Abstract
We studied leaf fluctuating asymmetry in Myrtus communis occurring around the "I Borboi" natural CO2 spring (Tuscany, Italy) and in a nearby control site, in a Mediterranean environment. Developmental instability, measured as leaf fluctuating asymmetry, is expected to be positively related to environmental stress and negatively to habitat quality. A gradiental decline in leaf width and leaf angle fluctuating asymmetry was found along the decreasing CO2 concentration from double to ambient. The correlation is ascribed to the positive effect of elevated CO2 on developmental stability. Probably, the adaptation process of individuals grown in close proximity to the CO2-enriched area took advantage of improved water use and carbon balance of M. communis plants.