Ancient DNA in the seagrass Posidonia oceanica

Posidonia oceanica is a seagrass endemic to the Mediterranean, characterized by low genetic polymorphism, with potential effects on its survival and expansion.In the last 2 decades, a progressive decline of P. oceanica meadows was recorded.This could derive either from intrinsic characteristics of the plant or from habitat fragmentation and isolation induced by external sources of impact.P. oceanica forms large meadows whose remains can persist in the matte and in the sediment for thousands of years.In this paper we illustrate a protocol for the extraction of DNA from old remains of P. oceanica (between 300 and 1100 yr old) collected in the matte and in marine sediments in order to gather information on the evolution of genetic diversity over time.We also report a first genetic analysis of old seagrass DNA using species-specific microsatellite markers.