BUFFALO, N.Y. -- The beautiful patterns on butterfly wings are
emerging as exceptional model systems that may reveal much about
how the shapes, sizes and colors of specific organisms have
evolved, a type of study called morphological evolution, according
to the authors of the paper featured on the cover of the current
(March 2002) issue of Trends in Ecology and Evolution.
In "Development and evolution on the Wing," Antonia Monteiro,
Ph.D., University at Buffalo assistant professor of biological
sciences, and W. Owen McMillan and Durell Kapan of the University
of Puerto Rico describe butterfly wing patterns as possibly the
best animal system for understanding the developmental and genetic
processes that produce morphological variation in nature.
The next step in understanding the genetics of butterfly wing
patterns, they note, is development of the first transgenic
butterfly -- a butterfly in which gene expression is manipulated to
see if certain genes control color pattern -- an effort that is
underway in Monteiro's UB laboratory. She expects to have it
developed by the end of this summer.
"Butterfly wing patterns are a very amenable system for studying
morphological evolution because they develop on a two-dimensional,
epidermal surface made up of tiny scales, each of which produces
only one pigment," Monteiro explained. "A single sheet of cells is
not nearly as complex as a three-dimensional structure."
While Drosophila, the common fruit fly, traditionally has been
the model system of choice for genetic and developmental biology
studies, mostly carried out in the laboratory, the butterfly
provides an exciting opportunity to connect genetic changes with
important ecological and evolutionary processes that mould
variation in natural populations, she said.
Whereas tiny, nearly invisible differences among different
species of Drosophila have become important subjects of study for
biologists, the ecological importance of some of these slight
differences, Monteiro added, remains to be seen.
"On the other hand," she stressed, "the striking variation of
wing patterns of butterflies has
a clear function in the wild."
Monteiro noted that the differences in wing patterns
differentiate one species of butterfly from another and are used by
males and females to determine with which individuals to mate.
They also have been shown to serve an adaptive purpose, as
demonstrated by numerous studies focusing on seasonal changes in
wing coloration of individuals in a species. For instance, Monteiro
said, the darker wing patterns that show up in butterflies that
emerge in the spring serve to warm up the butterfly faster, whereas
butterflies that emerge in the summer have lighter colors.
"Also, many butterflies that emerge in the wet season in the
tropics have large, conspicuous marks on their wings that deflect
the attacks of predators while the butterflies are actively finding
mates and laying eggs, while the dry-season cohorts are very
cryptic, trying to blend in with their environment and not attract
any attention from predators until the rains arrive again," she
The authors note that what's not known about wing patterns in
butterflies are the genetic mechanisms that result in the great
variety of patterns that exist and an understanding of how those
mechanisms have evolved through time.
"Evolution of these patterning mechanisms has enabled the
ancestors of the generally drabber looking moths to also give rise
to the butterfly lineages, where an explosion of pattern and color
have occurred," Monteiro said.
In an attempt to identify those mechanisms, Monteiro is working
to create the world's first transgenic butterfly, one that she will
breed in her lab to determine the particular genetic code that is
responsible for the beautiful colors and patterns on butterfly
The researchers then will be able to test whether genes that
seem to be involved in color pattern formation actually are
important in directing the production of different pigments.
"A transgenic system is needed to test the causal involvement of
genes that have already been shown through their suggestive
expression patterns to be involved in color pattern formation," she
"Even more important, it will allow us to figure out the
regulatory regions of these genes that are turning them 'on' in a
particular spatial area on the wing. These will be, in my view, the
prime candidate regions to look for variability in DNA sequences
that correlates with variability in color pattern. My job is to
find out what are the signals that tell each scale-cell on a
butterfly wing to produce a particular pigment during development
and to find out how those signals change across different species
and through evolutionary time."
Monteiro's research on the published work was funded by a grant
from the Human Frontiers Science Program, an international
organization based in France that supports basic research focused
on complex mechanisms of living organisms.