When the male genitalia do not provide useful taxonomic characters: species delimitation of the Aulacizes conspersa Walker complex (Hemiptera: Cicadellidae)

The genus Aulacizes is recorded from Brazil and Argentina and has nine known species. Among them, Aulacizes conspersa has a complex taxonomy and unclear boundaries, with seven synonyms identified to date, due to considerable variation in colour pattern. This study seeks to delimitate distinct evolutionary lineages within A. conspersa. Molecular methods of species delimitation are employed together with a morphological study. We applied single-locus delimitation methods (ABGD, ASAP, GMYC, bPTP, mPTP, PTP) to mitochondrial (COI) and nuclear (ITS2) DNA sequences. The analyses included specimens previously identified as A. conspersa and of the similar Aulacizes insistans, as well as two outgroups. COI analyses recovered a group including only specimens previously identified as A. conspersa and delimited from 3–5 putative species within it, whereas ITS2 delimited from 2–15 putative species and was not able to distinguish A. conspersa from A. insistans. The discordant results of COI and ITS2 are likely caused by low variability in ITS2 sequences. Based on COI results and type specimen studies, we reinstate and redescribe Aulacizes repanda and Aulacizes persistans and synonymize Aulacizes conspurcata with A. persistans and Aulacizes divergens with A. conspersa. Although molecular methods delimited at least three species within A. conspersa s. stricto, no consistent morphological differences were found, a situation that supports its treatment as a cryptic species complex. This study highlights the limited interspecific variation in the terminalia of both sexes within Aulacizes. Homogeneity of male terminalia hinders species delimitation, explaining the long-standing challenges in resolving Aulacizes taxonomy based on morphology. Formal taxonomic treatments are provided for A. conspersa, A. repanda, and A. persistans.