An evolutionary laboratory
Marettimo is the most remote and mountainous of the Egadi Islands, an archipelago off the western coast of Sicily. Geologically, it is the oldest of the islands, composed primarily of Triassic and Lias limestones and dolostones. Its separation from the mainland occurred much earlier than its neighbors, Favignana and Levanzo. While those islands were connected to Sicily by a plain during the Last Glacial Maximum around 20,000 years ago, Marettimo remained isolated, separated by a deep channel. This long-term isolation turned the island into a natural laboratory for evolution.
The island's unique flora is a direct result of this separation. Cut off from their mainland relatives, plant populations on Marettimo followed their own evolutionary paths. This process, known as allopatric speciation, led to the emergence of species found nowhere else on Earth. The island has at least eight exclusive endemic plant species. Genetic studies on these plants indicate they diverged from their Sicilian counterparts between one and two million years ago, a timeline consistent with the island's geological history of isolation due to sea level changes.
The Marettimo specialists
Among the island's unique flora, three species are particularly important for their evolutionary story. These paleoendemics—species that were once more widespread but are now restricted to a smaller area—are relics of a past Mediterranean landscape.
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Bupleurum dianthifolium: Known as the Hare's-ear of Marettimo, this small, evergreen cushion-shaped shrub is a member of the Apiaceae family. It has linear-lanceolate leaves and produces small umbels of flowers between May and June. It grows exclusively on the north-facing limestone cliffs of the island, from 20 to 600 meters above sea level, rooting itself in tight rock crevices. Genetic analysis shows it is part of a group of woody Bupleurum species found scattered across the SW Mediterranean and Macaronesian islands, suggesting it evolved from a more widespread ancestor.
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Brassica macrocarpa: This critically endangered wild cabbage grows as a small shrub, reaching heights of 60–150 cm with a woody stem. It thrives on maritime limestone cliffs up to 300 meters in elevation. While also found on the neighboring island of Favignana, the Marettimo population is distinct. As a wild relative of crops like broccoli and cabbage, it is valuable for breeding programs, particularly for its high concentration of antioxidant compounds and glucosinolates.
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Pseudoscabiosa limonifolia: Formerly known as Scabiosa limonifolia, this plant is also called the "Trapani Widow". Like other pincushion flowers, it has distinctive blooms with a central cone surrounded by petals. Its range is mostly limited to Marettimo, with only a few other small populations found on promontories in western Sicily. It grows on limestone cliffs, a habitat where it has survived for millennia.
The preservation of these species and their habitat is a primary goal of the Egadi Islands Marine Protected Area, the largest marine reserve in the Mediterranean.