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Wing patterns, key to morphological evolution


The patterns on butterfly wings reveal much about how the shapes, sizes and colours of specific organisms have evolved.

THE BEAUTIFUL patterns on butterfly wings are emerging as exceptional model systems that may reveal much about how the shapes, sizes and colours of specific organisms have evolved, a type of study called morphological evolution, according to the authors of the paper featured in Trends in Ecology and Evolution.

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, researchers note, is development of the first transgenic butterfly a butterfly in which gene expression is manipulated to see if certain genes control colour pattern an effort that is underway.

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 .

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.

Tiny, nearly invisible differences among different species of Drosophila have become important subjects of study for biologists, the ecological importance being of some of these slight differences.

On the other hand, the striking variation of wing patterns of butterflies has a clear function in the wild. Researchers 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, 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 colours.

Also, many of the butterflies that emerge during the wet season in the tropics have very large, conspicuous marks on their wings. These markings 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.

The researchers then will be able to test whether genes that seem to be involved in colour 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 colour pattern formation.

Even more important, it will allow researchers to figure out the regulatory regions of these genes that are turning them `on' in a particular spatial area on the wing.

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