Montecristo scorpion mystery traced back 26 million years

A tiny scorpion living on Montecristo, one of the most protected islands in the Tuscan Archipelago, has revealed an evolutionary history stretching back almost 26 million years.

A new study published in the Journal of Biogeography has investigated the origins of Euscorpius oglasae, a species endemic to Montecristo, and found that its closest relative lives hundreds of kilometres away in Spain’s Balearic Islands.

Genetic analysis indicates that the Montecristo scorpion and the Balearic species Euscorpius balearicus belong to lineages that separated around 25.9 million years ago, during the Oligocene.

The finding poses an apparent geographical puzzle: Montecristo did not emerge until between about 8.4 and 7.2 million years ago. The evolutionary lineage that eventually gave rise to the island’s scorpion is therefore far older than the island on which the species now survives.

An ancient Mediterranean landscape

Researchers believe the explanation lies in the complex geological history of the western Mediterranean.

The fragmentation and movement of ancient microplates separated populations that had once been geographically much closer. According to the study, the lineage associated with Euscorpius oglasae was transferred to the Corsica-Sardinia geological block as these land masses moved and separated.

Montecristo was colonised much later, after the island had emerged. The researchers consider passive dispersal across temporary land connections or geological formations a likely explanation, possibly during the Messinian Salinity Crisis between about 5.97 and 5.33 million years ago, when dramatic changes in Mediterranean sea levels transformed connections between land masses.

Populations related to the Montecristo scorpion may subsequently have disappeared elsewhere, leaving the small Tuscan island as the surviving refuge of this ancient evolutionary lineage.

The findings illustrate how tectonic movements, changing sea levels and the formation of islands helped shape the biodiversity that exists across the western Mediterranean today.

Research spanning Tuscany, Lisbon and New York

The study, titled Ancient Divergence, Recent Island: Microplate Fragmentation and Dispersal Explain Disjunct Distributions of Western Mediterranean Scorpions, was published in September 2026 in the Journal of Biogeography.

The research involved Javier Blasco-Aróstegui, Marco Isaia, Jose Barba-Montoya, Marco Tolve, Massimiliano Roppo and Lorenzo Prendini, with researchers linked to institutions including the University of Lisbon, the American Museum of Natural History in New York and the University of Turin.

Isaia, an arachnologist at the University of Turin, coordinated the research activities in Italy, from collecting specimens to reconstructing the biogeographical history of the Tuscan Archipelago.

The Italian research was carried out under an agreement between the University of Turin and the Tuscan Archipelago National Park. The Carabinieri’s biodiversity unit in Follonica also provided support with permits, logistics and fieldwork on Montecristo.

Montecristo lies in the Tyrrhenian Sea, roughly halfway between the Tuscan coast and Corsica, and forms part of the Tuscan Archipelago National Park. Access to the island is strictly controlled to protect its particularly sensitive natural environment.

For researchers, the scorpion’s history provides another example of how Mediterranean islands can preserve species and evolutionary lineages that have disappeared from surrounding areas.

(Cover photo via Observation.org)

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