Estimating the genetic diversity and structure of Quercus trojana Webb populations in Italy by SSRs: implications for management and conservation

Studying the genetic diversity and structure of the current forest populations is essential for evaluating the ability to survive to future biotic and abiotic changes and planning conservation strategies. Quercus trojana is an eastern Mediterranean tree species with a fragmented distribution range, and its westernmost outposts are located in southern Italy. The demand for timber and cropland over the centuries has severely reduced its occurrence in this part of the range. We assessed the genetic diversity and structure of the extant Italian populations of Q. trojana and derived conservation guidelines. A total of 322 samples were genotyped with six polymorphic nuclear microsatellite markers. Our results revealed a high genetic diversity in all populations, structured into two main gene pools, and a highly divergent single population. Based on the allelic richness and heterozygosity estimation, we identified populations which can be considered as valuable source material for conservation programs, and those requiring adequate measure to re-establish gene flow and reduce fragmentation. Finally, a comparison with a set of eastern Mediterranean samples indicated a relationship between the Italian and the Greek gene pool; different hypotheses on the Italian gene pool origin were discussed. The need to protect these marginal, disjunct populations was further reinforced.