal species than the present, a world that we will explore in Chap-
ter 5. But their data have also shown how, as human infl uence grows stron-
ger with each passing year, this ecosystem is beginning to lose its unique
character. As Datta and I tramped through the forest, we found that it had
been invaded by alien plants that we humans have spread throughout the
world—the ubiquitous Impatiens and Lantana fl owers, and the tough and
resourceful prickly pear cactus. As we change the world's ecosystems, we
are bringing new evolutionary pressures to bear on the plants and animals
that live in them.
I have spent most of my biological career in the laboratory, applying
deliberate artifi cial selection to produce evolutionary changes in simple
organisms with brief lifespans. Then, about fi fteen years ago, I joined a col-
laborative project to look at the diversity of Mudumalai and other tropical
forests, which make up some of the world's most complex ecosystems. It
has been most rewarding to analyze the dynamic changes taking place over
decades in these forests. And it has been equally rewarding to fi nd that the
diversity of these ecosystems is maintained by processes similar to those that
evolutionary biologists study in the laboratory. Working with this world-
wide group of collaborators, I was able to show that the evolutionary force
of natural selection acts in tandem with ecological processes to increase the
diversity of the world's ecosystems.
In the course of this work I have had the pleasure of traveling around the
world, both on the land and beneath the surface of the oceans. Some of these
Figure 2 ( opposite ) H. S. Dattaraja surveys the Tropical Forest Dynamics Plot at Mudum-
alai in southern India that has inspired much of his scientifi c career.