Plant DNA analysis for forensic and environmental purposes.

Among the disciplines included by forensic science, forensic biology is one of the most applied, particularly for human identity testing. But other biological evidence can be found at a crime scene, which can possibly be helpful to solve the case and among the possibilities a very frequent one is the presence of plant material. Since the same molecular techniques used for human DNA are suited for plant DNA, they can be used to establish links between the victim, the suspect and the crime scene. In the last decade a good amount of knowledge about the genetic structure of many plant species has been made available, whose provenance is mainly from population and conservation genetics studies. In fact, the assessment of the amount and distribution of genetic diversity and of the kind of differentiation in a given species are useful tool to understand evolutionary issues and to plan sound conservation strategies. The aim of this project has been therefore to investigate the limits and potentials of forensic botany, still under-utilized in forensic casework, and investigate the use of the same genetic data for the floristic heritage management. The main species chosen was Turkey Oak (Quercus cerris L.), because of its wide distribution on the Italian territory and its ecological importance. A total of 509 trees from 16 populations have been sampled and genotyped by 8 heterologous microsatellites or SSRs (Single Sequence Repeats). The amount of variability and genetic differentiation within and among populations was estimated, and the genetically homogenous groups were identified by the Bayesian clustering method. The species appears derived from no more than two homogeneous gene pools of origin and displays low differentiation (FST = 0.057), this indicating that the colonization of the Italian peninsula after the last glaciation is still under way. Analysis of molecular variance (AMOVA), performed to partition the total genetic variation among the regions indicated by the Bayesian analysis revealed a significant amount of variability between the populations derived from the two putative gene pools. The low differentiation observed between the Turkey oak populations unfortunately prevents this species from being a good candidate to be used as forensic tool. However, a population assignment test indicated that some welldifferentiated populations can be easily recognized by a multilocus genotyping. Finally, after necessary authorization, we applied the knowledge acquired till now to a murder casework analyzing, by means of 4 SSRs, leaves of Hophornbeam tree (Ostrya carpinifolia Scop.), found near the corpse of a young woman. In this second case, albeit the area under study was small and the genetic information non-existent in this species, we were able to pinpoint the provenance of the leaves to a specific tree present on the crime scene.