Recent paper on "Development and Evolution on the Wing" (Butterflies)

[Michael Gochfeld]

I can guess that many people on this list will be interested in the following
paper.  I hesitate to forward the full PDF file with color photos to the entire
list (since I know that some of us don't like to download large PDF filoes).  .
I'll forward it to Ron (if he likes) and he can link it.   MIKE GOCHFELD

Development and evolution on the wing

W. Owen McMillan a wmcmilla at rrpac.upr.clu.edu, Antónia Monteiro b and Durrell
D. Kapan a
Trends in Ecology & Evolution 2002, 17:125-133

[a] Dept of Biology, University of Puerto Rico, PO Box 23360, San Juan, Puerto
Rico[b] Dept of Biological Sciences, State
University of New York, Buffalo, NY 14221, USA
 Article Outline

 Abstract
Butterfly wing patterns are more than just visually stunning examples of the
evolutionary process. They are also emerging
as exceptional model systems with which to link the developmental and genetic
processes that generate morphological
variation with the ecological and evolutionary processes that mould variation
in natural populations. Work over the past
few years has proceeded simultaneously on key developmental and evolutionary
aspects of patterns on butterfly wings.
Important clues into molecular and developmental events occurring during wing
development are now available that refine our
understanding of pattern formation. In addition, recent behavioural, field and
molecular phylogenetic work places butterfly
wing pattern change in a solid ecological and evolutionary context. There are
still large gaps in our understanding, but
current research priorities are well laid out and experimental methodologies
are in place to address them. The challenge is
to synthesize diverse research strategies into a cohesive picture of
morphological evolution.

Butterfly wing patterns are thin mosaics created by overlapping thousands of
coloured scales. Each scale, which is a
modified sensory bristle [1], contains a single colour pigment and has a
characteristic morphology [2]. Scales are tiled in
rows laid down within a well-defined network of wing veins. In its simplest
conception, pattern formation begins when
groups of scales are specified to produce particular colour pigments. It is the
size, shape and position of clusters of
similarly coloured scales that produce the bewildering array of butterfly wing
patterns. However, there is nothing
particularly simple about these patterns. The developmental genetic programmes
that specify the fate of wing scales are
modified by natural and sexual selection to produce complex mosaics that can
warn predators or blend perfectly with the
environment.

Nearly all of the 12 000 described butterfly species can be distinguished by
differences in wing pattern [2]. In spite of
this daunting diversity, we continue to unravel the genetic, developmental and
evolutionary underpinnings of butterfly wing
patterns. Quantitative genetic and molecular developmental research is fuelling
new ideas about how patterns form on
butterfly wings. Insights into the molecular developmental details of pattern
formation are being grounded in research that
demonstrates the importance of butterfly wing patterns in adaptation [3,4] ,
mate choice [5] and speciation [5,6] .
Although there are still wide gaps in our understanding, there is perhaps no
better animal system where the 'transitions
from genes, through developmental pathways, to phenotype, function, and
fitness' can be clearly illuminated [7]. The
current challenge is to synthesize and expand this research to produce a
cohesive picture of the interplay between
development and evolution of butterfly wings.



 Nature's palette


Research on butterfly wing pattern spans nearly 150 years and figures
prominently in the maturation of developmental and
evolutionary theory [2]. There are several reasons why butterfly wing patterns
are such rich study systems. The patterns
are essentially 2D structures, greatly simplifying the conceptualization and
modelling of pattern change [2]. Additionally,
butterfly wings are large and easy to manipulate. Haemolymph can be extracted
from individual insects, and developing wing
tissue can be excised and transplanted, revealing the developmental processes
that give rise to these patterns (reviewed in
[2,7,8] ). Research on butterfly wing patterns also benefits from developmental
genetic work on Drosophila. In spite of
230*280 million years of separation [9], the developmental 'toolkit' (sensu
[10]) is remarkably preserved between flies and
butterflies, and homologues of many of the patterning genes first identified in
Drosophila have been identified in
butterflies [10*15] . Lastly, and perhaps most importantly, wing patterns are
the most prominent feature of a butterfly.
Colour patterns have been strongly shaped by natural and sexual selection and
often the agent of selection, whether
predation, thermoregulation, mate choice, or a combination of these factors,
can be readily identified and studied
[4*6,12,16] .




 
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