Smell-wars between butterflies and ants

Jan 03, 2008

Among humans, making yourself smell more alluring than you really are is a fairly harmless, socially accepted habit that maintains a complete perfume industry. However, it is a matter of life and death for caterpillars of large blue butterflies that dupe ant workers into believing them to be one of the ant’s own larvae. In a publication in the journal Science this week , researchers from the Centre for Social Evolution (CSE) at the University of Copenhagen show that caterpillar deception is also a matter of smell, and that there is an ongoing co-evolutionary arms race in smell similarity between cheaters and their victims.

Most people are familiar with animal confidence tricksters such as cuckoos, which grow up at the expense of 4-5 chicks of hapless songbirds. Less well known, but at least as spectacular, are the large blue butterflies of the genus Maculinea, whose larvae are adopted by ant colonies and deceive the ants into feeding them while letting their own brood starve. Jutland, and the island Læsø in particular, are among the last European strongholds of one of these species, the Alcon blue, which has enabled researchers from the CSE to study these spectacular butterflies in great detail.

David Nash, Jacobus Boomsma and colleagues show that superb chemical mimicry manipulates the ants into neglecting their own brood to care almost exclusively for their caterpillar parasites, but also that the ant hosts can evolve resistance against this exploitation by changing how they smell. However, this only works when the host ants that live close to the initial foodplant of the caterpillars, the rare marsh gentian Gentiana pneumonanthe, do not interbreed with ants from neighbouring sites where the gentian does not occur. In the sites without the foodplant, ant colonies are never parasitized, so ants do not evolve resistance. Any resistance that has evolved in areas with butterflies is not effectively passed on to future generations because it is diluted by the flow of non-resistant genes from the uninfected areas.

In their study, the CSE researchers show that the two red ant species of the genus Myrmica that are host for the Alcon blue in Denmark differ dramatically in their degree of gene-flow among neighbouring sites, even though they live in the same gentian patches. Exactly as expected from evolutionary theory, they demonstrate that selection for resistance only works when the ant queens mate locally with males from colonies that have likewise suffered from butterfly parasitism.

With this study, the CSE researchers show that a study that was initially inspired by an interest in the suitable conservation of these large blue butterflies in Denmark can give important insights into the fundamentals of evolutionary biology. They achieved this result by an interdisciplinary collaboration with a British group of chemists, specializing on the study of chemical profiles on the surface of insects.

Source: University of Copenhagen

Explore further: Factors that drive sexual traits

add to favorites email to friend print save as pdf

Related Stories

US northeast braces for flooding after record snow

3 hours ago

Weather forecasters and emergency officials warned Sunday that melting snow would lead to heavy flooding in parts of the US northeast, with hundreds of thousands of people told to brace for fast-rising waters.

How the hummingbird achieves its aerobatic feats

10 hours ago

(Phys.org) —The sight of a tiny hummingbird hovering in front of a flower and then darting to another with lightning speed amazes and delights. But it also leaves watchers with a persistent question: How ...

'Mind the gap' between atomically thin materials

11 hours ago

In subway stations around London, the warning to "Mind the Gap" helps commuters keep from stepping into empty space as they leave the train. When it comes to engineering single-layer atomic structures, minding ...

Recommended for you

Dogs hear our words and how we say them

12 hours ago

When people hear another person talking to them, they respond not only to what is being said—those consonants and vowels strung together into words and sentences—but also to other features of that speech—the ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.