DNA Barcoding for pollen detectives

I have to admit that I knew little about today's topic before. The term 'forensic palynology' was unknown to me. Forensic palynology has been a law enforcement tool for over 60 years. It is the application of pollen and spores in solving legal issues, either civil or criminal. Pollen can be a critical forensic marker in cases where determining geographic origin is important, including investigative leads, missing persons cases, and intelligence applications. Pollen and spores can be obtained from an extremely wide range of items, including bodies and thereby providing clues as to the source of the items and the characteristics of the environments from which the material on them was sourced. 

Despite these clear advantages, the use of palynology has been rather limited in forensic studies and this has likely to do with that fact that you need highly trained, specialized experts to reliably identify pollen via microscopy. The process is slow which in some criminal cases or in the field of intelligence might be crucial. In addition the taxonomic resolution is rather poor (family or genus level at most) even if done by experts. In recent years automated analysis of pollen samples has been developed and the most prominent idea was image processing of microscope images combined with a statistical or machine learning classifier. Other microscopy technologies have been tested as well but what all of them have in common is a general limitation: the lack of morphological characters in pollen for species-level taxonomic resolution in many plant groups.

In a recent review paper colleagues discuss the utility of DNA Barcoding for the identification of pollen. The paper discusses some key challenges that might have prevented DNA Barcoding from being used much wider but the authors also highlight recent progress.

Based on these recent methodological developments in pollen DNA barcoding, we believe that now is the time to start applying these techniques in forensic palynology. In this article, we discuss the potential for these methods, and outline directions for future research to further improve on the technology and increase its applicability to a broader range of situations.

Overall a very nice read and the take home message is that DNA Barcoding is very close to being feasible for routine analysis in forensics, and improvements on technical issues are occurring so rapidly that there is no more excuse to not start using it already.