Re: Limits of Kinds - now its crabs

Arthur V. Chadwick (
Tue, 18 Nov 1997 19:26:07 -0800

At 06:10 PM 11/18/97 -0600, Glenn wrote:
>OK, then how much change can one get if he changes 2 or 3 or 4... of the
>homeotic genes? What is the limit to change? and why must we only allow one
>of the homeotic genes to change? I don't think you will hold to a position
>that only one can change, but there have been some recently who have said
>that there is a limit to change and I see none.

Again, Hawaii provides the perfect laboratory for testing your theory.
There are 600 species of Drosophila in the Hawaiian Islands that are
endemic (give or take a hundred). There are no insects putatively derived
from Drosophila that are not Drosophilines. There are groups such as the
Honeycreepers that are only known from the islands, but they are believed
to be derived from some finch-like ancestors. We already know the extent
of change possible in this group from Darwin's own studies in the
Galapagos. But the Drepanididae are a family endemic to the Hawaiian
Islands and their derivation and relations to other finch like groups is
far from clear. The plants in the tarweed alliance in Hawaii, including
the famous Silversword of Maui and the Iliau (Wilkesia) of Kauai which
generally have the life habits of yucca (a monocot) and Dubautia latifolia,
which grows with a vine-like habit, are as different as any three plants
can be from the lowly progenitor of the California coast. Yet at least in
the laboratory, all are reported to be interfertile, and thus still closely
allied within the family Asteraceae. So as far as seeing new forms in the
Hawaiian Islands, yes we do. But within the insects they are still in
genera we know from elsewhere. The plants are still allied within families
we are familiar with and often genera, and the birds are less like anything
we are familiar with from other places. (we teach a class there every
summer we don't go to Costa Rica, adn two of our staff are doing research
on Hawaiian forms. THey will be going over in December to study the life
history of a little known butterfly. Life is tough.
When we were there last two years ago, we found an endemic flightless
beetle that was last seen officially 20 years ago, from a genus that is
widely known from other parts of the world.