Using complementary techniques to distinguish cryptic species: A new Erysimum (Brassicaceae) species from North Africa

Abstract

• Premise of the study : Cryptic species are superfi cially morphologically indistinguishable and therefore erroneously classifi ed under one single name. The identifi cation and delimitation of these species is usually a diffi cult task. The main aim of this study is to provide an inclusive methodology that combines standard and new tools to allow accurate identifi cation of cryptic species. We used Erysimum nervosum s.l. as a model system. • Methods : Four populations belonging to E. nervosum s.l. were sampled at their two distribution ranges in Morocco (the Atlas Mountains and the Rif Mountains). Fifteen individuals per population were collected to assess standard taxonomic traits. Additionally, corolla color and shape were quantifi ed in 30 individuals per population using spectrophotometry and geometric morphometrics, respectively. Finally, we collected tissue samples from each population per species to study the phylogenetic relationships among them. • Key results : Using the standard taxonomic traits, we could not distinguish the four populations. Nonetheless, there were differences in corolla color and shape between plants from the two mountain ranges. The population differentiation based on quantitative morphological differences were confi rmed and supported by the phylogenetic relationships obtained for these populations and the rest of the Moroccan Erysimum species. • Conclusions : The joint use of the results obtained from standard taxonomic traits, quantitative analyses of plant phenotype, and molecular data suggests the occurrence of two species within E. nervosum s.l. in Morocco, one located in the Atlas Mountains ( E. nervosum s.s.) and the other in the Rif Mountains ( E. riphaeanum sp. nov.). Consequently, we suggest that combining quantitative and molecular approaches with standard taxonomy greatly benefi ts the identifi cation of cryptic species.