A little lizard has long lived on a volcanic rock off the coast of Filicudi, in one of the most remote areas in the Mediterranean. The Podarcis raffonei, also known as the Aeolian lizard, is an exceptionally uncommon species found only in a few locations of the archipelago and is currently the subject of an international study coordinated by the University of Ferrara. The research, which was published in the scientific journal Heredity, reveals a remarkable discovery: the population living on the sea stack known as La Canna, one of the analyzed species, has the lowest level of genetic diversity ever observed in a wild eukaryote studied at the genomic level. On average, the researchers identified just one variable site every 300,000 bases of the genome. The study concentrated on two populations of Aeolian lizards found on La Canna and Strombolicchio, and compared them to the Sicilian lizard, a related and far more widespread species. The purpose was to look into the relationship between genomic diversity and genetic load, or the accumulation of potentially dangerous mutations, in extremely tiny and isolated populations. "This population represents an extraordinary case for conservation genomics", the researchers write. "Its genetic variability is so low that it is exceedingly fragile; however, it enables us to investigate the degree to which a natural population can endure in the face of severe genetic erosion". The loss of genetic diversity is regarded as one of the primary risk factors for threatened species. When a population is reduced to a few individuals and remains isolated, the probability that unfavorable mutations will accumulate or become more apparent in consecutive generations increases, thereby compromising the ability to adapt and survive. However, the case of the Aeolian lizard reveals a more nuanced picture. Despite the La Canna population's extremely low genetic diversity, the actual genetic burden expressed is comparable to that of the larger and more genetically variable Strombolicchio group. "The result suggests that a population can survive even with very low genetic diversity, as long as the burden of harmful mutations remains within limits compatible with survival", the researchers say. "This is important information because it helps distinguish between a loss of genetic variability and a real increase in the risk of extinction", they conclude.