The sequencing of short standardised pieces of DNA (DNA barcodes) is commonly used to tell species apart. This approach is thought to be of limited value in complex plant groups where species have evolved recently. In a recent study published in AoB PLANTS, Wang et al. use DNA barcoding in the taxonomically complex British Euphrasia genus.
The 19 currently recognized British Euphrasia species are all annual, selfing or mixed-mating small herbaceous plants, which occur in a wide range of habitats including coastal turf, chalk downland, mountain ridges and heather moorland. The study included representatives of all British Euphrasia species as well as a number of hybrids. An initial phylogenetic analysis showed that Euphrasia colonized Britain from mainland Europe on multiple occasions, after which local speciation events gave rise to endemic taxa. While DNA barcoding found no species with a consistent diagnostic sequence profile, there were clear evolutionary patterns, such as divergence between two different species groups with different chromosome numbers. This study highlights the important role of DNA barcoding for studying evolutionary patterns in complex plant groups.