Genetic survey on a reed-bed in Central Italy showing early die-back symptoms

Phragmites australis die-back is a well known phenomenon in Central Europe and rather recently observed also in some Mediterranean wetlands. In this study we analyze the genetic structure of a reed-bed in a protected wetland in N-W Tuscany (Italy) recently showing some clear symptoms of die-back, in particular the clumped growth-form, searching for any possible relationships with the ecological condition or the health status of common reed stands. After a diachronic analysis of vegetation maps (from 1988 to 2013) and a field survey, we have sampled four temporarily emerged and four permanent submerged reed stands, being the submersion regime a crucial trigger of reed die-back. Aquatic plots showed two clear conditions, with the presence of clumped and non-clumped stands. Emerged stands have been sampled in areas showing temporarily stable, increasing and decreasing reed-bed surface. In order to investigate the genetic structure of the population, the AFLP technique was applied on 69 individuals. The total reedbed surface showed a decrease in the observed time, partly due to the human activities and partly attributable to the RDBS. In several areas of the Lake the reed-bed appeared clumped and fragmented. The genetic analysis put in evidence a rather high level of genetic diversity, compared to the results of previous international studies on other populations of the same species. No significant differences between temporarily and permanently submerged stands were found. The major portion of genetic variation appeared within sampling sites rather than between sampling sites, indicating the absence of isolation between the different reed stands of the lake and a negligible role of genetic diversity in the occurrence of die-back symptoms.