NSF PR 97-25 - March 27, 1997
This material is available primarily for archival purposes. Telephone
numbers or other contact information may be out of date; please see current
contact information at media
contacts.
Natural Selection Study Shows Animals Can Adapt Dramatically
Fast
In a unique, real-world test of the theory of evolution,
a National Science Foundation (NSF)-supported research
team has demonstrated that animals can adapt to sudden
changes in their environment with surprising speed.
It's a finding that challenges current methods of
evaluating evolutionary changes through the fossil
record.
The study of wild guppies on the West Indies island
of Trinidad, reported in the newest (March 28) issue
of the journal Science, found that the
fish could evolve between 10,000 and 10 million times
faster than the rate of evolution inferred from the
fossil record. It suggests that characterizing evolution
from the palaeontological record alone may yield a
misleading picture.
"We feel that our work is part of a growing body of
studies that clearly demonstrates that it is possible
to evaluate evolution with experiments in natural
populations," David Reznick, professor of biology
at the University of California at Riverside and lead
author of the study said.
The team's findings add fodder to a current scientific
debate. "The perennial problem in evolution is relating
things that we can observe in real time to long-term
patterns that are unobservable in our lifetime, but
are traced out in the fossil record," said Reznick.
"The question is whether or not we can explain larger-scale
events of evolution in terms of what we can see and
study."
In the study of wild guppies in Trinidad, Reznick,
along with researchers Frank Shaw and Ruth Shaw of
the University of Minnesota, St. Paul, and F. Helen
Rodd of the University of California, Davis found
that fish that were moved from a predator-infested
pool to a pool with just one predator grew larger,
lived longer and produced fewer but larger offspring.
In the span of seven to 18 generations -- between
four and 11 years - they became more like the native
guppies in the relatively predator-free environment.
The NSF-funded study took place in a unique river
system in Trinidad where populations of fish are,
for the most part, separated from one another by a
series of waterfalls. Downstream guppies coexist with
at least three predators, including two species of
cichlids, the wild version of the common aquarium
fish. Guppies in that downstream pool have a generally
high mortality rate, become mature at an earlier age,
are relatively small at maturity and produce litters
more frequently. Upstream guppies, which share a pool
with the omnivorous killifish which only sometimes
preys on guppies, have a lower mortality, grow larger
and have fewer but larger offspring.
The study, he said, shows it is possible to use short-term
experiments of natural selection to gain a greater
understanding of evolutionary changes that occur over
millions of years. "Such studies are important because
people tend to think of evolution as a historical
process that is not subject to experiments. It is
the scarcity of experiments that is the source of
some of the criticism of the theory."
Reznick stressed that formation of new species is
not addressed by the study, but noted that body size
-- one of the principal traits used in palaeontology
to distinguish evolutionary changes from formation
of new species -- was the prominent characteristic
adapted in the guppies studied.
"While the amount of change that we have witnessed
seems small, if this rate of change persisted for
even 1,000 years, it would result in a radically different
animal," Reznick observed.
|