An international team of researchers has decided to discover why some unrelated species of butterflies living in South America had similar wing patterns. And according to PLos Biology, they used genetics and genomics tools to find how butterflies got their spots. Their simple answer is that a 'supergene' controls wing pattern diversity. But read more...
Butterflies are known to employ some interesting convergent evolutionary tactics to survive -- some nonpoisonous species have similar wing patterns to those of noxious species that predators avoid.
Below you can see the color pattern diversity of various butterflies (Credit: PLos Biology). The two first rows show various species of H. numata from northern Peru, while the third and fourth row show respectively species of H. melpomene and H. erato coming from other parts of South America.
In "Jack-of-All-Trades 'Supergene' Controls Butterfly Wing Pattern Diversity," Lisa Gross gives additional details. Here is an excerpt.
The researchers crossed different races of each of the three species to explore the genetic basis of the variations. For example, two different subspecies of H. melpomene from different regions in Ecuador were crossed with an H. melpomene subspecies stock from French Guiana to produce second-generation offspring. Offspring were then genotyped to identify genes responsible for the resulting color patterns and to map the relevant major color-patterning loci—N, Yb, and Sb loci for H. melpomene crosses, Cr for H. erato, and P for H. numata -- in individual offspring.
This research work has been published by the open-access journal PLos Biology under the title "A Conserved Supergene Locus Controls Colour Pattern Diversity in Heliconius Butterflies" (Volume 4, Issue 10, September 2006). Here is a link to the full text of this paper and below is a short excerpt
Mimetic insects are known for their diversity of patterns as well as their remarkable evolutionary convergence, and they have played an important role in controversies over the respective roles of selection and constraints in adaptive evolution. Here we contrast three butterfly species, all classic examples of Müllerian mimicry. We used a genetic linkage map to show that a locus, Yb, which controls the presence of a yellow band in geographic races of Heliconius melpomene, maps precisely to the same location as the locus Cr, which has very similar phenotypic effects in its co-mimic H. erato.
And what can we deduct from this study? Liza Gross writes that "researchers can begin to identify and determine the modus operandi of the genes at the center of what has been called a 'developmental hotspot' to better understand how they drive the adaptive evolution of mimetic color pattern shifts."
For your viewing pleasure, here is another link to a PDF version of this article (10 pages, 3.4 MB), from which the above diagram has been extracted.
Sources: Public Library of Science, via EurekAlert!, September 25, 2006; and various websites
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