The taxonomy and phylogeny of Cuerna, a widespread North American leafhopper genus, were examined. Eight species (C. cuesta, C. inflata, C. lugens, C. nielsoni, C. pseudoalba, C. reducta, C. septentrionalis, and C. xyla) are synonymized and three new species (C. emeljanovi, C. lyrifora, and C. oaxacensis) are described, making a total of 26 species in the genus. An annotated checklist with distribution records, brief descriptions, and details on intraspecific morphological variation and separate dichotomous keys to males and females of Cuerna are provided. In addition, a web-based interactive key to species is made available online using 3I software. Four species groups are recognized based on morphology, but only three of them are recovered as monophyletic, with minimal or no node support, in phylogenetic analysis of the morphological data set of 21 characters. Phylogenetic analyses using DNA sequences from mitochondrial Cytochrome oxidase I and II genes yielded nearly identical, well-resolved topologies with most nodes well supported. The resulting tree is only partly consistent with the species groups defined based on morphological characters. Moreover, at least seven species have not been recovered as monophyletic. In at least one case this may be due to interspecific mitochondrial introgression.
Cytochrome oxidase I and II