Excerpted Interview with Ken Kaneshiro, Biologist at the University of Hawaii:


NOVA: What are some of the unique features of the Hawaiian Islands that have given rise to the tremendous number of species in even one family of flies?

KANESHIRO: Well, the first thing is that the Hawaiian Islands are probably the most isolated island system in the world. It's sitting just about smack dab in the middle of the Pacific Basin, nearly two thousand miles from the West Coast of California and two thousand miles from Japan. So that not many organisms made it to the Hawaiian Islands. Those that did make it however fell on a very open niche, habitats that were available for it to occupy. So when the first (insects) arrived in the Hawaiian Islands and laid (their) first batch of eggs and produced some progeny, they found tremendous numbers of opportunities to radiate into these different habitats. So that's the other thing about the Hawaiian Islands, the climatic situation is such that it's within very short distances, you have tremendous diversity of environmental conditions; you have on the windward side of the islands very wet rain forest. And on the leeward side of the islands, almost desert-like conditions.

NOVA: You have pointed to a particular family of flies that has many species on this island. Did they all come from the same original parents?

KANESHIRO: Based on data from many lines of study, for example using chromosomal data, behavioral data, electrophoresis and so on, seem to indicate that these one thousand species are all descedents from one ancestor, perhaps two at the most. Now this one thousand species represent approximately 25 percent of the total number of species that are known from the rest of the world. If you are to consider the small land mass of the Hawaiian Islands, if you're to take all the Hawaiian Islands and put them all together, you can probably stick them into the state of Connecticut. Geologically, it's a very young land mass and yet we have 25 percent of the total number of species that are found in the world in this family of flies.

NOVA: Is a kapuka in a way sort of a microcosm of the island itself, an isolated area?


KANESHIRO: The volcanic activity of the Hawaiian Islands have created a situation whereby for example a, a large piece of forest with recent volcanic activity now can be cut into two or three or more patches of forest which are sort of islands of vegetation that are surrounded by a sea of larva and this is what we're in right here a kapuka and these kepukas create situations where populations of (most species) are subjected to small population sizes. And it's the small population that is most important for understanding speciation process.

NOVA: Is there a substantial difference between what you find among flies in this kapuka and number 14 a mile or so away?

KANESHIRO: We've been studying (one fly) species in this kapuka which we've been arbitrarily calling Kapuka 9 and another adjacent kapuka which is about a quarter of a mile away, Kapuka 14. Some of the studies that have been done on one of the species by using molecular tools, electrophoresis for example, indicate that within the 140 years or so that these two kapukas, Kapuka 9 and 14 have been separated, that there are significant genetic differences between these two populations. There are very significant genetic differences that have already evolved within the last 140 years.

NOVA: Now what does that tell you about the nature of evolution that is news to scientists, the speed with which these things are changing, is this a new discovery?

KANESHIRO: Well, one of our ideas is that even though there has been tremendous adaptive radiation, in other words, many of these species have been able to adapt to different habitats and niches and so on, our idea is that changes within the sexual environment, within the mating behavior of these flies, have been more important in the speciation process than most of us ever believed before. And so we've been focusing most of our efforts now in understanding the mating system of these species. It turns out that under small population size, there's a very strong selection for less discriminate females. In other words, females that are very choosy as to who they mate with, may never encounter a male that is able to satisfy her mating requirements. So, while the population is under small population size for a few generations, there's a very strong selection for females that are less choosy and there is an increase in frequency of these types of females. So along with that shift in frequency of mating types then there is a shift in the genetic system as well. And it's the natural selection, the forces of the environment, predator pressure, changes in the temperatures and, and changes within the ambient environment that act on the shift in the genetic system that is pulled along by the shift in the mating system.

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