This acts like a "developmental switching mechanism"

Oct 13, 2006 08:23 GMT  ·  By

Many butterfly species achieve some interesting convergent morphologies in order to survive.

Nonpoisonous species may have wing patterns which are similar to toxic species avoided by predators, a tactic called mimicry. Scientists have studied the genetic mechanisms behind the molecular mimicry in three species of Heliconius genus. Two distantly related species (H. melpomene and H. erato (photo center above)) had similar wing patterns and a third species, H. numata (photo center bellow), closely related to H. melpomene (photo above), possesses a very different wing pattern.

Heliconius is a genus of harmless butterflies, and each Heliconius species imitates a poisonous species of the Melinaea genus (photo bellow M scylax).

Previous studies already located gene loci responsible in part to determine the wing patterns and coloration. To determine the genetic background of the color models, the researchers used cross breeding of different morph variations of each species and identified the genotype (the combination of gene which produce a certain morph) of the offspring in order to identify genes which determine the color patterns.

They determined three genes to determine the color pattern in H melpomene, and one distinct gene for H. erato and H. numata. All the five genes determined were distinct. Using molecular markers, the research team found that the loci where these genes are situated on the chromosomes were exactly in the same location for all these three species.

It seems that in Heliconius butterflies there is a "supergene" region responsible for producing wing pattern diversity. This locus functions like a "jack-of-all-trades flexibility" rather than like a constraining gene. Natural selection activates this "developmental switching mechanism" to respond to a wide range of mimetic pressures by splitting into divergent wing patterns adapted to local imitated species.

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