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Genes,Spots and Butterflies
Source: ENN, Date: February , 2010
different species can evolve the same colors and pattern has always
puzzled biologists. Now, scientists at Cambridge University have found
"hot spots" in the butterflies’ genes that might one of the most
extraordinary examples of mimicry in the natural world. A gene is a
hereditary unit consisting of a sequence of DNA that occupies a
specific location on a chromosome and determines a particular
characteristic in an organism. Genes undergo mutation when their DNA
Heliconius, or passion
vine butterflies, live in the American continents from southern United
States to southern South America. Although they cannot interbreed two
types from two different physical locations (H. melpomene and H. erato)
have evolved to mimic one another perfectly.
butterflies have splashes of red and yellow on their black wings,
signaling to birds that they contain toxins and are extremely bad to
eat. The butterflies are identical in colors and patterns as a visible
warning to predators.
Scientists have studied these butterflies
for over a century as a classic case of parallel evolution in action,
but only now is modern sequencing technology unlocking the underlying
genetics. Parallel evolution have other examples such as old and new
world porcupines, leaf patterns, and gliding mammals such as the flying
lemurs and squirrels.
The Cambridge team of researchers from
United Kingdom and US universities has been searching for the genes
responsible for the butterflies' wing patterns and the answer to the
question of whether the same genes in two different species are
responsible for the parallel evolution of colors and patterns.
to Dr Chris Jiggins of the Department of Zoology at the University of
Cambridge, one of the authors of the study: "The mimicry is remarkable.
The two species that we study - erato and melpomene - are quite
distantly related, yet you can't tell them apart until you get them in
your hand. The similarity is incredible even down to the spots on the
body and the minute details of the wing pattern."
That the two
species have evolved to look exactly the same is due to predation by
birds. "The birds will try anything that looks different in the hope
that it's good, so they learn that certain wing patterns are
unpalatable and avoid them, but anything that deviates slightly from
what they've experienced before is more likely to be attacked," he
For years, scientists have pondered whether when
different species evolve to look the same, they share a common genetic
Because there are thousands of genes in the
butterflies' genome, most scientists felt it was unlikely that the same
genes should be involved. But the results of this study suggest that
this is, in fact, the case.
The new results (published today in
two parallel papers in the journal PLoS Genetics) show that the regions
of the genome associated with the wing patterns are very small or
genetic "hot spots".
"This tells us something about the
limitations on evolution, and how predictable it is. Our results imply
that despite the many thousands of genes in the genome there are only
one or two that are useful for changing this color pattern. It seems
like evolution might be concentrated in quite small regions of the
genome, or hot spots, while the rest of it does not change very much,"
The next stage of the research is to look at other
traits, such as behavior, because the butterflies have preferences for
particular colors and use wing patterns to select mates. "It seems the
same regions of the genome control this behavior as well as the wing
pattern. We'd like to understand this," he says.
For further information see: http://www.admin.cam.ac.uk/news/dp/2010020405 or http://en.wikipedia.org/wiki/Parallel_evolution
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