DNA barcodes highlight unique research models in European butterflies

There is a widely recognized need for more comprehensive understanding of global biodiversity patterns. Such information will not only provide insights into major scientific issues, such as speciation mechanisms, but it will also add new rigor to conservation programs (a critical need given the looming extinction crisis). We exploit the power of DNA barcoding to explore biodiversity patterns in European butterflies, one of the best-studied invertebrate groups in the world. Ongoing research allowed the detection of unexpected genetic patterns (exemplified here by Leptidea and Spialia), illustrating the biological complexity that awaits discovery even in exhaustively studied regions. Results: The intensively studied model species pair Leptidea sinapis and Leptidea reali has recently been shown to actually represent a triplet of species displaying genetic differences and reproductive isolation due to female mate choice. Additional research has shown that L. sinapis is currently the metazoan with the highest intraspecific chromosome number variability unrelated to polyploidy (2n = 56 to 2n = 110) and that its chromosomal races seem to follow a longitudinally-oriented cline. This unique system prompted us to test the role of chromosomal rearrangements in speciation and the concept of clinal species by mating extreme chromosomal races based on laboratory lines of L. sinapis. Within the genus Spialia, recent research stimulated by DNA barcodes suggests the presence of a new cryptic species confined to Iberia that has likely speciated through a shift in larval host–plant. Complex patterns of Wolbachia infections have been detected in both Leptidea and Spialia. Significance: Leptidea and Spialia represent some of the most striking cases of cryptic species in European butterflies. These taxa exemplify the effort that lies ahead when documenting biodiversity and show how patterns detected by DNA barcodes can lead to the discovery of exciting systems that can often act as models to improve our understanding of fundamental evolutionary processes.