Identifying the scene of a crime through pollen analysis

There has been considerable debate, but little consensus regarding locus choice for DNA barcoding land plants. This is partly attributable to a shortage of comparable data from all proposed candidate loci on a common set of samples. In this study, we evaluated the seven main candidate plastid regions (rpoC1, rpoB, rbcL, matK, trnH-psbA, atpF-atpH, psbK-psbI) in three divergent groups of land plants [Inga (angiosperm); Araucaria (gymnosperm); Asterella s.l. (liverwort)]. Across these groups, no single locus showed high levels of universality and resolvability. Interspecific sharing of sequences from individual loci was common. However, when multiple loci were combined, fewer barcodes were shared among species. Evaluation of the performance of previously published suggestions of particular multilocus barcode combinations showed broadly equivalent performance. Minor improvements on these were obtained by various new three-locus combinations involving rpoC1, rbcL, matK and trnH-psbA, but no single combination clearly outperformed all others. In terms of absolute discriminatory power, promising results occurred in liverworts (e.g. c. 90% species discrimination based on rbcL alone). However, Inga (rapid radiation) and Araucaria (slow rates of substitution) represent challenging groups for DNA barcoding, and their corresponding levels of species discrimination reflect this (upper estimate of species discrimination = 69% in Inga and only 32% in Araucaria; mean = 60% averaging all three groups). © 2009 The Authors. Journal compilation © 2009 Blackwell Publishing Ltd.

Identification of the species origin of pollen has many applications, including assessment of plant-pollinator networks, reconstruction of ancient plant communities, product authentication, allergen monitoring, and forensics. Such applications, however, have previously been limited by microscopy-based identification of pollen, which is slow, has low taxonomic resolution, and has few expert practitioners. One alternative is pollen DNA barcoding, which could overcome these issues. Recent studies demonstrate that both chloroplast and nuclear barcoding markers can be amplified from pollen. These recent validations of pollen metabarcoding indicate that now is the time for researchers in various fields to consider applying these methods to their research programs. In this paper, we review the nascent field of pollen DNA barcoding and discuss potential new applications of this technology, highlighting existing limitations and future research developments that will improve its utility in a wide range of applications.

The internal transcribed spacer 2 (ITS2) is a well-established marker for phylogenetic analyses in eukaryotes. A reliable resource for reference sequences and their secondary structures is the ITS2 database (http://its2.bioapps.biozentrum.uni-wuerzburg.de/). However, the database was last updated in 2011. Here, we present a major update of the underlying data almost doubling the number of entities. This increases the number of taxa represented within all major eukaryotic clades. Moreover, additional data has been added to underrepresented groups and some new groups have been added. The broader coverage across the tree of life improves phylogenetic analyses and the capability of ITS2 as a DNA barcode.