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         Environmental Change Can Trigger Rapid Evolutionary Adaptation

   by Rosanne Skirble

   A new study challenges the widely held belief that evolutionary changes
   in living organisms take place slowly, over hundreds, thousands or
   millions of years.  Researchers have found evidence that species can
   evolve much more quickly than that when they have to respond to
   environmental change.
   Tim Benton studies how living organisms respond to changes in their
   environment. In a paper he and his colleagues have just published in
   the journal Ecology Letters, the professor of biological sciences at
   the University of Leeds in England examines why, for example, marine
   species have declined so rapidly in size and number over the past fifty
   years.
   "Is this a response that is due to them having less food or the
   temperature of the water changing from climate change or is it a
   response that is due to natural selection working and evolutionary
   biology happening?" he asked.
   To find out, Benton's team of researchers conducted a series of
   laboratory experiments with soil mites, tiny spider-like creatures
   that, among other things, reproduce rapidly.
   "We brought them in from the wild and put them in test tubes, where
   each test tube maintained about 1,000 individuals in a free running
   population, " said Benton. "Every day we just put in a little bit of
   food. And in some of the populations we took out juveniles and in other
   populations we harvested adults. And then we just left them to it over
   about 100 weeks."
   That's normally long enough for about 20 generations of soil mites.  In
   their new test tube environments, the tiny creatures competed for food,
   sex and survival in different ways than they would have in the wild.
   And in charting the mites' growth rates, genetics and reproduction over
   this relatively brief span of time, the scientists observed that
   natural selection produced significant evolutionary changes.  For
   example, Benton says, the length of time the mites needed to reach
   adulthood doubled during the course of the experiment.
   "And because it is taking them so much longer to grow up, then that
   means that the population responds to changes in a different way," he
   said. "Population growth rate is slower, which means that there are
   very large changes in population dynamics, the way the population size
   responds to environmental change in itself."
   Benton says the mite study suggests there is a powerful interplay
   between environmental and evolutionary change.
   "And [after] one or two more complementary studies like ours in
   different groups, then people will quite happily accept, I think, the
   force of evolutionary change in ecological time," he said. "So over a
   single human life time, 100 years, there are likely to be very large
   changes and if we don't start thinking about the evolutionary changes
   as well as the changes in the environment, then the things we put in
   place to protect the species we want to manage won't actually work."
   One place where this might have a critical impact, Benton says, is in
   fisheries management:
   Given that we are harvesting large animals all the time - that's what
   we do when we go out fishing - the phenotypic response that we see in
   the reduction of size is likely to be an evolutionary response," said
   Benton. "And that's what we found in our laboratory study.  So what
   that means is, if you stop fishing because your stock is getting
   depleted and the animals are increasingly smaller and smaller and
   smaller, there is no necessity that they will be able to recover
   because you've had a hard-wired evolutionary change. So they won't just
   be able to spring back."
   And there's no guarantee that they will again grow larger and larger.
   Benton adds that environmentally-induced evolutionary changes could
   also have serious implications for other wildlife conservation efforts,
   as well as for disease and pest control programs.
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   [1]http://www.voanews.com/content/environmental-change-can-trigger-rapi
   d-evolutionary-adaptation/1640436.html

References

   1. http://www.voanews.com/content/environmental-change-can-trigger-rapid-evolutionary-adaptation/1640436.html