DNA barcode reference library for Iberian butterflies enables a continental-scale preview of potential cryptic diversity

How common are cryptic species - those overlooked because of their morphological similarity? Despite its wide-ranging implications for biology and conservation, the answer remains open to debate. Butterflies constitute the best-studied invertebrates, playing a similar role as birds do in providing models for vertebrate biology. An accurate assessment of cryptic diversity in this emblematic group requires meticulous case-by-case assessments, but a preview to highlight cases of particular interest will help to direct future studies. We present a survey of mitochondrial genetic diversity for the butterfly fauna of the Iberian Peninsula with unprecedented resolution (3502 DNA barcodes for all 228 species), creating a reliable system for DNA-based identification and for the detection of overlooked diversity. After compiling available data for European butterflies (5782 sequences, 299 species), we applied the Generalized Mixed Yule-Coalescent model to explore potential cryptic diversity at a continental scale. The results indicate that 27.7% of these species include from two to four evolutionary significant units (ESUs), suggesting that cryptic biodiversity may be higher than expected for one of the best-studied invertebrate groups and regions. The ESUs represent important units for conservation, models for studies of evolutionary and speciation processes, and sentinels for future research to unveil hidden diversity.
Support for this research was provided by the Spanish Ministerio de Economía y Competitividad (project CGL2010-21226/BOS and CGL2013- 48277-P), by Marie Curie International Outgoing Fellowships within the 7th European Community Framework Programme to V. Dincă (project no. 625997) and G. Talavera (project no. 622716), by grant 1.50.1617.2013 at Saint Petersburg State University for G. Talavera, and by the government of Canada through Genome Canada and the Ontario Genomics Institute in support of the International Barcode of Life project.