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Army ants tolerate multiple evolutions of beetle mimics

By JW. Dowey - 15 Mar 2017 9:50:0 GMT
Army ants tolerate multiple evolutions of beetle mimics

The pair here are from different orders but the beetle has achieved a level of physical, behavioural and olfactory mimicry that convinces the ant that it is “one of its own!” The beetle , one of many species, is Ecitophya simulans; the army ant is a worker of the common South American Eciton burchellii --- but take a look at those soldiers! (in our first reference)army ant and beetle image; Credit: © Current Biology

OK, so the army ants have been covered here before, I have mentioned the great South American species of Eciton and the equally feared Dorylus and other species of SE Asia and Africa. These animals are a magnificent super-organism, sweeping up prey like the largest known predator, including humans and domestic animals in their diet if they could.

Evolving these unique habits, as many ants have, other species have long ago jumped onto the bandwagon and evolved alongside each ant species. Outnumbering the others are the staphs or rove beetles, which can be found in almost any group of ants, living in the nests. Some have evolved to look like ants, smell like ants and behave exactly like ants, but they are the great pretenders, feeding on the ants young, as well as the captured prey! This convergence of beetle symbionts is investigated by sequencing the DNA of these elusive ant guests in Munetoshi Maruyama and Joseph Parker’s paper in Current Biology. They work in Kyushu University Museum, Japan, and Columbia University, US, respectively.

This ancient system of complex convergence between beetle and ant allows the former to fully exploit the ant, just as butterflies, mites and even some mammals and birds have done, since the Cenozoic began 65mya. Early in the previous period – the Cretaceous – the ancestors of both the ants and rove beetles developed close links. The beetles have evolved such close anatomical and other similarities to their hosts that quite closely-related beetles look nothing like each other.

Even though we know about these mimics, it has proved hard to locate them within such a fearsome assembly as the ant army. Over centuries, few beetles have been collected from the Dorylines, compared to the many found with other ants. The detailed evidence is enough, though, to prove that the close mimicry has evolved not once but repeatedly, with different groups evolving to resemble each ant species long ago. Many lineages of beetle have paralleled each other’s evolution throughout a vast time-span. The DNA sequencing has revealed how these little-known organisms can reveal the secrets of how we all evolve, especially over such a lengthy period (since the Cretaceous.)

The work involved in studies like these, themselves taking decades in the truly challenging conditions of tropical forests, demands dedication, but the authors can gain in the knowledge that these animals are revealed as tremendous adaptations to habitats and ecologies. We rarely appreciate forests and their denizens properly, but here is evidence over 100 million years that we are all part of a great (and rewarding) evolutionary pathway.