Re: [asa] (fruit flies???) A Message from the RTB Scholar Team (fwd)

From: David Campbell <pleuronaia@gmail.com>
Date: Mon Apr 21 2008 - 12:37:43 EDT

Bear in mind that most work on Drosophilia fruit flies has been
seeking genetic characterization. No one to my knowledge has tried to
create new species of fruit flies. The only deliberate attempts to
create new species that I know of are in agriculture, and there the
focus is on commercial potential, not on documenting features of
evolutionary interest.

> What examples can you give to proof of new species made in the lab? My
> understanding is that all these mutants are downward- devo, not upwards in
> any way. Even fruit flies, as far as I know, can't be changed into
> something better. Extra wings don't work, and extra legs on a head are no
> good. If you have evidence- I'd like to know. It would help me.

Downward is totally relative to the situation. If it works, or at
least does not keep anything important from working, it's OK.

Extra legs on the head of a fruit fly, though not especially useful to
the fly, are quite remarkable in that they create something that does
not fit into any existing class of arthropods. Insects have 6 legs, 2
antennae, and 3 body regions; arachnids have 8 legs, no antennae, and
1 or 2 body regions, etc.

A classic example of creating a new species in the lab was the Soviet
attempt at combining cabbage and raddish to produce a new genus and
species that could feed the masses. They did make a new genus and
species, but it had cabbage roots and raddish leaves.

Not exactly in the lab, but the hybrid or autopolyploid event
producing corn (or maize, for those across the Atlantic, i.e. Zea
mays) generated the ears through feminization of previously male
reproductive structures.

A good example of speciation in progress comes from a different sort
of fruit fly. This North American species courts, mates, and lays
eggs on hawthorn fruit, and the larvae feed on the fruit as they
develop. Thanks to Johnny Appleseed et al., a new food option is now
available in the form of apples. However, apples have some important
differences from hawthorn. They smell a bit different, ripen at
different times, take longer to rot (giving the larvae more time to
feed and grow), etc. Any fly that happened to mutate in a way
favoring its use of apples rather than hawthorn would be better able
to exploit the new resource. Because courtship takes place on the
fruit, flies that prefer hawthorn and flies that prefer apples will
rarely interbreed. There are now genetic differences between the two
populations, some of which evidently came into the North American
population through hybridization with Mexican hawthorn flies
(hawthorns ripen at different times down there). Are the two
populations differet species yet? A similar example in plants comes
from a flower where a single mutation changes it from red to white.
This also changes it from attracting hummingbirds as pollinators to
attracting moths. As a result, almost no cross-pollination takes
place.

-- 
Dr. David Campbell
425 Scientific Collections
University of Alabama
"I think of my happy condition, surrounded by acres of clams"
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Received on Mon Apr 21 12:39:01 2008

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