When we read the Latin name of a plant or an animal, we tend to assume that it identifies a species whose status is certain and definitive. In reality, this is not the case. In biology, a species is a scientific hypothesis based on the available evidence, which may be confirmed, revised or even rejected as new evidence emerges. The Latin name, however, says nothing about this.
To address this gap, researchers from the Department of Biology at the University of Pisa have developed the Turrill’s Omega Index (TOI), the first standardised index designed to measure the strength of the scientific evidence underpinning species classification. The study, published in the journal Biology, was authored by Lorenzo Peruzzi, Jacopo Franzoni and Antonio Giacò of the University of Pisa.
The index takes into account all the main types of evidence used to distinguish one species from another, ranging from morphological characteristics and genetic analyses to reproductive isolation and geographical and ecological distribution. By integrating these data, the TOI produces a score indicating the strength of the scientific evidence supporting the recognition of one or more populations as a distinct species.
“Although the study presents examples involving plants from the Italian flora, the new index has been designed to be easily applicable to any group of organisms—from animals to fungi—whenever there is a need to assess the robustness of species classification,” explains Professor Lorenzo Peruzzi of the Department of Biology.
Among the case studies, the Elban crocus (Crocus ilvensis), a crocus endemic to the Tuscan Island, achieved the highest score possible under the new index. Its distinction from closely related species is supported by consistent morphological, chemical, genetic, cytogenetic and geographical evidence. By contrast, the Elban hawkweed (Hieracium elbanum), an herbaceous plant endemic to the same island, received a much lower score because the available scientific evidence is still insufficient to determine whether it should truly be regarded as a distinct species.
“Our aim is to make the quality of the scientific evidence underpinning species classification more transparent,” concludes Peruzzi. “This new index could also prove valuable for ecologists, biologists and conservation organisations in helping to guide priorities and resource allocation for biodiversity conservation and the protection of threatened species. At a time when financial and human resources are limited—and it is unfortunately impossible to conserve everything—it is wiser, all other risk factors being equal, to prioritise species whose taxonomic status is supported by strong scientific evidence. A pilot project led by the Group for Floristics, Systematics and Evolution of the Italian Botanical Society is already under way to apply the newly developed index to all endemic plant species in a number of Italian geographical areas of outstanding biogeographical and conservation importance, with the aim of testing the usefulness of the TOI as a tool for establishing conservation priorities.”
