Natures wonders: beetles look like army ants, eat young (Introduction)

by David Turell , Friday, March 10, 2017, 21:36 (2813 days ago) @ David Turell

A real trick of mimicking as a look alike. these beetles really resemble army ants and hang around to eat their young:

https://www.newscientist.com/article/2124050-sneaky-beetles-evolved-disguise-to-look-li...

"It’s one of the sneakiest ploys that has ever evolved. Rove beetles blend seamlessly into army ant societies, but instead of helping out, they devour the young of their unsuspecting companions.

"The deceit is so successful that it has independently evolved in at least 12 parasitic rove beetle species – a phenomenon called convergent evolution.

"The beetles’ entire body shape evolved to resemble the army ants they prey on, and they smell and act like the ants too. They even go marching on raids with them.

“'What we found is that multiple times, the ancestors of these rove beetles adapted to life inside army ant colonies,” says Joseph Parker at Columbia University in New York. “Each time, their body shape and behaviour underwent the same radical changes.”

"Parker discovered the phenomenon with his colleague, Munetoshi Maruyama of Kyushu University Museum in Fukuoka, Japan. He says the finding challenges arguments by famous palaeontologist and author Stephen Jay Gould and others that completely different creatures would evolve if the evolutionary clock was restarted from scratch.

"Instead, the findings suggest that evolution may take the same predictable path whenever a certain scenario arises. In this case, beetles first prey on army ants directly, but later evolve to sneak into the army itself.

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"DNA analysis of the beetles allowed him and Maruyama to assemble a family tree showing how all the species were related and to estimate their divergence from each other. The creatures seem to have last shared a common ancestor 105 million years ago, around the same time that our ancestors diverged from mice.

"Parker says the length of time since the common ancestor in this example of convergent evolution is remarkable, because most known examples from elsewhere in the animal kingdom — including marsupials, cichlids, stickleback fish, and mammal teeth and ears – happened in the past few million years.

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"The beetles are remarkably adept at mimicking the shape of the ants, which have disproportionately long hind legs, tiny constricted waists and a rear body segment that protrudes upwards at an angle.

“'The ants are blind and use chemical and, we believe, tactile signals to recognise nest mates, so our evidence indicates that the beetles mimic the ant shape to ‘feel’ like a real one,” says Parker.

“'The most remarkable thing is the fact that this exceptional body shape has independently evolved at least 12 times, indicating a certain level of predictability in the evolution of ant-associated rove beetles,”

***

"The beetles have also evolved to smell like ants, developing hydrocarbon-based scents on their outer body surface that mimic those on ants. “The beetles are often seen grooming the ant bodies, presumably to physically procure these chemicals from their hosts,” says Parker.

"But over the millennia, have the beetles evolved to earn their keep by serving some useful purpose for the army ants?

“'This is something we’re very interested in,” says Parker. “Maybe the beetles produce something in their various glands that’s in some way beneficial to the ants. Perhaps they also feed on things like mites attached to the ants’ bodies, and this kind of effect might keep the colony’s parasite burden down.”

"How the rove beetles seek out mates among the army hordes is also a mystery.

“'If their main chemical profiles match those of the host ants, maybe they use alternative chemicals to recognise mates,” says Parker. “The likelihood is that they breed within the army ant colony, but there’s much we don’t know, including where they lay their eggs, where their larvae develop, and what the larvae even look like.'”

Comment: This could not have developed stepwise or the ants would have attacked the beetles. Saltation? DNA studies showing the convergence in many beetle species indicate the adaptation was built into their DNA perhaps as the beetles developed.