Female Heliconius butterflies have taste receptors next to spikes on their legs in order to spear and ‘taste’ plants to find the most beneficial ones on which to lay their eggs, new research reveals. As male Heliconius butterflies do not lay eggs, they have no taste receptors on their legs. The research was published today, 11 July, in the journal PLoS Genetics.
For the research, the scientists studied the genes that code for the taste receptor proteins. Using new high-throughput sequencing methods, they were able to identify genes expressed at very low levels, including the great diversity of taste receptor genes unique to female Heliconius butterflies.
Because, unlike their parents, caterpillars cannot fly away to find a more suitable plant, it is imperative that the female butterflies choose the best host plant for their eggs or risk the survival of their offspring. The proteins that are coded for by the taste receptor genes enable the female butterflies to identify the most advantageous plants on which to lay their eggs.
Dr Chris Jiggins, lead author of the paper from the University of Cambridge said: “It appears that a new set of taste receptor genes have evolved to help identify toxic plants and are used by females to find the plant that will increase their caterpillars chance of survival.”
It is a long-standing hypothesis that butterflies are so diverse partly because of the complicated evolutionary arms race with the plants that their larvae eat - as plants develop new ways to prevent being eaten, butterflies develop new ways to eat plants.
For example, Heliconius butterflies evolved in a way that allows them to feed on the highly-toxic, cyanide-containing leaves of passion flower vines.
The Heliconius butterflies have not only evolved to overcome the plant’s defences, but can now even synthesise their own cyanide-containing compounds that protect them from predators.
Professor Adriana Briscoe, who conducted the research while a visiting scholar at the University of Cambridge and is currently at the University of California, Irvine, said:
“This study is important for understanding the co-evolution of butterfly species and their host plants, uncovers a new set of genes that are critical to the species' survival, and reveals that female butterfly behaviour shapes the hereditary make up of butterflies.”
Unlike their male counterparts, the female Heliconius butterflies have taste receptors on their legs in order to pick the best plants on which to lay their eggs.
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