The diverse and colorful wing patterns of butterflies and moths provide some of the most iconic examples of the evolutionary process. Researchers studying gene expression in a range of moth and butterfly species report this week that a certain class of wing patterns has likely evolved through seemingly simple alterations in the timing of various types of gene expression.
The class of wing patterns in question, so-called "intervein" patterns, have lines of symmetry halfway between the insect's wing veins and occur in a range of shapes, including eyespots, ellipses, and midlines. How these dramatic markings have evolved is not completely understood.
Previous work had implicated several genes in the formation of eyespot wing patterns, but little was known about how changes in the activity of these genes translated into the diversification of color patterns over evolutionary time. In their new study, Dr. Robert Reed of Duke University and Dr. Michael Serfas of the University of Wisconsin, Madison, show how the regulation of developmental patterning genes changed during the evolution of line and eyespot color patterns. Comparing eight species of moths and butterflies, the researchers found that signature alterations in the timing of expression of two well-studied genes, Notch and Distal-less, mark an early event in the development of eyespots and other intervein patterns in multiple species. By making a phylogenetic comparison of the species' characteristics, the authors were able to form new ideas about how these patterns evolved.
It is thought that morphological evolution frequently occurs through the relative acceleration or delay of development between different parts of an organism. This idea was first proposed around the time of Darwin, but finding a molecular basis for the phenomenon in nature has proven difficult. In their study, Reed and Serfas show that changes in a gene-regulation time sequence are associated with an evolutionary switch between line and spot color patterns. These findings demonstrate how dramatic evolutionary changes in discrete characteristics of an organism may occur through simple changes in the timing of gene regulation.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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