Colobopsis imitans. Credits: Daniele Giannetti, Università di Parma.
Ants make up a large proportion of animal biomass and are a key component of ecosystems as, like a few other species, including humans, they manipulate their environment. Ant biodiversity is crucial, but its assessment is hampered by the challenge of distinguishing different species based on their appearance alone.
This difficulty was highlighted by an international team of scientists led by Enrico Schifani and Donato Grasso from Università di Parma, whose work led to the discovery of a new species of ant1. The new species, Colobopsis imitans, had always been confused with the similar Colobopsis truncata, but a multidisciplinary approach including different points of view such as ethology, morphology, ecology, genetics and biogeography led to its identification as a distinct species.
The first clue, says Donato Grasso, came from the observation of two different mimicry behaviours among Colobopsis ants. Some of them follow the foraging trails of the ant Crematogaster scutellaris and replicate its colour pattern. “However, the true Colobopsis truncata more closely resembles yet another ant species, Dolichoderus quadripunctatus” says Grasso. Colobopsis ants mimic other species presumably as a defensive strategy: they pose as an aggressive or unpalatable ant, and mix with it to avoid predators.
To confirm that the Colobopsis ants that mimic Crematogaster scutellaris are indeed a new species, the researchers collected data on their morphology and colour patterns (also relying on citizen science image platforms), sequenced their DNA, and mapped their geographical distribution.
While Colobopsis truncata is widely distributed throughout Europe and West Asia, Colobopsis imitans appears to have a more limited range, covering Sicily, southern Iberia, and the Maghreb, possibly matching the distribution of the ant species they mimic. Genetic and morphometric data suggest that speciation occurred recently, and that mimicry of different ant species acts as a rapid driver of phenotypic differentiation.
“Schifani and colleagues are like ant species detectives”, says Brian Fisher, Curator of Entomology at the California Academy of Sciences, who was not involved in this study. “Following their initial observations, they built a strong case that two sister ant species are involved in the mimicry system. Mimicry is widespread in ants and these authors have provided a successful approach for other ant detectives to follow.”
The study was published in the Zoological Journal of the Linnean Society, in which Charles Darwin’s and Alfred Wallace’s seminal article on natural selection was published in 1858.
