From: bivalve (firstname.lastname@example.org)
Date: Tue Dec 03 2002 - 12:51:29 EST
>Until, and unless, a firm theory is proposed and real data supports
>it (For example, scientists induce circumstances which give rise to
>an evolutionary new species) then it mostly a matter of philosophy
Humans have been producing new species for thousands of years via
domestication and artifical selection. Speciation is also frequently
observed in progress in nature. Deliberate production of new species
in the lab has also been achieved many times; most recently:
Duncan Greig, Edward J. Louis, Rhona H. Borts, Michael Travisano.
2002. Hybrid Speciation in Experimental Populations of Yeast.
Science, Volume 298, Number 5599, Issue of 29 Nov 2002, pp. 1773-1775.
Abstract: Most models of speciation require gradual change and
geographic or ecological isolation for new species to arise.
Homoploid hybrid speciation occurred readily between Saccharomyces
cerevisiae and Saccharomyces paradoxus. Hybrids had high
self-fertility (about 82%), low fertility when backcrossed to either
parental species (about 7.5%), and vigorous growth under different
thermal environments that favored one or the other of the parental
species. Extensive karyotypic changes (tetrasomy) were observed in
the hybrids, although genic incompatibilities accounted for 50% of
the variation in self-fertility.
In other words, by hybridizing two species of yeast, they obtained
new kinds of yeasts that were able to reproduce within the new
strain, but had limited reproductive compatibility with either
parent. Creation of a new species in this manner is almost
instantaneous and thus it makes up most of the unambiguous examples
of the full creation of new species. A more gradual isolation of two
populations makes it much harder to draw a firm line as a point at
which new species exist. We can see this process in progress, e.g.
with the hawthorn fruit flies that are evolving into apple flies
instead (they mate on the fruit, so a strictly hawthorn fly and a
strictly apple fly wil never get together), but it is difficult to
say when we can recognize it as two species.
Again, this does not prove universal common descent, but it does show
that organisms indeed change over time.
Dr. David Campbell
University of Alabama
Biodiversity & Systematics
Dept. Biological Sciences
Tuscaloosa, AL 35487 USA
That is Uncle Joe, taken in the masonic regalia of a Grand Exalted
Periwinkle of the Mystic Order of Whelks-P.G. Wodehouse, Romance at
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