First published: 03 September 2025.
A recent study by Juvé et al. published in Systematic Entomology reveals the evolutionary history of Messor harvester ants, a genus adapted to arid environments that developed some of the most complex reproductive systems known so far. By analyzing 2,524 genetic loci from 58 species, researchers uncovered how these ants originated in the Irano-Indian region around 20 million years ago and rapidly diversified across the Old World, driven by ancient climate shifts.
Phylogeny of main Messor groups, speciation rate and geographical distribution of species through time. Credit Y. Juvé
Unlike most ants, Messor species are highly specialized granivores, thriving in dry, open habitats from the Mediterranean area to South Africa and Eastern Asia. By chewing seeds thanks to a dedicated worker caste with massive mandible muscles, they are able to prepare a sort of “ant bread” that feeds all the colony members. The ability to harvest, store and process seeds has made them a dominant force in arid ecosystems.
But how did they achieve such a wide distribution?
The study, led by Jonathan Romiguier at the University of Montpellier, used advanced phylogenomic techniques to reconstruct the ants’ family tree. The results show that Messor ants emerged during the early Miocene, a period of global warming and grassland expansion. Their diversification peaked during the mid-Miocene Climatic Optimum, when warmer temperatures created ideal conditions for their spread.
The researchers found a strong link between temperature and speciation rates: Messor ants diversified faster during warmer periods. This pattern suggests that their ecological specialization—relying on seeds from grasses and forbs—made them particularly sensitive to climate changes. As global temperatures fluctuated, so did their opportunities to colonize new regions.
“It is likely that the expansion of grasslands during the Miocene provided Messor ants with abundant food resources, fuelling their diversification.”
Strikingly, their dispersal route mirrors that of Cataglyphis desert ants, suggesting that extreme specialists evolve in predictable ways when faced with climate change. Both genera expanded from the Middle East toward Europe and North Africa around the same time.
“These parallel histories with Cataglyphis suggests that extreme specialists often follow similar evolutionary paths. This might mean that their responses to future climate shifts may be more predictable than those of generalist species.”
The study also sheds light on the ants’ complex reproductive strategies, including hybridization between species. For example, we already knew that Messor barbarus relies on an unusual reproductive system where hybridization is required to produce workers. Genetic analyses of this study suggest that other species in the genus may practice similar reproductive strategies, but further work is needed to confirm that.
“Messor is a fascinating genus where some species need to hybridize to produce workers or even clone other species as part of their lifecycle. By mapping their taxonomy and evolutionary history, this work establishes a solid backbone for future genetic and ecological studies”.
– Jonathan Romiguier
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