Evolutionary Origins of Social Parasites in Ants

October 1, 2021

Department of Entomology, Plant Pathology and Nematology Assistant Professor Marek Borowiec and collaborators from Arizona State University and Harvard University explore the evolutionary origins of social parasitism in ants in a new paper published in Proceedings of the National Academy of Sciences.

Look down anywhere in temperate regions of the northern hemisphere, and there is a good chance that the first ant you see belongs to the group of species with the scientific name Formica—meaning “ant” in Latin. Despite countless studies on their biology and conservation, scientists have only had a vague idea about the evolution of these ants.

Like all ants, Formica are social insects that live in colonies consisting of a queen and workers. Unlike other ants, queens in many Formica species do not start new colonies on their own but invade existing colonies or return to the colony they were born into. This behavior of taking advantage of other colonies is called “social parasitism”.

In their paper, Borowiec and co-authors use genomic data to build a tree of evolutionary relationships for all major lineages of Formica ants and trace how they moved around the globe and how their behaviors evolved.

They found that the most recent common ancestor of Formica lived between 21 and 31 million years ago and its queens were capable of starting colonies independently. Then, around 18 million years ago, a species lost the ability to start colonies on its own and later gave rise to almost half of all Formica species, among which other kinds of social parasitism evolved. Their findings emphasize that social parasite syndromes readily originate in socially polymorphic organisms and evolved convergently across the ant phylogeny.

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