Iterative taxonomy based on morphological and molecular evidence to estimate species boundaries: a case study in Cypella (Iridaceae: Iridoideae)

Cypella Herb. is one of the largest genera of Tigridieae (Iridaceae: Iridoideae) with more than 30 species accepted by the World Checklist of Iridaceae. The current infrageneric taxonomy rests exclusively on morphological characters, which are more or less reliable because of their intraspecific variability, and the delimitation of various species recently described remains obscure. Therefore, multiple lines of evidence were used to assess species boundaries in a morphologically conserved group of five species, including various populations of Cypella pusilla and the closely related C. gloriana. Phylogenetic analyses based on ten genetic markers (eight plastid and two nuclear loci) and multivariate analyses of 38 qualitative and quantitative phenotypic characters were performed. Results revealed that species-level diversity was overestimated and intraspecific morphological variability of C. pusilla underestimated. Overall, our findings support the utility of combining genetic evidence and broad morphological sampling to validate and describe species using complementary approaches. Consequently, an updated taxonomic treatment of C. pusilla is presented, including an expanded description of the species.