Ancient Lupine Discovery Rewrites Mediterranean Plant History

A long-standing botanical mystery has been unraveled on the slopes of Mount Etna, where researchers have identified a species of lupine previously thought to be exclusive to the Iberian Peninsula. The discovery of five distinct populations of Lupinus gredensis in Sicily, Italy, challenges established views on the distribution of this legume and suggests a far more complex history of plant migration in the Mediterranean region. For decades, L. gredensis was classified as an endemic species to Spain and Portugal, with any occurrences in the eastern Mediterranean attributed to recent human introduction. However, new morphological and ecological data indicate that the species has likely been present in Sicily for centuries, if not longer, prompting a reevaluation of its taxonomic status and biogeographical range.

The identification process required a rigorous comparison of fresh specimens collected from the southeastern slopes of Etna with herbarium samples of closely related species, specifically Lupinus luteus and Lupinus hispanicus. While L. luteus is a native species in Italy, it is characterized by bright yellow flowers and densely hairy leaves, traits that distinguish it sharply from the newly identified populations. L. gredensis, by contrast, features a unique floral coloration that begins as cream or pale yellow in the upper whorls and transitions to lilac or mauve in the lower whorls as the flowers age. This color shift, combined with specific leaf and pod characteristics, provided the definitive evidence needed to separate the Sicilian plants from their native counterparts.

Microscopic analysis of the seeds further supported the taxonomic distinction. Using scanning electron microscopy, researchers examined the microstructure of the seed coats, revealing that L. gredensis possesses smooth seeds with cohesive, isodiametric palisade cells. In comparison, L. luteus seeds exhibit significantly larger cells and a more prominently sculptured surface. Statistical analysis of these measurements confirmed that the differences between the two species are significant, with the Sicilian specimens aligning closely with L. gredensis rather than L. luteus. This micromorphological evidence is crucial for resolving taxonomic ambiguities in the genus Lupinus, where visual similarities can often lead to misidentification in historical records.

The ecological context of the discovery provides additional clues to the species’ history. The Sicilian populations of L. gredensis are found exclusively on volcanic sands at altitudes between 700 and 1,100 meters above sea level. They colonize clearings in deciduous and holm oak forests, roadsides, and uncultivated lands, preferring substrates with highly incoherent and poorly developed soils. This specific ecological niche allows the species to thrive despite competition from other ruderal plants, such as Lupinus angustifolius, which is more abundant in similar environments. The presence of the species in these semi-natural habitats suggests a long-standing adaptation to the local conditions, rather than a recent introduction that would typically be confined to more disturbed or anthropogenic sites.

Historical herbarium specimens played a pivotal role in establishing the timeline of the species’ presence in Sicily. Researchers examined samples collected as early as 1829, which had previously been misidentified as L. luteus or Lupinus termis. Upon re-evaluation, these specimens were found to match the morphological characteristics of L. gredensis, indicating that the species has been present on Mount Etna for at least two centuries. This historical continuity undermines the hypothesis of a recent introduction and supports the idea that the species may be native to the region, or at least the result of an ancient introduction that has since become naturalized. The misidentification of these plants in the past highlights the challenges of botanical classification and the importance of revisiting historical collections with modern analytical tools.

The phytosociological analysis of the plant communities hosting L. gredensis revealed a new association named Linario aetnensis-Lupinetum gredensis. This community is characterized by a dominance of L. gredensis accompanied by a limited number of other species, including Linaria multicaulis subsp. aetnensis and Isatis tinctoria subsp. canescens. The association is typical of pioneer vegetation on coarse sandy soils, exhibiting a meso-Mediterranean bioclimatic character. The floristic poverty of this community, compared to other ruderal vegetation in the region, underscores the specific ecological requirements of L. gredensis and its ability to form distinct populations in suitable habitats. This new association provides a framework for understanding the ecological dynamics of the species in Sicily and may serve as a model for studying similar plant communities in other parts of the Mediterranean.

From a biogeographical perspective, the presence of L. gredensis in Sicily expands its known distribution range to include the western and central Mediterranean. While the species is considered native to the Iberian Peninsula, its occurrence in Sicily, along with reports from Greece, Turkey, and Bulgaria, suggests a disjunct distribution pattern that may reflect ancient migration routes or historical introductions. The status of the species in these eastern Mediterranean regions remains controversial, with some authors arguing for a native status based on its behavior in natural environments, while others maintain that it is an alien species. The Sicilian discovery adds a new dimension to this debate, as the historical evidence and ecological integration of the populations suggest a long-term presence that may warrant a reclassification of its status in the region.

The implications of this discovery extend beyond taxonomy and ecology, touching on broader questions of plant conservation and biodiversity management. If L. gredensis is confirmed as a native or long-established species in Sicily, it may be eligible for protection under local and international conservation frameworks. The species’ restricted habitat and specific ecological requirements make it vulnerable to environmental changes, including habitat degradation and climate change. Further research, including population genetic studies using molecular markers such as SNPs or ribotyping, is needed to clarify the evolutionary history of the Sicilian populations and their relationship to other Mediterranean populations. Such studies could provide insights into the mechanisms of plant migration and adaptation in the region, contributing to a more comprehensive understanding of Mediterranean biodiversity.

In conclusion, the identification of Lupinus gredensis on Mount Etna represents a significant advance in our understanding of the flora of the Mediterranean region. The combination of morphological, micromorphological, ecological, and historical evidence provides a robust foundation for reevaluating the species’ distribution and status. This discovery not only corrects past misidentifications but also opens new avenues for research into the biogeography and ecology of leguminous plants in the Mediterranean. As scientists continue to explore the complex interactions between plants and their environments, the case of L. gredensis serves as a reminder of the dynamic nature of biodiversity and the importance of rigorous, interdisciplinary approaches to botanical science.

Subject of Research: New data on the morphology, ecology and distribution of Lupinus gredensis (Fabaceae) in the Mediterranean region

Article Title: New data on the morphology, ecology and distribution of Lupinus gredensis ( Fabaceae ) in the Mediterranean region

Article References: Cambria, S., Blandino, C., & Cristaudo, A. (2024). New data on the morphology, ecology and distribution of Lupinus gredensis (Fabaceae) in the Mediterranean region. Italian Botanist, 18, 123-140. https://doi.org/10.3897/italianbotanist.18.132924

Image Credits: AI Generated

DOI: 10.3897/italianbotanist.18.132924

Keywords: data, morphology, ecology, distribution, Lupinus, gredensis, Fabaceae, Mediterranean, region, scientific research