Butterflies lost a gene and lost their chemical flexibility
Pinheiro de Castro EC, Cicconardi F, Warren IA, Rueda-M N, Salazar C
Plant Signaling
The passionflower vines climbing a trellis in your garden are locked in a chemical arms race with the caterpillars that eat them, and this study shows how those caterpillars evolved to either steal the vine's toxins or brew their own.
Heliconiini butterflies are toxic because they carry cyanide-based defense chemicals, and they get these two ways: either they pull the chemicals straight out of the passionflower vines their caterpillars eat, or they manufacture the chemicals themselves from scratch. Researchers used gene-editing to find the exact gene, called CYP405, that lets a caterpillar make its own toxins, and they discovered that some butterfly groups lost working copies of this gene entirely, which is why they're now stuck relying solely on their host plant for defense. It's a rare case where scientists can point to the precise DNA change behind a species narrowing its options over evolutionary time.
Key Findings
CRISPR knockout of the CYP405 gene in Heliconius erato confirmed caterpillars can no longer biosynthesize cyanogenic glucosides without it
Chemical analysis of over 700 individual butterflies showed biochemical plasticity (ability to both sequester and biosynthesize toxins) was the ancestral state in Heliconiini, later lost in specific clades like the Sapho group
CYP405A genes were duplicated in all Heliconius species, but most copies in the Sapho clade lack key structural domains, explaining why those species specialized in stealing toxins from plants instead
chevron_right Technical Summary
Scientists found the exact gene that lets some toxic butterflies switch between making their own poison and stealing it from the plants they eat, and losing that gene locks a butterfly into one strategy forever.
Abstract Preview
Original paper
Plasticity-first evolution via CYP405 loss shaped chemical defences in butterflies.
Phenotypic plasticity allows a single genotype to maintain its fitness across different environments. This facilitates colonisation of new niches but can be further refined or even lost as lineages...
open_in_new Read full abstractAbstract copyright held by the original publisher.
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Passiflora, known also as the passion flowers or passion vines, is a genus of about 550 species of flowering plants, and the type genus of the family Passifloraceae.