NOVA: And what about the stability of the habitat? Is this a stable or
instable habitat, volcanic activity?
KANESHIRO: Well the volcanic activity in the Hawaiian Islands, especially on
the island of Hawaii where we have constant volcanic activity, we constantly
have change in the landscape of the forests. So many of these forests, I think
the geologists will tell you, are probably no more than two thousand or four
thousand years old and so the forests are continuously being burned by new lava
flows. So the populations of flies or other organisms that may be trapped in
these forests are continuously subjected to small population sizes. So what we
have here is a situation where you have volcanic activity creating kapukas
which results in small population sizes in these flies which then causes a
shift in the mating system which then results in a shift in the genetic system,
the genetic background of the population which then leads the population in a
different evolutionary pathway.
NOVA: Going back to something we touched on a minute ago, does what you're
learning about the speed with which evolution takes place in Hawaii, give new
insights into the overall nature of evolution in general and, and the way
people have always thought it worked?
KANESHIRO: The Hawaiian Islands and especially the flies, have given us the
opportunity not only to test some of the classical ideas of evolution but also
to formulate new ideas of evolutionary processes. And the recent work on the
mating behavior and the sexual selection process in these flies, for example,
have challenged some of Darwin's classical ideas about natural selection being
the most dominant force in the evolutionary processes. We believe now that
perhaps sexual selection plays a much more important role in at least the
initial stages of speciation.
NOVA: Anywhere else in the tropics, if we were sitting here, we would be eaten
alive by mosquitoes and other biting insects. Why aren't there any mosquitoes
or gnats in Hawaii?
KANESHIRO: Good question. They never made it here.
There are mosquitoes of course in the Hawaiian Islands, but most of these are
restricted to the lowlands. They're not species that are adapted to the higher
elevations so we're very fortunate in Hawaii where there are very few biting
insects—mosquitoes and gnats and things like that in the native
NOVA: Because they never arrived and nothing else that got here ever evolved
into something like that?
KANESHIRO: Apparently not. I have no answer
for that, I mean they're just not here.