Travel Reference
In-Depth Information
In an ideal world, diversity might actually increase as ecological niches
multiply and new species evolve that can take advantage of them. But this is
not an ideal world. We are destroying and fragmenting forests and other eco-
systems. The animals and birds that help to disperse seeds are being hunted
down. Even the insects that contribute to the delicate frequency-dependent
balance in the forests are being reduced in numbers as older trees, with their
thousands of ecological niches, are replaced by scrubby second-growth.
And as our climate changes, fi re is sweeping through forests that have never
before experienced it.
All these changes put at risk the specialized pathogens and herbivores
that abound in these complex ecosystems. One might be less inclined to
mourn their loss than the disappearance of the many colorful and charis-
matic creatures that also populate the forests. But all these nastier and less
lovable organisms turn out to be essential for the survival of the charismatic
organisms as well. If the deadly invisible world is lost, or if its own diversity is
diminished, then the motive force that drives the Janzen-Connell ef ect will
disappear and the diversity of the world's forests will be reduced.
Darwinian evolution and the evolution of ecosystems
Ecologists deal with the measurement of present-day diversity. But we have
already seen that rainforests have changed greatly since the beginning of the
Age of Mammals. Large numbers of new species have appeared through the
evolutionary processes that we have explored in this topic. And it turns out
that ecology can work hand-in-glove with evolution to increase diversity.
We saw in the previous chapter that during the process of speciation
new species will be actively driven apart from each other genetically if any
hybrids between them cannot occupy any of the available ecological niches.
The two species will become more and more dif erent from each other, and
therefore less likely to mate and produce hybrids. The fi tness of members
of both species will be harmed if they succumb to the allure of the exotic
Figure 82
(
opposite
) These stingless bees in Sarawak's Lambir Forest defend their nest,
and their host tree, fi ercely. Although the bees cannot sting, they are very good at biting!
